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Appendix B

B–30

TA I

NSTRUMENTS

TGA 2950

These samples form bubbles which can rise up

and touch the end of the thermocouple, ruining

the experiment and possibly contaminating the

thermocouple. Just as the largest chewing gum

bubbles are produced by blowing slow pro-

longed breaths, the largest gas bubbles form in

samples which are gradually heated. For this

reason bubble formation is more of a concern for

Hi-Res

than conventional TGA.

Another effect of bubble formation is a sudden

small unexpected change in weight and accom-

panying spike in the percent/minute curve as the

bubble bursts. An excellent example of bubble

noise can be seen in the scan of ethylene-vinyl

acetate in figures B.7 and B.8. In figure B.7 the

effect of bubble formation and bursting can be

seen as a sudden drop in weight at about 400

during the second weight loss. This appears in

the derivative curve as a peak shoulder. In

Figure B.8 we can clearly see the formation and

bursting of several large bubbles in the percent/

minute curve between 65 and 85 minutes into

the run. Again, these effects tend to be more

noticeable in Hi-Res

TGA because larger

bubbles form due to the slow heating process.

The best solution to bubble noise is to decrease

resolution setting and/or increase maximum

heating rate. Reducing sample size may also

help.

Содержание TGA 2950

Страница 1: ...TA INSTRUMENTS TGA 2950 i Thermal Analysis Rheology TGA 2950 Thermogravimetric Analyzer Operator s Manual PN 925602 001 Rev D Text and Binder PN 925602 002 Rev D Text Only Issued July 2000 ...

Страница 2: ...y This publica tion is not a license to operate under or a recommendation to infringe upon any process patents TA Instruments Operating Software and Mod ule Data Analysis and Utility Software and their associated manuals are proprietary and copyrighted by TA Instruments Inc Purchasers are granted a license to use these software programs on the module and controller with which they were purchased T...

Страница 3: ...s xiv Safety xv Using This Manual xviii CHAPTER 1 Introducing the TGA 2950 1 1 Introduction 1 3 Components 1 4 The 2950 Instrument 1 5 2950 Display 1 5 2950 Keypad 1 6 HEATER Switch 1 10 POWER Switch 1 10 Accessories 1 11 Gas Switching Accessory 1 11 Other Accessories 1 11 Specifications 1 12 ...

Страница 4: ...g the System 2 8 Choosing a Location 2 9 Filling the Heat Exchanger 2 10 Connecting Cables and Gas Lines 2 12 Heat Exchanger Cable and Water Lines 2 12 GPIB Cable 2 15 Purge Lines 2 17 Cooling Gas Line 2 18 Power Cable 2 19 Unpacking the Balance 2 20 Installing the Hang Down Wires 2 22 Aligning the Sample Hang Down Wire 2 25 Adjusting the Sample Platform 2 29 Starting the 2950 2 30 Shutting Down t...

Страница 5: ... Platform Calibration 3 6 Running a TGA Experiment 3 7 Experimental Procedure 3 7 Preparing Samples 3 8 Selecting Sample and Tare Pans 3 8 Taring the Sample Pan 3 9 Automatic Tare 3 10 Manual Tare 3 10 Loading the Sample 3 11 Setting Up an Experiment 3 14 Setting Up Accessories 3 15 Using the Air Cool Option 3 16 Using a Purge Gas 3 16 Using the Gas Switching Accessory 3 19 Starting an Experiment ...

Страница 6: ...xygen Free Atmosphere 3 22 Purge Gas System 3 22 Instrument Set Up 3 23 CHAPTER 4 Technical Reference 4 1 Description of the TGA 2950 4 3 Components 4 5 Balance 4 6 Sample Loading Assembly 4 8 Furnace 4 9 TGA Standard Furnace 4 9 EGA Furnace 4 11 Cabinet 4 13 Heat Exchanger 4 15 Theory of Operation 4 16 Status Codes 4 17 ...

Страница 7: ...Instrument 5 4 Cleaning the Furnace Housing 5 5 TGA Standard Furnace Only 5 5 Heat Exchanger 5 6 Maintaining Heat Exchanger Coolant 5 6 Draining and Refilling the Water Reservoir 5 6 Replacing the Thermocouple 5 9 Removing and Reinstalling the Furnace 5 11 Furnace Removal 5 11 Furnace Replacement 5 14 Diagnosing Power Problems 5 16 Fuses 5 16 Power Failures 5 18 ...

Страница 8: ...1 Appendix B High Resolution TGA Option B 1 Overview B 5 Option Installation B 6 Using Hi ResTM TGA B 7 Background B 7 The TA Instruments Hi ResTM Technique B 8 The Hi ResTM Ramp Segment B 9 Calcium Oxalate Example Scans B 13 Advanced Hi ResTM Techniques B 18 What Can Be Resolved and What Cannot B 18 Unresolved Transitions B 19 Selecting a Hi ResTM Technique B 22 ...

Страница 9: ...nalysis B 27 Sample Quantity and Orientation B 28 Exposed Surface Area B 28 Bubble Formation B 29 Thermocouple Placement B 32 Data Analysis Effects B 32 Derivative Plots B 33 Adjusting Heating Rate B 34 Adjusting Resolution Setting B 37 Useful Resolutions Settings B 39 Temperature Calibration B 41 Hi ResTM Transition Temperatures B 42 Hi ResTM Sensitivity Segment B 43 ...

Страница 10: ...Reaction Rate Mode B 47 Abort Segment B 51 Stepwise Isothermal Heating B 53 Hi ResTM TGA Examples B 58 Mixture of Bicarbonates B 58 Dynamic Rate Scans B 59 Varying Resolution Setting B 61 Varying Sensitivity Setting B 62 Constant Reaction Rate Scans B 63 Stepwise Isothermal Scans B 65 Monosodium Glutamate B 68 Banana Taffy B 69 Plastic Laboratory Tubing B 71 References B 75 ...

Страница 11: ...ting Started C 4 The TGA 2950 Instrument C 6 Calibrating the Auto TGA C 10 Running Experiments C 11 Preparing the Samples C 12 Selecting Sample and Tare Pans C 12 Taring the Sample Pans C 13 Loading the Samples C 16 Setting Up an Experiment C 18 Manual Operation C 19 Tracking the TGA Autosampler Status C 19 Interrupting a Run C 20 ...

Страница 12: ... EGA Furnace D 3 EGA Furnace Specifications D 5 Installing the EGA Furnace D 6 First Time Installation D 6 Removing and Reinstalling the EGA Furnace D 14 EGA Furnae Removal D 14 EGA Furnace Installation D 16 Connecting the Spectrometer D 18 Using the EGA Furnace D 21 Cleaning the Quartz Furnace Tube D 22 Index I 1 ...

Страница 13: ... instructions A NOTE highlights important information about equipment or procedures A CAUTION emphasizes a procedure that may damage equipment or cause loss of data if not followed correctly A WARNING indicates a procedure that may be hazardous to the operator or to the environment if not followed correctly NOTE t t t t t CAUTION WARNING ...

Страница 14: ...TA INSTRUMENTS TGA 2950 xiv Hotlines To TA Instruments For Technical Assistance 302 427 4070 To Order Instruments and Supplies 302 427 4040 For Service Inquiries 302 427 4050 Sales 302 427 4000 ...

Страница 15: ...personnel After transport or storage in humid condi tions this equipment could fail to meet all the safety requirements of the safety standards indicated Refer to the NOTE on page 2 9 for the method used to dry out the equipment before use Chemical Safety Use only the purge gases listed in Table 1 4 in Chapter 1 Use of other gases could cause damage to the instrument or injury to the operator Do n...

Страница 16: ...mount of volatile hydrocarbons e g lubricating oils you need to clean the furnace more frequently to prevent dangerous buildup of debris in the furnace If you are using samples that may emit harmful gases vent the gases by placing the instrument near an exhaust The TGA 2950 EGA furnace assembly also contains refractory ceramic fiber RCF insulation This insulation is enclosed within the furnace hou...

Страница 17: ... down before you touch them During a sample run the furnace base see Figure 1 1 can be hot enough to burn skin Avoid contact with the furnace base during experiments Mechanical Safety Keep your fingers and all other objects out of the path of the furnace when it is mov ing The furnace seal is very tight WARNING WARNING ...

Страница 18: ...essories Chapter 4 Provides technical information and explains prin ciples of TGA operation Chapter 5 Describes how to perform routine maintenance replace the thermocouple remove and reinstall the furnace and diagnose power problems also provides an explanation of the confidence test Appendix A Lists TA Instruments offices that you can contact to place orders receive technical assis tance and requ...

Страница 19: ...ng This Manual continued Appendix C Provides instructions needed to operate the TGA Autosampler option to automatically load and run samples Appendix D Provides instructions needed to install and use the EGA furnace with the TGA 2950 ...

Страница 20: ...TA INSTRUMENTS TGA 2950 xx ...

Страница 21: ...Introducing the TGA 2950 Introduction 1 3 Components 1 4 The 2950 Instrument 1 5 2950 Display 1 5 2950 Keypad 1 6 HEATER Switch 1 10 POWER Switch 1 10 Accessories 1 11 Gas Switching Accessory 1 11 Other Accessories 1 11 Specifications 1 12 ...

Страница 22: ...Introducing the TGA 2950 TA INSTRUMENTS TGA 2950 1 2 ...

Страница 23: ...re or isothermally as a function of time in a controlled atmosphere It can be used to characterize any material that exhibits a weight change and to detect phase changes due to decomposition oxidation or dehydration This information helps the scientist or engineer identify the percent weight change and correlate chemical structure processing and end use performance Your controller is a computer th...

Страница 24: ...GA system The sample platform which loads and unloads the sample to and from the balance The furnace which controls the sample atmosphere and temperature The cabinet where the system electronics and mechanics are housed The heat exchanger which dissipates heat from the furnace Figure 1 1 TGA 2950 Components Heat Exchanger Furnace Thermocouple Balance Chamber Keypad Display Heater Switch Power Swit...

Страница 25: ... display is the lighted area of the keypad Figure 1 2 It contains two rows of 20 characters each During normal operation the display is seg mented into three areas The left eight charac ters on the upper line show the instrument status the right nine characters show the sample temperature and the bottom line is a realtime signal display e g weight TGA 2950 Thermogravimetric Analyzer Standby 23 25 ...

Страница 26: ...rument constants are entered from the controller keyboard not the instrument keypad Table 1 1 TGA 2950 Keypad Function Keys Key Function Explanation SCROLL Scrolls the realtime signals shown on the bottom line of the display For more details on the experiment refer to status and signal displays on the controller TARE Zeros the displayed weight of an empty sample pan automatically loads the pan fro...

Страница 27: ...NACE Toggles between the furnace closed up and furnace open down functions depending on where the furnace is when you press the key This key can be pressed while the furnace is moving to reverse the direction of movement START Begins the experiment This is the same function as Start on the controller Forced Start can be done by pressing the START key while the status line displays Set Up Forced st...

Страница 28: ...aved This is the same function as Stop on the controller If an experiment is not running the instrument is in a stand by or method end state the STOP key will halt any activity air cool all mechanical motion etc REJECT If an experiment is running SCROLL STOP ends the method normal Hold down ly as though it had run to SCROLL and completion i e the press STOP method end conditions go into effect and...

Страница 29: ... the STOP key AUTO SELECT This key appears only on instruments with an autosampler installed See Appendix C for details Automatic Keypad Functions Some of the TGA instrument keys automatically perform additional functions under certain conditions START automatically loads the sample pan and closes the furnace if necessary before beginning the experiment TARE LOAD and UNLOAD automatically open the ...

Страница 30: ... 1 2 turns the power to the instrument heater on and off This switch should be in the ON 1 position before you start an experiment The light in the HEATER switch will glow only when an experiment is in progress POWER Switch The POWER switch see Figure 1 2 turns the power to the instrument on and off NOTE ...

Страница 31: ...ysis Furnace The TGA 2950 EGA furnace is an accessory to the instrument which allows you to perform combined TGA and evolved gas analysis experiments Other Accessories The TGA can be used with many standard analytical accessories offered by various manu facturers including vacuum FTIR mass spec trometers gas chromatographs and evolved gas analyzers Consult the appropriate local instru ment manufac...

Страница 32: ... 2 TGA 2950 Operating Parameters Temperature range 25o C to 1000o C Thermocouple Platinel II Heating rate with standard furnace 0 1 to 100o C min with EGA furnace 0 1 to 50 C min Platinel II is a registered trademark of Engelhard Industries Table 1 3 TGA 2950 Instrument Characteristics Operating line voltage 115 volts 50 60 Hz Energy consumption 1 5 kVA ...

Страница 33: ...ent2 Resolution 0 1 µg Accuracy 0 1 Ranges 100 mg range 0 1 µg _ 100 mg 1000 mg range 1 µg _ 1000 mg 1 The total mechanical capacity of the balance is 5 gm In order to avoid damaging the balance assembly never allow the total weight of the sample tare weight hang down wires and pans to exceed 5 gm 2 The TGA balance mechanism is sensitive to changes in the surrounding room tempera ture For optimum ...

Страница 34: ...rnace Atmosphere Purge gases Helium nitrogen oxygen air argon3 Purge rate Up to 100 cc min 3 Do not use hydrogen or any other explosive gas in the TGA 2950 furnace or theTGA2950EGAfurnace Oxygen may be used How ever thefurnacemustbe keptcleanofvolatilehydro carbonstopreventcombus tion ...

Страница 35: ...8 Choosing a Location 2 9 Filling the Heat Exchanger 2 10 Connecting Cables and Gas Lines 2 12 Heat Exchanger Cable and Water Lines 2 12 GPIB Cable 2 15 Purge Lines 2 17 Cooling Gas Line 2 18 Power Cable 2 19 Unpacking the Balance 2 20 Installing the Hang Down Wires 2 22 Aligning the Sample Hang Down Wire 2 25 Adjusting the Sample Platform 2 29 Starting the 2950 2 30 Shutting Down the 2950 2 32 ...

Страница 36: ...TA INSTRUMENTS TGA 2950 Installing the 2950 2 2 ...

Страница 37: ...to retain all of the shipping hardware the plywood and boxes from the instrument in the event you wish to repack and ship your instrument Unpacking the 2950 Refer to Figures 2 1 to 2 3 while unpacking your instrument Have an assistant help you unpack this unit Do not attempt to do this alone Figure 2 1 Shipping Boxes NOTE WARNING Unpacking Repacking the 2950 ...

Страница 38: ... lifts his her end 4 Place the unit on a lab bench with one side hanging over the edge of the bench see Figure 2 2 Someone must be holding onto the unit at all times while it is in this position Figure 2 2 Removing the Plywood Board 5 While your assistant holds the unit use a wrench to remove the two nuts and washers from the bottom Then lift and rotate the unit so that the other end hangs over th...

Страница 39: ...d remove the shipping feet from the other side in the same manner 7 Have your assistant lift the entire unit while you slide the plywood board out from under the unit 8 Have your assistant lift one side of the unit while you use a wrench to install two mounting feet on the other side see Figure 2 3 Rotate the unit and install the two remaining mounting feet in the same man ner 9 Remove the furnace...

Страница 40: ...TA INSTRUMENTS TGA 2950 Installing the 2950 2 6 Repacking the 2950 To pack and ship your instrument use the hardware retained during unpacking and reverse the instructions found on pages 2 3 to 2 5 ...

Страница 41: ...ger Connecting the TGA to the TA Instruments controller Connecting the heat exchanger cable and water lines purge gas lines accessories and power cable Unpacking the balance Installing the hang down wires Leveling the instrument and aligning the hang down wires Adjusting the sample platform If you wish to have your TGA installed by a TA Instruments Service Representative call for an installation a...

Страница 42: ...ntainer carefully for signs of shipping damage and check the parts received against the enclosed shipping list If the instrument is damaged notify the carrier and TA Instruments immediately If the instrument is intact but parts are missing contact TA Instruments A list of TA Instruments phone numbers can be found in Appendix A of this manual ...

Страница 43: ... lower line voltage your TA Instruments thermal analysis controller compressed lab air and purge gas supplies with suitable regulators and flowmeters Away from dusty environments exposure to direct sunlight direct air drafts fans room air ducts poorly ventilated areas noisy or mechanical vibrations Drying out the instrument may be needed if it has been exposed to humid conditions It is important t...

Страница 44: ...at exchanger through the supply line circulates to the furnace and comes back to the reservoir via the return line as seen in Figure 2 4 for instructions on how to connect the water lines turn to page 2 12 To fill the heat ex changer follow the directions given below Figure 2 4 Rear Panel of Heat Exchanger 1 Unscrew the water reservoir cap on the heat exchanger see Figure 2 4 Screws Heat Exchanger...

Страница 45: ...to add to the reser voir Then fill the bottle to the inner rim see Figure 2 5 with distilled water After the system has been started recheck the level of water in the reservoir bottle and refill to the inner rim if necessary Do not put any liquid other than distilled water in the heat exchanger reservoir 3 Replace and tighten the water reservoir cap Installing the Instrument Fill to bottle s inner...

Страница 46: ...outlets Tighten the thumbscrews on all computer cables Whenever plugging or unplugging power cords handle them by the plugs not by the cords Protect power and communications cable paths Do not create tripping hazards by laying the cables across accessways Heat Exchanger Cable and Water Lines 1 Locate the cooling accessory connector on the left rear of the instrument cabinet Figure 2 6 2 Connect th...

Страница 47: ...right side of the instrument cabinet 5 Connect the other end of the water line marked SUPPLY to the connector labeled SUPPLY on the heat exchanger 6 Connect one end of the unmarked water line to the connector labeled RETURN on the right side of the instrument cabinet 7 Connect the other end of the unmarked water line to the connector labeled RE TURN on the heat exchanger Installing the Instrument ...

Страница 48: ...changer Air trapped in the heat exchanger system must be purged before starting the first run After installa tion of the TGA is complete turn on the instru ment by placing the HEATER and POWER switches in the ON position Then start the heat exchanger pump by turning on Air Cool from the controller Refill the coolant reservoir as needed Repeat this process until all the air has been purged from the...

Страница 49: ...s from 1 to 9 Then use the binary address switches on the TGA connec tor panel to set the desired address See Table 2 1 Figure 2 8 on the next page shows a instrument address of 7 If you have a multi instrument system each instrument must have a different a different address If you change the address after the TGA is powered on you must press the TGA s Reset button to enter the new address Wait un...

Страница 50: ...ADDRESS 1 2 3 4 5 O N Table 2 1 Binary Address Settings Address Switch Pattern 1 2 3 4 5 1 0 0 0 0 1 2 0 0 0 1 0 3 0 0 0 1 1 4 0 0 1 0 0 5 0 0 1 0 1 6 0 0 1 1 0 7 0 0 1 1 1 8 0 1 0 0 0 9 0 1 0 0 1 0 OFF 1 ON Figure 2 8 Binary Address Switches Showing an Address of 7 ...

Страница 51: ...GE Fittings 2 Make sure that the pressure of your purge gas source does not exceed the manufactur ers recommended pressures for flowmeters and other regulated devices you are using If you are using laboratory purge rather than bottled purge you will need to install an external drier The use of corrosive gases is not recommended WARNING NOTE t t t t tCAUTION Furnace Purge Balance Purge Installing t...

Страница 52: ...flowmeter consult your compressed gas vendor for specific requirements Then connect each flowmeter to the purge gas source 4 The recommended setting for the purge rate is 100 mL per minute or less The flow distribution should be as follows a for the standard furnace 40 percent to the balance chamber and 60 percent to the furnace and b for the EGA furnace 10 percent to the balance and 90 percent to...

Страница 53: ... as a cooling gas Power Cable 1 Make sure the TGA POWER switch Figure 2 11 is in the Off 0 position Figure 2 11 TGA POWER Switch 2 Plug the power cable into the TGA Before plugging the TGA power cable into the wall outlet make sure the instrument is compatible with the line voltage Check the label on the back of the unit to verify the voltage 3 Plug the power cable into the wall outlet NOTE Instal...

Страница 54: ...essory kit loosen and remove the six screws securing the balance chamber faceplate to the instrument 2 Take off the faceplate 3 Loosen and remove the thumbscrew holding the balance cover on the sample left side of the balance mechanism Figure 2 12 and take off the cover Figure 2 12 Interior of Balance Chamber Before Unpacking Balance Cover Sample Side Tare Side Tare Tube Balance Cover Screw Hang D...

Страница 55: ... foam with the tweezers being careful not to touch the balance b Remove the foam insert from the balance chamber Figure 2 13 Removal of Foam Insert from Balance Chamber 5 Replace the sample side cover and screw 6 Repeat the procedure to remove the foam insert in the tare right side of the balance Unpacking the Balance Foam Insert ...

Страница 56: ...3 Locate the sample hang down wire in your TGA Accessory Kit 4 Hold the wire in your hand so that the doubly bent top hook is pointing to the left and the bottom hook is pointing to the right 5 Carefully insert the bottom of the hangdown wire into the top of the furnace far enough so that you can insert the top of the wire into the thermocouple tube without bending the wire Figure 2 14 Figure 2 14...

Страница 57: ...o the left pass the double bend through the hang down loop so the wire is hanging from the loop 8 Unscrew and remove the tare tube 9 Locate the tare hang down wire in your accessory kit 10 Hold the wire in your hand so that the doubly bent top hook is pointing to the left and the bottom hook is pointing to the right 11 Using brass tweezers insert the tare hang down wire into the balance chamber on...

Страница 58: ...an you will use in your experiments and load one of the same size and type onto the tare hang down wire 14 Replace the tare tube and finger tighten it to compress the O ring seal You are now ready to align the hang down wires Figure 2 15 Installing the Tare Hang Down Wire ...

Страница 59: ...nd bottom of the sample hang down wire and level the instrument using the following procedures To align the top of the sample hang down wire 1 Place an empty sample pan on the sample platform 2 Press the LOAD key on the instrument keypad The TGA will automatically lower the furnace if necessary move the sample platform over to the furnace and load the pan onto the balance If the pan will not autom...

Страница 60: ...be inside the balance chamber 4 If the wire is not roughly centered inside the thermocouple tube turn the balance adjust ment screw Figure 2 16 with the 7 64 inch ball driver until the wire is centered Turning the balance adjustment screw clockwise will move the wire backwards turning the screw counterclockwise will move the wire frontwards Figure 2 16 Location of Balance Adjustment Screw ...

Страница 61: ...nace or the thermo couple tube Figure 2 18 3 If the sample pan is not centered and hang ing freely within the furnace level the TGA instrument by adjusting the feet on the bottom Turn the feet clockwise to lengthen or counterclockwise to shorten the legs Continue adjusting until the pan hangs correctly Figure 2 18 Aligning the Sample Pan in the Furnace Installing the Hang Down Wires Thermocouple T...

Страница 62: ...ce 5 Press the UNLOAD key to remove the sample pan from the furnace 6 Replace the balance chamber faceplate and its 6 screws If you had to load the sample pan manually in order to align it in the furnace you should now adjust the sample platform using the procedure described on the next page ...

Страница 63: ...he Sample Platform Adjust procedure This procedure is part of the Instrument Control software program Refer to the online help and documentation for further information on adjusting the sample platform shown in Figure 2 19 This procedure assumes that the instrument has been properly levelled see page 2 26 and that the sample hang down wire is straight Figure 2 19 Sample Platform Assembly NOTE Adju...

Страница 64: ...n the unit The HEATER and POWER indicator lamps may flicker under low AC voltage conditions 3 Watch the instrument display during the confidence test for any error messages that may be indicated If an error occurs make a note of the test number in which the error occurred and call TA Instruments for service After the confidence test the screen will briefly display the system status indicating the ...

Страница 65: ...50 Standby Display 4 Bring the instrument online with the TA controller Allow the TGA to warm up for at least 30 minutes before performing an experiment TGA 2950 Thermogravimetric Analyzer Standby 23 25 C Weight 238 247 mg NOTE Starting the TGA 2950 ...

Страница 66: ...ore reliably if power fluctuations caused by turning units on and off are minimized For these reasons turning the system and its components on and off frequently is dis couraged When you finish running an experiment on your instrument and wish to use the thermal analysis system for some other task leave the instrument on it will not interfere with whatever else you wish to do If you do need to pow...

Страница 67: ...Platform Calibration 3 6 Running a TGA Experiment 3 7 Experimental Procedure 3 7 Preparing Samples 3 8 Selecting Sample and Tare Pans 3 8 Taring the Sample Pan 3 9 Automatic Tare 3 10 Manual Tare 3 10 Loading the Sample 3 11 Setting Up an Experiment 3 14 Setting Up Accessories 3 15 Using the Air Cool Option 3 16 Using a Purge Gas 3 16 Using the Gas Switching Accessory 3 19 ...

Страница 68: ...ng Experiments TA INSTRUMENTS TGA 2950 3 2 Starting an Experiment 3 20 Stopping an Experiment 3 21 Unloading the Sample 3 21 Use in an Oxygen Free Atmosphere 3 22 Purge Gas System 3 22 Instrument Set Up 3 23 ...

Страница 69: ...mple and instrument information Creating and selecting the thermal method Selecting and taring the sample pan Loading the sample Setting the purge gas flow rate Starting the experiment Unloading the sample at the end of the experiment To obtain accurate results follow procedures carefully and check calibration periodically once a month Before You Begin Before you set up an experiment ensure that t...

Страница 70: ...TRUMENTS TGA 2950 3 4 Connected all gas lines Powered on each unit Installed all appropriate options Configured the instrument online with the controller Become familiar with controlleroperations Calibrated the TGA if necessary ...

Страница 71: ...riments in which precise transition temperatures are essential To temperature calibrate the TGA you need to analyze a high purity magnetic standard for its curie tempera ture and then enter the observed and correct values in the temperature calibration table see the online help and documentation for further information The standard most often used is nickel with a curie temperature of 354 4 C NIST...

Страница 72: ...ation procedure step by step see the online help and documentation for further information Sample Platform Calibration The sample platform adjustment procedure is used if the sample hang down wire fails to pick up a sample pan during an automatic loading procedure The sample platform must be adjusted so that the instrument can properly load and unload the sample pans To avoid weight signal noise t...

Страница 73: ...cting the pan type and material Loading the pan Taring the empty sample pan Loading the sample into the pan Entering experiment information through the TA controller sample and instrument information Creating and selecting the thermal method on the controller Attaching and setting up external accessories as required e g purge gas Gas Switching Accessory Starting the experiment Running a TGA Experi...

Страница 74: ...in size The criteria for choosing a sample pan are as follows For most experiments platinum is the desirable choice It is easy to clean and does not react with most organics and polymers Ceramic pans are more porous and are therefore more easily contaminated There are some conditions however in which other types pans are desirable as explained below Use ceramic pans for samples that might amalgama...

Страница 75: ...libration procedure to mechanically tare the balance Taring the Sample Pan Taring the sample pan ensures that the weight measured by the balance reflects the weight of the sample only You should tare the sample pan before each experiment even if you use the same pan in consecutive experiments When you tare a pan the TGA reads the weight of the empty pan and then stores the weight as an offset whic...

Страница 76: ... unload the pan Manual Tare Manual tare operates in the weight range indi cated by storing the current reading as an offset and estimates the tare weight for the other weight range typically the 1 gm range The estimate is accurate if the TGA 2950 has been tared or weight calibrated recently 1 Place the empty sample pan on the sample platform 2 Press the LOAD key to load the pan onto the balance 3 ...

Страница 77: ...tom of the sample pan should align with the groove in the panhole so that the sample pan can be picked up by the sample hang down wire Always use brass tweezers to handle the sample pans Manually loading the sample pan onto the hang down wire may damage the balance mechanism Figure 3 1 Sample Pan Ready to Load NOTE t CAUTION Running a TGA Experiment Thermocouple Sample Hook Furnace Housing Sample ...

Страница 78: ...osition the thermocouple at the edge of the sample pan rather than in the middle for best results Figure 3 2 The position of the thermocouple should be the same as it was during temperature calibration Figure 3 2 Adjusting the Thermocouple NOTE Thermocouple Sample Hook Sample Pan Furnace Thermocouple should be about 2 mm from pan surface ...

Страница 79: ...TA INSTRUMENTS TGA 2950 3 13 4 Press the FURNACE key to close the furnace by moving it up around the sample Figure 3 3 Figure 3 3 Furnace in Closed Position Running a TGA Experiment ...

Страница 80: ...trument Control Refer to the online help and documentation to learn how to perform the following steps 1 Select the Instrument 2 Select the Instrument Mode 3 Enter Sample Information 4 Enter Instrument Information 5 Create and Select Thermal Methods The first time you use your TGA you will need to create at least one thermal method to control experiments Each method is made of several segments or ...

Страница 81: ...ribes how to use the following accessories with the TGA 2950 Air cool option Purge gas TA Instruments Gas Switching Accessory Evolved Gas Analysis EGA Furnace see also Appendix D For the TGA HiResTM Option see Appendix B and for the TGA Autosampler see Appendix C The TGA can also be used with other acces sories such as vacuum FTIR gas chromato graphs mass spectrometers and evolved gas analyzers Co...

Страница 82: ...you are using the EGA furnace Air Cool can be used with the furnace closed However if the temperature is above 500 C the EGA furnace will cool naturally until it is 500 C or less then Air Cool will begin Using a Purge Gas You can control the sample atmosphere during TGA experiments by connecting a purge gas to the system Purge gas is distributed separately to two parts of the TGA the furnace and t...

Страница 83: ...ty section on page xv for further details Do not use hydrogen or any other explosive gas in the TGA 2950 furnace or the TGA 2950 EGA furnace Oxygen may be used as a purge gas but the furnace must be kept clean of volatile hydrocarbons to prevent combustion Do not use any liquid in the purge lines Purge gas can be obtained from a pressurized cylinder or an in house supply source Gas supplied from a...

Страница 84: ...nace the flow distribution should be 10 percent to the balance chamber and 90 percent to the furnace To maintain this flow distribution you will need to connect a flowmeter to each of the purge fittings on the back of the TGA instrument Set the purge gas flow rates by adjusting these meters The PURGE port goes to the TGA furnace and the BALANCE PURGE goes to the balance chamber Before you start th...

Страница 85: ...ower switch is on and make sure the necessary gas sources are properly connected The Gas Switching Accessory can be controlled by the Gas segment in the method see the online help and documentation for further information Connect the Gas Switching Accessory to the purge port only when switching between gases during an experiment Attach the inert gas to GAS 1 and the other gas to GAS 2 Consult your...

Страница 86: ...tation for further information When you press the START key the system automatically loads the sample pan and closes the furnace if necessary and then runs the loaded method to completion Forced Start If you wish to start collecting data during instrument setup you can use the forced start feature This is most useful for samples that loose a significant amount of weight during the set up period i ...

Страница 87: ...o the point at which the experiment was stopped The Heat Exchanger will continue to run as long as the Air Cool option is activated or until the indi cated temperature is below 50o C TheREJECTfunctiondiscardsallexperimentdata Unloading the Sample If you select the method end option that enables the furnace to open and unload at the end of the experiment the TGA will automatically unload the sample...

Страница 88: ...cautions Use a high purity inert gas of grade 5 or better It may be necessary to use an oxygen trap in line depending on the purity grade Choose a 2 stage regulator of diaphragm construction for high purity applications Use copper or stainless steel tubing from the gas regulator to the flowmeters and to the TGA purge inlet ports Allow the TGA to prepurge under closed conditions for at least 30 min...

Страница 89: ...ad sample and close system Purge 20 minutes if possible before starting a run When run is complete allow the furnace to cool in the closed position until the temp erature is less than 350 C This can be automatically programmed into your method after last segment add an equilibrate at 350 C step Another option is to change method end conditions to leave furnace closed at method end When using air o...

Страница 90: ...Running Experiments TA INSTRUMENTS TGA 2950 3 24 ...

Страница 91: ...4 Technical Reference Description of the TGA 2950 4 3 Components 4 5 Balance 4 6 Sample Loading Assembly 4 8 Furnace 4 9 TGA Standard Furnace 4 9 EGA Furnace 4 11 Cabinet 4 13 Heat Exchanger 4 15 Theory of Operation 4 16 Status Codes 4 17 ...

Страница 92: ...Technical Reference TA INSTRUMENTS TGA 2950 4 2 ...

Страница 93: ...es The unbalanced signal called the error signal is acted upon by the control circuitry and reduced to zero or nulled This is accomplished by an increase or decrease in the current to the meter movement causing it to rotate back to its original position null position The change in current necessary to accomplish this task is directly proportional to the change in mass of the sample This current is...

Страница 94: ...operation of the TGA the sample may evolve gases To prevent back diffusion of these liberated gases to the balance chamber the balance chamber is purged with an inert gas standard furnace 40 mL min EGA furnace 10 mL min An inert gas must be used to prevent contamination or corrosion of the balance Heating rate and sample temperature are mea sured by the thermocouple located above the sample ...

Страница 95: ... 2950 Components The balance the most important part of the TGA system provides precise measurement of the sample weight The sample loading assem bly automatically loads and unloads samples from the TGA balance The furnace controls the sample atmosphere and temperature The cabinet contains the system electronics and mechanics The heat exchanger dissipates heat from the furnace Description of the T...

Страница 96: ...d the tare pan Figure 4 2 TGA Balance Assembly The balance meter movement is a taut band meter movement to which the balance arm is attached The balance arm is a rhombic piece of alumi num attached to the meter movement It is in a null balance system A hang down loop is attached to each end to hold the hang down wires Balance Arm Sensor Hang Down Wire Assembly Sample Pan Balance Arm Balance Meter ...

Страница 97: ...y consists of a hang down wire and loop The hang down wire has hooks at each end and connects the pan to the loop The loop has eyelets at each end it is used to connect the hang down wire to the balance arm The longer hang down wire 4 inches is for the sample pan Sample pans are available in platinum in 50 and 100 µL sizes alumina ceramic in 100 250 and 500 µL sizes and aluminum in 100 µL All pans...

Страница 98: ... loading assembly Figure 4 3 is a platform that pivots the sample pan to the furnace area where the pan engages the hang down wire from the balance assembly It also pivots the platform away from the furnace area for easy sample loading and unloading Figure 4 3 Sample Loading Assembly ...

Страница 99: ...x D is an optional accessory that allows you to connect a spectrometer to the instrument so that the gases evolved by sample decomposition can be analyzed TGA Standard Furnace The TGA standard furnace Figure 4 4 consists of a furnace housing a heater and a furnace base that moves these parts up to closed posi tion and down to open position Figure 4 4 TGA Furnace Description of the TGA 2950 ...

Страница 100: ...r if desired The heater is a resistance wound unit of low thermal mass alumina material that can be heated and cooled rapidly Controlled heating rates of up to 100 C per minute can be obtained to an upper limit of 1000 C Cooling air enters through the holes in the base of the furnace assembly at the completion of test runs if desired A Platinel II thermocouple extends through the bottom of the bal...

Страница 101: ...ace base that raises and lowers the furnace for sample loading and unloading See Figure 4 5 Figure 4 5 EGA Furnace The sample tube has a purge gas inlet that passes through the right side of the furnace housing A fitting on the left side of the housing allows connection of a transfer line to carry exhaust gas to a spectrometer such as a FTIR Because the heater is external to the sample tube evolve...

Страница 102: ...de of the sample tube and the inside of the furnace completely separating the cooling air from the sample and the sample zone The furnace is a resistance heater wound on alumina ceramic which allows sample zone temperatures as high as 1000 C with heating rates up to 50 C min The thermocouple and furnace base are the same as those described above for the standard TGA furnace Platinel II is a regist...

Страница 103: ...e preparation tray The base casting is one piece casting of heavy weight aluminum designed to provide a stable platform for the TGA instrument parts The rear cover is injection molded using a heavy gauge thermoplastic material designed for easy cleaning The removable sample preparation tray is located on the right side of the instrument The tray is designed to keep liquids from spilling into the i...

Страница 104: ...purge fittings are located on the left side of the instrument back one for the balance chamber and one for the furnace housing The cooling gas fitting is located on the right side of the instrument back and is for furnace cool down air The rear panel Figure 4 7 has the signal and power connections for the instrument the fuses the ready light the address switches and the Reset button Figure 4 7 Rea...

Страница 105: ...air The water reservoir holds additional water that may be required by the system The pump pushes the water through the system The temperature switch detects over tempera ture conditions which could be caused by failure of the fan The flow switch detects lack of flow which could be caused by failure of the pump or a leak in the system Figure 4 8 Heat Exchanger Description of the TGA 2950 Water Res...

Страница 106: ... function of temperature and time It is used to characterize any material that exhibits weight loss or phase changes as a result of decomposition dehydra tion and oxidation Two modes are commonly used for investigating thermal stability behavior in controlled atmospheres 1 dynamic in which the temperature is increased at a linear rate and 2 isothermal in which the tempera ture is kept constant ...

Страница 107: ...rument Table 4 1 Status Codes Code Meaning Air Cool The furnace air cool line has been opened to cool the furnace Calib The TGA is in calibration mode Closing The furnace assembly is closing Cold The instrument heater cannot supply heat fast enough to keep up with the thermal program This may be caused by a large ballistic jump in the program a faulty heater or a faulty control thermo couple signa...

Страница 108: ... Equilb The temperature is being equilibrated to the desired set point Err n An error has occurred The instrument display will give the error code number n a two or three digit code the controller screen will also show the complete error message Heating The heater temperature is increasing as specified by a Ramp segment Holding Thermal experiment conditions are holding the program is suspended Cho...

Страница 109: ... tempera ture Initial The temperature is being equilibrated to the desired set point When the temperature has reached equilibrium the status will change to Ready Iso The thermal program is holding the current tem perature isothermally Jumping The heater is jumping ballistically to the set point temperature Load The TGA is loading a sample pan onto the balance No Power No power is being applied to ...

Страница 110: ...next segment Choose Start to continue the method Reject The experiment has been terminated and the data erased Repeat The method is executing a repeat loop that does not involve temperature control segments Set Up The system is loading the sample closing the furnace and letting the weight stabilize before beginning the first seg ment Stand by The method and method end operations are com plete tabl...

Страница 111: ...pleted Tare The TGA is measuring the weight difference between an empty sample pan and the tare pan The measured weight is used as an offset so that the displayed weight value indicates the weight of the sample only Temp C The heater is in stand by mode and the experiment has been terminated Temp Temperature calibration is in effect The heater is in stand by mode and the experiment has been termin...

Страница 112: ...Technical Reference TA INSTRUMENTS TGA 2950 4 22 ...

Страница 113: ...leaning the Furnace Housing 5 5 TGA Standard Furnace Only 5 5 Heat Exchanger 5 6 Maintaining Heat Exchanger Coolant 5 6 Draining and Refilling the Water Reservoir 5 6 Replacing the Thermocouple 5 9 Removing and Reinstalling the Furnace 5 11 Furnace Removal 5 11 Furnace Replacement 5 14 Diagnosing Power Problems 5 16 Fuses 5 16 Power Failures 5 18 ...

Страница 114: ...TA INSTRUMENTS TGA 2950 Maintenance and Diagnostics 5 2 TGA Test Functions 5 19 The Confidence Test 5 19 Replacement Parts 5 21 ...

Страница 115: ...stomer s responsibility Any further mainte nance should be performed by a representative of TA Instruments or other qualified service personnel Because of the high voltages in this instru ment untrained personnel must not at tempt to test or repair any electrical circuits Overview WARNING ...

Страница 116: ...ore the next experiment Cleaning the Instrument You can clean the TGA instrument keypad as often as you like The keypad is covered with a silk screen Mylar overlay that is reasonably water resistant but not waterproof or resistant to strong solvents or abrasives A household liquid glass cleaner and paper towel are best for cleaning the instrument keypad Wet the towel not the keypad with the glass ...

Страница 117: ...nd 5 9 Disconnect the purge line and invert the furnace housing over paper towels Clean the inside with a solvent and cotton squabs Be sure to dry the housing and purge ports with air to remove any solvent traces before replacing the furnace housing Follow the instructions on page 5 10 and 5 11 for replacing the standard furnace housing After replacing the furnace heat the TGA to 900 C to remove a...

Страница 118: ...the level and condition of the heat exchanger coolant periodically We recom mend routine checks every three to six months depending on use of the instrument Add distilled water to the reservoir if necessary to keep the reservoir at least 2 3 full If algae growth is visible drain the reservoir bottle refill it with distilled water and add TA Instruments TGA Conditioner as described in the next sect...

Страница 119: ...p by activating Air Cool and allow the water to circulate for several minutes f Turn off the pump by deactivating Air Cool and check the clarity of the water in the reservoir bottle g If the water clarity is still unacceptable disconnect the heat exchanger cable and water lines from the instrument cabinet and repeat steps a through f h Continue repeating this procedure until you are satisfied with...

Страница 120: ... 8 5 Turn on the pump again by activating Air Cool and circulate the water until the air bubbles disappear from the water lines You may see Err 119 on the instrument display until all the air has been removed 6 Replace and tighten the water reservoir cap ...

Страница 121: ...n and remove the six screws securing the balance chamber faceplate to the instrument 3 Take off the faceplate 4 Push the thermocouple up from the bottom to feed it back into the balance chamber Figure 5 1 Figure 5 1 Removing the Thermocouple 5 Unplug the thermocouple from its connector and remove the thermocouple from the balance chamber Replacing the Thermocouple ...

Страница 122: ...ead the end of the thermocouple just through the ceramic disk at the end of the thermocouple tube 9 Load a sample pan to make sure that the end of the thermocouple does not touch it Figure 5 2 Figure 5 2 Checking Position of Thermocouple 10 Make sure that the hang down wire does not touch the top of the thermocouple inside the balance chamber 11 Replace the balance chamber faceplate and screws ...

Страница 123: ...upplied in your TGA Accessory Kit loosen the two screws on each side of the furnace arm connection within the slot on the front of the instrument cabinet In Figure 5 3 on the next page the furnace arm base has been removed to better show the location of the screws and alignment of the cleats To obtain access to the upper left screw and cleat loosen the three hold down screws on the furnace base Ro...

Страница 124: ...ove in the furnace arm Figure 5 3 4 While holding the furnace base in one hand press the FURNACE key to raise the furnace about 1 4 of the way up and press STOP 5 Unplug and remove the furnace arm base from the instrument cabinet Figure 5 4 6 Loosen the hold down screws if necessary and remove the furnace housing from the furnace base being careful not to disturb the coolant connections Lay the fu...

Страница 125: ...Cabinet 7 Unplug the Air Cool line from the bottom of the furnace arm base Figure 5 4 The furnace arm base is now completely free of the instrument When you remove the Air Cool line do not let it slip back into the instrument cabinet Removing and Reinstalling the Furnace NOTE ...

Страница 126: ...t edge of each cleat so that it is parallel with the groove on the furnace arm Loosening the screws one more turn each will give you a bit more room to maneu ver the arm into its connection In order to loosen the screws press the FURNACE key to lower the connection so that you can reach it through the wide part of the slot When you have aligned the cleats press the FURNACE key again to raise the f...

Страница 127: ...furnace housing gently counterclock wise This will move the purge and coolant connec tions away from the front of the cabinet slot 7 Rotate the furnace housing clockwise until it is aligned correctly and tighten the three hold down screws completely NOTE Removing and Reinstalling the Furnace ...

Страница 128: ...uses blows a hazard may exist Call your TA Instru ments service representative The only fuses that you should service yourself are the external fuses located on the TGA s rear panel Both are housed in safety approved fuse carriers labeled F1 and F2 Figure 5 5 Always unplug the instrument before you examine or replace the fuses Figure 5 5 Fuse Locations WARNING Fuse 1 Fuse 2 ...

Страница 129: ...e 2 protects the heater coils in the furnace Because fuse 2 does not power the internal logic you may not know that this fuse is blown until you try to heat a sample the TGA passes the confidence test with fuse 2 open Fuse 2 is always checked at the beginning of a method Power supplied by this circuit is switched by a computer controlled relay as well as by the HEATER switch located on the instrum...

Страница 130: ...is message means that the system has detected a power failure and has shut down The instrument will not restart until it is reset To reset press the Reset button on the TGA s back panel If Err F02 appears at start up and remains even after you have tried to restart the instru ment the detection circuitry itself is probably at fault Do not try to repair it yourself call your TA Instruments service ...

Страница 131: ... repairing the instrument The Confidence Test The TGA confidence test is run each time the instrument is turned on or reset The confidence test checks most of the computer and interface components in the system When the confidence test is running the number of the test currently being performed is shown on the display The test number appears as a two digit hex number on the lower right of the disp...

Страница 132: ...essential to the operation of the instru ment has failed the confidence test the instru ment cannot reliably perform any further functions The system stops when the fatal error is posted and the Ready light remains off Table 5 1 summarizes the primary confidence tests for the TGA If any errors occur during the confidence test call your TA Instruments service representative Table 5 1 TGA Confidence...

Страница 133: ...Sample hang down wire 952040 902 Tare hang down wire 952011 906 Class M calibration weight kit 100 mg and 1 gm 269931 001 Class M cal wt 100 mg 269931 002 Class M cal wt 1 gm 952018 908 50 µL platinum sample pan kit 952323 902 100 µL aluminum sample pan kit 952018 909 250 µL ceramic sample pan kit 952018 910 500 µL ceramic sample pan kit 952384 901 TGA Temperature Calibration kit 952385 901 TGA ni...

Страница 134: ...ture calibration standard 900905 901 Calcium oxalate sample 990806 901 Air purge valve assembly 952324 001 TGA 2950 keypad assembly 990820 010 Instrument keypad 990828 901 Power supply assembly 990850 901 Central processor PCB 990880 901 Communications PCB 990870 901 Triac drive PCB 259508 000 Brass tweezers 259509 000 Spatula curved 165 mm long 265303 001 Instrument display 265749 001 O ring bott...

Страница 135: ... weight kit 1 mg to 500 mg 952160 901 TGA 2950 Cooling Accessory 952160 903 Heat exchanger fan assembly 952162 901 Cooling Accessory tubing 952166 901 Cooling Accessory water reservoir bottle 952172 901 Cooling Accessory pump assembly 952161 901 Flow switch assembly 269932 001 Solid state relay 952377 901 Conditioner Kit ...

Страница 136: ...TA INSTRUMENTS TGA 2950 Maintenance and Diagnostics 5 24 ...

Страница 137: ...s applications please call the Thermal Analysis Help Desk at1 302 427 4070 SERVICE U S A For instrument service and repairs pleasecall1 302 427 4050 TA Instruments Ltd Europe House Bilton Centre CleeveRoad Leatherhead SurreyKT227UQ England Telephone 44 1372 360363 Fax 44 1372 360135 TA Instruments GmbH Max Planck Strasse11 D 63755Alzenau Germany Telephone 49 6023 9647 0 Fax 49 6023 9647 77 TA Inst...

Страница 138: ...e B P 608 78056Saint Quentin Yvelines Cedex France Telephone 33 1 30 489460 Fax 33 1 30 489451 TA Instruments Spain WatersCromatografía S A División TA Instruments Avda Europa 21 Pta Baja 28108Alcobendas Madrid Spain Telephone 34 91 203 9100 Fax 34 91 661 0855 TA Instruments Australia Unit 3 38 46 South Street RydalmereNSW2116 Autstralia Telephone 61 29 9331 705 Fax 61 29 8981 455 TA Instruments I...

Страница 139: ... Instruments Hi ResTM Technique B 8 The Hi ResTM Ramp Segment B 9 Calcium Oxalate Example Scans B 13 Advanced Hi ResTM Techniques B 18 What Can Be Resolved and What Cannot B 18 Unresolved Transitions B 19 Selecting a Hi ResTM Technique B 22 Dynamic Rate Hi ResTM Ramp B 22 Constant Reaction Rate Hi ResTM Ramp B 23 Weight Gain Experiments B 26 Signature Analysis B 27 ...

Страница 140: ...B 33 Adjusting Heating Rate B 34 Adjusting Resolution Setting B 37 Useful Resolutions Settings B 39 Temperature Calibration B 41 Hi ResTM Transition Temperatures B 42 Hi ResTM Sensitivity Segment B 43 Understanding Sensitivity Setting B 44 Adjusting Sensitivity in Dynamic Rate Mode B 45 Adjusting Sensitivity in Constant Reaction Rate Mode B 47 Abort Segment B 51 Stepwise Isothermal Heating B 53 ...

Страница 141: ...Mixture of Bicarbonates B 58 Dynamic Rate Scans B 59 Varying Resolution Setting B 61 Varying Sensitivity Setting B 62 Constant Reaction Rate Scans B 63 Stepwise Isothermal Scans B 65 Monosodium Glutamate B 68 Banana Taffy B 69 Plastic Laboratory Tubing B 71 References B 75 ...

Страница 142: ...Appendix B B 4 TA INSTRUMENTS TGA 2950 ...

Страница 143: ...GA capability The new method segments are High Resolution Ramp High Resolution Sensitivity Abort Next Segment With the addition of these segments method programming becomes more versatile and powerful than ever before The Hi ResTM ramp can be used alone as a simple single segment method or the method segments can be com bined with more traditional segments such as constant heating rate ramps and t...

Страница 144: ...oftware Included in Kit Version 8 2 or higher controller operating system Instrument Software Option circuit board Included in Kit Hi ResTM TGA software option key Included in Kit A TGA instrument with Hi ResTM capability properly installed can be identified by the Hi Res TGA Installed message on the instrument display screen following the confidence test and by the letters HR in the instrument id...

Страница 145: ...e It has long been known that using very slow heating rates will improve the separation of some overlapping transitions and thus increase the resolution of the TGA scan Another technique to increase resolution is to increase furnace temperature until the onset of decompo sition and then hold temperature isothermally until the decomposition is complete After which the temperature is raised again un...

Страница 146: ...such as humidity and pressure The TA Instruments Hi ResTM Technique The TA Instruments Hi ResTM technique dynamic rate TGA DRTGA differs from previous control techniques in that the heating rate of the sample material is dynamically and continuously modified in response to changes in the rate of decomposition of the sample so as to maximize weight change resolution This technique allows the use of...

Страница 147: ...ing rate 0 01 to 200 C minute res_setting is the resolution setting 8 0 to 8 0 temp is the ramp final temperature 200 to 1000 C example Ramp 50 00 C min res 4 0 to 800 00 C The Hi ResTM ramp segment operates similarly to the traditional constant heating rate ramp segment except that the heating rate is varied dynamically during the ramp in response to the derivative of weight change minute As perc...

Страница 148: ...tive resolution settings are the most univer sally useful settings and the least likely to have undesirable side effects Although there are no hard and fast rules about which resolution setting to use for a given experiment there are some general guidelines which will be helpful It has already been stated that higher resolution settings usually provide better resolution results and lower settings ...

Страница 149: ...If you are uncertain what the resolution setting and heating rate should be then try setting 3 0 and 50 C minute Negative resolution settings are covered in the Advanced Hi ResTM Techniques section 2 When trying to obtain better resolution try progressively higher resolution settings 1 0 at a time while leaving the heating rate fixed 3 The most useful resolution settings are 3 0 to 5 0 because the...

Страница 150: ...orten experiment time Generally speaking you no longer need to use very slow heating rates less than 5 C minute because the dynamic rate Hi ResTM technique automatically reduces heating rate with the accompanying improvement in resolution There are no special method programming constraints on Hi ResTM ramp segments They may appear anywhere in a method that a normal ramp could appear The maximum ra...

Страница 151: ...or Hi ResTM ramp segment from ambient to 800 C was used for the method Figures B 1 and B 2 show the results of constant heating rate scans at 20 C minute and 1 C minute Figures B 3 B 4 and B 5 show the results of Hi ResTM scans at 50 C minute with resolution settings 3 0 4 0 and 5 0 respectively Figure B 6 shows a composite plot of the derivative of weight loss for each of the five scans The deriv...

Страница 152: ...Appendix B B 14 TA INSTRUMENTS TGA 2950 Figure B 2 Figure B 3 ...

Страница 153: ...TA INSTRUMENTS TGA 2950 B 15 Hi ResTM Option Figure B 4 Figure B 5 ...

Страница 154: ...minute and the 1 C minute scans Figures B 1 and B 2 we see some improve ment in resolution of the water loss 1st transi tion but little improvement in the other two transitions Note that the transition temperatures in the slower scan are shifted to lower temperatures as expected The 20 C minute scan took 39 minutes and the 1 C minute scan took nearly 13 hours to complete a 1 C min Normal Ramp b Re...

Страница 155: ...scale Note how much taller and narrower the Hi ResTM peaks are compared to the conventional scans We can also clearly see that transition temperature is reduced by increasing the resolution setting This effect is normal because with progressively higher resolution settings transitions are con strained to lower decomposition rates which can only be maintained at lower temperatures As can be seen in...

Страница 156: ...Hi ResTM TGA improve the resolution of my transitions This is one of the first ques tions asked by most people when they are introduced to Hi ResTM TGA It would be wonderful if the answer were always an un qualified yes Unfortunately there are some applications where resolution enhancement will be minimal Therefore some criteria for select ing likely candidates for resolution improvement is needed...

Страница 157: ...y sis There are some general rules of thumb which will help you decide if the material you are working with will be a successful candidate for resolution improvement First do the compo nents of the sample material decompose at sufficiently different temperatures This can often be determined by running a slow heating rate survey scan of the material at 1 C minute and comparing the result to a 20 C ...

Страница 158: ...rmine if the components of the sample material have significantly differ ent rates of decomposition If so it may be possible to improve resolution using stepwise isothermal heating or using the constant reac tion rate Hi ResTM mode negative resolution settings To find out run a conventional constant heating rate ramp up to the transition temperature and then hold isothermally After the decompositi...

Страница 159: ... will build a slight vapor pressure inside the sample con tainer This pressure may reduce or stop one or more of the overlapped reactions and thereby allow completion at a higher temperature To make this test simply try running the sample using a Hi ResTM ramp with and without the sample containment to see if a difference in separation can be observed Generally the temperature of reaction will shi...

Страница 160: ...ne technique may give better results than another and present additional guidelines for selecting techniques and setting parameters Dynamic Rate Hi ResTM Ramp In dynamic rate Hi ResTM mode one or more Hi ResTM ramp segments are used with positive resolution settings In this mode the furnace heating rate is varied between a fixed minimum and the maximum specified in the ramp seg ment but is never r...

Страница 161: ...re used with negative resolution settings In this mode the heater control system varies the temperature of the furnace as required to maintain a constant preselected rate of weight change minute Whenever the rate of weight change exceeds the percent minute threshold the heating rate of the furnace is reduced even to the point of cooling if necessary When percent minute falls below the threshold th...

Страница 162: ...tion These may include pyro technics self heating reactions auto catalyzing reactions and gas diffusion reactions Constant reaction rate mode is also a good choice when it is important to accurately determine the transi tion temperature at a given reaction rate Another area where constant reaction rate heating can be helpful is when the sample material exhibits a relatively large and some what con...

Страница 163: ... heating rates may be required This is particularly true for very small reaction rates less than 0 1 minute Since the heater control system concentrates on a very narrow band of reaction rates transitions with slightly different reaction rates in the same scan are often given very different treatment For example a transition which falls short of the minute threshold may be passed at a fairly high ...

Страница 164: ...lysis some applications involve weight gain such as in oxidation studies The Hi ResTM heating control techniques apply equally well to weight gains as to weight losses In this case the absolute value of the weight change signal is used for control Weight gains of up to 200 can be accommo dated The rates of weight gain minute and their relationship to heating rate resolution setting and sensitivity...

Страница 165: ...change peaks of the TGA scan or the weight curve itself is used to create a unique pattern or signature of the sample material Signature scans of standards and the unknown material are then compared to make the identification or accept don t accept decision Since the various components of a sample when run separately usually decompose or evolve at unique and reproducible rates and temperatures it ...

Страница 166: ...than the individual components Sample Quantity and Orientation As with conventional constant heating rate TGA sample quantity and orientation in the sample holder can be important during Hi Res experiments This is particularly true if the sample is not homogeneous e g a laminated sheet or coated surface With these types of samples it is wise to try scans with different surfaces exposed Be aware th...

Страница 167: ...action rate Hi ResTM mode On the other hand larger sample quantities 50 to 100 mg are recommended for reactions in which a very small weight change less than 1 percent is being measured For maximum weight resolu tion it is advisable to keep sample weight below the TGA 2950 weight range change at 100 mg A problem with very large samples which decompose rapidly and almost completely is that the furn...

Страница 168: ...minute curve as the bubble bursts An excellent example of bubble noise can be seen in the scan of ethylene vinyl acetate in figures B 7 and B 8 In figure B 7 the effect of bubble formation and bursting can be seen as a sudden drop in weight at about 400 C during the second weight loss This appears in the derivative curve as a peak shoulder In Figure B 8 we can clearly see the formation and burstin...

Страница 169: ...TA INSTRUMENTS TGA 2950 B 31 Hi ResTM Option Figure B 7 Figure B 8 ...

Страница 170: ...is not a problem when making plots but when automatic limit selection is used during data analysis report generation the analysis program can sometimes become confused about where to place the limits This situation can be identified by curve tick marks and tangent lines which are poorly placed on the weight curve or may even be plotted off of the curve The difficulty is caused by the fixed size of...

Страница 171: ...re equally distributed over a moving window the smoothing window used to compute the derivative If the derivative smoothing window is too wide derivative peaks will flattened and apparent resolution will be reduced If the window is too narrow derivative peaks will be needle sharp and noisy The default smoothing window is 0 2 minutes for derivatives with respect to time min and min min and 10 C for...

Страница 172: ...and determining the rate of reactions Adjusting Heating Rate Heating rate has long been used to control transition resolution The typical thermal analyst makes most runs at 20 C minute and drops down to 5 or 1 C minute for hard to resolve transitions or just to see if there is anything else interesting going on that might have been missed in the faster scan 1 C minute scans are generally not routi...

Страница 173: ...e is usually not required For negative resolution settings the selection of heating rates is usually quite different because reaction rate overshoot must be minimized Generally 1 2 5 and 10 C minute are the most useful rates to use with negative resolution settings Try 5 C minute to start An important difference between the dynamic rate positive resolution setting and constant reaction rate negati...

Страница 174: ...his will move the background percent minute closer to the control point you have selected with the resolution setting If noise is present in the background percent minute it may fool the control algorithm into thinking a transition is starting and result in a premature reduction in heating rate to avoid predicted set point overshoot In extreme cases heating rate cycling can occur particularly at h...

Страница 175: ...nute values selected by each resolution setting is fairly wide about two orders of magnitude This width is adjustable using the sensitivity parameter In constant reaction rate mode negative resolu tion settings the resolution setting specifies the percent minute value that will be used as the control set point for furnace heating In this case the system will adjust heating rate as required to main...

Страница 176: ...62 3 5 0 562 5 5 0 056 7 5 0 0056 1 6 5 01 3 6 0 501 5 6 0 050 7 6 0 0050 1 7 4 47 3 7 0 447 5 7 0 045 7 7 0 0045 1 8 3 98 3 8 0 398 5 8 0 040 7 8 0 0040 1 9 3 55 3 9 0 355 5 9 0 036 7 9 0 0036 2 0 3 16 4 0 0 316 6 0 0 032 8 0 0 0032 The process of initially picking and then adjusting resolution setting is not exacting or calculated It is based largely on experience and some general guidelines Thi...

Страница 177: ...his will give a rapid scan with moderate application of the Hi ResTM heating technique Results should be at least as good as a 20 C minute conven tional scan of the same material and will usually be better If time permits it is often helpful to have a constant heating rate 20 C minute scan of the material available for comparison Useful Resolution Settings After some experience with Hi ResTM TGA y...

Страница 178: ... on what resolu tion setting to live with The benefit to having more range and resolu tion to the resolution setting than seems to be necessary is that on a rare occasion a material requires a very fine adjustment or an extreme treatment Don t forget that the maximum heating rate is a factor in determining resolution as well as the resolution setting Lower resolution settings allow materials which...

Страница 179: ...nsitions Another way to reduce the effect of thermal gradients is to temperature calibrate the TGA The general procedure for temperature calibra tion is found in theonline help and documentation Temperature calibration involves analyzing a magnetic standard to determine its curie tem perature The curie temperature corresponds to the extrapolated endpoint on the S shaped thermal curve However when ...

Страница 180: ...the apparent transition temperature of a decomposition reaction The shift in measured transition temperature caused by changing resolution setting can easily be an order of magnitude larger than the thermal gradients you are trying to correct with calibra tion This effect can be clearly observed in the mixture of bicarbonates example Figure B 13 page B 61 In light of this fact it is acceptable in ...

Страница 181: ...s_setting is the Hi ResTM sensitivity setting 1 0 to 8 0 example Hi ResTM sensitivity 2 0 Hi ResTM sensitivity segments execute immedi ately when encountered in a method and simply set the sensitivity setting to the new value provided The last value set is used for all subsequent Hi ResTM ramps until a new value is set If no Hi ResTM sensitivity segment has been encountered in the method before th...

Страница 182: ...y is knowing when and how to make the adjustment It is easy to confuse resolution setting and sensitivity setting since both values can affect the resolution of the TGA scan However there is a simple way to think of the difference between the two parameters Resolution setting controls the temperature at which the transition will occur i e how far from the theoretical isothermal decomposition tempe...

Страница 183: ...urve Adjusting Sensitivity in Dynamic Rate Mode In dynamic rate Hi ResTM mode positive resolution settings the sensitivity setting is used to further increase the resolution of some transitions once an appropriate resolution setting has been determined This is accomplished by narrowing the range of percent minute values over which the heating rate is proportionally varied Higher sensitivity settin...

Страница 184: ...nd adjust resolution setting to get the best separation possible in the desired time frame Then increase sensitivity to 2 0 4 0 and 8 0 to see if a useful improvement in resolution results It is possible that no improvement in resolution will result This is usually caused by overlapped transitions which are weakly temperature dependant and strongly time dependant In this case it doesn t matter how...

Страница 185: ...tivity settings are generally preferred because they help dampen noise and greatly reduce the possibility of control cycling How ever when it is very important to avoid percent minute overshoot or if the sample is highly reactive then higher settings will be required The problem with too high a sensitivity setting is that control cycling or heating rate ringing may occur see Figure B 11 The recomm...

Страница 186: ... gener ally give the best results When heating rates higher than 5 0 C minute are used proper adjustment of sensitivity setting becomes critical to maintaining smooth heating control The default sensitivity of 1 0 is usually too low at these higher heating rates and typi cally results in significant transition temperature overshoot and heating control ringing as shown in Figure B 9 At high heating...

Страница 187: ...TA INSTRUMENTS TGA 2950 B 49 Hi ResTM Option Figure B 9 Sensitivity Setting Too Low Figure B 10 Correct Sensitivity Adjustment ...

Страница 188: ...Appendix B B 50 TA INSTRUMENTS TGA 2950 Figure B 11 Sensitivity Setting Too High ...

Страница 189: ...hich is compared with the real time signal example Abort next seg if 20 0 Abort segments execute immediately when encountered in a method and simply establish conditions for testing the next segment The specified limit designated by the signal condition and value parameters is tested before and during the execution of the next method segment If the limit is reached at the beginning of a segment th...

Страница 190: ... than 100 are permitted to accommodate weight gains min If the condition operator is and the derivative of sample weight percent is less than or equal to the limit percent minute or if the condition operator is and the derivative of weight percent is greater than or equal to the limit percent minute then the limit is reached Negative values indicateweight gain and positive values indicate weight l...

Страница 191: ...ing the first transition then an abort segment can be used to terminate the ramp after the beginning of the second weight loss by specifying a limit condition This is particularly useful for Hi ResTM ramps because the reduced heating rate during a weight loss causes the majority of the transition to occur during a very narrow tem perature range making termination by final temperature difficult to ...

Страница 192: ...3 Abort next seg if min 0 05 4 Isothermal for 500 minutes 5 Repeat segment 1 til 700 C The min limit for the isothermal segment is selected to be equal to the baseline rate of weight change encountered during the onset of the transition of interest via a normal constant heating rate scan of this material Be sure to use the same ramp rate as that selected for stepwise heating The min limit for the ...

Страница 193: ...sitions are separated by 10 C then use 1 C min as the heating rate prior to between and following the transitions If precise reaction temperatures are important then slow heating rates should always be used prior to encountering transitions of interest even though they may be well separated in temperature and the min limit for the ramp segment should be set closer to the limit for the isothermal s...

Страница 194: ...h follows the transition Any small amount of sample material which did not finish decomposing during the transition will now quickly decompose due to the rapid eleva tion of the furnace temperature This will cause the decomposition rate minute to rise substantially If the rising decomposition rate crosses the abort threshold for the ramp segment then a second isothermal period will be intro duced ...

Страница 195: ...mp rate the increasing temperature causes the remaining sample to quickly decompose which raises the rate of weight loss minute to a high level and either triggers another isothermal hold period or shows up as a backside shoulder on the weight loss curve An example of using stepwise isothermal heating is shown in the following Hi ResTM TGA Examples section ...

Страница 196: ...ifferent Hi ResTM techniques and parameter settings The indi vidual bicarbonates decompose to carbonates between 100 C and 200 C with the simultaneous release of CO2 and H2 O Potassium bicarbonate decomposes at approximately 50 C higher temperature than sodium bicarbonate When mixed together the decompositions of the two bicarbonates are overlapped in temperature and are very difficult to resolve ...

Страница 197: ...n homogeneity of the sample mixture and variations in ambient humidity from run to run Dynamic Rate Scans In Figure B 12 on the next page we have overlaid the individual bicarbonate decomposi tions curves b and d along with the decomposi tion of the mixture by conventional TGA curves a and e and by dynamic rate Hi resTM TGA curve c Reducing the heating rate of the mixture from 20 C minute curve e ...

Страница 198: ...RUMENTS TGA 2950 Figure B 12 a 1 C min Normal Ramp of Mixture b 20 C min Res 4 0 Hi ResTM Ramp of NaHCO3 c 50 C min Res 4 0 Hi ResTM Ramp of Mixture d 20 C min Res 4 0 Hi ResTM Ramp of KHCO3 e 20 C min Normal Ramp of Mixture ...

Страница 199: ...settings curves 1 through 8 All of the Hi ResTM scans were run at 50 C minute with the default sensitivity setting of 1 0 Note that increasing resolution setting increases the resolution of each transition and simultaneously reduces the transition temperature The initial weight losses of approximately 1 on each curve are due to the evaporation of surface water absorbed by the mixture Figure B 13 a...

Страница 200: ...can at four different sensitivity settings curves b through e All of the Hi ResTM scans were run at 20 C minute with a resolution setting of 5 0 Note that increasing sensitivity setting increases the sharpness of each transition but does not substantially change the transition temperature Figure B 14 a 1 C min Normal Ramp b Sensitivity setting 1 c Sensitivity setting 2 d Sensitivity setting 4 e Se...

Страница 201: ... 0 1mm pin hole in the top All of the Hi ResTM scans were run at 5o C min Comparing curve b to curves a and d we can see a significant improvement in resolution due to the vapor pressure build up in the semi hermetic sample container Because the sample pan was open in curve b there was no opportunity for a vapor pressure reaction rate equilibrium to occur as the sample decomposed resulting in only...

Страница 202: ...Appendix B B 64 TA INSTRUMENTS TGA 2950 Figure B 15 a Res 5 0 Sens 2 0 Semi hermetic Pan b Res 4 0 Sens 1 0 Open Pan c 1 C min Normal Ramp d Res 4 0 Sens 2 0 Semi hermetic Pan e 20 C min Normal Ramp ...

Страница 203: ...itions is in question because there is no inflection point in the plateau and the rate of weight loss immediately increases after the isothermal segment is aborted This indicates that the two decompositions are still overlapped and that holding for a longer isothermal time period during the first transition would have resulted in a lower weight loss plateau between transitions In Figure B 17 the s...

Страница 204: ...i tions The minute limit for the ramp segment was then chosen to be ten times larger than that for the isothermal segment Although the weight loss result in Figure B 17 seems more reasonable we are suspicious that the decomposition of the potassium bicarbonate 2nd transition has already started because the rate of weight loss immediately increases as heating is resumed at 88 C Another problem is t...

Страница 205: ...TA INSTRUMENTS TGA 2950 B 67 Hi ResTM Option Figure B 16 Figure B 17 ...

Страница 206: ... Curve b shows the result of a dynamic rate Hi ResTM scan at resolution setting 4 0 and sensitiv ity setting 1 0 As can be seen by the derivative of weight loss curves the Hi ResTM scan gives resolution comparable to the 1 C minute scan in a fraction of the time Figure B 18 If you should decide to run this sample be aware that MSG foams significantly at these temperatures If a sample size greater ...

Страница 207: ...ample pan Banana Taffy In Figures B 19 and B 20 we analyzed a sample of artificial banana taffy a common confection ery product composed primarily of water and sugar which has a number of overlapped transitions between 100 C and 500 C Figure B 19 shows the result of a conventional constant heating rate scan of taffy at 10 C minute Figure B 20 shows the result of a 50 C minute dynamic rate Hi ResTM...

Страница 208: ...tional scan This is possible because the Hi ResTM TGA ramp heats the taffy sample rapidly during baseline portions of the scan and slowly during transitions resulting in an average heating rate of about 10 C minute A 200 C minute Hi ResTM scan of this sample takes about the same time as a 20 C minute conventional scan while providing resolution improvement similar to that observed with the 50 C mi...

Страница 209: ...ial overlapped transitions is good in the 1 C minute scan but poor in the 20 C minute scan In contrast the resolution of the two transitions at 400 C and 500 C are best in the 20 C minute scan and reduced in the 1 C minute scan In both cases however the small backside transi tion at 25 to 35 weight loss is barely discernable Comparing the conventional TGA results in figures B 21 and B 22 to the 50...

Страница 210: ...es about 50 longer to complete when heating rate is reduced by 50 Most notice able however is that transition resolution is best in the fastest scan This is because higher maximum heating rates allow the TGA furnace temperature to change more quickly between transitions which reduces transition overlap and flattens weight loss baseline As an added benefit experiment time is reduced compared to tra...

Страница 211: ...TA INSTRUMENTS TGA 2950 B 73 Hi ResTM Option Figure B 22 Figure B 23 ...

Страница 212: ...Appendix B B 74 TA INSTRUMENTS TGA 2950 Figure B 24 Figure B 25 ...

Страница 213: ...f any one sample material Each paper contains an extensive list of additional references for specific materials and techniques 1 Thermoananlytical Examinations Under Quasi Isothermal Quasi Isobaric Conditions F Paulik J Paulik Thermochimia Acta 100 1986 23 59 2 Controlled Transformation Rate Thermal Analysis The Hidden Face of Thermal Analysis J Rouquerol Thermochimica Acta 144 1989 209 224 Hi Res...

Страница 214: ...Appendix B B 76 TA INSTRUMENTS TGA 2950 ...

Страница 215: ...ng Started C 4 The TGA 2950 Instrument C 6 Calibrating the Auto TGA C 10 Running Experiments C 11 Preparing the Samples C 12 Selecting Sample and Tare Pans C 12 Taring the Sample Pans C 13 Loading the Samples C 16 Setting Up an Experiment C 18 Manual Operation C 19 Tracking the TGA Autosampler Status C 19 Interrupting a Run C 20 ...

Страница 216: ...Appendix C TA INSTRUMENTS TGA 2950 C 2 ...

Страница 217: ...terial Experiments are performed as they normally would be using the TGA but now you can run samples on a continual basis and keep a log of the results using the Autosampler screens The six 6 standard TGA pans listed below are used with the Auto TGA 100 µL aluminum 50 and 100 µL platinum pans and 100 250 and 500 µL alumina ceramic pans This appendix provides information on the set up of the Auto T...

Страница 218: ...Appendix C TA INSTRUMENTS TGA 2950 C 4 Figure C 1 Auto TGA ...

Страница 219: ...Option Getting Started The Auto TGA as an accessory to the TGA does not alter the procedures used to start up and shut down the TGA instrument and the control ler refer to the procedures found in Chapter 3 of this manual when starting your instrument ...

Страница 220: ...key has been added to the TGA instrument keypad the AUTO SELECT key shown in the figure below Figure C 2 TGA Instrument Display and Keypad with Auto TGA Accessory Table C 1 on page C 5 explains the functions of the instrument keys when used in conjunction with the Auto TGA accessory TGA 2950 Thermogravimetric Analyzer ...

Страница 221: ...the online help and documen tation Auto TGA function This key has an added func tion to act as a shift key for the AUTO SELECT TARE and LOAD keys AUTO SELECT Auto TGA function Increments the next pan to be loaded when pressed alone SCROLL Auto TGA function Decrements the next pan to be loaded when you AUTO SELECT hold down the SCROLL key while pressing AUTO SELECT The selected sample is loaded or ...

Страница 222: ...tect the pan from air currents weighs the pan stores the weight as an offset and then unloads the pan Performs a tare on the selected pan when pressed alone SCROLL TARE Auto TGA function Tares all of the pans on the sample platform when you hold down the SCROLL key while pressing TARE LOAD Loads the selected pan from the sample platform onto the balance Auto TGA function Loads the selected sample ...

Страница 223: ...inuously loads and unloads all of the pans on the sample platform when you hold down the SCROLL key while pressing LOAD LOAD functions can be stopped by pushing the STOP key on the instrument keypad UNLOAD Functions of these re maining keys do not change when used with the Auto TGA accessory see Chapter 1 START STOP REJECT SCROLL STOP ...

Страница 224: ...ion remains the same weight calibration and temperature calibration are recommended at least once a month or when replacing the thermocouple and the platform adjustment procedure needs to be performed if the sample hang down wire fails to pick up a sample pan See the online help and documenta tion for further information ...

Страница 225: ...ve the following general outline In some cases not all of these steps will be performed Selecting the pan type and material Loading the pans Taring the empty sample pans Loading the samples into the pans Entering experiment information through the TA controller sample and instrument information Creating and selecting the thermal method on the controller Attaching and setting up external accessorie...

Страница 226: ...red in the following ranges 1 16 samples 17 32 samples 33 48 samples 49 64 samples Once you have selected the type of pan that you wish to use you must use the same type of pan for all of the samples on the sample platform disk The same type of pan that you use for experiments must also be used as a tare pan Tare Pan 1 Obtain a pan of the same type and size to be used for your experiments 2 Remove...

Страница 227: ...secutive experi ments Taring the Sample Pans When you tare the sample pans the TGA reads the weight of the empty pans in their numbered order and then stores these weights as a set of offsets These offsets are subtracted from subsequent weight measurements for each numbered sample You can tare the pans manually or automatically as explained here ViewtheAutosamplerlog foundontheInstrument Controlso...

Страница 228: ...nstrument for the appropriate weight range 1 Place the platform on the sample arm as shown in Figure C 3 Make sure that the small pin is inserted in the hole in the platform This will seat the platform correctly 2 Using brass tweezers place each sample pan in a numbered place on the platform making sure it is stable Figure C 3 Loading the Auto TGA Sample Platform ...

Страница 229: ...the pan The Auto TGA will automatically tare each of the remaining pans in sequence It should take approximately 45 minutes to tare all 16 pans on one sample platform When the Auto TGA has completed taring each pan on the sample plat form the tare status message will disappear The advantage to using the Auto TGA is to save time and effort therefore it would not be efficient to perform manual tare ...

Страница 230: ...ake sure that the wire on the bottom of the sample pans align with the groove in the panhole so that the sample pan can be picked up by the sample hang down wire Always use the brass tweezers to handle the sample pans Manually loading the sample pan onto the hang down wire may damage the balance mechanism 3 Press the LOAD key The TGA will auto matically load the selected sample 4 Position the ther...

Страница 231: ...TA INSTRUMENTS TGA 2950 C 17 TGA 2950 Autosampler Option 5 Press the UNLOAD key The TGA will unload the sample and be ready for auto matic sequencing Figure C 4 Adjusting the Thermocouple ...

Страница 232: ...ument 2 Select the Instrument Mode 3 Access the Autosampler Sequence 4 Enter Sample Information 5 Enter Instrument Information If you are planning to run the Autosampler be sure to specify furnace open at method end as well as air cool to cool down the furnace between samples 6 Create and Select Thermal Methods The first time you use your TGA you will need to create at least one thermal method to ...

Страница 233: ...ocedures found on in Chapter 3 to start stop and monitor an experiment For details setting up the methods consult the online help and documentation Tracking the TGA Autosampler Status To monitor the current run observe the status of the Auto TGA etc you will need to access the TA Instruments Instrument Control software Refer to the online help and documentation for further information ...

Страница 234: ...d and run and causes the Auto TGA to unload the pan and start the next run However the data file for the interrupted run is saved Reject Terminates the current method and AS run and causes the Auto TGA to unload the cell and start the next run The data file for the interrupted run is discarded Other options are available through the controller functions see the online help and documentation for fu...

Страница 235: ...the EGA Furnace D 3 EGA Furnace Specifications D 5 Installing the EGA Furnace D 6 First Time Installation D 6 Removing and Reinstalling the EGA Furnace D 14 EGA Furnae Removal D 14 EGA Furnace Installation D 16 Connecting the Spectrometer D 18 Using the EGA Furnace D 21 Cleaning the Quartz Furnace Tube D 22 ...

Страница 236: ...Appendix D TA INSTRUMENTS TGA 2950 D 2 ...

Страница 237: ...lows you to connect a spectrometer to the instrument so that the gases evolved by sample decomposi tion can be analyzed The EGA furnace and the standard TGA furnace can be exchanged easily on the instrument after initial hardware installa tion Version 3 3B or higher of the TGA 2950 instrument software is required for the EGA furnace Figure D 1 TGA 2950 EGA Furnace ...

Страница 238: ...to a spectrometer such as a mass spectrometer Because the heater is external to the sample tube evolved gases from sample decomposition within the sample tube do not come in contact with the resistance elements or the furnace ceramic refractory Cooling air enters through the furnace base and passes upward between the outside of the sample tube and the inside of the furnace completely separating th...

Страница 239: ...e pan to the open position EGA Furnace Specifications Refer to Table D 1 below for the specifications of the EGA furnace Some of these may be similar to the standard furnace for the TGA 2950 Table D 1 EGA Furnace Specifications Temperature range 25 C to 1000 C Thermocouple Platinel II Heating rate 0 1 to 50 C min Platinel II is a registered trademark of Engelhard Industries ...

Страница 240: ... replacement of the four furnace mounting screws and cleats with those supplied with the EGA furnace After this has been completed according to the following directions you may interchange the two types of furnaces without changing the mounting hardware Refer to page D 13 Re moving and Reinstalling the EGA Furnace for subsequent furnace exchanges 1 Place a drip pan to the left of the instrument to...

Страница 241: ...at the hose connections are positioned over the drip pan Visually note the left AAA and right CCC orientation of the water lines so that you do not cross them later when they are reconnected See Figure D 2 Then carefully snip the wire ties and disconnect the cooling water lines from the housing A small amount of cooling water will drain out into the pan when the hoses are discon nected 5 Press the...

Страница 242: ...ied with the EGA installation kit to replace the screws with the new screws spacers and cleats provided with the kit Refer to Figure D 3 Replace the upper screws using the long screws with spacers and replace the lower screws using the short screws without spacers W a t e r L i n e C C C Water Line AAA Water Line CCC Mounting Screws ...

Страница 243: ...en loosen each of them no more than one full turn so that the flat sides of the cleats are aligned vertically as shown in Figure D 4 Now tighten the lower two mounting screws fully then loosen each of them two full turns plus a fraction of a turn so that the flat sides of the cleats are aligned vertically as shown in Figure D 4 Cleat Short Screw Spacer Cleat Long Screw ...

Страница 244: ...h the inside of the instrument cabinet causing damage to the instrument 9 Plug the AIR COOL line into the base of the EGA furnace then connect the two water cooling lines making sure that the lines are not crossed See Figure D 5 for the correct placement of the lines Be sure to install the wire ties supplied in the kit around the cooling lines to prevent water leakage WARNING ...

Страница 245: ... lower mounting screws are below the top edge of the en larged cutout in the instrument faceplate Then press the STOP key 11 Plug the EGA furnace arm into the connec tor on the carriage and tighten the lower two mounting screws using the 3 32 inch ball driver supplied with the TGA 2950 EGA See Figure D 6 on the next page Wire Ties Water Cool Lines Air Cool Line ...

Страница 246: ...s 12 Press the FURNACE key to completely lower the furnace Use the 3 32 inch ball driver to tighten the upper furnace mounting screws To reach the upper left mounting screw insert the ball driver between the water connections on the left side of the furnace housing as shown in Figure D 7 ...

Страница 247: ... the purge hose to the gas purge inlet on the right side of furnace Hold onto the glass purge tube with one hand while you install the purge hose to avoid breaking the glass 14 Check the Heat Exchanger reservoir water level and add water if needed See Chapter 2 Filling the Heat Exchanger for instruc tions t CAUTION ...

Страница 248: ... EGA furnace use the following procedure 1 Press the FURNACE key to open the furnace completely 2 Locate the top two mounting screws on each side of the furnace arm connection found in the slot on the front of the instrument Using the 3 32 inch ball driver supplied with the EGA furnace loosen the two screws no more than one full turn To reach the upper left mounting screw insert the ball driver be...

Страница 249: ...let it slip back into the instrument cabinet 7 Place a drip pan to the left of the instrument to catch the coolant that will leak from the hose connections when the EGA furnace is removed 8 Lay the furnace assembly down on the left side of the instrument so that the hose connections are positioned over the drip pan Then carefully snip the wire ties and disconnect the cooling water lines from the h...

Страница 250: ...ts are aligned vertically as shown in Figure D 4 on page D 10 Now tighten the lower two mounting screws fully then loosen each of them two full turns plus a fraction of a turn so that the flat sides of the cleats are aligned vertically as shown in Figure D 4 on page D 10 Loosening the upper two mounting screws any more than one full turn may cause the screws to interfere with the inside of the ins...

Страница 251: ...er to tighten the upper furnace mounting screws To reach the upper left mounting screw insert the ball driver between the water connections on the left side of the furnace housing as shown in Figure D 7 on page D 13 7 Connect the purge hose to the gas purge inlet on the right side of furnace Hold onto the glass purge tube with one hand while you install the purge hose to avoid breaking the glass 8...

Страница 252: ...hould be made of heat resistant alloy capable of resisting corrosion by the evolved gas and oxidation at temperatures up to 1000 C The transfer line must pass through the exhaust gas fitting and a glass branch tube in the sample tube It should end at a point just short of the inside diameter of the sample tube to ensure that the evolved gases do not condense before entering the transfer line The t...

Страница 253: ...wage the ferrule then cut the end of the transfer tube off so that two inches of the tube projects beyond the ferrule See Figure D 8 below Extending the transfer line more than two inches beyond the SwagelokTM fitting may cause the TGA 2950 to operate improperly Figure D 8 EGA Transfer Line with Ferrule 3 Make sure that the end of the transfer line is straight and free of oxide deposits before you...

Страница 254: ...SwagelokTM nut to seal the connector When you tighten the SwagelokTM nut use a 3 8 inch wrench on the exhaust fitting flats to prevent them from turning If the transfer line is not straight or has heavy oxide deposits on it the sample tube may be broken as the line is inserted WARNING ...

Страница 255: ... as you would normally use the TGA standard furnace No special procedures must be followed when preparing TGA samples setting up methods or running experiments Refer to the appropriate sections in the main manual for information Follow the manufacturer s instructions for the use of your spectrometer when connected to the EGA furnace ...

Страница 256: ... the sample tube to scrape or chip contaminants from the sample tube as breakage may result To clean the furnace quartz sample tube use the following procedure Do not disturb the hangdown wire and furnace thermocouple located directly above the furnace when cleaning the fur nace as damage may result 1 Press the FURNACE key to open the furnace completely 2 Remove any sample pans 3 Remove the rubber...

Страница 257: ...inside of the furnace tube allowing the handle to bend freely see Figure D 9 Figure D 9 Cleaning the Inside of the Funace Tube 6 Rinse the furnace tube with the solvent again 7 Replace the rubber cap on the quartz tube stem when you have completed the cleaning procedure 8 Purge the system with nitrogen for one hour 9 Heat the furnace to 900 C to remove any remaining solvent ...

Страница 258: ...Appendix D TA INSTRUMENTS TGA 2950 D 24 ...

Страница 259: ...inet 1 4 4 13 cable GPIB 2 15 Calib status code 4 17 calibration 3 5 sample platform 3 6 temperature 3 5 weight 3 6 cleaning 3 9 EGA furnace quartz tube D 22 Closing status code 4 17 Cold status code 4 17 Complete status code 4 17 components 1 4 4 5 confidence test 5 19 controller description 1 3 Cooling status code 4 18 cooling gas line 2 18 D description TGA 2950 4 3 display 1 5 E EGA furnace 1 ...

Страница 260: ...5 EGA 4 9 4 11 D 1 reinstalling 5 11 removing 5 11 standard 4 9 furnace base 4 10 furnace housing 4 10 furnace tube cleaning D 22 FURNACE up key 1 7 fuses 5 16 G gas purge 3 16 types 3 17 Gas Switching Accessory 1 11 3 19 gases recommended 2 17 GPIB cable 2 15 H hang down wires 4 7 aligning 2 25 installing 2 22 heat exchanger 1 4 4 15 5 6 cables 2 12 coolant 5 6 filling 2 10 lines 2 12 water reser...

Страница 261: ...4 6 N No Power status code 4 19 O Opening status code 4 20 ordering information A 1 oxygen free atmosphere 3 22 P pans 3 8 4 7 cleaning 3 9 unloading 3 21 parts 5 21 power problems failures 5 18 POWER switch 1 10 purge gas 2 18 3 16 purge lines 2 17 R Ready status code 4 20 Reject status code 4 20 REJECT function 1 8 Repeat status code 4 20 routine maintenance 5 4 S sample loading 3 11 4 8 prepari...

Страница 262: ...al 3 10 Temp C status code 4 21 Temp status code 4 21 test functions 5 19 TGA 2950 accessories 1 11 to 1 12 address switches 2 15 air cool 3 16 autosampler C 3 to C 20 cables GPIB 2 15 power 2 19 calibrating 3 5 temperature 3 5 weight 3 6 cleaning 5 4 furnace 5 5 components 1 4 4 5 balance 4 6 cabinet 4 13 hang down wire 4 7 confidence test 5 19 description 1 3 4 3 display 1 5 EGA furnace D 3 to D...

Страница 263: ...5 21 routine maintenance 5 4 sample pans 4 7 loading 4 8 sample platform adjusting 2 29 sampling system 1 13 setting up an experiment 3 14 specifications 1 12 starting 2 30 status codes 4 17 stopping 2 32 tare pans 4 7 test functions 5 19 theory of operation 4 16 thermocouple replacing 5 9 unpacking 2 3 2 6 weight ranges 4 3 thermocouple 4 10 4 12 replacing 5 9 Thermogravimetric analysis 4 16 Ther...

Страница 264: ...Index TAINSTRUMENTSTGA2950 I 6 ...

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