LCR7000 & RHEOSIGHTS P/N: 974194 |
Rev: A
|
ECO: 52468
www.dynisco.com
From lab to production,
providing a window into the process
-21-
The test will run automatically from here on. When the test is finished the rheometer will
purge the remaining material automatically. The cross head will then move back up to the
park position (if set) and the data will be transferred to the Edge Device.
Clean the Rheometer, and set up for the second test. This test should be a standard shear
rate test or a rate sweep test. It is called a rate sweep test because it shows how the
viscosity of a material, flowing through a die, changes with the flow rate. For most
polymers the faster the flow rate the lower the viscosity. In this simple run we ask the
rheometer to move through 10 unique speeds. It makes measurements at specified
positions in the barrel (more about how these are obtained later). We want the rheometer
to perform this test as quickly as possible, so we set no time delay between each
measurement point. In RheoSights, go to the Setup Page, select the second test called
“Control Polymer” and press the Send button. This sends the setup details to the
rheometer. The display on the rheometer should read “#1 Control Polymer”.
Load the barrel as described previously. Once the plunger is in place, the swing arm is fully
closed, and the plunger guide bushing is in place, click the
RUN
button on the Rheometer
Control screen of RheoSights and fill in your test sample information and click on “OK” to
start the test. The test will automatically acquire the data, purge the barrel of remaining
material, move back to park position and send the data to the Edge Device.
What's happening during the run:
When
RUN/OK
is pressed on the Rheometer Control Page, the rheometer starts an internal
timer which keeps track of the total test time, the
Melt Pause Delay
, and the
Melt Time
.
The rheometer will now adjust speed and reach the
start position
to achieve the allotted
melt pause delay. The melt time and piston position are displayed. Once the melt pause
delay expires the test starts.
Big messes tend to occur when the die nut is not screwed in completely. Material runs
down the die nut holder threads and coats the threads with a sticky polymeric slop. This
can be very difficult to remove. We have tried several methods including solvents but
found a tap and die set for the die holder nut or wire brushes work best. The tap is an
English 3/4" 10 with a mating die. It is imperative the tap be ground flat at the top
("Bottom Tap") so that the tapered end does not go into the main bore and destroy the
finish. A tap ground flat at the top will hit the bottom of the barrel when it is screwed
entirely up into the barrel from below. Low torque (force) turning of the tap is usually all
4.
The Second Test: A Rate Sweep
5.
Cleaning up a Really Big Mess