TA Instruments RSA-G2, Manual

Page: 19 / 127

DYN AMIC MECHANICAL AN ALYSIS I TESTING MODES & APPLICATIONS
Temperature Ramps
Data Acquisition Interva
: :
These are the most common DMA experiments. Measuring the viscoelastic properties over a range of temperatures is an extremely sensitive
technique for obtaining the
a
or glass transition temperature, Tg, as well as any additional
�
or y transitions in a material. In a temperature
ramp, a linear heating rate is applied. Typical heating rates are on the order of 1 to 5°C/min. The material response is monitored at one or
multiple frequencies at an amplitude within the LVR with data taken at defined time intervals.
!
;
: !
! ! !
The figure below shows a temperature ramp on Polycarbonate run in single
cantilever. Note the data start in the glassy region and are measured into the
melt demonstrating the advantage of the RSA-G2 technology. Multiple parameters
can be used to determine transitions including E' onset point or peaks in the E" or
tan
b.
The temperature at which the transition occurs depends on the parameter
selected.
(/)
(/)
..9
108
,--..,
o
CL
Temperature Ramp on Polycarbonate
tan
b
Peak Tg: 156.8 ·C
E' Onset Tg: 148.6 ·C
E" Peak Tg: 150.6 ·C
�
:;
\J
o
E
(j)
106
C»
Q
a
Strain: 0.1 %
Heating Rate: 3 ·C/min
Single Cantilever
10-2
1 05 10-3
� 00 � 100 1� 100 1�
WO
2�
! ! ! !
! ! ! !
: : : :
Time
Because the Tg has a kinetic component. it is strongly influenced by the frequency
(rate) of deformation. As the frequency increases, the molecular relaxations can
only occur at higher temperatures and, as a consequence, the Tg will shift to a
higher temperature. An example of the frequency dependence of a glass transition
is shown below for a sample of Polyphenyl Sulfide. Note the shape and intensity of
the tan
b
peak and the slope of the storage modulus in the transition region will
be affected.
1010
Temperature Ramp on PPS at Multiple Frequencies
Frequency
-
0,5Hz
- -5,0 Hz
Strain:
0.1
%
Heating Rate: 3·e/min
Three-Point Bending
0.25
0.225
0.2
0,175
0,15
Q
::J
0, 125
On
0,1
0,075
0.05
108
0,025
�
00 � 100
1� 100 1�
�
Temperature
C
e)
Temperature
C
e)
Testing Modes and Applications
18