Loss modulus vs. temperature

Fig. 20. Logarithmic decrement (related to tan 5 and loss modulus) vs temperature for a fluorocarbon dibenzoxazole (148). After drying up to 200°C, the...

TDI Polyurethanes. Two 2,4-T-lP samples with different hard-segment concentrations were studied and found to display a broad a-relaxation maximum, also characterized by a decline in storage modulus of about two and one half orders of magnitude, as shown in Figure 5, a plot of storage and loss modulus vs. temperature at 11 Hz. The position... 

The dynamic mechanical properties of four 2,6-T-2P samples containing from 19 to 43 wt% hard segments are summarized in Figure 10. A low temperature s relaxation is apparent at about — 70°C for all compositions examined. The transition temperatures of these loss maxima and the associated activation energies are given in Table III. A second process, the c relaxation, can be noted as a shoulder on the high temperature side of the 8-loss maximum. The conclusion of this relaxation is marked by a change in slope of the loss modulus vs. temperature plots... 

An additional relaxation can be detected in plots of the loss tangent as a function of temperature for 2,6-T-2P-43, not shown. The relaxation occurred at 60°C (11 Hz) in the first examination of this sample. A weak ah relaxation can be detected in the loss modulus vs. temperature plots in Figure 13, but the process is more readily apparent in the tan(8) data. Upon retesting of this sample, the h dispersion was shifted to 71 °C. The activation energy for the ah relaxation did not change significantly with thermal history and was extremely weak or undetectable in 2,6-T-2P samples which contained less than 43 wt% hard segments. 

The glass transition temperature, T, was also determined for some of the test materials. Values given in this paper are somewhat higher than reported literature values as they were obtained from the temperature location of the principal maximum in the loss modulus vs. temperature data from tests made at 3 Hz. 

This approach is limited, however, to data obtained within the temperature range where the chosen type of function is applicable. A wider range is possible using empirical shift factors as done in this work. Figure 9 depicts the algorithm employed to transform resonant (varying frequency) loss modulus vs temperature curves into calculated constant... 

Figure 8.33 Elastic and loss modulus vs. temperature for ExxonMobil Santoprene ...

Figure 7.61 (a) Storage modulus E and tan a vs. temperature and (b) loss modulus " vs temperature curves for polypropylene and its composite containing wollastonite [47].---, PP 1330 ., composite... 

Pig. 17. L< arithmic decrement (related to tan S and loss modulus) vs temperature for a fluorocarbon dibenzoxazole (174). After drying up to 200°C, the experiment was conducted at 200 —180 200°C AT/At = 1.5°C/min in a helium atmosphere. The Tg gives a sharp damping peak, whereas the secondary glassy state transitions, Tsec, are very broad. 

Figure 23.16. Loss modulus vs. temperature curves of pure LLDPE, LHl and LH5 obtained by DMA measure...

Fig. 18 (a) Storage modulus vs. temperature, (b) loss modulus vs. temperature (c) tan 5 vs. temperature. Traces of NR vulcanizates filled with 75 % Psi weight fraction in FASi/PSi hybrid filler (reproduced with permission of Elsevier,... 

The areas under the loss modulus vs. temperature plots for the various homopolymers could be used to predict the areas for the corresponding IPN s. An additive equation was written... 

Figure 11 Additivity of loss modulus vs. temperature areas. The loss area, L.A.y is shown to be a simple additive function for a number of acrylic/methacrylic sequential IPN s. The x axis was determined from the individual homopolymer loss modulus...

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