Zur Dehnungskalorimetrie einseitig verstreckter Polyäthylenterephthalat-Folien

Thermoelastic behaviour of polyethylene terephthalate on approaching the glass transition range

“…Divergence from the theoretical curves given by (4) shows that the reversible range has been left and plastic deformation has begun.…”

“…Due to the frozen state of the chains, thermal effects as known from low molecular weight solids are expected when the polymer undergoes linear reversible deformation. There are two publications dealing with thermoelastic calorimetric measurements of PETE Morbitzer et al [4] investigated the dependence of the thermoelastic values on orientation and Godovsky [5] has shown that these dates are controlled by coefficient of thermal expansion.…”

Thermophysical behaviour of solid polymers in simple elongation: A structural and molecular interpretation

“…It is a highly characteristic fact that orientation only reverses the sign of the thermal effect without affecting the overall thermoelastic behaviour. Such thermody- namic behaviour is observed in many oriented and non-oriented crystalline polymers [4,6,12,13]. Thus, notwithstanding the fact that there are amorphous regions in crystalline polymers, the thermoelastic behaviour of such polymers above the glass transition temperature of the amorphous regions is described closely enough by formulas that are valid for rigid rather than elastometric bodies.…”

“…Thus far there has been no reliable method for calculating the elasticity modulus of amorphous regions and all estimates have been, to a larger or lesser degree, based on comparison with elastomers. An example of such approach, and thus of a different point of view on the mechanism of thermoelastic behaviour of oriented crystalline polymers, are the conceptions developed by Bonart et al [13] on the basis of calorimetric measurements of the thermophysical processes accompanying deformation of PETP. They studied the effect of degree of orientation of PETP on internal energy variations under small elongation and found that highly oriented films, in contrast to non-oriented or weakly oriented ones, liberated heat during deformation which inverted U.…”

Thermodynamics of Deformation

“…The form of these functions has been confirmed several times for natural rubber by Muller (21 ), Godovskii ( 22 ) and Killian (14 ), using deformation calorimetry. (35) and proton NMR (36) (48) and Foster and Benner (49 Figure 4, for an actual heat pulse of 3 mi 1 1 ica lories . The way in which the original heat flow, Q(t), is recreated using Equation 64 and the measured gas pressure is shown schematically in Figure 5 for a square wave heating function.…”