The increment of heat capacity at the glass transition for semi-crystalline poly(ethylene terephthalate) (PET) observed by
temperature-modulated differential scanning calorimetry (TMDSC) shows significant deviations from a simple crystalline/amorphous
two-phase model. Introduction of a rigid amorphous fraction, which is non-crystalline but which also does not participate
in the normal glass transition, allows a much better description of the transition behaviour in semi-crystalline PET. Certain
questions arise such as what is the rigid amorphous fraction and over what temperature range do these rigid amorphous segments
devitrify? These TMDSC results show that the rigid amorphous component may be treated as an interphase between amorphous and
crystalline phases. This interphase does not exhibit a separate glass transition temperature at temperatures above the normal
Tg. The suggestion is made that the glass transition of the rigid amorphous component occurs continually between the glass transition
temperature of the amorphous phase and up to about 135C for this particular sample of PET.
Authors:M. Song, D. Hourston, M. Reading, H. Pollock, and A. Hammiche
A modulated-temperature differential scanning calorimetry (M-TDSC) method for the analysis of interphases in multi-component
polymer materials has been developed further. As examples, interphases in a polybutadiene-natural rubber (50:50 by mass) blend,
a poly(methyl methacrylate)-poly(vinyl acetate) (50:50 by mass) structured latex film, a polyepichlorohydrinpoly(vinyl acetate)
bilayer film, and polystyrene-polyurethane (40:60 by mass) and poly(ethyl methacrylate)-polyurethane (60:40 by mass) interpenetrating
polymer networks were investigated. The mass fraction of interphase and its composition can be calculated quantitatively.
These interphases do not exhibit clear separate glass transition temperatures, but occur continually between the glass transition
temperatures of the constituent polymers.
Authors:D. Hourston, M. Song, H. Pollock, and A. Hammiche
Modulated-temperature differential scanning calorimetry was used to measure the glass transition temperature,Tg, the heat capacity relaxation in the glassy state and the increment of heat capacity, δCp, in the glass transition region for several polymers. The differential of heat capacity with respect to temperature was used
to analyseTg and δCp simply and accurately. These measurements are not affected by complex thermal histories.