Glass Transitions by DSC, TMA and DMA

摘要

The glass transition is an important property of polymers. It has been correlated to manyrnphysical properties of the polymer, such as: impact resistance, molecular weight, ratio ofrncopolymers, and polymer identification. Traditionally, DSC has been the favored technique forrnmeasuring the glass transition. About 20 years ago, the dynamic mechanical analyzer (DMA)rnstarted to become used for measuring the glass transition of polymers. The DMA gainedrnpopularity for measuring the glass transition because it was more sensitive to the glass transitionrnof polymers with a small amount of amorphous content or large amounts of filler. DMA neverrnreplaced the DSC for this analysis for one main reason; the glass transition temperature wasrnobserved at higher temperatures than the DSC results. This shift could range from 10 to 40 Crndepending on the sample thickness, heating rate and frequency of oscillation. This paper willrnexplore the causes of this disparity between DSC and DMA. Data will be presented to show thatrnthe DMA (as well as the TMA) is capable of measuring the glass transition of polymers andrnobtaining similar results compared to the DSC.