Property modeling across transition temperatures in polymers: a robust stiffness–temperature model

The variation of stiffness with temperature in polymers is widely discussed in the literature. Previous studies have been concerned with the effects of temperature for highly specific materials and for limited ranges of temperature. Representations or predictions of stiffness variations for wide classes of polymers (thermosets, thermoplastics, amorphous, semi-crystalline, filled, unfilled, linear, crosslinked, etc.) and over wide ranges of temperature (from fully glassy to fully rubbery) have not been established. However, modern engineering design tools, especially those based on virtual design environments, require robust property models that apply over the entire range of temperatures that extend far below and substantially above the Tg of the matrix. The present paper addresses that need. The influence of temperature on secondary bonding in polymers is the basis of the approach. Weibull statistics are used to represent the failure of secondary bonds during the relaxation processes that lead to stiffness change over the full range of use temperatures. The feasibility of the approach was illustrated by applying the model to experimental data chosen at random from the literature. The behavior of six polymers of very different nature was successfully described.