Thermal stresses Stress reduction methods

The delivery of heat into the material prior to its entering the die is accomplished via Radio Frequency (RF) preheating, induction heating or by conventional conductive heating of the resin. Desirable characteristics such as increased process rates and the reduction of thermal stresses induced by gradient of temperature and less content of voids can be achieved by the heating methods listed over more conventional approaches (8). 

The dynamic mechanical thermal analyzer (DMTA) is an important tool for studying the structure-property relationships in polymer nanocomposites. DMTA essentially probes the relaxations in polymers, thereby providing a method to understand the mechanical behavior and the molecular structure of these materials under various conditions of stress and temperature. The dynamics of polymer chain relaxation or molecular mobility of polymer main chains and side chains is one of the factors that determine the viscoelastic properties of polymeric macromolecules. The temperature dependence of molecular mobility is characterized by different transitions in which a certain mode of chain motion occurs. A reduction of the tan 8 peak height, a shift of the peak position to higher temperatures, an extra hump or peak in the tan 8 curve above the glass transition temperature (Tg), and a relatively high value of the storage modulus often are reported in support of the dispersion process of the layered silicate. 

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