AbstractMany papers have reported on the thermal shrinkage mechanism of drawn polymers. The cause of the thermal shrinkage is very complex, because that relates to many factors. In this study, atactic polystyrene, a noncrystalline polymer, was used to eliminate factors related to the melting and crystallization effects, and it is considered that there is a relation between the change of the polymer's structure due to heat treatment and thermal shrinkage. It is observed in a certain temperature range that the thermal shrinkage of drawn polystyrene is not caused by increase of the entropy but results in decrease of the entropy.
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