Characterization of superheatable flow-induced polymer crystals by optical microscopy

Abstract

Crystallization from an oriented melt produces superheatable fibrous crystalline structures contained in a matrix of polymer which melts normally. A polarizing optical microscope fitted with a well-controlled heated specimen stage can detect very small amounts of superheatable oriented material, and the form and distribution of these crystals may be observed directly. The presence of even smaller amounts of organized material at high temperature may be inferred from its effect on the recrystallization of the specimen. Superheatable crystals are often produced by crystallization during flow, and sometimes unintentionally in processing. Hot-stage optical microscopy is shown to be a rapid and highly sensitive technique for detecting such structures.