The time dependence of melting of morphologically different crystals of polyethylene was investigated. New DTA and calorimeter techniques were developed. A microscope hot stage allowing heating rates of up to 3000°C/min was built for melting-point determinations. The superheating of extended-chain crystals was clearly demonstrated by qualitative DTA and isothermal quantitative calorimetry. Smaller crystals and folded-chain crystals showed decreasingly less superheating. Crystals which are less perfect and have large surfaces show increasing reorganization. A region of approximately zero entropy production melting seems to lie between reorganization at slow heating rates and superheating at faster heating rates.
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Hellmuth et al. (1965) studied this question.