A new method for monitoring rather than controling thermal history has been applied recently to analyze the crystallization kinetics at high cooling rate of a highly pure isotactic polypropylene, proving that the cooling history relevant to the structure of quenched samples is in the neighborhood of 90°C. A continuous variation of morphology and crystal structure was obtained with cooling rate. At cooling rates above 20°C/s, mesomorphic and α-monoclinic phases coexist with a morphology characterized by negatively birefringent spherulites surrounded by a weakly birefringent medium; below this value of cooling rate only α-monoclinic phase is formed, composed of mixed spherulites.
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Stefano Piccarolo (1992) studied this question.
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