Effects of cooling rates on crystallization behavior and melting characteristics of isotactic polypropylene as neat and in the TPVs EPDM/PP and EOC/PP

Non-isothermal crystallization behavior and melting characteristics of polypropylene (PP) in EPDM/PP and EOC/PP TPVs were studied at various cooling rates using differential scanning calorimetry (DSC). The results revealed that the crystallization of PP in the TPVs occurs at a lower degree of undercooling, relative to neat PP, with smaller size PP crystals. The vulcanized EPDM and EOC particles could accelerate the crystallization of the PP phase either by providing nucleation or by promoting interfacial crystallization. The crystallization exotherm and melting endotherm peaks of the TPVs were broad, and they shifted towards lower temperatures as the cooling rate was increased. The analysis of non-isothermal crystallization kinetics indicates that the crystallization of the PP in the TPVs is heterogeneous nucleation, with two or three-dimensional growth during primary and secondary crystallization. Furthermore, the vulcanized EPDM and EOC particles promote the initial crystallization activation energy of the PP in TPVs to exceed that of the neat PP. The developed mathematical models show an approximately power-law dependence on the cooling rate for the crystallization behavior and the melting characteristics of PP in the TPVs.