A comparison study on the melt crystallization kinetics of long chain branched and linear isotactic polypropylenes |
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Authors: | Wei Zeng JiChun Liu JunFeng Zhou JinYong Dong ShouKe Yan |
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Institution: | [1]Beijing National Laboratory for Molecular Sciences, and Joint Laboratory of Polymer Science and Materials, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China [2]State Key Laboratory of Polymer Physics and Chemistry and Key Laboratory of Engineering Plastics, Chinese Academy of Sciences, Beijing 100080, China [3]Key Laboratory of Polymer Science and Nanotechnology, College of Chemical Engineering and Pharmaceutics, Henan University of Science and Technology, Luoyang 471003, China |
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Abstract: | The isothermal and non-isothermal crystallization kinetics of LCBPP and linear-iPP was investigated by optical microscopy and differential scanning calorimetry (DSC). The optical microscopy results in the isothermal crystallization process show that the crystals of LCBPP grow slower than the crystals of the linear-iPP. This originates from the low chain mobility, or in other words, the lower chain diffusion rate of LCBPP due to the existence of long side chains. The DSC results in the isothermal crystallization process show that the LCBPP exhibits, however, a higher overall crystallization rate with respect to the linear-iPP. This is related to the higher nucleation ability of LCBPP since the isothermal crystallization process of both LCBPP and linear-iPP are nucleation-dominated. Avrami analysis indicates that the nucleation nature and crystal growth manner of LCBPP and linear-iPP are about the same. The analy- ses of the non-isothermal crystallization processes indicate an increment in crystallization rate with increasing cooling rate. But at any cooling rate, the linear-iPP crystallizes more quickly than the LCBPP. This implies that the non-isothermal crystallization processes of LCBPP and linear-iPP are diffu- sion-dominated, in which the lower chain diffusion rate of LCBPP results in the slower crystallization of it. |
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Keywords: | long chain branched polypropylene linear isotactic polypropylene crystallization kinetics |
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