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首页> 外文期刊>Thermochimica Acta: An International Journal Concerned with the Broader Aspects of Thermochemistry and Its Applications to Chemical Problems >Enthalpy relaxation in the cooling/heating cycles of polypropylene/organosilica nanocomposites - I: Non-isothermal crystallization
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Enthalpy relaxation in the cooling/heating cycles of polypropylene/organosilica nanocomposites - I: Non-isothermal crystallization

机译：聚丙烯/有机硅纳米复合材料在冷却/加热循环中的焓松弛-I：非等温结晶

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摘要

Non-isothermal crystallization of the neat isotactic polypropylene homopolymer (PP-0) and of a series of nanocomposites (PNC) containing up to 4.68 vol.% of organosilica was studied in the standard DSC mode during constant-rate cooling from the melt state.Analysis of the nucleation parameters derived from cooling rate dependencies of the temperatures for the onset of crystallization exotherms revealed a slight but systematic increase of the nucleation barrier for lamellar crystallization of PP in the PNC concomitant to stronger restrictions to transport of PP segments across the melt/lamellar crystal interface. The overall crystallization rate data for the PNC were consistent with the assumption of two separate contributions from the initial (unconstrained), and the subsequent (constrained) growth mechanisms, respectively.The obtained results were considered as evidence for the coexistence in undercooled PP melts of the PNC of initial crystal nucleation and growth sites characteristic for the neat PP-0, and the basically different sites (presumably, PP chains anchored by both ends to the surfaces of two adjacent nanoparticles). (c) 2004 Elsevier B.V. All rights reserved.
机译：在标准的DSC模式下，在从熔融态开始的恒定速率冷却过程中，研究了纯全同立构聚丙烯均聚物（PP-0）和一系列纳米复合物（PNC）的非等温结晶，该纳米复合物包含高达4.68 vol。％的有机硅。对结晶放热开始时温度的冷却速率依赖性得出的成核参数的分析表明，PNC中PP的层状结晶的成核壁垒略有系统地增加，同时对PP链段跨熔体/层状晶体界面。 PNC的总体结晶速率数据与初始（不受约束）和随后（受约束）生长机制分别有两个贡献的假设相一致，获得的结果被认为是过冷PP熔体共存的证据。原始PP-0的特征在于初始晶体成核和生长位点的PNC，以及基本不同的位点（大概是PP链的两端锚定到两个相邻纳米粒子的表面）。 （c）2004 Elsevier B.V.保留所有权利。

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