纸质出版日期:2003-6-20
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应用差示扫描量热方法研究了不同表面改性碳酸钙纳米粒子对聚丙烯 (PP)等温与非等温结晶动力学的影响 ,并研究了上述各聚丙烯结晶样品的熔融行为和晶型 .研究发现纳米碳酸钙具有明显的成核效应 ,并具有较强的诱导β-型结晶的能力 ,而且与粒子的表面处理密切相关 .
Mechanical properties of polymers can be improved by incorporating nanoparticles,however,there are few works about the influence of nanoparticles on the crystallization mechanism of polymers.To develop an understanding of the important role of nanoparticles in polymer crystallization,the current paper introduced different surface modifications for calcium carbonate nanoparticles,and studied their effects on the crystallization behavior of isotactic polypropylene (iPP) by DSC measurement.The CaCO3 particles used are 40 nm in diameter,and their surfaces were treated by stearic-coating,PS-grafting,and PBA-grafting methods,respectively.The isothermal crystallization results show that the addition of both neat and modified nono-CaCO3 into PP has an obvious nucleating effect on the crystallization of iPP,resulting in lower supercooling degree,higher rate of nucleation and overall rate of crystallization,and higher crystallinity.Even through grafted PBA and PS belong to amorphous polymers,their evident nucleating effects indicate some regular structure forming on the particles surface.However,the grafted PBA exhibits different effect from PS because of its distinct molecular polarity and stiffness.On the other hand,the non-isothermaI crystallization results show that the addition of these nano-CaCO3 reduced the rate of nucleation and overall rate of crystallization of iPP,which is related with the slower formation procedure of β-form crystallites of iPP.The melting behavior and WAXD results revealed that all of these nano-CaCO3 have a strong promoting effect on the nucleation and crystallization of β-form crystallites of iPP,especially for the systems containing modified fillers,implying that this promoting effect was strongly dependent on the surface modifications of the nano-CaCO3 particles.
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