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首页> 外文期刊>Journal of Applied Polymer Science >Effects of Molecular Weight and Componomer Content on the Optical Clarity of Crystallized Syndiotactic Polystyrene Sheets
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Effects of Molecular Weight and Componomer Content on the Optical Clarity of Crystallized Syndiotactic Polystyrene Sheets

机译：分子量和共聚单体含量对结晶间规聚苯乙烯片的光学清晰度的影响

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摘要

Clear and high-crystallinity sheets can be prepared consitently from syndiotactic polystyrene (sPS) simply by annealing amorphous sPS sheets at a temperature ranging from 150 to 180deg C. The combination fo its high clarity and high crystal-linity makes sPS sheet suitable for many food/medical packaging applications. A series of sPS polymers with various molecular weight and para-methylstyrene (PMS) comonomer content were used in this study for gaining a mechanistic understanding of the cause for this unusual coexistence of high crystallinity and high clarity. Results show that high molecular weight is preferred for high sheet clarity. The effect of the comonomer content, however, ismore complicated; instead of a monotone response to % PMS, the sheet clarity was found to peak at 4% PMS. Amechanism based on the regime growth theory of crystallization was used to interpret successfully the above behavior. Briefly, increasing molecular weight reduces the crystal growth rate and thus shifts the growth pattern to regime III, resulting in more clear sheet. Increasing % PMS reduces both the nucleation and crystal growth rates and thus shifts the grwoth pattern to either regime I (lower clarity) or III (higher clarity) as controlled by teh relative magnitude of the two rate reductions.
机译：只需在150至180摄氏度的温度范围内对无定形sPS片材进行退火，即可简单地从间同聚苯乙烯（sPS）制备出透明且高结晶度的片材。由于其高清晰度和高结晶度的组合，使得sPS片材适用于许多食品/医疗包装应用。在这项研究中，使用了一系列具有各种分子量和对甲基苯乙烯（PMS）共聚单体含量的sPS聚合物，以机械方式了解这种异常的高结晶度和高清晰度共存的原因。结果表明，高分子量对于高片材清晰度是优选的。但是，共聚单体含量的影响更为复杂。发现纸页清晰度在4％PMS时达到峰值，而不是对％PMS的单调响应。基于结晶态增长理论的机理被成功地解释了上述行为。简而言之，增加分子量会降低晶体的生长速率，从而将生长模式转变为方案III，从而获得更透明的薄片。 PMS的增加％会同时降低成核速率和晶体生长速率，因此，由两种速率降低的相对幅度所控制，常规模式会转变为方案I（较低的透明度）或III（较高的透明度）。

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