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首页> 外文期刊>Journal of Applied Polymer Science >Melt fracture behavior of polypropylene-type resins with narrow molecular weight distribution. 1. Temperature dependence
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Melt fracture behavior of polypropylene-type resins with narrow molecular weight distribution. 1. Temperature dependence

机译：窄分子量分布的聚丙烯类树脂的熔体断裂行为。 1.温度依赖性

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摘要

Polypropylene (PP)-type resins with narrow molecular weight distribution, such as PP-type thermoplastic elastomer PER and controlled-rheology PP (CRPP) made by peroxide degradation of high molecular weight PP, have a problem of easy generation of skin roughness at extrusion. To examine the present state, the occurrence of skin roughness in PER and CRPP at extrusion was investigated with a capillary rheometer in a shear rate range of 12-6100 s(-1) and a temperature range of 180-280degreesC. A homo-PP (HPP) and a block-PP (BPP) with usual molecular weight distributions were used for comparison. HPP and BPP with usual molecular weight distributions show smooth extrudates at low shear rates and abruptly generate severe skin roughness "elastic failure" originating at the die entrance at a higher shear rate. PER and CRPP with narrow molecular weight distributions easily generate "sharkskin" melt fracture originating at the die exit, from a shear rate nearly one decade lower than rates of elastic failure of HPP and BPP. The sharkskin becomes more severe, with increasing shear rate, and attains to the elastic failure. The critical shear rate at which sharkskin occurs increases with increasing extrusion temperature. The critical shear rate is about 20 s(-1) at 180degreesC and about 120 s(-1) at 280degreesC, which is in the range encountered by the molten resin at extrusion processing. (C) 2002 Wiley Periodicals, Inc. [References: 29]
机译：分子量分布窄的聚丙烯（PP）型树脂，例如通过高分子量PP的过​​氧化物降解制成的PP型热塑性弹性体PER和流变学控制的PP（CRPP），存在在挤出时容易产生皮肤粗糙的问题。 。为了检查当前状态，使用毛细管流变仪在12-6100 s（-1）的剪切速率范围和180-280℃的温度范围内研究了挤出时PER和CRPP中皮肤粗糙的发生。比较具有通常分子量分布的均聚PP（HPP）和嵌段PP（BPP）。具有通常分子量分布的HPP和BPP在低剪切速率下显示出光滑的挤出物，并以较高的剪切速率突然在模具入口处产生严重的表皮粗糙度“弹性破坏”。具有窄分子量分布的PER和CRPP的剪切速率比HPP和BPP的弹性破坏速率低近十倍，因此很容易在模头出口产生“鲨皮”熔体破裂。随着剪切速率的增加，鲨鱼皮变得更严重，并达到弹性破坏。鲨鱼皮的临界剪切速率随挤出温度的升高而增加。临界剪切速率在180摄氏度时约为20 s（-1），在280摄氏度时约为120 s（-1），处于熔融树脂在挤出加工过程中遇到的范围内。 （C）2002 Wiley Periodicals，Inc. [参考：29]

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