Ultrahigh molecular weight polyethylene (UHMWPE) is one of the most promising polyolefins, but its processability and consequently applications are limited by its high melt viscosity. An effective method to improve the processability is to introduce another polymer component. Yet it is challenging to deform the sample if the components are not compatible with each other. In this work, we blended the UHMWPE with isotactic polypropylene (iPP) and successfully processed the iPP/UHMWPE samples via die-drawing at temperatures below, near, and above the melting temperature of UHMWPE. It was found that the melting behavior of the die-drawn samples was determined by the deformation temperature. The molecular chain orientation slightly decreased, while the long periods first increased and then decreased with increasing deformation temperature. Three melting peaks observed in the samples deformed at 130 and 140 °C originated from the melting of cooling-induced UHMWPE crystallites, deformation-induced fibrillar UHMWPE crystallites, and deformation-induced fibrillar iPP crystallites, respectively. The melting peak of deformation-induced fibrillar UHMWPE crystallites could not be observed in the sample deformed at 150 °C because it is unlikely for UHMWPE chains to crystallize at such a high temperature. This sample also has the lowest melting point since the UHMWPE lamellae formed during deformation could serve as nucleation sites in the other two samples.

中文翻译：

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模拉 iPP/UHMWPE 共混物中微观结构演变的变形温度依赖性


超高分子量聚乙烯（UHMWPE）是最有前途的聚烯烃之一，但其加工性能和应用受到其高熔体粘度的限制。提高加工性能的有效方法是引入另一种聚合物组分。然而，如果组件彼此不兼容，则使样品变形是一项挑战。在这项工作中，我们将 UHMWPE 与等规聚丙烯 (iPP) 共混，并在低于、接近和高于 UHMWPE 熔融温度的温度下通过模拉伸成功加工 iPP/UHMWPE 样品。结果发现，模拉样品的熔化行为由变形温度决定。随着变形温度的升高，分子链取向略有下降，而长周期先增加后减少。在 130 和 140 °C 变形的样品中观察到的三个熔融峰分别源自冷却诱导的 UHMWPE 微晶、变形诱导的纤维状 UHMWPE 微晶和变形诱导的纤维状 iPP 微晶的熔融。在 150 °C 变形的样品中无法观察到变形引起的原纤维状 UHMWPE 微晶的熔融峰，因为 UHMWPE 链在如此高的温度下不太可能结晶。该样品还具有最低的熔点，因为变形过程中形成的 UHMWPE 片层可以充当其他两个样品中的成核位点。