Abstract Processing isotactic polypropylene (iPP) from cast film into biaxially oriented polypropylene (BOPP) involves plastic drawing of a semi-crystalline morphology in the melting range of iPP, where the crystal phase is reduced and the polymer has high mobility. The literature claims that plastic drawing in general and at elevated temperatures in particular depends predominantly on the structure of the amorphous entanglement network. We investigated this aspect using laboratory-scale biaxial drawing experiments. Three iPP homopolymer types differing in chain isotacticity and molecular weight distribution were extruded into 200-μm-thick primary sheets using 10 different extrusion settings. The sheets were biaxially drawn on a laboratory stretcher at 157°C and 160°C, recording the respective stress-strain curves. These curves were evaluated according to a rubber elasticity model to obtain the network modulus, G N, of the entanglement network. The effects of iPP type, the extrusion parameters, the resulting cast film properties, and the draw temperature on G N are discussed.

中文翻译：

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双轴拉伸聚丙烯 (BOPP) 工艺中的塑料拉伸响应：聚合物结构和薄膜流延效应

摘要 将全同立构聚丙烯 (iPP) 从流延膜加工成双轴拉伸聚丙烯 (BOPP) 涉及在 iPP 熔融范围内对半结晶形态进行塑性拉伸，其中晶相减少且聚合物具有高流动性。文献声称塑料拉伸通常和特别是在升高的温度下主要取决于无定形缠结网络的结构。我们使用实验室规模的双轴拉伸实验研究了这方面。使用 10 种不同的挤出设置，将三种在链全同立构规整和分子量分布上不同的 iPP 均聚物挤出成 200 微米厚的初级片材。将片材在实验室拉伸机上在 157°C 和 160°C 下双轴拉伸，记录各自的应力-应变曲线。根据橡胶弹性模型评估这些曲线以获得缠结网络的网络模量GN。讨论了 iPP 类型、挤出参数、所得流延膜性能和拉伸温度对 GN 的影响。