Multiaxial Reinforcement of Cross-Linked Isotactic Poly(propylene) upon Uniaxial Stretching
Multiaxial Reinforcement of Cross-Linked Isotactic Poly(propylene) upon Uniaxial Stretching
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DOI：
10.1002/mame.201600308
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发表时间：
2017
影响因子：
3.9
通讯作者：
Thomas Raidt;Robin Hoeher;F. Katzenberg;J. C. Tiller
中科院分区：
文献类型：
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作者：
Thomas Raidt;Robin Hoeher;F. Katzenberg;J. C. Tiller
等规聚丙烯（iPP）是少数具有同外延特性的聚合物之一，即形成的晶体充当所谓子晶体的核，子晶体的形成几乎垂直于原生结晶母晶体的主干。轻交联等规聚丙烯（x-iPP）提供了在拉伸方向上形成几乎所有母晶的机会，同时允许形成子晶。由于聚合物中的晶体沿链方向起强化作用，这种独特的行为允许iPP中仅通过一个方向的拉伸诱导的多轴强化。本研究探讨了施加单轴应变对所得到的多轴晶体取向和杨氏模量平行、垂直以及与试样拉伸方向成45°角的影响。结果表明，结晶过程中出现的多轴取向强烈依赖于外加应变，使平行于拉伸方向和垂直于拉伸方向的杨氏模量显著提高，而45°角下的杨氏模量略有下降。本文描述的获得多轴取向形貌的技术不仅限于薄膜，而且可以有效地应用于大块样品。
Isotactic poly(propylene) (iPP) is one of a few polymers that show homoepitaxy, i.e., the formed crystals act as nuclei for so-called daughter crystals that are formed nearly perpendicular to the backbones of the primary crystallized mother crystals. Lightly cross-linked isotactic poly(propylene) (x-iPP) offers the opportunity to form nearly all mother crystals in stretching direction and simultaneously allow formation of daughter crystals. Since crystals in polymers act as reinforcement along chain direction, this unique behavior allows multiaxial reinforcement in iPP induced only by stretching in one direction. In this study the influence of applied uniaxial strain is explored on the resulting multiaxial crystal orientations and Young's moduli parallel, perpendicular as well as under an angle of 45° to the stretching direction of the sample. It is shown that the occurring multiaxial orientations strongly depend on applied strain during crystallization and cause significantly improved Young's moduli parallel as well as perpendicular to the prior stretching direction while that under an angle of 45° is slightly decreasing. The here described technique to obtain multiaxially oriented morphologies is not restricted to thin films but can be efficiently applied also to bulk samples.