Specific deformation behavior of isotactic polypropylene films under a multiaxial stress field
Specific deformation behavior of isotactic polypropylene films under a multiaxial stress field
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多轴应力场下等规聚丙烯薄膜的特定变形行为
DOI：
10.1039/d2sm00147k
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发表时间：
2022
期刊：
影响因子：
3.4
通讯作者：
Atsushi Takahara
中科院分区：
文献类型：
--
作者：
Ken Kojio;Aya Fujimoto;Chigusa Nagano;Shuhei Nozaki;Kazutoshi Yokomachi;Kazutaka Kamitani;Hirohmi Watanabe;Atsushi Takahara
研究了结晶聚合物薄膜，即无取向结晶等规聚丙烯（itPP）薄膜在多轴应力场作用下的特殊变形行为。使用原位小角X-射线散射，广角X-射线衍射（WAXD）测量，和偏振高速摄像机观测的膜的聚集结构的变化进行了研究。薄膜厚度约为10 μm。将聚丙烯薄膜固定在平板的孔中，然后使用N2或He气体压力施加凸起变形，然后由所施加的压力和凸起高度计算应力-应变曲线。在应力-应变曲线中观察到屈服。在屈服点以下，原位WAXD测量显示，晶格在凸起孔的中心、边缘和底部各向同性地膨胀。在屈服点以上，中心附近开始轻微形成银纹，随着应变的进一步增加，银纹在各个方向上形成，而晶格在边缘和底部沿着圆周沿着单轴膨胀。在各个方向上取向的银纹合并并失去双折射，表明各向同性取向的变化。银纹的不同方向表明应力的几个方向。换句话说，即使将多轴变形施加到结晶性it PP膜，线状结晶性聚合物链结构也产生局部各向异性单轴应力。
The specific deformation behavior of crystalline polymer films, namely unoriented crystallized isotactic polypropylene (it PP) films, was investigated under a multiaxial stress field. Changes in the aggregation structure of the films were investigated during the bulge deformation process using in situ small-angle X-ray scattering, wide-angle X-ray diffraction (WAXD) measurements, and polarized high-speed-camera observations. The films had a thickness of approximately 10 μm. The it PP films were fixed at the hole of a plate, then bulge deformation was applied using N2 or He gas pressure, and stress–strain curves were then calculated from the applied pressure and bulge height. Yielding was observed in the stress–strain curves. Below the yield point, in situ WAXD measurements revealed that the crystal lattice expanded isotropically at the center, edge, and bottom of the bulge hole. Above the yield point, a craze started to form slightly near the center, and crazes formed in various directions with a further increase in strain, while the crystal lattice expanded uniaxially along the circumference at the edge and bottom. Crazes oriented in various directions merged and lost birefringence, indicating a change to the isotropic orientation. The different directions of the crazes indicated several directions of stress. In other words, even if multiaxial deformation is applied to a crystalline it PP film, the string-shaped crystalline polymer chain structure produces local anisotropic uniaxial stress.