Multiscale Structure and Microscopic Deformation Mechanisms of Gel-Spun Ultrahigh-Molecular-Weight Polyethylene Fibers
Multiscale Structure and Microscopic Deformation Mechanisms of Gel-Spun Ultrahigh-Molecular-Weight Polyethylene Fibers
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DOI：
10.1021/acs.macromol.9b00247
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发表时间：
2019-07-23
期刊：
影响因子：
5.5
通讯作者：
Lellinger, Dirk
中科院分区：
文献类型：
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作者：
Balzano, Luigi;Coussens, Betty;Lellinger, Dirk
我们研究了高性能凝胶纺丝超高分子量聚乙烯UHMWPE纤维（SK 75，由DSM发明和制造）的分子特征，并提出了一个多尺度结构模型，该模型描述了分子从晶胞到长丝水平的组织，基于静态和动态条件下（拉伸试验期间）的X射线衍射。该模型强调了结晶相的不连续性，它嵌入在一个膨胀的非晶相中，并通过非晶相运行的领带分子连接。连接分子在拉伸性能中起关键作用（例如，杨氏模量和声学模量）。我们分析了拉伸变形过程中材料的微观力学，并表明，在弹性状态下，应力传递机制（例如，系分子）是如此有效，以实现通过各种长度尺度（从细丝水平到晶胞水平）的均匀应力分布。细丝的塑性变形始于晶体的剪切破裂，这会触发或被一种不寻常的、尚未充分探索的斜方晶胞变形模式（a轴收缩，b轴同时膨胀）触发。我们还表明，不连续结晶相的形态模型提供了一个合理的解释超高分子量聚乙烯纤维的声波模量的基础。在材料的非结晶区域中的分子的重新排列可以解释在拉伸试验期间测量的声波模量的显著增加。
We investigate the molecular features of high-performance gel-spun ultrahigh-molecular-weight polyethylene UHMWPE fibers (SK75, invented and manufactured by DSM) and propose a multiscale structural model that describes the organization of molecules from the unit cell to the filament level, based on X-ray diffraction in static and dynamic conditions (during tensile testing). The model emphasizes the discontinuous nature of the crystalline phas e, which is embedded in a percolating amorphous phase and connected by tie molecules running through the amorphous phase. The tie molecules play a critical role in the tensile properties (e.g., Young's modulus and sonic modulus) of the material. We analyze the micromechanics of the material during tensile deformation and show that, in the elastic regime, the stress-transfer mechanisms (e.g., tie molecules) are so efficient to realize a homogeneous stress distribution through the various length scales (from filament level to unit cell level). Plastic deformation of filaments begins with shear break-up of crystals that triggers or is triggered by an unusual, not well explored, deformation mode of the orthorhombic unit cell (contraction of the a-axis with simultaneous expansion of the b-axis). We also show that the morphological model with discontinuous crystalline phase provides a logical base for the interpretation of the sonic modulus of UHMWPE fibers. Realignment of molecules in the noncrystalline regions of the material can explain the remarkable increase of the sonic modulus measured during tensile tests.