Stretching temperature and direction dependency of uniaxial deformation mechanism in overstretched polyethylene
Stretching temperature and direction dependency of uniaxial deformation mechanism in overstretched polyethylene
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DOI：
10.1002/polb.23474
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发表时间：
2014-05
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通讯作者：
Lianlian Fu;Zhiyong Jiang;H. Enderle;D. Lilge;Zhonghua Wu;S. Funari;Yongfeng Men
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文献类型：
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作者：
Lianlian Fu;Zhiyong Jiang;H. Enderle;D. Lilge;Zhonghua Wu;S. Funari;Yongfeng Men
为了阐明各向同性半结晶聚合物中不同位置的微观变形行为，采用同步辐射小角X射线散射（SAXS）和广角X射线衍射（WAXD）相结合的方法，研究了预取向高密度聚乙烯样品在不同温度和沿预取向沿着不同方向拉伸变形过程中的结构演变.对于沿沿着预取向拉伸的样品，发现两种情况：（1）在30 ° C下，样品在适度变形后断裂，这是通过微纤丝的滑移实现的;（2）在80和100 ° C下，观察到原始层状结构的断裂，随后是重结晶过程，导致取决于拉伸温度的不同厚度的新层状晶体。对于垂直于预取向或相对于预取向成45度拉伸的样品，样品总是以新的取向层状结构结束，其法线沿着拉伸方向通过应力诱导的碎裂和再结晶途径。在这种情况下，最终获得的薄片的厚度仅取决于拉伸温度。与沿预取向方向沿着拉伸的样品相比，垂直于预取向方向并相对于预取向方向成45度拉伸的样品在宏观失效之前显示出至少数倍的最大可实现应力，这可能是由于这些片层堆叠中的微缺陷的有利发生和发展，其法线平行于拉伸方向。这一结果可能对设计最佳工艺以从固态生产高性能聚乙烯产品具有重要意义。(c)2014 Wiley Periodicals，Inc. J.波利姆科学，部分B：聚合物2014，52，716-726
In order to elucidate microscopic deformation behavior at different locations in isotropic semicrystalline polymers, the structural evolution of a preoriented high-density polyethylene sample during tensile deformation at different temperatures and along different directions with respect to the preorientation was investigated by means of combined in situ synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. For samples stretched along preorientation, two situations were found: (1) at 30 degrees C, the sample broke after a moderate deformation, which is accomplished by the slippage of the microfibrils; (2) at 80 and 100 degrees C, fragmentation of original lamellae followed by recrystallization process was observed resulting in new lamellar crystals of different thickness depending on stretching temperature. For samples stretched perpendicular or 45 degrees with respect to the preorientation, the samples always end up with a new oriented lamellar structure with the normal along the stretching direction via a stress-induced fragmentation and recrystallization route. The thickness of the final achieved lamellae depends only on stretching temperature in this case. Compared to samples stretched along the preorientation direction, samples stretched perpendicular and 45 degrees with respect to the preorientation direction showed at least several times of maxima achievable stress before macroscopic failure possibly due to the favorable occurrence and development of microdefects in those lamellar stacks with their normal parallel to the stretching direction. This result might have significant consequence in designing optimal procedure to produce high performance polyethylene products from solid state. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 716-726