二维X射线衍射光谱原位检测单轴拉伸过程中等规聚丙烯晶体的结构演变  

In Situ Detection of Structural Evolution of Isotropic PolypropyleneCrystals During Uniaxial Stretching by Two-Dimensional X-RayDiffraction Spectroscopy

作　　者：徐明锟 林嘉翔 张效琳 李贞印 王亚明[1] 刘春太[1] 申长雨[1] 邵春光[1] XU Ming-kun;LIN Jia-xiang;ZHANG Xiao-lin;LI Zhen-yin;WANG Ya-ming;LIU Chun-tai;SHEN Chang-yu;SHAO Chun-guang(Key Laboratory of Materials Processing and Mold,Ministry of Education,National Engineering Research Center for Advanced Polymer Processing Technology,Zhengzhou University,Zhengzhou 450001,China)

机构地区：[1]郑州大学材料成型及模具技术教育部重点实验室,橡塑模具国家工程研究中心,河南郑州450001

出　　处：《光谱学与光谱分析》2023年第5期1426-1433,共8页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(51573171,52273027)资助。

摘　　要：聚合物制品在使用过程中,人们最关心的是它的使用失效条件,失效的重要体现就是材料的屈服。目前为止,人们普遍利用位错理论来解释聚合物材料的屈服现象,该理论关注的是晶体的取向和破坏现象,而忽略了晶体的形变和受力情况。事实上,晶体的取向和破坏只是屈服的结果,晶体承受应力的能力才是屈服的直接原因。因此,从晶体的受力和非均匀形变入手研究了聚合物制品的屈服行为,期望为理解聚合物材料的失效行为提供新思路。这里选取被人们广泛使用的等规聚丙烯(iPP)材料作为研究对象,将iPP熔体在不同温度下等温结晶制备出具有不同片晶厚度iPP样品,利用二维广角X射线衍射光谱原位监测了拉伸过程中iPP样品的晶体破坏和晶体取向过程。首次利用“覆盖法”对二维X射线衍射图进行了处理,原位观察了(110)晶面在拉伸过程中的2θ角的变化,区分出了两个方向上(平行于拉伸方向和垂直于拉伸方向)晶体形变的非均一性。结果表明:对于不同片晶厚度的iPP晶体,在单轴拉伸过程中,晶体在不同方向上的受力和形变均是不同的,即晶体的非均一形变是一种普遍现象;晶体的破坏和取向总是同时发生,都是从屈服点位置处开始,这和片晶厚度无关;而晶体破坏时对应的临界应力和晶体厚度有关,片晶越厚,晶体越稳定,需要的临界应力就越大。以上结果表明,原位X射线衍射光谱技术可以实时观测晶体结构在拉伸过程中的变化情况,从而将晶体结构演化和宏观力学性能直接关联。In using polymer products,people are most concerned about their failure conditions,and the important manifestation of failure is the yield of the material.So far,the dislocation theory has been widely used to explain the yielding phenomenon of polymer materials.This theory usually focuses on the crystal orientation and destruction while ignoring the crystal deformation and the stress acting on the crystal.The orientation and destruction of the crystal are only the results of the yielding,and the ability of the crystal to withstand stress is the direct cause of yielding.Therefore,this paper will start from the stress and inhomogeneous deformation of crystals to study the yielding behavior of polymer products,hoping to provide new ideas for understanding the failure behavior of polymer materials.Here,the widely used isotactic polypropylene(iPP)material is selected as the research object,and iPP samples with different lamellar thicknesses are prepared by isothermal crystallization of iPP melt at different temperatures.Two-dimensional wide-angle X-ray diffraction spectroscopy was used to monitor in situ the crystal destruction and crystal orientation processes of the iPP samples during stretching.The“covering method”was used to process the two-dimensional X-ray diffraction patterns for the first time,the change of the 2θangle of the(110)crystal planes during the stretching process was observed in situ,and the deformation of the crystal in two directions(parallel to the stretching direction and perpendicular to the stretching direction)was distinguished.The results show that for iPP crystals with different lamellar thicknesses,the inhomogeneous deformation of the crystals during the uniaxial stretching process is a common phenomenon;the destruction and orientation of the crystals always occur at the same time,starting from the yield point,which is independent of the lamella thickness;the critical stress corresponding to the crystal destruction is related to the thickness of the crystal.The thicker the lamellae an

关 键 词：二维广角X射线衍射光谱 等规聚丙烯 原位检测 单轴拉伸 晶体形变 

分 类 号：O657.3[理学—分析化学]