In situ WAXD study of structure changes during uniaxial deformation of ethylene-based semicrystalline ethylene-propylene copolymer
In situ WAXD study of structure changes during uniaxial deformation of ethylene-based semicrystalline ethylene-propylene copolymer
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DOI：
10.1016/j.polymer.2006.01.090
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发表时间：
2006-04
期刊：
影响因子：
4.6
通讯作者：
Lizhi Liu;B. Hsiao;S. Ran;B. Fu;S. Toki;F. Zuo;A. Tsou;B. Chu
中科院分区：
文献类型：
--
作者：
Lizhi Liu;B. Hsiao;S. Ran;B. Fu;S. Toki;F. Zuo;A. Tsou;B. Chu
用同步辐射广角x射线衍射（WAXD）研究了含78wt%（或85mol%）乙烯片段的乙烯-丙烯共聚物在单轴变形过程中原位应变诱导的结构变化。根据退火条件的不同，所选择的样品可以结晶成正交、伪六边形或混合形式。在高温（如50℃）下结晶有利于形成正方晶型，而在低温（如20℃）下结晶有利于形成伪六方晶型。变形时，在相对较低的应变（如0.12）下，观察到从正交型到伪六边形的转变。在较高应变下，WAXD数据表明，在应变<0.25时发生方向依赖性晶体破坏，随后在高应变（>1.0）下发生扩展链构象的再结晶，全部为伪六边形。在室温下，非晶态乙烯-丙烯片段的高迁移率导致了中等应变下晶体结构（正方晶向伪六方晶转变）和相变（晶体破坏和再结晶）的剧烈变化。
In situ strain-induced structure changes during uniaxial deformation of an ethylene–propylene copolymer, containing 78wt% (or 85mol%) of ethylene moiety, were studied by synchrotron wide-angle X-ray diffraction (WAXD). The chosen sample could crystallize into orthorhombic, pseudo hexagonal or a mixed form, depending on the annealing conditions. Crystallization at high temperatures (e.g. 50°C) favored the formation of orthorhombic form, while crystallization at low temperatures (e.g. 20°C) favored the formation of pseudo hexagonal form. Under deformation, the transition from orthorhombic to pseudo hexagonal form was observed at relatively low strains (e.g. 0.12). At higher strains, WAXD data indicated the occurrence of direction-dependent crystal destruction at strains <0.25 and subsequent re-crystallization with extended-chain conformation at high strains (>1.0) all of the pseudo hexagonal form. The drastic changes in the crystalline structures (orthorhombic to pseudo hexagonal) and phase transitions (crystal destruction and re-crystallization) at modest strains can be attributed to the high mobility of the amorphous ethylene–propylene segments at room temperature.