Structural evolution of β – iPP during uniaxial stretching studied by in–situ WAXS and SAXS
Structural evolution of β – iPP during uniaxial stretching studied by in–situ WAXS and SAXS
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DOI：
10.1016/j.polymer.2014.10.049
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发表时间：
2014-12
期刊：
影响因子：
4.6
通讯作者：
Chunbo Zhang;Guoming Liu;Yan Song;Ying Zhao;Dujing Wang
中科院分区：
文献类型：
--
作者：
Chunbo Zhang;Guoming Liu;Yan Song;Ying Zhao;Dujing Wang
多晶型和晶型转变对高分子材料的性能调节具有重要意义。β晶型等规聚丙烯（iPP）是一种广泛应用于制备高性能塑料或薄膜的材料。利用同步辐射原位X射线散射技术研究了初始各向同性β-成核聚丙烯（β- iPP）在不同温度下单轴拉伸过程中的结构演化。广角X射线散射（WAXS）结果证实，在拉伸过程中，β晶在较低温度（30 °C）下转变为中间相，在较高温度（60、100和120 °C）下转变为α晶。发现分子链垂直于拉伸方向的β晶体有一个有趣的取向。小角X射线散射（SAXS）结果表明，在低于120 °C的拉伸温度下，β- iPP发生了空化现象.用扫描电镜观察空洞的大小和形状。提出了β- iPP的结晶转变、空穴化和取向相结合的变形机制。
Polymorphism and crystal transition are of great significance for property mediation in polymer materials. Isotactic polypropylene (iPP) withβ– crystal has been widely utilized for the preparation of high performance plastics or films. In the present work, the structural evolution of initially isotropicβ– nucleated iPP (β– iPP) during uniaxial stretching at different temperatures was investigated byin–situX – ray scattering using synchrotron radiation. The wide – angle X – ray scattering (WAXS) results confirmed that theβ– crystal transformed either to the mesophase at lower temperature (30 °C) or to theα– crystal at higher temperature (60, 100 and 120 °C) during stretching. An interesting orientation ofβ– crystal with molecular chains perpendicular to the tensile direction was identified. As revealed by small – angle X – ray scattering (SAXS), cavitation took place inβ– iPP stretched at temperatures lower than 120 °C. The size and shape of the cavities were observed by scanning electron microscope. A deformation mechanism ofβ– iPP combining the crystal transition, cavitation and orientation was proposed.