Tetragonal → twinned hexagonal crystal phase transformation in polybutene-1
Tetragonal → twinned hexagonal crystal phase transformation in polybutene-1
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DOI：
10.1007/bf00553329
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发表时间：
1986-09
影响因子：
4.5
通讯作者：
K. W. Chau;Y. Yang;P. Geil
中科院分区：
文献类型：
--
作者：
K. W. Chau;Y. Yang;P. Geil
The spontaneous transformation of the metastable (Form II) tetragonal crystals into the stable twinned hexagonal (Form I) crystals in polybutene-1 was studied using several techniques. The mechanical properties of the heat moulded material undergo significant changes in the process and the crystalline melting point increases from 112 to 128‡ C. Results from an Avrami analysis suggest the nucleation of the stable crystalline phase occurs shortly after crystallization from the melt and the subsequent growth of the nuclei follows a rod-like geometry. Transmission electron microscopy of melt-grown thin films shows that nucleation occurs at random positions within a spherulite and growth propagates along the radially oriented fibrillar crystals. As a result of multiple nucleation, each tetragonal crystal generates several twinned hexagonal crystallites with different crystallographic orientations. Besides exhibiting multiple nucleation within each individual tetragonal crystal, solution-grown single crystals also reveal twisting of the crystal lattice about thec-axis. The information obtained shows that residual stresses present in the material do not appear essential for the nucleation of the stable phase. Current concepts of the transformation mechanism are examined.
