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Stretching‐induced β‐crystal of iPP: Influence of stretching ratio
Author(s) -
Shen ChangYu,
Zhou YingGuo,
Zheng GuoQiang,
Liu ChunTai,
Chen JingBo,
Li Qian
Publication year - 2008
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.21202
Subject(s) - crystal (programming language) , materials science , composite material , mass fraction , crystal structure , fraction (chemistry) , crystallography , crystal growth , chemistry , organic chemistry , computer science , programming language
The iPP sheet is extruded through a slit die, in which the extruding rate is set small enough to eliminate the shear stress as much as possible. Simultaneously, the extruded sheets were stretched with different stretching ratios (SR). With SR increasing from 1 to 6.67, fraction of β‐crystal increases dramatically from 1.5 to 13%, which indicates that SR is favorable to the occurrence of β‐crystal. However, as SR further increases, it gradually decreases to 0, which reveals that SR can steadily restrain the formation of β‐crystal. As the thickness of the sheets decreases with the increase of SR, higher cooling rate occurs for the sheets extruded at larger SR. When SR is in the range of 1–6.67, the cooling rate might probably fix the oriented chains and provide a proper thermal environment for subsequent growth of β‐crystal, thereby, fraction of β‐crystal increases. Growth of β‐crystal could be restricted by higher cooling rate, which leads to the gradual decrease of β‐crystal fraction with the further increase of SR. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers