Critical role of depressurization and effects of saturation conditions in the formation of β-Crystal during isotactic polypropylene foaming with supercritical CO2

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• 作者：XianWu Cao ; YaHui Qiao ; YiXin Chen ; GuangJian He and Hong Lin
• 刊名：Polymer Engineering & Science
• 出版年：2016
• 出版时间：September 2016
• 年：2016
• 卷：56
• 期：9
• 页码：980-986
• 全文大小：442K
• ISSN：1548-2634

文摘

The melting behavior and crystalline forms of isotactic polypropylene (iPP) samples crystallized under different conditions of pressure and temperature were investigated using differential scanning calorimeter (DSC) and wide-angle X-ray diffraction (WAXD), respectively. When treated with dynamic supercritical CO₂(Sc-CO₂), iPP samples undergo the formation of β-crystal that does not occur on the treatment with atmospheric pressure and static supercritical CO₂(Sc-CO₂) pressure. In addition, the relative content of β-crystal has deep dependence on melt state and depressurization rate. Depressurization plays very critical role in the formation of β-crystal by means of imposing three-dimensional tensile field during cell growth. The tensile field induced α-row nuclei where the formation of β-crystal occurred. This finding will provide one new method to induce β-crystal in iPP parts. POLYM. ENG. SCI. 56:980–986, 2016.