离子-偶极相互作用下压力诱导聚偏氟乙烯多晶型生成研究
首发时间:2015-10-19
摘要:调控聚偏氟乙烯(PVDF)的多晶型结构可以通常改变结晶压力完成,相关研究对丰富聚合物结晶以及获得高性能材料都有重要意义。在这个工作中,通过对比PVDF和添加1wt.%的十六烷基三甲基溴化铵(CTAB)非等温结晶,研究了高压和离子偶极相互作用对其多晶型行为的影响,研究发现,在低压下(<10 MPa),在PVDF/CTAB(1.0 wt%)得到的是γ 晶的折叠链晶体(FCC),而不是α FCCs,在中等压力下(100 MPa),获得了纯的β FCCs,表明离子-偶极相互作用和压力具有协同诱导β FCCs的作用;在高压下(200-400 MPa),最终的样品由β/γ 的FCCs和伸直链晶体(ECCs)共同构成,这与纯的PVDF中由α FCCs和α/β/γ构成不同。我们利用PVDF的T-P相图对这些多晶型的形成机理进行了讨论。
关键词: 聚偏氟乙烯 高压非等温结晶 离子-偶极相互作用 晶型 伸直链晶体
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Polymorphism of Poly(vinylidene fluoride) Induced by Pressure and Ion-Dipole Interaction
Abstract:Manipulating polymorphism can be achieved by different pressures during crystallization of poly(vinylidene fluoride), and understanding of its crystallization under pressure is important for achieving high performance materials. In this study, the influence of high pressure and ion-dipole interaction on the polymorphism was investigated by comparing neat PVDF and PVDF with 1 wt.% cetyltrimethylammonium bromide (CTAB) non-isothermally crystallized from the melt at 210℃. Under low pressures (≤10 MPa), γ folded-chain crystals (FCCs), rather than α FCCs, were obtained for PVDF/1 wt.% CTAB because of the ion-dipole interaction. Under a moderate pressure (100 MPa), pure β FCCs were formed in PVDF/1 wt.% CTAB, owing to the synergistic effect of both high pressure and ion-dipole interaction. Under high pressures (≥200 MPa), mixtures of β/γ FCCs and ECCs were obtained for PVDF/1 wt.% CTAB. This was different from the neat PVDF, where mixtures of α FCCs and α/γ/β ECCs coexisted when the pressure was between 200 and 400 MPa. The formation mechanisms of various crystalline forms and FCCs versus ECCs during the non-isothermal crystallization are discussed by T-P phase digram.
Keywords: PVDF high pressure induced nonisothermal crystallization ion-dipole interaction crystalline structure extended chain crystals
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No.4657439109927214****
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离子-偶极相互作用下压力诱导聚偏氟乙烯多晶型生成研究
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