Mechanism of Flow Induced Crystallization of Polymers

聚合物流动诱导结晶机理

• 批准号: 12450379
• 负责人: TAKIMOTO Jun-ichi
• 金额: $ 6.14万
• 依托单位: Yamagata University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12450379/
• 关键词: Crystallization; Shear flow; Viscosity; Pressure; Simulation

[1]Direct observation of Crystallization under shear flow (Takimoto)An original device for the direct observation of crystallization under shear flow has been developed. It has been found that the nucleation rate of spherulites is strongly accelerated as the shear stress increases (i.e., shear rate and/or molecular weight increase), but the growth rate is only weakly affected. At high shear stress, the row nucleated structure is observed.[2] Simultaneous measurement of heat of crystallization and viscosity under shear flow (Koyama)We have developed a shear flow thermal rheometer which can measure the heat of crystallization and viscosity under shear flow simultaneously. It has been found that the shear viscosity η increases with the relative crystallinity Xc as η(Xc)=η(0)exp(αXc). The constant α depends on the shear rate, which indicates that the morphology at the same Xc differs for different shear rates.[3] PVT measurement under shear flow (Koyama)We have modified a PVT measurement system so that shear flow can be applied under high pressure. It has been found that i) effect of pressure on the crystallization rate can be described by the shift of the melting temperature, ii) effect of shear rate can be described by a induction strain which is independent of crystallization temperature and pressure, and iii) effect of pressure and shear rate can be separated.[4] Molecular Dynamics Simulation (Masubuchi)Crystallization of polyethylene oligomer under shear flow was studied by molecular dynamics simulation. Flow alignme of the molecules and the acceleration of the nucleation have been demonstrated.

[1]剪切流下直接观察结晶(Takimoto)一种新颖的剪切流下直接观察结晶的装置已经研制成功。结果表明，球晶的形核速率随剪切力的增大(即剪切速率和/或相对分子质量的增大)而显著加快，但对生长速率的影响较小。[2]剪切流下结晶热和粘度的同时测量(小山)我们研制了一种可以同时测量剪切流下结晶热和粘度的剪切流变仪。结果表明，剪切粘度η随相对结晶度Xc的增大而增大，其关系式为η(Xc)=η(0)exp(αXc)。恒定的α取决于剪切速率，这表明在不同的剪切速率下，同一XC处的形貌是不同的。[3)剪切流下的PVT测量(小山)我们改进了PVT测量系统，使其可以在高压下应用。发现压力对结晶速率的影响可以用熔融温度的变化来描述，剪切速率的影响可以用与结晶温度和压力无关的感应应变来描述，压力和剪切速率的影响可以分离。[4]分子动力学模拟(Masubuhi)用分子动力学模拟方法研究了剪切流动下聚乙烯齐聚物的结晶行为。证明了分子的流动对齐和成核的加速作用。