Computational thermodynamics of multicomponent compressible polymer solutions

使用溶液聚合方法生产聚烯烃在高压下进行，并产生多组分聚合物溶液反应器出水。商品聚合物，如聚乙烯，是在高压和高温下使用溶液聚合方法生产的。在下游热处理阶段，操作条件的变化导致相分离，出现含有不同聚合物组成的不同相以及复杂的形态。复杂的多相形态反过来又影响了加热器单元内的传热过程，导致加热器在整个过程中效率的变化和压力的下降。这种相分离可能发生到相反转的程度。这种多相多组分流动流的相分离是由不稳定性决定的，例如寻求减少系统能量的旋多分解。聚合物在液相之间分馏，得到不同的聚合物分子量分布曲线和相应的物理性质。为了优化这些加热装置的设计和控制，需要更好地了解在可压缩多组分聚合物溶液中控制相分离的热力学原理。本文提出了一项整合聚合物分子热力学、数学过程建模和高性能计算的研究计划，以准确预测聚乙烯三元溶液的热力学和界面性质，以及基于溶液聚合方法的聚烯烃制造相关条件下可压缩聚合物溶液的相分离动力学。

Production of polyolefins using solution polymerization methods takes place at high pressure and results in a multicomponent polymer solution reactor effluent. Comodity polymers , such as polyethylene, are produced using solution polymerization methods under high pressure and temperature. During the downstream heat processing stage , changes in operating conditions lead to phase separation and the emergence of different phases containing different polymer compositions as well as a complex morphology. The complex multiphase morphology in turn affects the heat transfer process in the heater unit, leading to changes in heater efficiency and pressure drops through the course of the heater. This phase separation may occur to such a degree that phase inversion occurs. The phase separation of this multiphase-multicomponent flowing stream is dictated by instabilities, such as spinodal decomposition, that seek to reduce the energy of the system. The polymer is fractionated between the liquid phases, yielding different polymer molecular weight distribution curves and attendant physical properties. To optimize the design and control of these heating units a better fundamental knowledge of the thermodynamic principles that govern phase separation in compressible multicomponent polymer solutions are required. This proposal presents a research program that integrates polymer molecular thermodynamics, mathematical process modeling, and high performance computing to accurately predict the thermodynamics and interfacial properties of polyethylene ternary solutions, and the kinetics of phase separation of compressible polymer solutions under condition relevant to polyolefin manufacturing based on solution polymerization methods.