Rapid Precipitation of Homogeneous Polymer Blends

该项目概述了以超临界流体（SCF）为溶剂从三元溶液中快速沉淀均相聚合物共混物的研究。尽管聚合物在SCF中具有很强的溶解度，但它们在气态的相同流体中是不溶的。因此，密度降低可以在声速下完成，导致溶解在SCF中的聚合物沉淀。由于沉淀的时间尺度可能比聚合物扩散发生相偏析的时间尺度短得多，因此扩大单相三元SCF溶液将导致固体聚合物的单相共混。因此，超临界流体沉淀技术表明，可以通过熔体共混或传统溶液共混技术生产出不相容的聚合物，从而生产出均匀、相容的共混物。该项目的目标是：(1)发展通过超临界流体共混工艺生产相容聚合物共混物的能力；(2)评估这些制备的共混物的稳定性。这些目标将通过对聚合物/聚合物/SCF相平衡的研究，通过对SCF膨胀过程动力学的实验和理论研究，以及通过对沉淀共混物相分离动力学的研究来实现。如果使用这种新技术可以开发出新的、精细状态的聚合物混合物，它们可能具有高强度或其他独特的性能，这将有助于制造高性能部件。

The project outlines a study of the rapid precipitation of homogeneous polymer blends from ternary solutions having a supercritical fluid (SCF) as the solvent. Although polymers can have substantial solubility in SCF's, they are insoluble in the same fluids in the gaseous state. Hence, density reduction, which can be accomplished at the speed of sound, results in precipitation of the polymer dissolved in the SCF. Because the time scale for precipitation can be significantly shorter than the time scale for phase segregation to occur by polymer diffusion, expanding a single phase ternary SCF solution will result in a single-phase blend of solid polymers. Thus, the supercritical fluid precipitation technique suggests the possibility of producing a homogeneous, compatible blend of polymers that otherwise have been found to be incompatible by melt blending or conventional solution blending techniques. The objectives of this project are: (1) to develop the capability of producing compatible polymer blends via a supercritical fluid blending process, and (2) to assess the stability of these prepared blends. These objectives will be achieved through studies of polymer/polymer/SCF phase equilibria, through experimental and theoretical investigations of the dynamics of the SCF expansion process, and through examination of the kinetics of phase separation in the precipitated blends. If new, fine-state polymer mixtures can be developed using this novel technique, they may have high strength or other unique properties that will be useful in the manufacture of high- performance components.