Rapid Precipitation of Homogeneous Polymer Blends

该项目概述了从以超临界流体(SCF)为溶剂的三元溶液中快速沉淀均质聚合物混合物的研究。虽然聚合物在超临界流体中有很大的溶解性，但它们在气态下不能溶解在相同的流体中。因此，密度的降低可以在音速下完成，导致溶解在超临界流体中的聚合物沉淀。由于沉淀的时间尺度比聚合物扩散产生相分离的时间尺度要短得多，因此扩展单相三元SCF溶液将导致固体聚合物的单相混合。因此，超临界流体沉淀技术表明，有可能生产出均质、相容的聚合物混合物，否则通过熔融共混或传统的溶液共混技术发现这些聚合物是不相容的。该项目的目标是：(1)开发通过超临界流体共混过程生产兼容聚合物共混物的能力，以及(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/超临界流体相平衡的研究，通过对超临界流体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中相分离动力学的研究来实现。如果能够利用这一新技术开发出新的、状态良好的聚合物混合物，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.