Supercritical Fractionation of Crystalline Polymers Near the Upper Critical End Point (Expedited Award)

结晶聚合物的有效分级应该是可能的 接近上临界终点（UCEP），对于尖锐的聚合物， 馏分，连接到三相点（熔点）的 聚合物通过三相线沿着固液气平衡 存在. 通过在略低于UCEP的温度下操作， 这种分馏可以在如下条件下进行 存在固体-超临界流体平衡。 优点 因此，与超临界流体萃取（SFE）相关的 获得。 研究了近界面的分馏作用和相平衡 UCEP是研究聚乙烯-正丙烷系统在约 100- 140 oC和400-600 bar。 在这些条件下，分馏 由分子量的差异引起，以及 微观结构不规则性（短链支化），预计将 发生.

The efficient fractionation of crystalline polymers should be possible near the upper critical end point (UCEP) which, for a sharp polymer fraction, is connected to the triple point (melting point) of the polymer by a three-phase line along which solid-liquid-gas equilibrium exists. By operating at temperatures slightly below that of the UCEP, such fractionation can be performed under conditions where solid-supercritical fluid equilibrium exists. The advantages associated with supercritical fluid extraction (SFE) should therefore be gained. The fractionation and relevant phase equilibrium near the UCEP are to be studied for the system polyethylene-n-propane at about 100-140oC and 400-600 bar. Under these conditions, fractionation induced by differences in molecular weight, as well as in microstructural irregularity (short-chain branching), is expected to occur.