On the mechanism of compatibilization of polyolefin/liquid crystalline polymer blends with graft copolymers

The compatibilization mechanism of some compatibilizers for blends of polyo lefins with a liquid crystalline polymer (LCP) was studied. Polyethylene (P E) and polypropylene (PP) were blended with a semirigid LCP (SBH) in a batc h mixer, either with and without compatibilizers. The latter were two comme rcially available samples of functionalized polyolefins, that is, a PE-g-MA (HDM) and a PP-g-AA (Polybond 1001) copolymer and some purposely synthesiz ed PE-g-LCP and PP-g-LCP copolymers. Microtomed films of the binary and the ternary blends were annealed at 240 degrees C on the hot stage of a polari zing microscope and the changes undergone by their morphology were recorded as a function of time. The results indicate that the compatibilizers lower the interfacial tension, thereby providing an improvement of the minor pha se dispersion. In addition to this, the rate of the coalescence caused by t he high-temperature treatment is appreciably reduced in the systems compati bilized with the PE-SBH and PP-SBH graft copolymers. Among the commercial c ompatibilizers, only Polybond 1001 displayed an effect comparable to that o f the above copolymers. HDM improved the morphology of the as-prepared PE b lends, but failed to grant sufficient morphological stabilization against a nnealing-induced coarsening. The results are discussed with reference to th e chemical structure of the different compatibilizers. (C) 2000 John Wiley & Sons, Inc.