Investigations On In-situ Compatibilized Polypropylene/Polystyrene Alloys Catalyzed By Nonhydrous Aluminum Chloride By Rheology

Polypropylene (PP) and polystyrene (PS) are two of the most important thermoplastics because of their abundant resources and convenient industrial production. PP and PS have different merits which are complementary, and in their molecular chains the elements of N, P, and S are all invisible. So PP/PS blends can be widely used in mobiles, electronics, packaging fields, and so on, with precious environmental potentials. And furthermore, if the interfacial adhesion can be improved by compatibilization, the obtained PP/PS alloys would be much more competitive compared with other polymer materials.In this paper, as a typical lewis acid, anhydrous aluminum (AlCl₃) was used as the catalyst to get PP/PS blends compatibilized by in-situ Fridel-Crafts alkylation. The effects on PP and PS components of AlCl₃ were investigated first, mainly by rheology, including steady rheology method and dynamic rheology method. Then the in-situ reactions in PP/PS alloys under different conditions were executed and studied in detail by selective Soxhlet solvent extraction. And at the same time, the evolutions of phase structures of PP/PS and the resulted PP/PS/AlCl₃ alloys were investigated by SEM(Scanning electric morphology) and SALS(Small angle laser scattering). The steady and dynamic rheological behaviors of in-situ compatibilized PP/PS alloys were obtained systematically.The results showed that, under melt mixing conditions, PP or PS degradation would take place catalyzed by AlCl₃, but not very seriously with lower AlCl₃ content. And at the same time, C-O-C structure and PS-AlCl₃ complex would be formed in PP/AlCl₃ and PS/AlCl₃, respectively, resulted in complex rheological behaviors of systems. In-situ compatibilized reaction of Fridel-Craft alkylation in PP/PS/AlCl₃ alloys catalyzed by AlCl₃ may form PP-g-PS copolymer distributed in interfacial surfaces as interfacial layer with a certain depth. The effects of compatibilization and the ratio of viscosities of PP/AlCl₃ and PS/AlCl₃ determined the evolution of phase structures of PP/PS/AlCl₃, together. And the compatibilization reaction was influenced by the area of interfacial surfaces and the concentration of PP+ ion in the reactive system. According to log-linearly additivity method, storage modulus, loss modulus, complex modulus and complex viscosity of PP/PS alloys or compatibilized PP/PS/AlCl₃ alloys could be divided into three parts, including contribution of components, contribution of geometrical phase structure, and contribution of the interfacial adhesion of phases. Thus the contribution of PP or PS component and contribution of geometrical phase structure could be separated away and contribution of interfacial adhesion of in-situ compatibilization could be calculated out. The dependence of interfacial adhesion on compositions calculated from static rheology and dynamic rheology, especially, was the same to the dependence of PP-g-PS yield determined by soxhlet extracted method, and also was the same to the dependence of interfacial layer thickness d obtained by SALS.Investigations on the influences of AlCl3 on PP and PS under melt mixing conditions and on the resulted phase structure evolutions, reactive characteristics, and rheological properties of PP/PS/AlCl3 alloys were helpful to understand the reactive mechanism, to explain the characteristic structure and property changes of alloys, and to prepare better PP/PS alloys with competitive potentials.