MODIFICATION OF POLYMERS: I. POLYSILOXANE MODIFIED EPOXIES. II. SEGMENTED POLYURETHANE BLENDS.

摘要

The research reported in this dissertation is concerned with the modification of thermosets and linear polymers via rubber toughening, copolymerization and blending.;The thermal stability of the siloxane oligomers and co-oligomers was also investigated and compared with that of the commercial epoxy rubber tougheners.;(2) Novel polydimethylsiloxane-polyhydroxyether copolymers were synthesized from the condensation reaction of aminoethylpiperazine-terminated polydimethylsiloxane oligomers with Bisphenol-A diglycidyl ether. The copolymers are designed to serve as new binder component for magnetic tapes with improved friction and wear resistance, hydrolytic stability and dimensional stability. Reasonably high molecular weight, linear, elastomeric and transparent copolymers were obtained. The copolymer structures were characterized by FTIR and ('13)C NMR. Thermal analysis (DSC) and Thermalmechanical analysis (TMA) suggested the possibility of microphase separation in the copolymers with siloxane Mn of 5000 or higher.;(3) Carboxypropyl-terminated polydimethylsiloxane oligomers were also investigated as rubber tougheners for cycloaliphatic epoxy networks. The siloxane modified cycloaliphatic epoxy networks are being studied as potential candidates for UV radiation resistant coatings.;(1) Aminoethylpiperazine-terminated polysiloxane oligomers and co-oligomers were synthesized by base-catalyzed equilibration and characterized. They are used as rubber tougheners for epoxy networks. The oligomers synthesized include: polydimethylsiloxane, poly(dimethyl-co-trifluoropropylmethyl) siloxane and poly(dimethyl-co-diphenyl) siloxane. The siloxane oligomers were used to modify an epoxy network obtained from the curing reaction of Epon 828 with p-aminocyclohexyl-methane. The trifluoropropyl and diphenyl siloxane units were incorporated into the oligomers to improve the miscibility of the siloxane phase with the epoxy matrix. The two-phase morphology of the siloxane modified epoxy networks were confirmed by both thermal analysis (DSC) and dynamic mechanical analysis (DMTA).;(4) Melt-mixed blends of a series of segmented polyurethanes with styrene-acrylonitrile copolymer (SAN), styrene-methyl methacrylate copolymer (SMMA) and ethylene-vinyl acetate-carbon monoxide terpolymer (EVACO) were investigated with respect to blend miscibility, mechanical properties, and melt flow properties. Blends of polyester-urethanes with SAN copolymer exhibit good mechanical properties characteristic of mechanically compatible blends. Blends of polyether-urethanes with SMMA copolymer are immiscible. On the other hand, blends of polyether-urethanes with EVACO copolymer are found to be miscible.