Journal of Polymer Science Part A: Polymer Chemistry, Vol.34, No.10, 1907-1922, 1996
Synthesis and Impact Properties of Siloxane-Dgeba Epoxy Copolymers
Siloxane-incorporated epoxy (ESDG) copolymers were prepared by a hot-melt method. IR, H-1- and C-13-NMR are used to determine the structures. The data on the molecular properties indicate that reaction proceeded with a random polycondensation without involving the opening of the oxirane ring in the epoxy structure. Lowering T(g)s with increasing siloxane content in copolymers are observed except for the copolymer modified with PDMS siloxane oligomer. Thermal stability data indicate that siloxane moiety exerts its thermal stability on the copolymer through dissipation of the heat, thus delaying thermal degradation of copolymers. Increasing impact strengths in J/M in the range of 22.0-59.0 are observed for copolymers and the improvement of the impact strength is closely related to the structure and content of siloxane oligomers in copolymers. A rough surface was observed by SEM examination on the propagation surface of the copolymeric impact specimen, while a smooth surface is observed on the unmodified epoxy specimen. The EDX analysis reveals these protruded features are Si-rich segments. The morphological observations suggest the siloxane segment may act as a toughening agent in the epoxy networks, thus contributing to the impact improvement of the copolymers.
Keywords:RUBBER-MODIFIED EPOXIES;TOUGHENING MECHANISMS;RESINS;FRACTURE;MICROSTRUCTURE;BEHAVIOR;SYSTEMS;CURE