Toughening of Anhydride Cured Epoxy Resins.

摘要

Anhydride cured DGEBA epoxy resins are toughened against crack propagation by incorporating functionally terminated liquid butadiene-acrylonitrile rubber (CTBN). Spherical domains of 2 - 3 micrometers diameter are formed in situ during cure. With increasing amounts of rubber, the size of the second phase particles decreases. Thermo-mechanical and dielectric properties of the modified resins deteriorate rapidly beyond 10% rubber content. The temperature, T sub g of the unmodified system is 129 deg C; it drops to 126 deg with 10 parts rubber and to 119 deg C with 20 parts. The excess rubber appears to copolymerize with the matrix resin. Also the coefficient of thermal expansion increases disproportionately. The appearance and growth of secondary relaxation peaks in the dielectric spectra due to nitrile groups may be associated with the plasticizing effect of the excessive rubber. Epoxy filled with liquid rubber-treated silica powder shows a twofold improvement in fracture surface work compared to untreated filler. An interaction of the secondary amino groups of the ATBN (amine terminated) rubber with the epoxy-silane coupling agent on the silica and the epoxy resin appears to take place.