Synthesis, properties and pyrolysis of siloxane- and imide-modified epoxy resin cured with siloxane-containing dianhydride

Abstract

Hydrosilylation of nadic anhydride with tetramethyl disiloxane yielded 5,5'-(1,1,3,3-tetramethyl disiloxane-1,3-diyl)-bis-norborane-2,3-dicarboxylic anhydride (1), which further reacted with 4-aminophenol to give N,N'-bis(4-hydroxyphenyl)-5,5'-bis-(1,1,3,3-tetramethyl disiloxane-1,3-diyl)-bisnorborane-2,3-dicarboximide (II). Epoxidation of II with excess epichlorohydrin formed a siloxane-and imide-modified epoxy oligomer (ie diglycidyl ether of N,N'-bis(4-hydroxyphenyl)-5,5'-bis(1,1,3,3-tetramethyl disiloxane-1,3-diyl)-bis-norborane-2,3-dicarboximide) (III). Equivalent ratios of IIIII of 1/1 and 1/0.8 were prepared and cured to produce crosslinked materials. Thermal mechanical and dynamic mechanical properties were investigated by TMA and DMA, respectively. It was noted that each of these two materials showed a glass transition temperature (T-g) higher than 160 degrees C with moderate moduli. The thermal degradation kinetics was studied with dynamic thermogravimetric analysis (TGA) and the estimated apparent activation energies were 111.4 kJ mol(-1) (in N-2), 117.1 kJ mol(-1) (in air) for III/I = 1/0.8, and 149.2 kJ mol(-1) (in N-2), 147.6 kJ mol(-1) (in air) for III/I = 1/1. The white flaky residue of the TGA char was confirmed to be silicon dioxide, which formed a barrier at the surface of the polymer matrix and, in part, accounted for the unique heat resistance of this material. (c) 2005 Society of Chemical Industry.