Synthesis, characterization and thermal stability of novel carborane-containing epoxy novolacs

Abstract

Carborane bisphenol novolacs (3 and 4) were synthesized in the presence of acid catalyst from carborane bisphenols (5 and 6) and formaldehyde. Further epoxidization of carborane bisphenol novolacs with epichlorohydrin gave carborane bisphenol epoxy novolacs (1 and 2). The molecular weight and epoxy value of obtained resins were determined using the molecular weight of their precursors. The epoxy values of 1 and 2 were 0.48 and 0.52 respectively, higher than the maximum theoretical epoxy value (0.45) of difunctional carborane bisphenol epoxy resins. FTIR and NMR were utilized to characterize 1 and 2. The curing behaviors were also studied by DSC and the optimized curing conditions were obtained. TGA analysis indicated that carborane moiety could shield its adjacent organic structures against initial decomposition. On the other hand, B―H on carborane cage could react with oxygen to form a three-dimensional network linked by B―O―B and B―C bonds, which further blocked the movement of formed radicals and thus the degradation process was inhibited.