Investigation of isothermal curing behaviour during the synthesis of polybenzoxazine-layered silicate nanocomposites via cyclic monomer

The curing reaction in the synthesis of polybenzoxazine (PBZ)–montmorillonite (MMT) nanocomposites was studied by differential scanning calorimetry in the isothermal mode. The experimental data obtained provided the evidence that the isothermal curing behaviour showed autocatalytic characteristics. Owing to the effects of catalysis and barrier of the MMT, the autocatalytic model proposed by Khanna [J. Appl. Polym. Sci. 49 (1993) 319], which includes two rate constants, k1 and k2 as well as two reaction orders, m and n could give fairly good description of curing behaviour in the whole range at relatively high temperatures such as 175, 180 °C even in the stage of diffusion control, which is quite different from that of pure PBZ, in addition with calculations of the activation energy and the overall reaction order.