Study on frontal polymerization of polyurethane/nanosilica sol hybrids

Frontal polymerization (FP) is a mode of converting monomers into polymers via a localized reaction zone that propagates through the reaction system. The three reactants, polyether, toluene 2, 4-diisocyanate and 1, 4-butanediol and the catalyst (stannous caprylate) were mixed together at room temperature along with nanosilica sol and dimethylbenzene (as the solvent). After the thermal ignition at one end of the tubular reactor and subsequent front formation, no further energy was required for polymerization to occur. The thermal front self-propagated throughout the vessel. The effect of different molecular weights of polyether and different concentration of catalyst on frontal polymerization were investigated, along with a comparison of frontal polymerization with batch polymerization. FT-IR, TEM and TGA were employed to characterize the polyurethane (PU) hybrids. The obtained polymer materials by FP displayed similar features compared with those obtained by batch polymerization (BP). The reaction time of FP is quite less than that of BP during preparing the PU hybrids. Nanosilica sol can be well dispersed in the polyurethane hybrid matrix even though no any stirring occurs during the FP process.