A kinetics study of diacrylic-styrene crosslinking copolymerization

Unsaturated acrylic resins such as hexanediol diacrylate (HDDA) are widely used in coating and adhesive materials because they provide excellent bonding properties and cosmetic surface finish. Styrene (St) monomer is often added to reduce the resin viscosity and facilitate acrylic reaction. In this study, we used an integrated analytical approach including differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectrometry, and rheometry, to monitor the kinetic and rheological changes of the diacrylic-styrene cross-linking polymerization at 100, 110 and 120 °C. Tert-butyl peroxybenzoate (TBPB) was used as initiator. It was found the reaction system gelled at <2 % conversion and overall conversions could only reach 94–95 % because of resin vitrification, suggesting most addition reactions were diffusion-controlled due to very low molecular mobility in the gel stage. Although conversions of HDDA and St, calculated from respective characteristic C=C absorption peak areas from isothermal FTIR sepectrum, followed the azeotropic co-polymerization pathway closely, styrene consumption was favored because of the lower molecular weight and higher mobility of styrene making it transfer comparatively faster than HDDA with pending double bonds.