Interrelations between mechanism, kinetics, and rheology in an isothermal cross-linking chain-growth copolymerisation

The free radical chain-growth cross-linking copolymerisation of an unsatura ted polyester resin with styrene is investigated in isothermal conditions u sing different techniques. By modulated temperature differential scanning c alorimetry (MTDSC) the rate of polymerisation is observed simultaneously wi th the (partial) vitrification of the reacting material. An important autoa cceleration closely before vitrification corresponds to an accelerating sty rene consumption. The autoacceleration occurs long after the gelation of th e material, which implies that termination reactions involving small radica ls are still important at an advanced conversion. The deceleration of these termination reactions causes the autoacceleration, which is stopped when t he propagation reaction slows down due to vitrification. MTDSC proves to be very suitable for studying the interrelations between vitrification and th e polymerisation kinetics. (C) 2001 Elsevier Science Ltd. All rights reserv ed.