Studies on curing behavior and molecular motion of polyacrylate/epoxy-amine adduct complex system with additional crosslinker

Abstract

The curing behavior of a three-component system—polyacrylate I, epoxy-amine adduct II, and polyglycol-2-ethylhexanol–blocked 2,4-toluene diisocyanate III (the crosslinker)—was studied by torsional braid analysis and in situ Fourier transform infrared (FTIR). Results show that the curing process consists of two close steps. The first step is a deblocking and curing period (the main period), in which the deblocked isocyanate group reacted with the hydroxyl in polyacrylate and epoxy-amine adduct to obtain a crosslinked network structure. The second step is a deep-curing period. The further deblocked isocyanate group reacted with NH group in urethane and the crosslinking density increased. The curing temperature of the first step could be lowered efficiently when the organotin catalyst was added into the system, and the curing time was shortened. Furthermore, the effect on the curing crosslinking extent of each system was studied when the types or content of the crosslinkers changed. The results show that, when the crosslinking density increased, the mutual molecular motion became more difficult and the glass temperatures (Tg) were heightened. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 247–254, 1998