Simultaneous interpenetrating networks consisting of polyurethane and graft vinyl ester resin: Effect of different radical initiators

A series of well-defined graft vinyl ester resins (graft VER), composed of butanol side chain (BO) or poly(oxypropylene) side chains with different molecular weights (200 or 390), were synthesized and characterized. The simultaneous interpenetrating networks (SINS) of graft VER and polyurethane (PU) were prepared. The effect of initiators for graft VER on the morphologies and mechanical properties of PU/graft VER SINS was studied through DSC, SEM, and FTIR observations. For PU/graft VER SIN formed with AIBN as initiator, the morphology and structure of these SINS are mainly controlled by the PU network formed first, and the structure of graft VER has almost no influence on the long-range order structure of hard segments in SIN. For PU/graft VER SIN prepared with BPO/DMA as initiator (redox system), the side-chain structure of graft VER greatly affects the morphologies of these SINS, although the PU network and graft VER network formed almost simultaneously. The reinforcement effect of the graft VER network on the PU network is significantly different by using these two different initiators for graft VER, which could be related with the morphologies of SINS and the formation rate of the two networks. (C) 2002 Wiley Periodicals, Inc.