Interpenetrating polymer networks of polyurethane and graft vinyl eater resin-polyurethane formed with diphenylmethane diisocyanate

For enhancing the compatibility and/or the interpenetration of the simultan eous interpenetrating networks (SINs) composed of polyurethane (PU) formed with uretonimine modified 4,4'-diphenylmethane diisocyanate and vinyl ester resin (VER), a series of graft VERs consisting of different lengths of sid e chains were synthesized and characterized. It was found that there exists some limited short-range order due to the strong hydrogen bonding in the g raft VER network composed of butanol side chains (BO-g-VER). The graft VER network composed of poly(oxypropylene) (PPO) side chains (M-n: 200, 200-g-V ER) showed compatible system, while the VER network consisting of longer PP O grafts (M-n: 390, 390-g-VER) exhibited microphase separated morphology. B ased upon the DSC and FTIR measurements as well as the SEM and TEM observat ion, the lengths of side chains existing in graft VER network have great ef fect on the morphologies of PU/graft VER SINs. For PU/BO-g-VER SINs, there has been some interpenetration between the two networks because of the misc ibility between the BO-g-VER network and the hard segments existing in the PU network. For PU/200-g-VER SINs, the good compatibility and/or the interp enetration between the two phases was observed, since the long-range ordere d structure of hard segments in PU phase was greatly suppressed, resulting from the excellent miscibility between the urethane groups as well as the P PO side chains existing in the 200-g-VER network and those in the PU networ k, respectively. Thus, the strong reinforcement effect of these two graft n etworks on the PU network and the excellent mechanical properties of the SI N systems were observed. However, the PU/390-g-VER SINs showed the complica ted morphologies because of existing microphase- separated morphology of 39 0-g-VER network in itself. In this case, the enhancement effect of such a g raft VER network on the PU network is limited. (C) 2000 John Wiley & Sons, Inc.