Mechanical and dynamic properties of graft polyurethane/allyl novolac resin simultaneous interpenetrating network

Two series of polyurethane (PU)/allyl novolac resin simultaneous interpenetrating networks (SINs) were synthesized. The PU components were prepared by reacting 4,4'-diphenyl methane diisocyanate with poly(tetramethylene oxide) (PTMO), whose molecular weight range was 600-700 (for convenience, this polymer was called UT1), 900-1050 (UT2) and 1900-2100 (UT3), respectively. The phenolic resin component was synthesized by substituting the hydroxy groups of the phenolic resin with the allyl group. To prove that the alkene group can be applied as a binding element between the networks to improve the network compatibility, trimethylol propane monoallyl ether (TMPME) with a double bond was chosen as the PU chain extender in one series of the PU/allyl novolac resin SINs (designated TUT1, TUT2 and TUT3 for different molecular weights of PTMO used as PU soft segments). After a detailed study of the thermal, mechanical, and dynamic properties and morphology, the extent of phase mixing of the graft PU/allyl novolac resin SINs (TUT series SINs) was significantly improved over that of UT series SINs. This result is consistent with the loss tangent shift in dynamic mechanical analysis measurements and with transmission electron microscope micrographs. The mechanical properties of the graft SINs (TUT series) were lower than those of the original SINs (UT series) because TMPME with bulky structure was used as the chain extender of PU.