Polyurethane/polystyrene one-shot interpenetrating polymer networks with good damping ability: Transition broadening through crosslinking,internetwork grafting and compatibilization

Good damping materials should exhibit a high loss factor value over a broad temperature range. Polyurethane and polystyrene are highly immiscible polymers with glass transition regions far apart. The interpenetrating polymer network topology can restrict phase separation and result in materials with a broad transition region. Simultaneous polyurethane/polystyrene interpenetrating polymer networks were synthesized by the one-shot route. Different methods of improving the miscibility of the two polymers were investigated. These included the vanation of the crosslink level in both polymer networks, the controlled introduction of internetwork grafting and the incorporation of compatibilizers into the polystyrene network. Dynamic mechanical thermal analysis indicated that the latter two were successful in achieving a compatibilization of the polymer components. With some materials, a high, broad transition region exhibiting a loss factor > 0.3 over more than 135°C was obtained. The morphology observed via transmission electron microscopy ranged from macrophase separated materials in the lightly crosslinked IPNs to a fine, microheterogeneous morphology in the grafted ones. Modulated differential scanning calorimetry measurements confirmed the trend of the glass transition locations observed with dynamic mechanical thermal analysis.