Two component interpenetrating polymer networks (IPN's) of polyurethane-polystyrene, polyurethane-poly (methyl acrylate) and polystyrene-poly (methyl acrylate) were prepared by the simultaneous polymerization or the sequential polymerization process. Three component IPN's were also prepared by first forming polyurethanepolystyrene SIN (simultaneous interpenetrating network) and swelling the SIN with methyl acrylate monomer (with crosslinking agent) and sequentially polymerizing the imbibed monomer.
The morphology, physical and mechanical properties of 2-component and 3-component IPN's were analyzed. The morphology was studied by scanning electron microscopy. Both 2-component and 3-component IPN's showed heterogeneous morphology with dispersed domain sizes of 1,000 to 5,000Å range and 2,000 to 10,000Å range, respectively. Increased density and reduced swelling were observed in both 2-component IPN's and 3-component IPN. Enhanced thermal stability was observed in 3-component IPN compared to the theoretically predicted stability in TGA analysis. The 3-component IPN exhibited three separate but shifted glass transitions, one for each phase, measured by differential scanning calorimeter (DSC). The dynamic mechanical analysis showed one broad glass transition of polyurethane and poly (methyl acrylate) in 3-component IPN, which implied the partial compatibility of the polyurethane-poly (methyl acrylate).