Microstructure-tensile properties relationships of polyurethane/poly(urethane-modified bismaleimide–bismaleimide) interpenetrating polymer networks

Abstract A series of polyurethane/poly(urethane-modified bismaleimide–bismaleimide) interpenetrating polymer networks (PU/P(UBMI–BMI) IPNs) including semi-IPNs and full-IPNs were synthesized. The microstructures were examined by TEM. The effects of the ratios of UBMI/BMI, molecular weight of PBAG in UBMI and P(UBMI–BMI)/PU on tensile strength and elongation at break were investigated. The fractograghs were examined by SEM. The results indicate that interpenetration occurs at the hard segment domains of PU, which leads to enhancement of phase separation of PU and the dispersing tendency of dispersed phase of IPNs. Mobility and interlocking of the chains are important factors affecting the formation of this particular structure in the dispersed phase, they must be considered together to satisfy the demand for comprehensive positive synergistic effect on tensile properties. This particular structure can delay crack resource formation and retard crack propagation, leading to improvement of strength and toughness of PU/P(UBMI–BMI) IPNs.