From the viewpoint of recycling of bio-based resources and environmentally friendly polymers, polyurethanes (PU) were prepared from diphenylmethane diisocyanate (MDI) and polyethylene glycol (PEG) with bean-curd refuse (BCR) as a polyol. Mechanical and viscoelastic properties of BCR-PUs containing various amounts of sorbed water were investigated. Stress at break (σb) of BCR-PUs decreased as the amount of sorbed water increased, while strain at break (εb) of BCR-PUs increased as the amount of sorbed water increased. Dynamic modulus (E′) in the glassy region of BCR-PUs increased as the amount of sorbed water increased and E′ in the rubbery region decreased as the amount of sorbed water increased. It was found that three dispersion peaks of α, β and γ were observed from high to low temperature in the loss modulus (E″) curve. β dispersion at- 30 to-20°C was observed in BCR-PU systems while β′ dispersion was not observed in PEG-MDI PU. In the wet state of PU, β′ dispersion near -80°C was observed. These results indicated that β and β′ disper sions were assigned to the molecular motion of the BCR-PU network and the PU networks with water, respectively.
