Abstract: Soy protein isolate(SPI) and polyaryl polymethylene isocyanate(PAPI) were mixed, the mixture was introduced into polycaprolactone(PCL) forming composites via hot press-molding. The structure, morphology and properties of the composites were investigated using differential scanning calorimeter analyzer, universal electronic tensile testing machine, dynamic mechanical analyzer, Fourier transform infrared spectroscopy, and scanning electron microscopy. FTIR analysis indicated that the reaction of PAPI and SPI changed the structure of soy protein isolate resulted in tighter compacting and thus affected the properties of composites. Upon adding PAPI, the tensile strength of soy protein plastic increased from 9.65 to 32 MPa, impact strength increased from 1.36 kJ/m2 to 11.7 kJ/m2. With increasing PAPI content, the 24 h water absorption of SPI/PAPI/PCL composites decreased from 33.89 % to 9.77 %.

Key words: soy protein isolate, polyaryl polymethylene isocyanate, mechanical property, water absorption ability