Effects of pea protein nanophase on structure and properties of waterborne polyurethane-based composites

New waterborne polyurethane (WPU)-based composites were prepared by incorporating high levels of pea protein isolate (PPI) as biomass filler, and it was observed by scanning electron microscope that the PPI in the form of nanophase dispersed into the WPU matrix. The resultant WPU/PPI composites exhibited prominent enhancement in both strength and Young's modulus, and maintained an elongation of greater than 290%. A PPI loading level of 20 wt% showed the maximum tensile strength (23.7 MPa) and had an enhanced Young's modulus (96.6 MPa), ca.1.1- and 31.2-fold, respectively, over those of neat waterborne polyurethane. The active surface and rigidity of the PPI nanophase facilitated formation of the interface for stress transfer and contributed to higher stressendurance. As the PPI loading level increased, the inevitable cleavage of the original interaction between the hard- and soft-segments in the WPU matrix became severe, and hence resulted in a decrease in strength in spite of the rigidity of the PPI nanophase that supported an increase in Young's modulus. The composites containing 40 wt% PPI had the highest Young's modulus (126.8 MPa). This work proves that superior performance of waterborne polyurethane-based composites can be established by simple incorporation of renewable pea protein. This work also promises to generate positive economic and environmental benefits.