Preparation and characterisation of bioplastics made from cottonseed protein

Abstract

Cottonseed protein bioplastics (CPBs) from cottonseed flour were successfully prepared by hot-press molding in the presence of urea, aldehydes and glycerol. The effect of cross-linking treatment on the thermal stability, water absorption resistance and mechanical strength was investigated, and found to improve all properties. Increasing glycerol concentration resulted in a decrease in denaturation and α-relaxation temperature of the cottonseed protein as well as storage modulus of the plasticised CPBs. Interestingly, the colour and odor of the CPBs before and after hot compression changed. The mechanism proposed involved urea induced protein denaturation and Maillard-driven generation of the cross-linked structure, both in thermal and alkaline processed conditions. According to Fickian diffusivity, liquid transport and liquid permeability, chemical interactions and physical transport processes are responsible for the different water transport behaviours in the CPBs and the cross-linked CPBs, respectively. These findings could provide valuable in-depth information for tailoring the properties of the environmentally sustainable CPBs, which are attractive for low-load bearing applications, such as agriculture, packing and garden amenities, etc.