On the improvement of properties of bioplastic composites derived from wasted cottonseed protein by rational cross-linking and natural fiber reinforcement

• Published in: Green chemistry : an international journal and green chemistry resource : GC 2020-12, Vol.22 (24), p.8642-8655
• Main Authors: Yue, Hangbo, Zheng, Yuru, Zheng, Pingxuan, Guo, Jianwei, Fernández-Blázquez, Juan P, Clark, James H, Cui, Yingde
• Format: Article
• Language: English
• Subjects: Adhesive strength; Biopolymers; Bonding strength; Chemical bonds; Composite materials; Contact angle; Crosslinking; Fiber reinforcement; Glass transition temperature; Green chemistry; Hydrophobicity; Interfaces; Interfacial bonding; Mechanical properties; Natural resources; NMR; Nuclear magnetic resonance; Polymer matrix composites; Polymers; Proteins; Raw materials; Sisal; Starch; Tensile strength; Thermal stability; Transition temperatures; Water resistance
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/d0gc03245j

An approach of largely improving the properties of protein-based biopolymers is reported. Cottonseed protein concentrate (CPC) purified from cottonseed protein powder waste, with a protein content of >70% and a plasticizing efficiency of 4.2, was used to produce bioplastic polymer. A prepreg consisting of relatively oriented sisal fiber (SF) was transferred into CPC matrix as reinforcement, giving rise to improved mechanical properties of CPC/SF composites. To enhance interfacial bonding forces between the fiber and polymer, dialdehyde starch, DAS, with varied content (5-30 wt%) was introduced, and the FTIR and NMR results showed that DAS can effectively bridge biomacromolecular chains and form strong chemical bonds within the crosslinked structure. This cross-linking treatment leads to the formation of tight CPC/SF interfaces with strong adhesion, as shown by microscopic images, translating into excellent mechanical performance ( e.g. tensile strength 21 MPa), water resistance ( e.g. water contact angle 80°) and thermal stability ( e.g. glass transition temperature 104 °C) of the composites. The all green composites derived from natural resources with comparable or even superior properties to state-of-the-art biomass-based composites hold great potential for being utilized in larger industries. Biocomposites made entirely by renewable biomass demonstrate excellent mechanical, hydrophobic and thermal properties thanks to rational cross-linking and fiber reinforcement.