Unveiling the reinforcement effects in cottonseed protein/polycaprolactone blend biocomposites

• Published in: Composites science and technology 2022-07, Vol.225, p.109480, Article 109480
• Main Authors: Li, Liangjun, Yue, Hangbo, Wu, Qiqi, Fernández-Blázquez, Juan P., Shuttleworth, Peter S., Clark, James H., Guo, Jianwei
• Format: Article
• Language: English
• Subjects: Bio composites (A); Biocompatibility; Biomedical materials; Bioplastics; Chains (polymeric); Compatibility; Compatibilization; Composite materials; Fourier transforms; Fracture toughness; Infrared spectroscopy; Interphase (B); Maleic anhydride; Mechanical properties (B); Melt blending; Photoelectrons; Plant protein; Polycaprolactone; Polymer blends; Polymers; Proteins; Scanning electron microscopy; Tensile strength; Thermal stability; X ray photoelectron spectroscopy
• ISSN: 0266-3538; 1879-1050
• DOI: 10.1016/j.compscitech.2022.109480

Cottonseed protein (CP) was compounded with polycaprolactone (PCL) in different concentrations by melt blending, and then hot-pressed to prepare CP/PCL blend films. A co-continuous phase is formed when the CP/PCL content is 50/50, and the tensile strength, modulus and toughness are 9, 10, and 63 times greater than that of neat CP film. This remarkable improvement is mainly due to the intrinsic flexibility of long PCL polymer chains, whilst the polymeric crystalline structure can still be formed. Furthermore, 1 wt% of compatibilizing agent — glycidyl methacrylate (GMA) or maleic anhydride (MA), is added to the blends. Measurements from scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) showed the presence of chemically reactive compatibilization between the compatibilizer and CP or PCL phase, and the two phases with strong binding forces are well dispersed. Meanwhile, the compatibilizer can induce the protein secondary structure to unfold, further increasing the physical compatibilization between the protein and polymer chains, which has a noticeable contribution to the blend's mechanical, hydrophobic properties and thermal stability. This work adds new element to the knowledge of compatibilization in terms of optimised interfaces of polymer blends, and provide new insights into fabricating high performance protein derived bioplastics and biocomposites. [Display omitted] •The reinforcement effects involve physically polymer chain interactions and chemically reactive compatibilization.•The addition of compatibilizer increases cottonseed protein/PCL interfacial bonding and co-continuous phase formation.•Mechanical and thermal properties of the biocomposites can be significantly improved by simply tuning the content of reinforcing polycaprolactone.•Cottonseed protein/polycaprolactone blend biocomposites can be easily fabricated by melt-compounding and hot pressing.