提高蛋白质生物塑料力学性能的研究进展

Improvement of mechanical properties of protein-based bioplastics

蛋白质生物塑料力学性能差是影响其商业化的主要因素。本文介绍了提高蛋白质生物塑料力学性能的几种手段,即蛋白质失活、生物纤维增强、与合成/天然可降解高分子共混、纳米复合增强等4个方面对提高其性能的有效性。对影响蛋白质失活的主要因素,即改变环境pH值、添加尿素、无机盐及交联剂等做了详细分析。对多种天然植物纤维的增强效果以及如何增强植物纤维在聚合物基体中的分散性、与其相容性等分别做了介绍。对多种纳米材料,如纳米纤维素、层状硅酸盐、碳纳米管/石墨烯等的增强效果也做了介绍。最后提出今后发展方向为:①提高蛋白质生物塑料的性能可控性,即兼顾可生物降解性与提高力学性能、延长使用寿命;②高性能化研究,以使蛋白质生物塑料满足某些特殊要求;③拓展蛋白质新来源。

Protein-based bioplastics （PBBs）, as a novel family of biodegradable plastics, have attracted increasing attentions thanks to their noticeable advantages in that they could be biodegraded completely and used by consumers in an environmentally friendly manner. However, PBBs are prone to be brittle under stress and their mechanical properties are inferior to their synthetic counterparts, which severely limits the commercialization of PBBs. Fortunately, numerous methods have been applied to overcoming these obstacles and have been found to be, in most cases, effective and successful. This paper summarizes four methodologies for improvement of mechanical properties of PBBs, namely protein denaturation, biofiber reinforcement, blends with synthetic/natural degradable polymers, and nanocomposites. Firstly, different factors influencing protein denaturation are analyzed, including pH value, addition of urea, inorganic salt, and cross-linking agents. Then, both the efficiency of mechanical properties improvement by incorporating natural plant fiber into protein matrix and the related fiber dispersion and compatibility between them are introduced. Next, the reinforcement efficiency of nano-sized fillers （nano whiskers/crystals, layered silicates, carbon nanotubes or grapheme） for mechanical enhancement is introduced. Finally, the future research trends are presented：① Controllable design of PBBs with combined and balanced properties such as biodegradable and mechanical properties, and the extension of service life; ② Value-added applications with desired functions, and ③ Exploring new protein resources.