关键词: 可生物降解塑料, 机械强度, 蛋白质失活, 纤维增强, 纳米复合

Abstract: 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.

Key words: biodegradable plastic, mechanical strength, protein denaturation, biofibre reinforcement, nanocomposites