Effects of cellulose nano crystal addition on the properties of polyhydroxybutyrate-co-valerate (PHBV) films

Polyhydroxybutyrate-co-valerate (PHBV) is a biodegradable and thermoplastic biopolymer which can be produced by a species of bacteria. This biopolymer has remarkably been noticed by scientific and industrial associations due to the similar properties with polypropylene. In spite of great benefits than petrochemical polymers, the use of PHBV to high-cost production process and also low range of physical and mechanical properties is limited. One solution to overcome this problem is to utilize nanoparticles as reinforcement. In this research, PHBV nanocomposite films containing cellulose nano crystals (CNC) has been provided. The effects of adding nanoparticles on the mechanical properties such as tensile strength and elongation, dynamic-mechanical properties such as modulus and tan δ were studied. Also, morphology and thermal features by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were investigated, respectively. For this purpose, CNC with ratio of 0, 1, 3 and 5 wt% were added to biopolymer matrix, then nanocomposite films were obtained by solvent casting method. After adding nanoparticles, the tensile strength and thermal stability of the PHBV/CNC composite films increased and the elongation decreased. SEM observations showed that existence of large amount of nanoparticles (3 wt%) are strongly agglomerated in the biopolymer matrix. This leads to decrease of mechanical properties of the composites for more than 3% by weight. Finally, the results of this study showed that CNC is an effective reinforcing agent for modifying physical and mechanical properties of biopolymer composite films.