Thermal and mechanical properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/cellulose nanowhiskers composites

Bacterial polyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was reinforced with cellulose nanowhiskers (CNW) in 1-5 wt.% concentrations using a solvent casting method. The CNW was prepared from microcrystalline cellulose (MCC) using sulfuric acid hydrolysis. The influence of CNW on the PHBV crystallization, thermal, dynamic mechanical and mechanical properties were evaluated using polarized optical microscope (POM), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), tensile and bulge tests, respectively. POM test results demonstrated that CNW was an effective PHBV nucleation agent. Tensile strength, Young’s modulus and toughness of PHBV increased with the increasing concentration of CNW. DMA results showed an increased tan δ peak temperature and broadened transition peak, indicating restrained PHBV molecular mobility in the vicinity of the CNW surface. Storage modulus of the PHBV also increased with the addition of CNW, especially at the temperatures higher than the PHBV glass transition temperature. These results indicated that the CNW could substantially increase the mechanical properties of PHBV and this increase could be attributed to the strong interactions between these two phases.