Thermo-mechanical properties of the composite made of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) and acetylated chitin nanocrystals.

Acetylated chitin nanocrystals were prepared through surface modification, and biodegradable poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/chitin nanocrystals films were produced via solution-casting method. Transmission electron microscopy observations and X-ray diffraction profiles revealed that the rod-like morphology and crystal structure of chitin nanocrystals were maintained. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy results showed that the hydroxyl groups were partly replaced by the acetyl groups on the surface of chitin nanocrystals. The hydrophobic performance of the acetylated chitin nanocrystals was significantly increased according to the contact angle measurements. Differential scanning calorimeter results indicated that the influence of chitin nanocrystals on the crystallization behaviors of PHBV matrix was changed from suppression to assistance after the surface modification. Tensile test showed that the tensile strength and Young's modulus of PHBV/acetylated chitin nanocrystals composites were improved by 44% and 67%, comparing to the improvement of 24% and 43% for PHBV/chitin nanocrystals composites with the addition of 5.0 wt.% nanocrystals into PHBV.