(517o) Improve the Thermal Processability of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Bioplastic with Natural Rubber

The plastic industry is looking for bio-based and biodegradable alternatives to improve its sustainability. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a promising bio-based and biodegradable thermoplastic made from bacterial fermentation of carbon-rich resources. However, industrial applications of PHBV has been limited by its brittleness and especially by its poor processability. PHBV has highly linear molecular structures, its polymer chains are easily untangled under strain, resulting in low melt strength and low resistance to stretching. This causes issues in processes that require high melt drawing or stretching flow, such as film blowing and blow molding. PHBV’s high degree of crystallinity and low thermal stability also makes its thermal processing changeling as it degrades at temperatures close to its melting points.

Natural rubber was incorporated into PHBV through reactive extrusion to improve the thermal processability of PHBV. Peroxide and coagent were used to improve rubber particle dispense and compatibility between PHBV and rubber. The PHBV/rubber blends had higher complex viscosity and more significant shear thinning behavior than pristine PHBV, indicating enhanced chain entanglements. The PHBV/NR blends also showed enhanced strain-hardening in their extensional viscosity. The presence of natural rubber limited PHBV degradation during heating due to rubber dissipating heat more efficiently than PHBV. The difference between Tp (peak degradation temperature) and Tm (melting temperature) of PHBV increased from 127 °C to 142 °C, suggesting expanded range of PHBV processing temperature and broadened PHBV processing window.

This new rubber enhanced PHBV bioplastic material with improved processability is promising to be thermally processed into bio-products such as food packages to improve the sustainability of the industry.