Aquatic Biodegradation of Poly(β-Hydroxybutyrate) and Polypropylene Blends with Compatibilizer and the Generation of Micro-and Nano-Plastics on Biodegradation

摘要

Poly((3-hydroxybutyrate) (PHB) is a well-known biodegradable bio-based polymer but can be brittle. Polymer blending of PHB with polyethylene (PE) or polypropylene (PP) has been proposed to improve the mechanical properties. Compatibilizers have been considered to improve the performance of the polymer blend with PHB; however, the effect of compatibilizers on biodegradation is controversial. In the present study, the PHB polymer was blended with PP, a non-biodegradable synthetic polymer, and spun into fiber form. Furthermore, the effect of increased interaction between the polymers was investigated by increasing the miscibility with compatibilizer, maleic anhydride-grafted polypropylene (MAPP). The biodegradation of PHB in the blends was investigated in aquatic aerobic conditions with a closed respirometer with activated sludge as inoculum. Since PP is not a biodegradable polymer, the PHB-based biodegradation was calculated based on the ratio of oxygen consumption to the theoretical oxygen demand of PHB polymer in the blends. The fibers with a concentration of PHB below 75 showed a significant decrease in PHB biodegradation. This result confirms that non-biodegradable polymers in the blend can hinder the biodegradation of biodegradable polymers. Additionally, this blending is shown herein to have unintended consequences, creating micro and nano pollution of residual synthetic PP material. MAPP has an effect of increasing the miscibility between PP and PHB; however, this increased miscibility rendered the PHB biodegradation to be very low, less than 25. This result suggests that even though increased miscibility can improve mechanical performance, it can decrease the biodegradation of biodegradable polymers in non-biodegradable/biodegradable polymer blends.