Accelerated Weathering Performance and Biodegradation of Polyhydroxybutyrate Modified With PHB-g-MA

Abstract

This study examined the effects of accelerated weathering on the structural, viscoelastic, rheological properties and biodegradability behavior of polyhydroxybutyrate (PHB) biopolymers modified with PHB grafted maleic anhydride (PHB-g-MA) copolymers. For this purpose, the PHB was first grafted using the microwave (MW) and extruder (Ext) methods at MA loading ratios of 5% and 10% (wt). Then, the obtained PHB-g-MA was blended with neat PHB in the twin screw extruder, and test samples were obtained after the injection molding process. The weathered and unweathered samples were characterized with scanning electron microscopy (SEM), structural properties, including color, surface roughness, and Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA) and rheological properties, and biodegradability behavior, including fungal resistance and biodegradation behavior. According to the results, SEM analysis exhibited that the surface deformation after the accelerated weathering test was lower in the blends with PHB-g-MA-MW than in the samples with PHB-g-MA-Ext. The sample surfaces of both PHB-g-MA types were flatter and smoother than those of neat PHB. It was observed that adding PHB-g-MA enhanced the color stability of the blends by 10%. DMA results showed that weathering increased E′, E″, and tan δ, indicating altered viscoelastic behavior. Rheological analysis confirmed a shift toward more viscosity-dominated behavior, and the accelerated weathering has no important effect on rheological properties. The addition of PHB-g-MA increased the biological decomposition of PHB blends, and lower fungal growth occurred in neat PHB according to the samples with PHB-g-MA.