Controlling the biodegradation of polyhydroxybutyrate (PHB) and polybutylene succinate (PBS) by different types of lignin

Abstract

This study delves into the effects of incorporating organosolv and neutralized alkali lignin on the biodegradability and structure of Polyhydroxybutyrate (PHB) and polybutylene succinate (PBS) matrices. Our investigation reveals that the inclusion of lignin additives can alter the rate of biodegradation, with outcomes contingent upon the type and concentration of lignin utilized. To comprehensively assess the impact of each additive, a series of experiments including CO2 evolution as an operational measure of mineralization (ISO 17556), Scanning Electron Microscopy (SEM), and Differential Scanning Calorimetry (DSC) were conducted. Overall, alkali lignin exhibits superior efficacy in augmenting the resistance of PBS and PHB against degradation, while organosolv lignin demonstrates greater efficacy in reducing PHB degradation, particularly at higher concentrations. Additionally, our experiments indicate that in high concentrations of lignin, the influence of both types of lignin on PBS is slightly more pronounced than on PHB. Specifically, the incorporation of 12% alkali and organosolv lignin resulted in a reduction of PBS biodegradation by approximately 63% and 60%, respectively, after 298 days. For PHB, the reduction was slightly lower, with approximately 40% degradation decrease observed with the use of 12% alkali and organosolv lignin. Notably, our findings suggest that employing lower concentrations of lignin is effective, particularly with alkali lignin, as the impact of organosolv lignin after nearly 300 days was less conclusive. Visual and microscopic analyses corroborate the influence of lignin additives on the surface morphology and degradation resistance of PHB and PBS. These results highlight the potential of lignin as a promising additive for enhancing the properties of biodegradable polymers.