High-performance hydroxypropyl black liquor lignin/poly (propylene carbonate) bio-composites with enhanced natural degradability

Abstract

This paper aimed to incorporate commercial lignin into poly (propylene carbonate) (PPC) by melt compounding method to prepare completely degradable bio-composites. To improve the dispersion and compatibility of lignin in PPC matrix, the black liquor lignin from pulp and paper industry was chemically modified by hydroxypropylation. The impact of this chemical modification on the microstructure and thermal transition behavior of lignin was studied. Results indicated that the modified hydroxypropyl black liquor lignin (HBL) showed a film-like aggregation structure with lower thermal transition temperature and higher melt fluidity while unmodified lignin was seriously aggregated spherical structure. The change in its chemical and physical structure made the HBL more compatible and dispersible within PPC matrix, which had been verified by morphology observation and dynamic mechanical analysis. Due to the improved affinity and dispersity of HBL, the high performance of the HBL/PPC bio-composites was achieved. The tensile properties, thermal stability and processing stability of the bio-composites were remarkably improved. More interestingly, the water contact angle and water uptake tests indicated that the HBL improved the hydrophilicity of the HBL/PPC bio-composites and thus accelerated the natural degradation process.