Lignin fractionation as an efficient route for enhancing Polylactide thermal stability and flame retardancy

Abstract

Due to its variable botanical origin, functionality, reactivity, and heterogeneity, using lignin in industrial application is not an easy task. In the present study, we investigate the effect of lignin fractionation as a simple way for reducing the variability in its properties. Kraft lignin was separated by ultrafiltration membranes in two fractions with a specific molecular weight and the properties of each fraction were characterized through FTIR, XPS, TGA and cone calorimeter test. Lignin fractions display different thermal and combustion behaviors. Thus, the two fractions have been evaluated as flame retardant additives for polylactide (PLA). PLA composites, containing well dispersed lignin (20 wt%), were produced by melt blending in an internal mixer. The thermo-degradant effect of each fraction on PLA during melt processing was investigated by rheological analysis and size exclusion chromatography while the composites thermal stability and fire properties were evaluated using TGA and cone calorimeter test. Results showed that using appropriate lignin fraction enables for obtaining PLA composites presenting enhanced properties