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

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