Effect of expanded graphite/layered-silicate clay on thermal, mechanical and fire retardant properties of poly(lactic acid)

Preparation of PLA based nanocomposites was carried out by using two different nanofillers: expanded graphite and organically modified montmorillonite. The addition and co-addition of these nanofillers to PLA using the melt-blending technique provides nanocomposites that showed significant enhancements in rigidity, thermal stability and fire retardancy of the polymer matrix. The presence of dispersed graphite nanolayers in PLA significantly accelerated the polyester crystallization, whereas the essential increase of thermal resistance is mainly connected to the addition of organoclay. The structure of the nanocomposites was examined by Wide Angle X-ray Scattering Analysis and Transmission Electron Microscopy. The improvement of thermal and mechanical properties obtained by the presence of both nanoparticles in PLA were associated to the good (co)dispersion and to the co-reinforcement effect, whilst the fire retardant properties were found to be related to the combined additive action of both nanofillers.