Effect of lignin nanoparticles and masterbatch procedures on the final properties of glycidyl methacrylate-g-poly (lactic acid) films before and after accelerated UV weathering

• Lignin nanoparticles (LNP) were used as nanofillers in poly (lactic acid) (PLA).
• LNP were premixed with PLA or glycidyl methacrylate (GMA) grafted PLA (g-PLA).
• GMA grafting of the matrix promoted the dispersion of LNP in PLA matrix.
• UV–Vis tests confirmed how LNP behave better as UV light barrier in g-PLA.
• Improved deformability of grafted PLA nanocomposites was lost after UV weathering.

This article reports the preparation, by means of an innovative masterbatch procedure, of poly (lactic acid) (PLA)/lignin nanoparticles (LNP) films via premixing 1% wt. of LNP into PLA or glycidyl methacrylate (GMA) grafted PLA (g-PLA). These films were obtained by reactive extrusion and subsequent filmature process. Films obtained by using the masterbatch steps were characterized and compared with the system realized by direct extrusion of 1% wt. of LNP in PLA/g-PLA. Thermal, optical and mechanical properties, as well as morphology of LNP reinforced PLA nanocomposites, were characterized. The performance of the produced films was also investigated after accelerated UV weathering (up to 480 h), with the aim of verify how the presence of lignin nanoparticles could modify transparency and mechanical performance of neat (and GMA grafted) PLA films. Results from UV–vis characterization showed how LNP better behave as UV light barrier in grafted PLA, and it has been also proved that GMA grafting onto PLA matrix promoted the dispersion of LNP in matrix. Mechanical tests after weathering also confirmed that both the presence of LNP and GMA accelerates the oxidation effect, since the increased deformability observed for systems containing 1% wt. of LNP in PLA and g-PLA systems at time 0 was lost after 240 h of UV exposure.

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