Lignin-containing cellulose fibrils as reinforcement of plasticized PLA biocomposites produced by melt processing using PEG as a carrier

The present work shows the feasibility of incorporating lignocellulosic nanofibers (LCNFs) from date palm waste, with diameters in the range of 10 and 30 nm, into polyethylene glycol (PEG)-plasticized polylactic acid (PLA). PLA/PEG/LCNF nanocomposites, with nanocellulose contents ranging from 2 to 10 wt%. were successfully prepared by one-step melt processing using PEG as a carrier to prevent the aggregation of LCNFs. The effect of the LCNFs content on the mechanical properties was assessed by tensile tests and dynamic mechanical analysis (DMA), pointing an enhancement in the tensile strength and Young's modulus by about 250% and 1100%, respectively, at 8% LCNFs content while maintaining a high toughness (around 16 MJ/m3). In addition, the proper dispersion in the form of a 3D-structured network and the good compatibility of LCNFs with the PLA/PEG matrix were confirmed by DMA and melt rheology measurements, as the stiffness in the rubbery state and the storage modulus increased with the content of LCNFs, respectively. The homogenous dispersion of LCNFs within PLA/PEG matrix was further confirmed by scanning electron microscopy (SEM) observation. Finally, from the disintegration tests in composting conditions, both PEG and LCNFs were found to positively contribute to the disintegration of PLA, mainly due to their affinity with water. Given the better sustainability of LCNFs owing to the absence of any chemical to isolate cellulose, along with their dispersibility within PLA matrix, the use of PEG as a carrier to produce PLA-LCNFs composites via melt processing may contribute to further highlight the merits of LCNFs as reinforcement in a biobased polymer matrix to produce composites with enhanced mechanical properties.

Automated summary

This study demonstrates the feasibility of incorporating lignocellulosic nanofibers from date palm waste into PLA/PEG matrix to enhance mechanical properties. The mechanical performance was significantly improved, with a 250% increase in tensile strength and 1100% increase in Young's modulus at 8% LCNFs content. The use of PEG as a carrier was effective in dispersing LCNFs within the matrix and contributing to the disintegration of PLA in composting conditions.