Performance of high lignin content cellulose nanocrystals in poly(lactic acid)

High lignin-containing cellulose nanocrystals (HLCNCs) were successfully isolated from hydrothermally treated aspen fibers and freeze-dried and compounded with poly (lactic acid) (PLA) by extrusion and injection molding. As a comparison, PLA composites containing commercial lignin-coated CNCs (BLCNCs) were also produced. HLCNCs showed higher crystallinity, larger surface area, lower degree of agglomeration, and more hydrophobic surfaces compared to BLCNCs, as characterized by electron microscopy, surface area measurements, thermal analysis, spectroscopy and water contact angle measurements. The effect of lignin and CNC morphology on the mechanical, thermal and viscoelastic properties and CNCs/polymer interfacial adhesion of nanocomposites was investigated with tensile test, DSC and DMA. Compared to neat PLA, the Young's modulus, elongation to break, and toughness of PLA/2%HLCNCs were improved by 14, 77, and 30%, respectively. HLCNCs and BLCNCs act as nucleating fillers, increasing the degree of crystallinity (χc) of PLA in nanocomposites. The presence of lignin nanoparticles in the HLCNC increased the compatibility/adhesion between CNCs and polymer matrix which increased the storage modulus. [Display omitted] •High-lignin-containing CNCs (HLCNCs) were used as nanofiller for PLA matrix.•HLCNC has lower agglomeration degree and higher hydrophobicity and surface area.•Lignin nanoparticles increased the compatibility of filler and polymer matrix.•HLCNCs based nanocomposites showed higher degree of crystallinity than neat PLA.•Adding HLCNCs increased the viscoelastic properties as compared to neat PLA.