Surface-modification of cellulose nanowhiskers and their use as nanoreinforcers into polylactide: A sustainably-integrated approach

In this study, bionanocomposites based on renewable cellulose nanowhiskers (CNWs) as nanofillers and renewable poly(l-lactide) (PLA) as polymeric matrix were successfully and straightforwardly prepared using melt-extrusion technique. Due to the affinity difference between hydrophobic PLA and hydrophilic CNWs, the surface of CNWs was directly modified in aqueous suspension (pH = 5.4 – citrate buffer) at ambient temperature in the presence of functional trialkoxysilanes bearing various organic moieties (alkyl, amino, and (meth)acryloxy). The surface-functionalization of CNWs was first investigated using methacryloxy-based trialkoxysilane as model. The influence of parameters such as the amount of silane agents and the post-treatment conditions were optimized on the surface-modification of methacryloxy-modified CNWs. FT-IR, TEM, WAXS and XPS analyses provided further evidences about the efficiency of the surface-modifications of CNWs. In a subsequent step, the chemically modified CNWs were successfully incorporated into PLA by melt-extrusion in the absence of solvent, without any alterations of their nanostructure after melt-processing. The thermal/mechanical properties of the resulting bionanocomposites were determined and shown to be enhanced when silanized CNWs were used as nanofillers.