Chemical Functionalization of Lignocellulosic Polymers for the Control of Interfacial Adhesion in Wood and Biofiber-Plastic Composites

摘要

Novel reaction pathways for the chemical functionalization of wood (and biofibers) have been proposed, with the view to improving interfacial adhesion in wood and biofiber-plastic composites. In a first approach, methyltrimethoxysilane (MTMS) was durably grafted in wood after prior modification of the lignocellulosic polymers with 3-isocyanatopropyltriethoxy-silane (IPTES), an alkoxysilane coupling agent. After the carbamoylation reaction between IPTES and wood, MTMS was attached at the grafted triethoxy-silane end groups in the form of polysiloxanes. In a second approach, K_2CO_3-catalyzed transesterification reactions between vinyl esters and wood hydroxyl groups were envisaged. The feasibility of the reaction was verified with vinyl acetate, which was used as a model reactant. The reaction was subsequently applied to a selection of commercial vinyl esters bearing varied functionalities and led to esterified wood in high yield. Finally, dibutyltin oxide-catalyzed ester/ester or ester/alkoxysilane interchange reactions were envisaged, with acetylated wood as a starting material: the exchange between the pendant ester groups of acetylated wood and methyl benzoate or MTMS, was successfully achieved at high temperature. All of the reactions investigated were confirmed by Fourier-transform infrared and ~(13)C (or ~(29)Si) CP-MAS NMR spectroscopy.