Delineating pMDI model reactions with loblolly pine via solution-state NMR spectroscopy. Part 1. Catalyzed reactions with wood models and wood polymers

Abstract

Abstract To better understand adhesive interactions with wood, reactions between model compounds of wood and a model compound of polymeric methylene diphenyl diisocyanate (pMDI) were characterized by solution-state NMR spectroscopy. For comparison, finely ground loblolly pine sapwood, milled-wood lignin and holocellulose from the same wood were isolated and derivatized with the pMDI model compound. One-bond 13C–1H correlation (HSQC) experiments on derivatized and dissolved ball-milled wood revealed which hydroxyl group positions of the cell wall polymers reacted with the pMDI model compound to form carbamates. The chemical shifts of the derivatized model compounds correspond precisely to the chemical shifts of derivatized wood polymers. These model experiments will be taken as a basis in the next phase of our research (Part 2), in which the reactions of pMDI model compounds will be studied with intact wood cell walls under conditions similar to those used in oriented strand-board production.