STRUCTURAL-CHANGES OF CELLULOSE, WOOD, AND PAPER UNDER SHEER DEFORMATION AND HIGH-PRESSURE

Structural changes of wood and its components have been studied after shear deformation under high pressure (SDHP) at up to 6 GPa. Cellulose amorphization and chain depolymerization was observed. Approximately 30% of microcrystalline cellulose was soluble in water after a 360-deg ree twist of the Bridgman anvils. The water-insoluble part was recryst allized into cellulose II lattice. Repeated treatment applied to the n ondissolved part of the sample, the so-called cascade experiment, perm its the dissolving of about 30% of the residual nondissolved material once again. Extraction with water, followed by 10% sodium hydroxide, a llows almost complete dissolving of microcrystalline cellulose (98%). Water-soluble saccharides were studied by HPLC and C-13 NMR. It was fo und that destruction of the wood lignin network needs more severe trea tment conditions than cellulose destruction does. Lignin domains in wo od act as ''grinding stones'' during cellulose destruction. Long-livin g lignin free radicals have been detected with EPR after SDHP. C-13 NM R CP/MAS spin diffusion studies showed that SDHP leads to separation o f wood components into different biopolymer domains, which turns the s ystem toward thermodynamic equilibrium. SDHP does not permit achieveme nt of initial compulsary compatibility of components in native wood. S DHP technique appears as a promising method for wood delignification a nd carbohydrate saccharification in the solid state without using harm ful chemical reagents or solvents, which is important for technologica l safety and ecology. (C) 1994 John Wiley and Sons, Inc.