Degradation of the Polymer Structure of Wood by Wetting and Drying. Viscoelasticity and Morphology of the Composite Cell Structure

The cracking and destruction of wood by inner and outer stresses is discussed in the light of previous works and the spectral (NMR and FTIR), microscopic (SEM), and mechanical stress experiments of the authors. The physical properties of wood are compared with those of synthetic high polymers. Wood components swelling in water, such as extractives and hemicellulose and lignin and their hydrogen-bond-forming power, are important chemical factors determining the mechanical stability of wood. Anisotropic shrinking of wood cells, resulting in cracking on drying, is a time-dependent process which has few analogues in synthetic polymers and their composites. This behavior lessens considerably the areas of technical use of wood.