Modification of wood cell wall with water-soluble vinyl monomer to improve dimensional stability and its mechanism

Abstract

In this work, a new simple and environmentally friendly wood modification method was used to improve the dimensional stability of fast-growing wood. The wood samples were submerged in a neutral aqueous solution of 40% N-isopropylacrylamide/2-hydroxyethyl methacrylate (NIPAM/HEMA) at a mass ratio of 1/6 in the presence of catalytic amounts of 2,2′-azobis[2-methylpropionamidine] dihydrochloride (AAPH). The impregnated samples were heated at 60 °C for 12 h, followed by a heating period at 103 ± 2 °C for 12 h, in the course of which an in situ graft polymerization occurred in the cell wall. The results of scanning electron microscopy and energy-dispersive X-ray analyses indicate that the water-soluble vinyl monomers could effectively permeate into the wood cell walls. Infrared spectra showed that water-soluble monomers were in situ polymerized in wood. The results of XPS indicate that the water-soluble vinyl monomers could graft onto wood cell walls. The dimensional stability of poplar wood modified by the water-soluble vinyl monomers treatment was remarkably improved compared with that of untreated poplar wood.