Impregnation of Hardboard with Poly(methyl methacrylate)

The increasing deficiency of natural woods has led to the use of agricultural residues in the preparation of pulp and boards. The important agricultural residues are bagasse, straws, and cotton stalks, which accumulate in vast amounts. Some studies concerning the use of bagasse (Lumen et al., 1963), rice straw (Mobarak et al., 1975; Fadl et al., 1984), cotton stalks (Mobarak and Nada, 1975), and other agricultural residues (Lathrop and Naffziger, 1949; Aronosky and Lathrop, 1949) for producing hardboards are available. Actually, resins are added to pulp before board formation to give a final board of high strength and water resistance. The common resins are phenol-formaldehyde, urea-formaldehyde, and melamine- formaldehyde. Also, in one of our previous works, whole black liquor (Nada et al., 1982), produced from rice straw pulping process or its separated components (lignin, hemicellulose, and silica) (El-Saied et al., 1982) in the presence or absence of phenol-formaldehyde resin during hardboard preparation, was used to improve the strength properties of board. Other treatments are used to modify the hardboard or paper sheet properties, by impregnation of the sheets in resin solution (Plomely and Cottstein, 1968; Nada et al., 1981) or by polymer solution (Calleton et al., 1970; Youssef et al., in press). In addition, chemical modifica-tions such as acetylation, grafting (Smraishi et al., 1982). and cyanoethylation are carried out on wood and hardboard to improve their dimensional stability.