Rice bran adhesive modified with potassium permanganate and poly(vinyl alcohol)

Abstract

PurposeThe purpose of this paper is to develop an environmental adhesive from defatted rice bran (RB) to increase its economic value and provide environmentally friendly products for the wood industry.Design/methodology/approachThe powder was mixed with water in a flask. After pH adjustment, potassium permanganate (KMnO4) solution was added. Then the mixture was heated in a shaking water bath. After maintaining the mixture at 70°C for 1 h, poly(vinyl alcohol) (PVA) powder was added to the slurry and heated at the same temperature for a further 0.5 h. The adhesive thus prepared was used to bond veneers to evaluate its bonding strength and analysed by IR. The optimised RB adhesive was mixed with phenol formaldehyde resin in a ratio of 8:8 to bond straw particleboard. Silane was used to improve the properties of the straw particleboard.FindingsAs an economically renewable resource, RB has potential use in the preparation of adhesives. When RB powder was treated with KMnO4 and PVA at pH 6, the resulting adhesive was able to produce a bonding strength of 1.29 MPa. Silane was found to be a useful coupling agent in the bonding of straw particleboard. Once the board had been bonded with the mixed adhesive, it was found to have a bending strength of 11.9 MPa and a modulus of elasticity of 2.2 GPa.Research limitations/implicationsChemical change was not obvious during RB modification, which led to a low water resistance. Further research is needed to modify the method.Practical implicationsRB adhesive was dark in colour, which limits its use for light‐coloured wood. Because of its lower water resistance, this adhesive has to be mixed with other synthetic resins to meet requirements.Originality/valueA new adhesive product was developed for the wood industry from economic RB. This will contribute to environmentally friendly wood products and the effective utilisation of agricultural residues.