An environmentally-friendly soybean based resin as an alternative to formaldehyde-based counterpart for biomass composites

Abstract

Wood based composites are widely used in furniture and other building construction, but the majority of which are bonded with formaldehyde-based resins that may cause serious health concern. This study presents an environmentally-friendly soybean based resin via combination of waste newspaper powder (WNP), soybean flour (DSF), and polyamidoamine-epichlorohydrin for woody composites, and its adhesion properties as investigated via shear strength. The results showed that the developed DSF-WNP resin (or soybean based resin) cured well at currently commercial plywood manufacture temperature (130 °C) and could be cured at a lower temperature of 85 °C for energy saving as well, through chemical cross-linking reactions between hydroxyl-azetidinium ring groups in the polyamidoamine-epichlorohydrin and hydrophilic groups, such as amido, carboxyl and hydroxyl in other components. WNP with particle sizes ranging from 120 μm to 250 μm were suitable for the resin applications. WNP resulted in poor dispersion, but lowered water absorption and increased insoluble fraction content and tensile strength in the cured resin. The wet shear strength of plywood bonded with DSF-WNP resin with a 2/5 dry weight ratio of WNP/DSF was 1.24 MPa, which met the requirements of the Chinese National Standard GB/T 9846–2015 for interior plywood. The resin characteristics including fast curing and excellent wet-cohesion performance are comparable to the mostly used urea-formaldehyde adhesives, which showed great potential in wood composites as an alternative to formaldehyde-derived adhesives.