Modified pine needles as a formaldehyde scavenger for urea-formaldehyde resin in plywood production

Abstract

Abstract The aim of presented work was to investigate whether it is possible to use ground pine needles as a formaldehyde-scavenging filler for urea-formaldehyde resin in the production of plywood. The scope of the research included determinations of both optimal amount of introduced filler and the effect of its modification (silanization, hydrothermal and alkaline treatments). Properties of adhesives such as viscosity, gel time and pH were investigated and their morphology was assessed using scanning electron microscopy. Manufactured plywood were tested in terms of wet shear strength, tendency to delamination and formaldehyde emission. It was found that the addition of pine needles lowers the pH and reduces gel time of the adhesive. Moreover, it was shown that despite a significant reduction in formaldehyde emission, the addition of non-modified needles causes a decrease in bonding quality of plywood. Based on the results, 10 parts by weight of needles per 100 parts by weight of resin can be considered as optimal loading. The use of ground needles modified hydrothermally and with silane allows to minimize the negative effect on the strength of glue lines and leads to further reduction of formaldehyde emission. Therefore, it can be concluded that pine needles powder has a strong potential for the application as formaldehyde-scavenging filler for urea-formaldehyde adhesive in plywood production.