Potential of glycerol as a bio-based wood adhesive

Abstract

The development of bio-based adhesives, to the extent possible without harmful chemicals derived from fossil resources, is very important for the sustainable use of wood-based materials. In this study, we investigated the possibility of glycerol as a bio-based adhesive by manufacturing wood-based moldings. The raw materials used were glycerol and wood powder of Japanese cedar (Cryptomeria japonica). The moldings were manufactured under hot-pressed at 160–220 °C and 4 MPa for 10 min. The glycerol content varied from 0 to 30 wt%. Color differences in the resulting molding increased with increasing glycerol content and hot-press temperature, suggesting that chemical changes occur during hot pressing in the presence of glycerol. The best bending properties of the moldings were obtained under manufacturing conditions of 15 wt% glycerol and 220 °C. In the water resistance test using boiling water, weight gain and thickness swelling of moldings were inhibited with increasing glycerol content. The moldings manufactured at hot-press temperatures above 200 °C developed water resistance. Ether linkages were detected by Fourier transform infrared spectroscopy and heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy. Our results demonstrated that good adhesiveness is achieved by ether linkages resulting from the chemical reaction between glycerol and wood powder.