From Wastes to Functions: A New Soybean Meal and Bark-Based Adhesive

Abstract

Due to the increased awareness of utilization of waste biomass utilization for higher sustainability and concern for indoor air pollution associated with formaldehyde emission by wood adhesives, there are strong interests in developing biobased formaldehyde-free wood adhesives for plywood production. In this study, bark and soybean meal were used as raw materials to develop a cost-effective and formaldehyde-free wood adhesive through epoxidation of bark extractives to enhance performance of soybean meal-based (SM) adhesive. The bark-based bioepoxy resin (BEP) reacted with functional groups on the protein and formed a cross-linked structure, which improved the water resistance, mechanical strength, and thermal stability of the cured adhesive. Plywood bonded by the adhesive with 10 wt % of BEP showed a wet shear bonding strength of 0.89 MPa, exceeding that of the SMonly adhesive by 187.1%, which met requirements for interior-use plywood. Meanwhile, the dry shear bonding strength and cold water soaking bonding strength were improved by 56.9% and 81.1%, respectively. Further, the viscosity of the adhesive reduced to 10700 mPa•s and solids content of the adhesive increased to 32.05%, which improved the technological applicability of the biobased adhesive for plywood production. Thus, this novel waste-biomass-derived formaldehyde-free adhesive has excellent potential to be applied as an environmental-friendly commercial wood adhesive for plywood production.

Graphene Oxide Functionalized Cottonseed-Lignin Resin with Enhanced Wet Adhesion for Woody Composites Application

“…Similar results were observed in the dry shear strength and wood failure ( Figure 8 ) of plywood. This is ascribed to three factors ( Figure 1 ): (i) the lubrication of GO further reduces the viscosity of adhesive, which was readily penetrated into the wood substrate and formed the mechanical interlocking structure; (ii) the functional groups of DCF and AL can form hydrogen bonds with carbonyl and hydroxyl groups of GO, which enhanced the mechanical properties of adhesives; and (iii) the epoxy group of GO cross-linked with the functional groups of DCF (-NH 2 , -COOH) to consume the hydrophilic groups [ 32 , 33 ]. The reactions are expected to form a three-dimensional cross-linked structure that significantly improves the wet adhesion of the adhesives.…”

Plant Polyphenol‐Inspired Crosslinking Strategy toward High Bonding Strength and Mildew Resistance for Soy Protein Adhesives

“…Preparation of SM-Based Adhesive: The preparation of soy proteinbased adhesives was carried out according to the previously reported method. [49,50] Specifically, SM (25 g) was suspended in DI water (50 g), then mechanically stirred for 15 min at room temperature. A certain amount of PAE and TA was then added sequentially and constantly stirred (at 20 °C) for half-hour to develop the SMPT adhesives.…”

Preparation and properties of a novel type of tannin-based wood adhesive

“…Finally, the third degradation stage showing a large weight loss can occur in the 400-600℃ range, is due to the degradation of the cured adhesive skeleton. Some more stable chemical bonds, such as C-C and C-O, are cleaved within this temperature range [34][35][36] . Remarkably, the degradation temperature peak shifts to a higher value, while the weight loss rate shifts to smaller value with the increase in GDE.…”

“…DTG curves show three peaks as well, corresponding to the three thermal degradation stages. For the first one, in the low-temperature range, this weight loss was attributed to the residual water evaporation and some small molecular impurities degradation [34,35] . The second stage occurs in the 150-400℃ range, a small peak appearing in this temperature range, which corresponds to some unreacted GDE [3] .…”