Formulation of a novel soybean protein‐based wood adhesive with desired water resistance and technological applicability

Abstract

A novel soybean protein‐based wood adhesive with good bond strength, excellent water resistance, and the desired technological applicability was formulated by combining thermal alkali degradation, thermal acid treatment, and crosslinking. The characterization results indicated that thermal alkali degradation could effectively improve the technological applicability, thermal acid treatment could positively improve the water resistance, and appropriate crosslinking modification could significantly enhance the bond strength and water resistance of the soybean protein adhesive. The crosslinker species, crosslinker level, and ratio of thermal alkali‐degraded soybean protein (DSP) to thermal acid‐treated soybean protein (TSP) had important effects on the primary properties of the soybean protein adhesives. The modified polyamide aqueous solution was the most preferable crosslinker because of its low viscosity, good crosslinking efficiency, and excellent miscibility with soybean protein solution. The optimal soybean protein adhesive that was formulated from 20 wt % modified polyamide as the crosslinker and a DSP/TSP ratio of 1:3 had a solid content of more than 35 wt %, suitable viscosity (∼2180 mPa s), a long work life (>16 h), good dry bond strength (2.94 MPa), and 28 h of boiling–dry–boiling cycled wet strength (1.29 MPa) that met the required values for structural use according to JIS K6806‐2003 commercial standards. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43586.

Plywood adhesives derived from distillers' dried grains with solubles (DDGS) incorporating 2‐hydroxyethyl acrylate

“…The dry and wet lap shear strengths of the present work are compared with those of common synthetic wood adhesives and various soy‐based wood adhesives in Table . The bonding strengths of the hybrid adhesives are comparable to other soy protein‐based glues that possess dry lap shear strengths ranging from 1.91 to 6.40 MPa . They are higher than the adhesives derived from soy meal, but lower than those made with soy flour .…”

“…Without modifications, these adhesives tend to fail when exposed to water due to their hydrophilic nature . The use of various denaturing agents and crosslinkers have resulted in the development of soy protein‐based adhesives with improved wet bonding strengths . The combination of soy protein‐based products with synthetic formaldehyde and epichlorohydrin‐based resins has shown to be especially effective .…”

Effects of inorganic filler on performance and cost effectiveness of a soybean‐based adhesive

“…Further, SM‐based adhesives are considered to have the most potential for replacing petroleum‐based adhesives in future because they are abundant, environmentally safe, renewable, and degradable . Many methods have been employed to enhance the bonding performance of SM‐based adhesives, including mainly chemical denaturation in the presence of alkalis, surfactants, or organic solvents, crosslinking by crosslinkers or synthetic resins, functional group modification, enzymatic treatment, thermal treatment, ultrasound treatment, and combinations of these methods . To date, the adhesion properties, especially the water resistance of SM‐based adhesives, have been improved sufficiently to withstand hydrothermal testing (soaking in water at 63 °C and boiling water).…”

Adhesive based on micellar lupin protein isolate exhibiting oxygen barrier properties

“…In recent years further investigations have been carried out on using plant‐based proteins as potential adhesive alternative in some industrial sectors. Adhesives made from soy protein, for example, are investigated in the wood industry and especially in particleboard production . As the composition of lupin protein is very similar to the one of soy protein, the development of chemically modified lupin protein adhesives for applications in wood industry has recently attracted attention …”