Preparation and Investigation of a Fully Biobased Adhesive Composed of Gum Arabic and Soy Protein Isolate for Plywood

In this study, a novel, fully biobased adhesive (GA-SPI) was formulated by using gum arabic (GA) and soy protein isolate (SPI). The preparation conditions, curing behavior, synthesis, and curing mechanism of this adhesive were investigated. The results indicated that the optimized adhesive with a 1:1 (GA:SPI) mass proportion and 70% solid content was synthesized by adding 5% FeCl2 center dot 4H(2)O as catalyst at 90 degree celsiusfor 2 h. When we tested the bonding ability of adhesive on plywood, the wet shear strength achieved 0.97 MPa, which exceeds the requirements of the China National Standard (>= 0.7 MPa). The curing behavior of the GA-SPI adhesive was researched by measuring the insoluble mass proportion and conducting thermal analysis. The results showed that 55% insoluble mass proportion was obtained when the adhesive was heated at 170degree celsius for 10 min, and the endothermic reaction occurred at around 150 degree celsius. To investigate the synthesis and curing mechanism of the GA-SPI adhesive, HPLC, ATR FT-IR, and Py-GC/MS analyses were utilized, and the results suggest that the hydrolysis of GA and Maillard reaction between GA, SPI, and hydroxymethylfurfural (HMF) occurred during the synthesis and curing process.