The Properties And Application Of Two Types Of Epoxy Resin Modified Soybean Adhesives

With the constantly improvement of living environment,the safety of manmade board has obtained more and more attentions,and the development of environmentally friendly wood adhesive has become an irresistible trend.It is one of the ways to prepare bio-based adhesives from biological proteins.Soybean is rich in protein,which is one of suitable materials for preparing bio-based wood adhesives.However,the traditional soybean adhesives need to overcome the bottleneck problems of poor water resistance and bond strength.In this paper,epoxy resin is selected as a modifier to study its modification mechanism on soybean adhesives.Firstly,bisphenol A epoxy resin(DGEBA)was used as a crosslink agent to synthesize bisphenol A epoxy resin soybean adhesive(SM/DGEBA adhesive).By adding formic acid or sodium hydroxide,p H of the soybean adheisves were controlled,the bond strength at the soybean adheisves were improved.The prepared of soybean adhesives were good water resistance and adhesion properties.At the optimal synthesis condition of the p H value of 5,the DGEBA addition amount of14 g,the wet shear strength of plywood reached at 0.91 Mpa.Secondly,cycloaliphatic epoxy resin 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester(TDE-85)was used as the crosslinking agent to synthesize TDE soybean-based adhesive.At the optimal synthesis condition of the TDE-85 addition amount of 5 g,the wet shear strength of plywood reached at 1.16 Mpa,which reached the national standard for class ?plywood.In order to study the modification mechanism of TDE-85.The modification effects of Trimethylolpropane triglycidyl ether(THPTG)and TDE-85 modified soybean adhesives were compared.The two modified adhesives was characterized by DSC,SEM,FTIR and TG.The results show that TDE-85 undergo curing crosslink reaction with groups in soy protein via epoxy groups,thus forming a cross-linked network structure,which improves the adhesive adhesion property and thermal stability,water resistance,Which is the same as THPTG's modification mechanism.Different from THPTG,TDE soybean adhesive curing reaction is divided into two stages.Firstly,the active glycidyl ester epoxy groups participates in the curing reaction of the soybean adhesive at 100-120 ?.Secondly,the epoxy groups on the aliphatic participates in the curing reaction of the soybean adhesive above 160 ?.Because TDE-85 has active glycidyl ester epoxy resin and rigid aliphatic ring structure,TDE soybean adhesive have higher thermal stability,water resistance and adhesion property thanTHPTG soybean adhesive.