Physicochemical Properties Of Plant Protein Adhesives Modified By Diacetyl Tartaric Acid

In this study,soy protein isolate(SPI)was modified by diacetyl tartaric acid-ethanol(DTA-EtOH)solution as modifier to prepare soy protein adhesive(SPA).Through a series of orthogonal reactions,the best ratio was obtained to prepare the adhesive,and the physical and chemical properties of the adhesive were studied.The results are as follows:(1)Determination of modifier:L-tartaric acid and acetyl chloride in a ratio of 1:2.5,heated with a very small amount of concentrated phosphoric acid as a catalyst.The resulting product has a high purity.The product was dissolved in anhydrous ethanol te.prepare modifier,and the SPI was modified to prepare SPA.(2)A series of orthogonal experiments were carried out to study the effects of the amount of SPI,pretreatment pH,modifier concentration,reaction time and other factors.The mechanical properties of SPA were tested and the molecular structure of soy protein(SP)was characterized.The amount of SPI was 17 g,the pretreatment pH range was 10.7～10.8,the modifier concentration was 0.04 g/mL,and the reaction time was 2 h.Through a series of properties of the test:the viscosity of SPA is small,good fluidity,easy to sizing,and the bonding strength is 2.22 MPa/1.15 MPa.Adhesive is far greater than the national standard on the type Ⅱ plywood with the requirements of plastic(≥0.7 MPa),and has good water resistance.(3)Combining the DSC test results in(2),the effect of hot pressing temperature on the physical and chemical properties of adhesives was investigated in the temperature range of 65～165 ℃.Through the bonding strength test found that the hot pressing at 90 ℃ under the bonding strength of 2.29 MPa/1.23 MPa.And after infrared testing found that by hot pressing at this temperature,the adhesive produced a further thermal denaturation.With this thermal denaturation,the adhesive mechanical properties of the adhesive can be improved,and the reduction of the hot pressing temperature can reduce the energy consumption during the preparation process of the plywood and save the energy.(4)The physical and chemical properties of the adhesive were analyzed by adding different preservatives to the soy protein adhesive prepared in the laboratory.The storage period of prepared soybean protein adhesive with borax as a preservative in the content of 20.6%is 111 d(adhesive without preservative for 24 d).Gluing strength of the soy protein adhesive is 2.54 MPa/1.37 MPa,and its performance is better than SPA without borax.Adhesive is far greater than the national standard on the type Ⅱ plywood with the requirements of plastic(≥ 0.7 MPa),and has good water resistance.