Study On The Characterization Of Interface Between Enzyme Treated Wheat Straw And Modified Soybean Protein Adhesive

By means of measuring the spreading-penetration constant (K value) of two kinds of interface:distilled water to wheat straw and modified soybean protein adhesive to wheat straw, the wettability on the surface of wheat straws which were separately sprayed with two chemicals (0.6% NaOH,0.3% H2O2) and three enzymes (cellulase, xylanase, lipase) was investigated. The K value of distilled water on the exterior surface of wheat straw treated with NaOH, xylanase and lipase was separately much higher than that of control, the wettability of treated wheat straw was improved greatly. The K value of modified soybean protein adhesive on the exterior surfaces of wheat straw treated with NaOH, hydrogen peroxide and lipase was respectively much higher than that of control. The surface morphologies of treated wheat straw and control sample were observed by SEM. It is clear to observe that the stratum corneum was partially exfoliated and the cork cells were destroyed by comparing the SEM images. With Micro-FTIR, the treated wheat straw was scanned and the peaks arrangements were analyzed. With X-ray photoelectron spectroscopy (XPS), element contents on the surface of wheat straw treated with NaOH and lipase were separately analyzed. The result shows that the chemical bond C-0 and O-C-O/C=O had been reduced and the silicon content was decreased from 18.99% to 1.57% and 1.51%, respectively.A novel hydrophobic adhesive was prepared by physical and chemical modification using soybean protein isolate as raw materiel. The optimized modification technique was determined based on the Lg(34) orthogonal test. The result shows that the optimized method for preparing modified soybean protein isolate adhesive was by adding 0.5%sodium dodecylbenzenesulfonate (SDBS) and 4.5% boric acid after ultrasonic treatment at 50℃and 100W for 60min. The three-layer plywood was manufactured to evaluate the properties of modified soybean protein isolate adhesive. The dried bonding strength of plywood prepared by modified soybean protein adhesive was 1.28MPa and the wet bonding strength was 1MPa, these data were higher than the requirements of the class II adhesive in GB/T 9846-2004 of Chinese Standard (≥0.7MPa). For evaluating the durability of the novel adhesive, the plywood was prepared by using the modified adhesive stored for 30 days, it was come out that the bonding strength was still met the requirements of the class II adhesive in GB/T 9846-2004 of Chinese Standard. The reaction mechanism was investigated by means of FTIR. The DSC test indicated that the appropriate hot press temperature for the modified adhesive was lower than 160℃. In this thesis, the antisepsis properties of soybean protein isolate adhesive were also discussed. The preservative of boric acid in modified soybean protein adhesive was mixed by adding 1,2-benzeisothiazoline-3-one (BIT). The antifungal test suggested that BIT and boric acid play an important role in inhibiting fungi growth, they were considered to be synergetic effect, and the optimized dosage of BIT was 0.lwt.%.On the basis of economic costs analysis, the cost of plywood using the modified soybean protein isolate adhesive was much lower than that of urea formaldehyde resin, additionally, the modified soy protein isolate adhesive was innoxious, environmental friendly and long storage. This kind of adhesive has a great market potential.