Research On The Properties Of Soy Protein Adhesive Modified With Nanocrystalline Cellulose And Preparation Technology

This dissertation was aimed to prepare soy protein adhesive by applying soy protein isolate(SPI) as raw materials and nanocrystalline cellulose (NCC) as enhanced modifier, which canalso be used for the study of plywood synthesize process. According to study of usingmelamine resin (MF) onto methylation nanocrystalline cellulose surface, the modification effectwas analyzed. This study was focusing on optimizing the reaction conditions and NCC contentby analyzing several factors such as pH, solids content, reaction time and reaction temperatureand the forth, which may influence the viscosity of soy protein adhesives. The methodology ofresponse surface method combined with establishing the relevant mathematical model wereused to study the process of preparation technology of plywood with soy protein adhesive. Theprocess conditions were also optimized in this study. The conclusions were summarized asfollowed:(1) After modified with MF, NCC maintain the basic structure of the cellulose molecules,MF diffraction peak was observed near the2θ=28°. With the increase of dosage of MF, thecrystallinity of NCC presented first increases then decreases. Because of hydroxyl werereplaced by a large number of hydrophobic groups on the surface, the disparity and invasivewere improved obviously, the reunion phenomenon was significantly reduced, the form wasmore loosely. The surface free radicals concentration were significantly increased, achieveabout free radicals concentration5times before modification.(2) Within the scope of this test, the optimum reaction conditions of soy protein adhesiveswere: solid content20%, pH8, the reaction temperature30℃, the reaction time1.5h. Afteradding5%NCC, soy protein adhesive peak for thermal denaturation temperature was70.5℃,promote the molecules stretch more fully, exposed more nonpolar groups. The initialdegradation temperature of soy protein adhesive was extended. After curing the soy proteinadhesive’s pore and surface drape were decreased significantly, which was beneficial to formdense rubber. For comprehensive consideration, the NCC addition amount with5%wasappropriate.(3) Effect of pressing temperature, pressure and resin content on the mechanicalproperties of soy protein adhesive was investigated. Quadratic regression equation (model) ofmechanical properties of bonding strength was established. This model was significant and thelack of fit showed no significant. Mechanical properties of plywood could be analyzed andpredicted well though the model. Pressing temperature and pressure, pressing temperature and resin content of soy protein adhesive interaction played a significant role in the bondingstrength of plywood, but the pressure and resin content of interaction was not significant.Within the scope of this test, bonding strength increased and then showed little change aspressing temperature increased. When pressure and resin content increased, the bondingstrength first exhibited increase the decrease. Optimal properties of plywood was obtained withpressing temperature150℃, pressure1.3MPa, resin content441.4g/m~2. At the optimalconditions, the physical and mechanical properties of plywood achieved the required of Ⅱgrade of GB/T9846-2004, with bonding strength0.70MPa.