Studies On The Modification Of Soy Protein By Blending

Nowadays, the utilization of natural polymers as raw materials for the research and development of new materials has been one of the frontiers in polymer science and material science. The modification and applications of natural polymers based on renewable resources not only prevent the environmental pollution from the non-biodegradable plastics, but also save the limited oil resource, suiting the strategy of sustainable development. Soy protein, the most abundant plant protein, is easy to be modified by chemical and physical treatment because it contains many reactive groups. Soy protein possesses biodegradability and belongs to ecomaterial. The jumped-up "Industrial Protein Plastic" has attracted much considerable attention. The soy protein has great potential applications in membranes, adhesives, plastics and medical materials. However, the brittleness, water-sensitivity and complexity of soy protein-based materials greatly restricted its research and development. Therefore, the main objective of this thesis was to prepare composites based on soy protein by chemical and physical modification and to search new blending modification methods to improve the processibility, mechanical properties and water-resistivity for the materials based on soy protein. The composites were prepared from soy protein isolate (SPI), soy dreg (SD) and soy flour (SF), respectively. At the same time, the structure and properties of these materials, and the relationship between the structure and properties were characterized and investigated by several advanced apparatus and methods.The creative points of this thesis are as the follows. (1) A series of protein composites were successfully prepared from SD, SF and SPI, respectively, by grafting and cross-linking with polypropylene glycol-based polyurethane prepolymer (PUP) through reactive extrusion and compression-molding process. Thus it provided a new way to improve the processibility, mechanical properties and water-resistivity of soy protein plastics without addition of low molecular weight plasticizers. (2) A series of SD composites were prepared by extruding and compression-molding from SD and castor oil-based polyurethane prepolymer containing different NCO/OH mole ratio (R). The processibility, tensile strength, water- and organic solvent-resistivity of the composites were obviously improved. The effect of the R values of the PUP and the content of SD on the structure and properties have been clarified. (3) A series of new SD composites were prepared by one-step reactive extrusion from the premixture of SD, castor oil and TDI (6.04-16.8 wt%) for the first time. The effect of in situ compatization of TDI on the structure was revealed and the relationship between the structure and properties of the composites were established. (4) The SD / benzyl konjac glucomannan (B-KGM)composite sheets were prepared by laminating and compression-molding process. It was revealed that the tight adhesion and the strong interactions between SD and B-KGM molecules formed at the interface, led to an improvement of the water resistivity and mechanical properties of the composites. (5) The blend membranes of cellulose/SPI were prepared for the first time in NaOH/thiourea aqueous solution by coagulating with 5 wt % H2SO4 aqueous solution. The resulted blend membranes exhibited good compatibility, perfect mechanical properties and thermal stability. At the same time, a series of microporous membranes were prepared from the above cellulose/SPI membranes by the post-treatment with 5 wt% of NaOH solution. These membranes possessed good functionality in separation field and in cell culture process.The main research contents and conclusions are described as the follows. Firstly, the polyurethane prepolymer (PUP) was synthesized from 2,4-Toluene diisocyanate (TDI) and polypropylene glycol (PPG). A series of protein composites were successfully prepared from the above PUP with SD, SF and SPI, respectively, by using reactive extrusion, compression-molding process without addition of other plasticizers o...