Study On The Preparation And Properties Of Soy Protein/PVA Blendings

Soy protein isolate (SPI)-based materials have been extensively studied as a potential replacement for petroleum-based plastic materials. Blending is an effective method for the modification of polymers to enhance properties by conventional processing techniques. In this thesis, SPI-based blend materials were fabricated by a solution-compounding method and the effects of various plasticizers and cross-linking agents were researched, their properties were also investigated to ensure these materials could be applied in the plastics, edible packaging and drug release fileds.Polymer blends were prepared by thermo-pressing mixtures of SPI and poly(vinyl alcohol)(PVA) using glycerol as a plasticizer. The properties of the blends were investigated using differential scanning calorimetry analyzer, thermogravimetry analyzer, universal electronic tensile testing machine, and scanning electron microscopy. The SPI/PVA blends possessed better compatibility. The results indicated that the long molecular of PVA had the main function to enhance the mechanical properties and the thermal stability, As the increase of PVA contents, there was the second Tg of SPI/PVA blends at the around of 130 ℃, and its glass transition temperature was higher. The addition of PVA significantly boosted water resistant properties, When the content of PVA was 30/phr, the tensile strength of SPI/PVA increased by 237%, compared with pure SPI.Influence of the three complex plasticizers containing glycerol and methanamide, glycerol and triethanolamine, sorbierite and methanamide on the SPI-based materials characteristics were studied. The comparison of the mechanical properties showed that the tensile strength of polymer blends with glycerol and triethanolamine increased. There was a maximum value of 12.06MPa when its mass ratio was close to 4:6. The comparison of the fluidity of materials showed that the effect of sorbierite and methanamide was the best. It flowed the easiest when its content was 2:8. Similarly, glycerol and triethanolamine made the biggest contribution to the water resistant properties of materials when its content was less than 4:6. Conclusions were reached through synthetic analysis that glycerol and triethanolamine were the best complex plasticizers in the range of 4:6 to 6:4.SPI/PVA blend materials separately crosslinked by epichlorohydrin(ECH), Sodium hexametaphosphate(SHMP) and borax were successfully fabricated by the same process, and they could make the SPI/PVA forming crosslinked structure. The thermostability and water resistant properties were significantly enhanced by the cross-linking. There were different content when the crosslinking action attained its maximum performance, Borax just needed the contend of 0.4/phr to the key point, SHMP had to be more than 3/phr, however, ECH could reach up to 30/phr-35/phr.