Study On Biodegradable Materials Of Modified Soy Protein Isolate

As the improvement of human environmental protection consciousness, and thecontinuous decrease of oil resources, it has become a development trend that biodegradablepolymer replace traditional petroleum based polymers. Non-biodegradable materials form the“White Pollution” easily. The disposing of these materials has brought the huge technicalproblems, it also promotes the development of biodegradable materials at the same time.Soybean protein isolate (SPI) was multiple modified by maleic anhydride and zinc acetate inthe system of tetrahydrofuran, then plasticized by glycerol and water, and a kind of SPIbiodegradable material was obtained through hot pressing molding. The SPI biodegradablematerial with good properties was prepared. The properties analysis of materials were done.The effects of modified conditions on the properties of SPI biodegradable material werestudied in this paper. The optimal modified conditions of preparing the SPI biodegradablematerial were as follows: the ratio that quality of SPI and volume of tetrahydrofuran is1:3.The modified conditions of SPI biodegradable material were optimized through six-factororthogonal rotation experiment. In the optimal conditions, the properties of SPI biodegradablematerial are as follows: tensile strength of8.61MPa, elongation of196.78%, water absorptionof31.6%.The changes of material composition, structure and characteristics were studied withFourier infrared spectrometer, thermo Gravimetric Analyzer, differential scanning calorimeteranalyzer, scanning electron microscope, X-ray diffraction instrument et al before and after theformation.⑴The results of FTIR reveal that: In the process of multiple modified soybeanprotein isolated, some cross-linking reactions took place between MA and SPI molecules, zincacetate is involved in the reaction of the hydrophilic group; the content of α-helical andunordered structure reduced, converting into more stable β-sheet and β-turn and improvingthe ordering of materials’ ordering structure. XRD test showed that: crystallinity of SPI wasimproved by hot-pressing and modification.⑵In thermodynamic performance test, thethermal stability of modified SPI material was enhanced, DSC analysis showed that the glasstransition temperature of modified SPI material rose, indicating that modification could improve thermoplasticity of materials.⑶The analysis of amino acid showed that: thecontent of hydrophilic amino acids(aspartic acid, lysine, arginine and so on) is reducedthrough the multiple modified of SPI.⑷The results of SEM test displayed that: the multiplemodification of soy protein isolate separated protein molecules of SPI, plasticizing effect wasgood after glycerin plasticizing, forming dense, relatively smooth surface under the conditionof high temperature and high pressure. The analysis of AFM showed that the surfaceroughness of multiple modified SPI material was lower than unmodified SPI material,indicating that modified SPI material possessed better processing performance. The test ofcontact angle displayed that the surface of unmodified SPI material was hydrophilic, while thesurface of modified SPI material would not be moistening easily. The XPS analysis ofmaterials showed that multiple modification had changed the composition of the surface ofthe material.The degradation results show: the rate of weight loss of the SPI biodegradable materialwas61.5%after49days in the aqueous soil solution environment. The rate of weight loss is65.8%after49days in the natural soil environment, according the requiremennts of nationalstandards more than60%of the rate of degradation.