The Hydrophobic Modification Of Starch By Complex Method And It’s Application In Biodegradable Plastics

The starch is a kind of polysaccharide compounds, It is belong to natural polymermaterials,starch has a wide range application in the industry of spinning、papermaking and oil.In recent years, with the decrease of oil resource, the biodegradable plastics have been thefavour of domestic and foreign research, as for the great biodegradability, act as the biomassin biodegradable plastics, the research of starch have achieved several achievements.However, the hydroxyl structures make the native starch has the characteristics of strongpolarity, it lead to wake mutual capacitive between starch and synthetic resin, and limit theapplication in biodegradable plastics. Currently, in order to solve this problem, we can takethe hydrophobization treatment. The modification methods include physical modification、chemical modification、coupling modification. Physical modification: the sonic oscillationcould refine the starch particles in effective. and increase the specific surface area, but thehydrophobic effect is not good; Chemical modification: The hydroxy is replaced by chemicalreagent, the degree of substitution is low, the effect of hydrophobic is non-significant;Coupling modification: the process is simple and green, the effect of hydrophobic is good, butthe particle size of the treated starch is uniform, It will influence the capacitive between starchand synthetic resin. The project use the complex method with physical and couplingmodification to achieve the hydrophobization treatment, and get the high hydrophobic starch.Add the high hydrophobic starch into PVC and PVA, and prepared the PVC plastic and PVAfilm. Take the structural characterization and performance test at the same time.The preparation and performance test of high hydrophobic starch: Firstly, take the cornstarch with ultrasonic refining processing, observe modification time, modificationtemperature, stirring rate, dosage of coupling agent and dosage of hydrophobic agent’sinfluence to the Hydrophobic performance of modified starch and confirm the best conditions.Contact angle test: the contact angle of modified starch increase obviously(141~143o). tetrabutyl phthalate ester/stearic acid system has the better hydrophobicity than silicane/peanutoil system. IR spectra analysis: The stretching vibration wave of O-H has changed to3436cm-1from3423cm-1after sonic oscillation, The stretching vibration wave of O-H fell to3411cm-1after hydrophobic modification, It’s the combine effect between hydroxyl group onsurface,coupling agent and hydrophobing agent. SEM analysis: The particle size of starchdecreased obviously, and dispersed homogeneously, the reunion phenomenon is reduced, there are uniform, mottling modified materials on surface, it prove that the modifying agenthave been coated on starch particles.Preparation and performance test of the starch-based PVC plastic: homemade modifiedhydrophobic starch in different proportions (20%,40%,60%) were respectively added to thePVC raw materials made in the same formula. At last, the degradable plastic sheet wasobtained after blending. Tensile test results showed that: in order to meet the performancerequirements of various starch-based plastics products, the proportion of the modified starchmust be up to20-60%, and the tensile strength must be up to25.49MPa-17.99MPa.Preparation and performance test of starch-based PVA membrane: Firstly, the PVA andwater were heated and dissolved completely, and then coupling agent, plasticizer andhydrophobic starch were added at one time. After stirring and stationary degassing, themembrane was obtained. Sedimentation rate being as the performance indicators, the optimalpreparation conditions were selected through single factor analysis.Biodegradation rate test: two methods which were the soil burial and bacteria cultureliquid method respectively were applied to test the biodegradable performance of starch-basedPVA plastic sheet and starch-based PVA membrane, the test results showed that: Testing thebiodegradability of starch-based PVC plastics and starch-based PVA films by soil burial andinoculum experiments, the results showed that: after4months of soil burial experiments,thebiodegradation rate of starch-based PVC plastics could reach to61.8%, after40days, thebiodegradation rate can reach to54%by using inoculum experiments, Under the sameconditions, the biodegradation rate of starch-based PVA films could reach to68%, indicatingthat the plastics and films have good degradability.This paper provided a process for preparing hydrophobic starch, which was simple buteffective, green composite production and had a good prospect of popularation andapplication. The highly hydrophobic starch could be well used as the biomass of PVC andPVA, and also could be used for the preparation of biodegradable plastics, for which thehighly hydrophobic starch could be expected to industrialized.