Preparation And Characterization Of Starch-based Biodegradable Film

Corn is an important agricultural crop,affordable and abundant resources,and as a natural polymer material,it has biodegradability.Corn starch as a raw material for biodegradable film is important to ease the pressure of environmental pollution and oil crisis.Esterification modified corn starch has been prepared with corn starch as raw material,acetic acid as activator,acetic anhydride as esterifying agent,and concentrated sulfuric acid as catalyst.Certain substitution degrees of starch acetate(SA)were prepared.Esterified starches reaction conditions were optimized by single factor and orthogonal experiment.Esterifications of starch were characterized using infrared spectroscopy,differential scanning calorimetry(DSC)and scanning electron microscope(SEM)analysis method.The results show that under the conditions that temperature is 75 ?,time is 1.5h,concentrated sulfuric acid is 0.13mL,acetic acid(acetic acid and acetic anhydride volume ratio)is 0.7,substitution degree of SA can reach 0.45.The esterified starch infrared spectroscopy proves a successful introduction of the acetyl group.DSC analysis shows that the melting temperature of starch decreased with the increase of the degree of substitution.Starch microstructures of SEM show that the esterified starch has a loose and porous structure.Polyvinyl alcohol(PVA)has a certain degree of biodegradability,and the film is good,improving effect on the film-forming properties of the starch.A certain degree of substitution of the esterified starch and PVA was cast into a film.The mechanical properties as the objective function,through single factor and orthogonal experiment to optimize the film-forming conditions:reactant mass ratio(SA:PVA)is 4:6,temperature 80 ?,time 2.Oh.After optimization,the tensile strength is 39.2 MPa;the elongation at break is 4.26%.The transparent as the objective function,through single factor experiment and orthogonal experiment to optimize the preparation of blend membrane reaction conditions:the ratio of reactants(SA:PVA)is 5:5,temperature 85 ?,time 2.Oh,esterification degree of substitution is 0.05.The film transmittance rate is 43.25%.Degradation of soil buried method to study film;degradation curve shows that with the increasing of the degree of substitution of esterified starch,membrane degradation rate decreasing,but the degradation rate has been still up to 70%for 60 day.Infrared spectroscopy analyses of membrane prove the existence of acetyl group.DSC analyses show that the compatibility of SA and PVA is improved.SEM microstructure observation shows that the surface structure of SA/PVA blend membranes become three-dimensional and osteoporosis.SEM results show that the compatibility membrane glycerol added glycerol has a better improvement.