| Excellent performance have been found in high amylose starch composites.In order to decrease gelatinization temperature of high amylose starch and its retrogradation rate,high amylose starch was modified prepared high amylose starch/montmorillonite nanocomposite films by solution casting in this paper.Effects of different modification degree of native starch to the performance of nanocomposites were investegated.X-ray diffraction(XRD),transmission electron microscopy(TEM)and small angle X-ray scattering(SAXS)were used to analysis of the microstructure of the composite films.Supplemented by mechanical properties,water vapor permeability and rheological properties,dynamic mechanical thermal analysis(DMA),thermal gravimetric analysis(TGA)and contact angle test(CA)were determined to characterize the other properties of these composites.In addition,scanning electron microscopy(SEM)and fourier transform infrared spectroscopy(FTIR)etc.were used to characterize the properties of the modified starch.Main results were showed as the following.(1)Montmorillonites types(Mt and D1821Mt)had significant effects on the performances of nanocomposites.Mt had better compatability with cationic starch(CS)than D1821 Mt and it can significantly improve the properties of nanocomposites,such as mechnical properties,water permeability performance and thermal stability.Mt exhibited exfoliation after being composited with CS.After CS composited with D1821 Mt,D1821Mt showed totally exfoliation with CS0.04,while weak intercalated structure formed in the other three CS matrix.TEM showed D1821 Mt stacked together to tactoids in CS0.20 matrix.(2)The degree of cationication had significant effects on the performances of nanocomposites.CS0.04 Mt composite had the maximum tensile strength,14.01 MPa.Compared with blank control groups,the water vapor perpeability(WVP)values of nanocomposites with lower DS were found,especially the WVP of CS0.11 Mt decreased 12.39%.And as the DS increased,the extent of exfoliation increased.The intromolecular force between CS0.16,CS0.20 and Mt were so weak that viscous behavior of composites were found at high frequency.In general,CS0.04 Mt had relatively the best performance of these composites.(3)Long chain dibasic acid effected the properties of cationic maize starch significantly.Dodecanedioic acid was used as esterification modifier to modify CS0.04 in N,N-dimethylacetamide solution to obtaine dodecanedioic acid cationic high amylose starch esters with different DS.FTIR spectra showed characteristic peaks of starch esters,which indicated acid had substituted the original groups in starch molecules during reaction,which also verified the esterfication.Crystal structure of starch esters transformed from B-type of CS to V-type,which indicated the esterification reaction occured in crystalline region of starch molecules.And the maxinmum crystalline was found in SE0.010.SEM displayed significant changes on starch esters profiles.The surface exhibied different extent of erosion andholes.Esterification in N,N-dimethylacetamide solution resulted in the starch granules tending to loose.SE0.010 composite had the the lowest thermal stability.(4)Effects of long chain dibasic acid ester effecting on the properties of cationic maize starch nanocomposites.XRD patterns displayed significant diffraction peak of SE0.010 Mt composite,which obtained the maximum crystallinity.Diffraction peak of SE0.020 Mt composite almost disappeared,and it had the lowest crystallinity.WVP values of all the starch esters nanocomposites decreased significantly,and SE0.010 Mt composite had the lowest value,1.35×10-10 g·m/m2·s·Pa.The contact angle of SE0.020 Mt reached at 100.17 °,which suggested esterification significantly improve the hydrophobic property of dodecanedioic acid cationic high amylose starch esters composite film.The strongest interface force was found between SE0.010 matrix and Mt,and it also had the highest thermal stability and almost the other performances. |
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