Preparation And Properties Of Starch/polyhydroxyalkanoate Composite Films With High Performance

The starch-based composite films enhanced with organically modified montmorillonite were prepared by extrusion blowing from hydroxypropyl distarch phosphate(HPDSP),compounded with polyhydroxyalkanoate(PHA)to obtain high performance starch/PHA composite films.The structure,microstructure,thermal stability and molecular interactions of composite films were analyzed by X-ray diffraction(XRD),scanning electron microscope(SEM),thermogravimetry analysis(TGA)and fourier transform infrared spectroscopy(FTIR),respectively.The water vapor barrier properties,oxygen and carbon dioxide barrier properties,mechanical properties,light transmittance and color of composite films were also tested.The main results were as follows:(1)Ethylene glycol(EG),polyethylene glycol 200(PEG200),polyethylene glycol 400(PEG400)and acetyl tributyl citrate(ATBC)as coplasticizers,respectively,was blended with glycerol(GLY)as mixed plasticizers.the composite films with EG/GLY had a higher tensile strength and the composite films with PEG200/GLY had a higher elongation at break.The composite films with ATBC/GLY had a better moisture barrier property.The composite films with PEG200/GLY and PEG400/GLY had better oxygen and carbon dioxide barrier properties and a lighter surface,and the former had better light transmittance.The addition of PEG200 and PEG400 increased the crystallinity of composite films suggested by X-ray diffraction(XRD)analysis.Scanning electron microscope(SEM)exhibited composite films with PEG200/GLY had the most uniform and smooth microstructure.Thermogravimetric analysis(TGA)indicated the addition of EG and PEG200 developed the heat stability of composite films.Composite plasticizing systems had better plasticizing effects than that of GLY suggested by Fourier Transform Infrared Spectroscopy(FTIR).These results suggested that PEG200 and PEG400 had better plasticizing effects on starch and PHA,and PEG200 was better than PEG400.(2)Effects of weight ratios of PEG200/GLY and PHA content on the properties of starch/PHA composite films.The addition of PEG200 could facilitate the formation of intercalated nanostructures between starch,PHA and OMMT,and enhance the intermolecular interaction.Meanwhile,the addition of PEG200 increased the crystallinity and whiteness values of the composite films.With the addition of PEG200,the surface of the composite films became flat and smooth when PHA content was 12% and 24%.When PHA content was 12%,the composite films showed a better moisture barrier property and a higher elongation at break when the weight ratio of PEG200/GLY was 8/92;the composite films exhibited a higher tensile strength and a better light transmittance when the weight ratio of PEG200/GLY was 12/88.When PHA content was 24%,the composite films showed a better moisture barrier property when the weight ratio of PEG200/GLY was 24/76;the composite films had a higher elongation at break when the weight ratio of PEG200/GLY was 8/92;the composite films had a better light transmittance when the weight ratio of PEG200/GLY was 12/88.When PHA content was 12% and 24%,the weight ratio of PEG200/GLY was better less than 12/88 in the preparation of starch/PHA composite films.When PHA content was 36%,the moisture barrier property of composite films was improved.And the property of composite films could not be developed effectively by composite plasticizers.How to develop the compatibility between starch and PHA and improve the property of composite films should be further investigated when the PHA content was high.(3)The starch/PHA composite films were prepared with different addition amount of maleic anhydride(MAH)as a compatibilizer by two different modification methods(direct addition and dry modification).When PHA content was 12%,the composite films had a higher elongation at break prepared by the process of dry modification 5%;the composite films had a better heat stability property prepared by the process of driect addition 3%,which was slightly better than that of composite films prepared by driect addition 1% and dry modification 1%;the composite films exhibited a higher tensile strength,light transmittance and whiteness values prepared by the process of direct addition 1%;the composite films showed a better moisture barrier property,and the microstructure of the composite films became flat,smooth and uniform prepared by the process of direct addition 1%.When PHA content was 12%,the compatibility between starch and PHA was better prepared by the process of direct addition 1%.When PHA content was 24%,the composite films had a higher tensile strength and elongation at break prepared by the process of dry modification 3%;the composite films showed a higher tensile strength and light transmittance prepared by the process of direct addition 3%;the composite films exhibited a better heat stability and showed a lower water vapor permeability,and the surface of the composite films became flat and smooth prepared by the process of direct addition 3%.When PHA content was 24%,the compatibility between starch and PHA was better prepared by the process of direct addition 3%.