The Influence of Maltodextrins on the Structure and Properties of Compression-Molded Starch Plastic Sheets

摘要

Starch plastic sheets were prepared by compression molding of starchbased plastic granulates.The granulates were prepared by extrustion processing of mixtures of tranular potato starch and several maltodextrins (5% w/w) in the presence of glycerol and water as plasticizers and lecithin as melt flow accelerator.The materials were semicrystalline,containing B0type,adn E_h-type crystallinity.The properties were dependent on water content.For the materials,a brittle-to-ductile transition occurred at a water content in the range of 11-12%,which was in accordance with the observed glass transition temperature.The structural and mechanical properties were a function of starch composition and maltodextrin source as well as molding temperature.The amount of granular remnants and residual B-type crystallinity decreased with increasing processing tremperature.The amount of recrystallized singlehelical amylose increased with increasing temperature.At molding temperatures in the range of 180-200 deg C,a sharp decrease in starch molecular mass occurred.The influence of molding temperature was reflected in a sharp increase in elongation at molding temperature above 160 deg C and a gradual decrease in elastic modulus.The tensile strength showed an initial small increase up to 160 deg C and a sharp decrease at higher molding temperatures.