The infuence of starch hydrophilization on the mechanical properties of the biodegradable starch/EAA composites

Abstract

The aim of this study is to investigate the infuence of chemically modifed native starch on the mechanical properties of composite materials. The starch (S) was modifed by diisopropyl D-tartarate (DIPT), ricinoleic acid (RA) and epoxidized soybean oil (ESO) in the frst step, S/(DIPT/RK/ESU), and by polypropylene functionalized with maleic anhydride (MAPP) in the second step, S/(DIPT/RK/ESU)/MAPP. The ethylene-acrylic acid copolymer (EAA) was used as the polymer matrix of composites. The composites were made with 30 wt.% of all obtained modifed starches as fllers. The chemical structure was examined by a Fourier transform infrared spectroscopy (FTIR). A morphology of starch particles and composites was examined by feld emission scanning electron microscope (FESEM). Tensile strength, the toughness of the composite materials (Charpy method) and biodegradability were investigated. Modulus of elasticity of composites was increased by the addition of modifed starch up to 89% for S/RK/MAPP/EAA which also exhibited the highest Charpy impact strength. Thermal stability of composites was evaluated by thermogravimetric analysis (TG) and diferential scanning calorimetry analysis (DSC). The composite with starch modifed by the two-step process, S/(DIPT/RK/ESO)/MAPP was the most difcult to undergo biodegradation than composites with S/(DIPT/RK/ESO).