Effect of corn starch content in thermoplastic starch/low‐density polyethylene blends on their mechanical and flow properties

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AbstractThe aim of this work is to prepare low‐density polyethylene (LDPE)/thermoplastic corn starch (TPCS) compounds containing the highest amount of starch for biodegradable applications. It is intended to increase concentration of corn starch into LDPE without affecting basic required mechanical properties of LDPE plastics for disposable products. LDPE/TPCS blends containing different contents of TPCS (0–40 wt %) and a constant amount of LDPE grafted maleic anhydride [PE‐g‐MA (3 wt %)] are prepared using a single‐screw extruder. The prepared blends are evaluated for their mechanical, flow, and water absorption properties. Scanning electron micrographs of the samples show improvement in dispersion of the starch particles in LDPE matrix in the presence of PE‐g‐MA as a compatibilizer. The Young's modulus and impact strength properties reduce by increasing corn starch content in TPCS. The ultimate tensile strength and elongation at break of the samples show that the blends with 25 wt % TPCS have the required mechanical properties to produce plastic packaging products, as evidenced by ASTM D 4976‐04. The results of rheological tests indicate that as shear rate increases, the apparent viscosity of the blends decreases (shear thinning). The addition of starch to LDPE also decreases the melt flow index values of the samples. The water absorption of the samples increases with increasing starch concentrations at a constant time of water immersion. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012