Effect of starch granule size on physical properties of starch-filled polyethylene film

Physical properties of blown films (25‐60‐μm thickness) from compounded mixtures of linear low‐density polyethylene (LLDPE) and starch were investigated. As starch content increased, tensile strength, percent elongation, and light transmittance decreased and film thickness increased. Among the tested films, small‐particle corn starch (2‐μm average diameter) film had the highest elongation rate and tensile and yield strength (560%, 3.15 kg/mm2, and 1.07 kg/mm2, respectively, at 15% starch content). Potato starch (35‐μm average diameter) film had the lowest values (508%, 1.52 kg/mm2, and 0.55 kg/mm2, respectively, at 15% starch content). Potato starch‐LLDPE film had the highest light transmittance and film thickness; small‐particle corn starch had the lowest. Tensile and yield strength of the films had strong negative correlations with average starch granule diameter (R=0.99 and‐0.94, respectively). Film thickness and light transmittance were linearly correlated with starch granule size (R=0.93 and 0.87, respectively). Using small‐particle corn starch substantially increased incorporated starch level in the film while maintaining the film quality.