EFFECT OF STARCH GRANULE SIZE ON PHYSICAL-PROPERTIES OF STARCH-FILLED POLYETHYLENE FILM

Physical properties of blown films (25-60-mu-m 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-mu-m 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-mu-m 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.