Development of a melt‐extrudable biobased soy flour/polyethylene blend for multilayer film applications

Monolayer and multilayer films from biobased linear low-density polyethylene and milled soy flour were produced through cast film coextrusion processes using conventional thermoplastic processing equipment. Films containing 10 and 20% by weight of soy flour milled to maximum particle sizes of 8, 11, and 22 µm were extruded and characterized as a packaging film material. Water resistance, tensile properties, and gas permeability were measured on each film and analyzed with respects to the soy particle size, soy loading, and layer configuration in the multilayer film structure. Mechanical properties results indicated that ultimate elongation of the soy-containing films decreased by as much as 14% compared to the control, while tensile strength and maximum load testing did not reveal any identifiable trends. Monolayer soy-containing film showed high moisture sensitivity, as measured by contact angle and absorption testing, while the multilayer films demonstrated a more hydrophobic nature as indicated by higher contact angle measurements. This increase in hydrophobic properties is due to protective polyolefin skin layers, which are more hydrophobic. Oxygen transmission rates of the multilayer films decreased by 38% due to the presence of soy flour as compared to the control that did not contain any soy flour. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40707.