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

Abstract

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 mm 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.

Soy‐filled polyethylene fibers for modified surface and hydrophilic characteristics

“…Soy flour has also been incorporated into PE and other polymers in films and bulk composite forms . Soy flour, which contains 36%–56% protein and up to 35% carbohydrates, is a renewable, inexpensive material which can be used as a bio‐based filler in polyolefin matrices . Literature studies indicate that some of the polysaccharides that have been incorporated into polyolefin matrices behave as component of the blend and not merely as fillers.…”

“…Prior studies have reported that sheets produced from pure soy protein absorbed water and led to weight gain of 75 wt % . Thellen et al . found that the water absorption of the composite soy/PE thin film increased with increasing soy content.…”

“…17,18 Soy flour, which contains 36%-56% protein and up to 35% carbohydrates, is a renewable, inexpensive material which can be used as a bio-based filler in polyolefin matrices. 19,20 Literature studies indicate that some of the polysaccharides 21,22 that have been incorporated into polyolefin matrices behave as component of the blend and not merely as fillers. The dispersion and property enhancements in soy flour/ PP/linear low density PE (LLDPE) composites were reported by Iyer and Torkelson.…”

The Potential of Proteins for Producing Food Packaging Materials: A Review

“…Soy protein has been also included in the formulation of monolayer and multilayer films with polyethylene by coextrusion process, achieving a reduction of oxygen permeability; however, the moisture sensitivity increased as compared to the control without soy protein, especially in monolayer films. 75 The properties of extruded soy protein isolate films have been also improved by the addition of montmorillonite 76,77 or phthalic anhydride modified soy protein. 78 In the latter work, modified soy protein lost its thermoplastic ability and was incorporated as a filler to reinforce the protein matrix.…”

“…They also tested the effect of partially replacing glycerol with a carbohydrate plasticizer (methyl glucoside), which produced more rigid films. Soy protein has been also included in the formulation of monolayer and multilayer films with polyethylene by coextrusion process, achieving a reduction of oxygen permeability; however, the moisture sensitivity increased as compared to the control without soy protein, especially in monolayer films . The properties of extruded soy protein isolate films have been also improved by the addition of montmorillonite or phthalic anhydride modified soy protein .…”