Thermal, Mechanical and Water Resistance Properties of LDPE/Starch Bio-Based Polymer Blends for Food Packing Applications

Abstract

In this study, low density polyethylene, LDPE was melt blended with starch using twin screw extruder to form biodegradable polymer blends. The LDPE/starch blend films used in food packing were obtained by hot pressing of the granules produced by extrusion process. The starch content was varied from 0 to 40 wt% of LDPE. To provide fine starch dispersion, glycerol and zinc stearate were used as plasticizer and compatibilizer, respectively. The effect of starch content on the properties of LDPE film was investigated. A good dispersion was achieved for low starch contents, but agglomeration of the starch particles occurred in the presence of high amounts of starch. The addition of starch to LDPE reduced the tensile strength, elongation at break, crystallinity and water resistance of LDPE. This decline in the LDPE properties was dramatic when the starch content was increased to 30 wt% in the blend. In addition, silver nanoparticles as antibacterial agent were incorporated to the biodegradable LDPE blend where LDPE/starch weight ratio of 60/40. Antimicrobial activities of the nanocomposite films against gram-negative bacteria (E. coli) and gram-positive bacteria (S. aureus) were determined by measuring the inhibition zone around each film. The effects of these nanoparticles on morphological, mechanical, thermal and water resistance properties of the LDPE/starch biodegradable blend were also investigated. It was observed that the incorporation of nanoparticles to the LDPE/starch blend was completely changed the morphology of the film, and accordingly, the mechanical, thermal and water resistance properties were varied depending on the nanoparticle content in LDPE/starch blend film.

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