Modified Porous Starch in Development of Biodegradable Composite Polymer Materials

Abstract

Introduction. Modern food industry needs composite polymer materials based on natural compounds that accelerate the biodegradability of packaging materials. Starch is one of the most effective organic fillers. It has an excellent compatibility with synthetic polymers during extrusion. The research objective was to perform a comparative assessment of the physical and mechanical characteristics of thermoplastic starch based on enzymatic modified porous corn starch. The starch included samples both purified and unrefined from reducing substances. The samples were tested in biodegradable film production. Study objects and methods. The research featured porous starch, hybrid compositions with thermoplastic porous starch (TPS), and films based on low density polyethylene (PLD). The study involved various methods for determining biochemical and structural features of starch, e.g. electron microscopy, and physicomechanical properties of compositions and films. Results and its discussion. Compared to native starch, porous starch had a 1.6 times higher water-binding capacity and a 4 times greater solubility. Its enzymatic attackability was 24% higher, while its dynamic viscosity was a 1.7 times lower. These properties had a positive effect on the biodegradability of the films. The film samples that had the PLD:TPS ratio of 60:40 and the porous starch ratio of 40:60 demonstrated higher indicators of breaking tensile stress than the native starch samples. When the ratio of PLD:TPS was 70:30, the difference reached 14%; with that of 60:40 – 23%. Similar results were obtained for the break elongation: the indicator increased by 74% at the ratio of 70:30, by 65% at the ratio of 60:40, and by 21% at 40:60. The superior tensile stress indicator of the porous starch samples proved its higher strength properties, while the better break elongation results denoted a greater biodegradability. Conclusion. Modified starch, unrefined from reducing substances, proved more expedient for TPS and PLD film production. Unlike refined starch, it reduced the biodegradability period of the final product. The biodegradability period can be specified in a prospective study of food properties during storage using the new film.

Keywords

• polysaccharides
• starch
• hydrolysis
• plastic film
• biodegradation
• hybrid composition
• physical and mechanical properties