Technological aspects of obtaining materials based on thermoplastic starch

The development of materials based on thermoplastic starch is relevant when creating eco-safe packaging, as well as promising for obtaining functional materials in other industries. Starch is one of the most affordable and cheap natural polysaccharides, but the production of films and body products based on it is complicated by retrogradation processes, and technological methods of plasticization, crosslinking and compounding are necessary to solve this problem. The aim of the study is to develop a formulation for obtaining a starch-based film material with satisfactory physical and mechanical properties. The objects of the study were two types of starch - potato and corn, polyvinyl alcohol (PVA) and gelatin were used as binding polymers, and a mixture of urea and glycerin in various ratios was used as a complex plasticizer. The films were obtained by liquid-phase compounding of 5% starch solution and 5% binder polymer solution, followed by casting and dewatering in air. The strength parameters of the obtained films were determined according to GOST 11262-2017 (using a RM-50 bursting machine with StretchTest software), water solubility was assessed visually, sorption properties were assessed through swelling by weight (when exposed in a desiccator with water, t = 20 ° C). It was found that the use of the complex plasticizer "glycerin + urea" effectively reduces retrogradation processes in the production of films from starch (it is preferable to use potato starch due to the higher content of amylopectin, which increases the elasticity of films), the optimal content of the plasticizer is 30 wt.h per 100 wt.h. starch, increasing the amount of urea increases the strength of the material, the minimum amount of binder (polymer) is 20 wt.h. per 100 wt.h. starch, while the films acquire flexibility (resistance to fracture), fragmentation of films during exposure in water begins when the temperature reaches 60 ° C (before that, the films swell, but retain the integrity of the shape), the fragmentation rate is maximum for samples containing gelatin as a binder, the sorption capacity of experimental samples for water vapor reaches 120-200 wt.%, while samples containing PVA as a binder have a better moisture retention capacity