Effect of Ultrasonication on Structural and Antimicrobial Properties of Polymer Compositions Based on Polyolefins Dispersed with Betulin

Food products have a limited shelf life, which remains a major challenge for the food industry. Active packaging with antimicrobial additives extends shelf life and prevents spoilage. This research tested two hypotheses: 1) ultrasonic treatment affects polymer blends based on thermoplastic polyolefins (polyethylene, polypropylene) dispersed with botulin; 2) their structural and antimicrobial properties depend on the formulation and processing parameters. The study featured polyolefin-based films (polyethylene and polypropylene), as well as polymer composites based on polyolefins and betulin. The melts of these composites were ultrasonicated during casting using a flat-die extruder (MashPlast, Russia). The structural and morphological properties of these composites were determined using a JSM-7500F scanning electron microscope (JEOL, Japan); their thermophysical properties were tested using a DSC 204 F1 calorimeter (NETZSCH, Germany). The chemical investigation relied on IR spectroscopy in an FSM-1201 device (Infraspek, Russia) with an NTR attachment. The strain and strength properties were measured on a Z010 tensile tester (ZwickRoell, Germany). The antimicrobial experiment involved the disk diffusion method. Ultrasonic vibrations were effective when the betulin content in the polyolefin blends exceeded 6 wt.%. This process provided targeted dispersion of agglomerated betulin particles od minimal size. It resulted in a homogeneous distribution of polyolefin blends during polymerization. The ultrasonic treatment slowed down the decline in strain and strength properties. The increased interfacial interaction between the polyolefins and betulin was due to the development of polar functional carboxyl and carbonyl groups during processing. Ultrasonication affected neither processing temperatures nor extrusion performance, which makes the method ergonomical and cost-effective. This research confirmed the positive antimicrobial effect of ultrasonicated polymer composites based on polyolefins dispersed with botulin. The growth inhibition coefficient for test microorganisms increased by 1.5 times, compared to the original polymer composites. For the polypropylene-based polymer composites, it was higher than for polyethylene-based ones. This phenomenon could be explained by the chemical structure of the original polyolefins. This coefficient also inhibited Candida albicans, Staphylococcus aureus, and Pseudomonas aeruginosa. However, it failed to inhibit Escherichia coli, rendering betulin unsuitable as an antimicrobial additive for this group of microorganisms. In general, the ultrasonic modification of polyolefin-based polymer composites blended with betulin showed good prospects as a component in new active food films.