Biodegradability of five commercial plastic bags labelled as "biodegradable" and two referent materials were studied by a soil test for three months. As a control experiment, for studying abiotic degradation under the climatic impact (ultraviolet, temperature, and moisture) a test in a weatherometer was performed. The changes in bag samples after tests were detected by optical microscopy, Fouriertransform infrared spectroscopy, differential scanning calorimetry, and tensile testing. It was found that all the bags may be separated into two groups: based on polyesters and based on polyolefins with oxo-additives. The second group demonstrated an ability to oxidation under UV radiation. The content of chalk filler provided a mass loss of the samples under soil and climatic tests due to its washing out. Three samples on the polyester basis filled with starch (the first group) had different compositions (polymers in the matrix were different). They showed a high biodegradability under soil conditions: mass loss was 14-21%, tensile strength decreased by more than 43%, and the surface was covered by the mycelium net. However, according to FTIR-spectroscopy, at the initial stage only starch filler biodegraded intensively, while polymer matrix was stable.
The structural features and antibacterial properties of polymer–porphyrin composites were investigated. Meso-substituted arylporphyrin 0.2–0.5 wt.% was immobilized in a polylactide matrix. The immobilization of porphyrin causes a bathochromic shift and splitting of the Soret band. This study of the morphology of the obtained composites demonstrated a uniform distribution of the meso-substituted arylporphyrin in the polylactide matrix. It was determined by the X-ray diffraction analysis that porphyrin does not affect the α-form of polylactide crystalline formations. However, its addition into the polymer somewhat reduces the melting point (by 1–2 °C) and the degree of crystallinity of polylactide (by 3–4%). The elastic characteristics of the resulting systems were determined by the ultrasonic method, and a decrease in the density of the samples with an increase of the arylporphyrin content was shown. According to the results of the biological test, the dark toxicity of the obtained composites against the microorganisms Staphylococcus aureus, Salmonella Typhimurium and Escherichia coli was shown. Immobilizates containing 0.4 and 0.5 wt.% porphyrin showed the best antibacterial effect. The antibacterial activity of the studied composites makes it possible to attribute the polylactide–porphyrin systems to promising materials in the field of medicine and bioengineering.
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