PHOTODEGRADATION OF BIODEGRADABLE POLYMER COATINGS BASED ON POLYLACTIDE AND POLYCAPROLACTONE
DOI:
https://doi.org/10.30857/2786-5371.2026.1.1Keywords:
biopolymer coatings, photooxidation, aqueous dispersions, film formation, contact angle, surface energy, IR spectroscopyAbstract
Purpose. Comparison of the photodegradation resistance of polylactide and polycaprolactone coatings depending on the nature of the polymer and the film-forming method.
Methodology. Aqueous dispersions were obtained by emulsifying a polymer solution in dichloromethane, followed by removal of the organic solvent, washing, and concentration. Films from the dispersions were formed by applying them to a metal substrate, followed by heat treatment until a continuous coating was formed.
To assess changes caused by UV irradiation, the water contact angle and surface energy were determined, and the IR spectra of the films were analyzed. The features of film formation were analyzed, and the melt flow index of polylactide and polycaprolactone granules was determined to assess a possible relationship between the polymer’s rheological characteristics and the particle coalescence temperature.
Findings. It was found that under the influence of UV irradiation, the surface of both polymers rapidly becomes hydrophilic. For films prepared from solutions, after 8 hours of irradiation, the contact angle decreased from 74±3° to 24±3° for polylactide and from 85±3° to 40±3° for polycaprolactone. For coatings formed from aqueous dispersions, the corresponding values changed from 79±3° to 33±3° and from 58±3° to 43±3°. According to IR spectroscopy data, an increase in the area of the carbonyl peak shoulder in the 1700–1690 cm-1 region was observed, which is associated with the accumulation of carboxylic acids as photooxidation products. It was shown that coatings formed from aqueous dispersions exhibit slightly higher resistance to UV radiation compared to films obtained from solutions.
Originality. The relevance of the study stems from the need to combine the environmental benefits of biopolymers with sufficient operational stability of coatings under the influence of external factors, particularly ultraviolet radiation.
The practical value of this work lies in establishing the influence of the coating formation method on their resistance to UV aging, which can be utilized in the development of biodegradable polymeric materials with specified performance properties. The results obtained can be used to justify the choice of a method for forming biodegradable coatings with predictable resistance to photoaging.
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