Biodegradable polyester blends containing multifunctional substances of plant origin

Purpose: The research aimed to develop polyester materials based on biodegradable polymers (blends of polylactide PLA and poly(hydroxybutyrate) PHB) with additives of plant origin. Substances such as chlorophyll, β-carotene, tannic acid and comparative Magenta KeyplastTM dye have been added as stabilisers and dyes of polymer blends. Design/methodology/approach: The samples were subjected to thermooxidation and UV aging. Based on changes in mechanical properties, the ageing coefficients K of the composition were calculated. In addition, the colour change was analysed. Thermal transformations of the samples were also determined by differential scanning calorimetry in order to determine the glass transition temperature, melting and crystallisation of materials, as well as to compare the resistance to thermal oxidation of polymeric composition. Findings: Chlorophyll, β-carotene and tannic acid increased resistance to thermal oxidation of PLA/PHB blends (higher oxidation temperatures in the DSC analysis, indicating a higher resistance to thermal oxidation). Materials with chlorophyll, β-carotene and Magenta organic dye had higher ageing coefficientsand, thus, better resistance to degradation. The sample containing β-carotene showed a significant colour change under the influence of heat and UV ageing. Research limitations/implications: Concerned the short ageing time of the samples, which may have been insufficient to analyse the degradation process of polymer compositions and the effects of plant stabilising substances. In the future, the ageing time of materials can be extended, and other types of degrading factors can be used. Practical implications: Practical implications include the possibility of using PLA/PHB blends as packaging materials. Adding substances of plant origin allowed obtaining colorful, visually attractive materials, similar to the Magenta dye dedicated to using in polymers. Moreover, the additives allowed control of the degradability of the samples. Originality/value: The originality of the research was the preparation of PLA/PHB polyester blends with the addition of plant substances as multifunctional agents (stabilisers and dyes)