Actually, in order to replace traditional fossil-based polymers, many efforts are devoted to the design and development of new and high-performance bioplastics materials. Poly(hydroxy alkanoates) (PHA_S) as well as polylactides are the main candidates as naturally derived polymers. The intention of the present study is to manufacture fully bio-based blends based on two polyesters: poly (3-hydroxybutyrate) (PHB) and polylactic acid (PLA) as real competitors that could be used to replace petrol polymers in packaging industry. Blends in the shape of films have been prepared by chloroform solvent cast solution methodology, at different PHB/PLA ratios: 1/0, 1/9, 3/7, 5/5, 0/1. A series of dynamic explorations have been performed in order to characterize them from a different point of view. Gas permeability to N₂, O₂, and CO₂ gases and probe (TEMPO) electron spin resonance (ESR) analyses were performed. Blend surface morphology has been evaluated by Scanning Electron Microscopy (SEM) while their thermal behavior was analyzed by Differential Scanning Calorimetry (DSC) technique. Special attention was devoted to color and transparency estimation. Both probe rotation mobility and N₂, O₂, and CO₂ permeation have monotonically decreased during the transition from PLA to PHB, for all contents of bio-blends, namely because of transferring from PLA with lower crystallinity to PHB with a higher one. Consequently, the role of the crystallinity was elucidated. The temperature dependences for CO₂ permeability and diffusivity as well as for probe correlation time allowed the authors to evaluate the activation energy of both processes. The values of gas transport energy activation and TEMPO rotation mobility are substantially close to each other, which should testify that polymer segmental mobility determines the gas permeability modality.

The hydrolytic and enzymatic degradation of polymer films of poly(3-hydroxybutyrate) (PHB) of different molecular mass and its copolymers with 3-hydroxyvalerate (PHBV) of different 3-hydroxyvalerate (3-HV) content and molecular mass, 3-hydroxy-4-methylvalerate (PHB4MV), and polyethylene glycol (PHBV-PEG) produced by the Azotobacter chroococcum 7B by controlled biosynthesis technique were studied under in vitro model conditions. The changes in the physicochemical properties of the polymers during their in vitro degradation in the pancreatic lipase solution and in phosphate-buffered saline for a long time (183 days) were investigated using different analytical techniques. A mathematical model was used to analyze the kinetics of hydrolytic degradation of poly(3-hydroxyaklannoate)s by not autocatalytic and autocatalytic hydrolysis mechanisms. It was also shown that the degree of crystallinity of some polymers changes differently during degradation in vitro. The total mass of the films decreased slightly up to 8–9% (for the high-molecular weight PHBV with the 3-HV content 17.6% and 9%), in contrast to the copolymer molecular mass, the decrease of which reached 80%. The contact angle for all copolymers after the enzymatic degradation decreased by an average value of 23% compared to 17% after the hydrolytic degradation. Young’s modulus increased up to 2-fold. It was shown that the effect of autocatalysis was observed during enzymatic degradation, while autocatalysis was not available during hydrolytic degradation. During hydrolytic and enzymatic degradation in vitro, it was found that PHBV, containing 5.7–5.9 mol.% 3-HV and having about 50% crystallinity degree, presents critical content, beyond which the structural and mechanical properties of the copolymer have essentially changed. The obtained results could be applicable to biomedical polymer systems and food packaging materials.

In our study, we investigated the accelerated aging process of PLA under 253.7 nm UV-C irradiation with the use of the GPC, NMR, FTIR, and DSC methods and formal kinetic analysis. The results of GPC and DSC indicated a significant degree of destructive changes in the PLA macromolecules, while spectroscopic methods NMR and FTIR showed maintenance of the PLA main structural elements even after a long time of UV exposure. In addition to that, the GPC method displayed the formation of a high molecular weight fraction starting from 24 h of irradiation, and an increase in its content after 144 h of irradiation. It has been shown for the first time that a distinctive feature of prolonged UV exposure is the occurrence of intra- and intermolecular radical recombination reactions, leading to the formation of a high molecular weight fraction of PLA decomposition products. This causes the observed slowdown of the photolysis process. It was concluded that photolysis of PLA is a complex physicochemical process, the mechanism of which depends on morphological changes in the solid phase of the polymer under UV radiation.

Because of the effort to preserve petroleum resources and promote the development of eco-friendly materials, bio-based polymers produced from sustainable resources have attracted great attention. Among them, polylactide (PLA) and natural rubber (NR) present prominent polymers with unique barrier and mechanical features. A series of samples with improved phase compatibility were obtained by blending PLA and NR using a double-rotor mixer. A plasticizing and enhancing effect on the polymers’ compatibility was achieved by using epoxidized soybean oil (ESO) as a natural plasticizer and compatibilizer. ESO compounding in the PLA-NR blends increased the mobility of the biopolymer’s molecular chains and improved the thermal stability of the novel material. The size of the NR domains embedded in the continuous PLA matrix decreased with the ESO content increment. The combination of thermal analysis and scanning electron microscopy enabled the authors to determine the features of potential packaging material and the optimal content of PLA-NR-ESO for the best mechanical properties.

Compositions of polylactide (PLA) and poly(3-hydroxybutyrate) (PHB) thermoplastic polyesters originated from the nature raw have been obtained by blending under shear deformations and electrospinning methods in the form of films and nanofibers as well as unwoven nanofibrous materials, respectively. The degrees of crystallinity calculated on the base of melting enthalpies and thermal transition temperatures for glassy state, cold crystallization, and melting point for individual biopolymers and ternary polymer blends PLA-PHB- poly(ethyleneglycol) (PEG) have been evaluated. It has been shown that the mechanical properties of compositions depend on the presence of plasticizers PEG with different molar masses in interval of 400–1000. The experiments on the action of mold fungi on the films have shown that PHB is a fully biodegradable polymer unlike PLA, whereas the biodegradability of the obtained composites is determined by their composition. The sorption activity of PLA–PHB nanofibers and unwoven nanofibrous PLA–PHB composites relative to water and oil has been studied and the possibility of their use as absorbents in wastewater treatment from petroleum products has been demonstrated.