Yu. V. Tertyshnaya

Environmentally friendly films based on poly(3-hydroxybutyrate) and poly(lactic acid): A review

A review of data on the thermo, photo-, and biodegradation of compositions of synthetic polymers with poly-3-hydroxybutyrate and poly(lactic acid) is presented. The influence of these polymers on the thermal, microstructural, and rheological properties of mixtures is examined. The destruction of pure biopolymers, as well as compositions thereof with polyethylene, poly-(3-hydroxybutyrate-co-3-hydroxyvalerate), and polycaprolactone is studied.

Degradation of poly(3-hydroxybutyrate) and its blends during treatment with UV light and water

The degradation of films of poly(3-hydroxybutyrate) and its blends with ethylene-propylene rubber during their treatment with water and UV radiation at 20 and 90°C is studied. Changes in the structural characteristics of both components during degradation are investigated via DSC, IR spectroscopy, and optical microscopy. It is shown that pure poly(3-hydroxybutyrate) features the highest weight loss during degradation in distilled water at 20°C. In the case of the blends, the most significant changes in the structures of the components are observed for the 50: 50 (wt %) sample.

Thermooxidative degradation of blends based on poly(3-Hydroxybutyrate). Specifics of the process

The relationship between the structure and the kinetics of the thermal oxidation of the poly(3-hydroxybutyrate) — ethylene propylene rubber and polyethylene — poly(3-hydroxybutyrate) systems is studied. For the first system containing 30–50 wt % poly(3-hydroxybutyrate), phase inversion is observed, which affects its reactivity. For the compositions with polyethylene, two stages of oxidation manifest themselves: before and after poly(3-hydroxybutyrate) degradation.

Effect of temperature on the molecular mobility in polylactide

The effects of temperature on the molecular mobility in the amorphous phase and on the structural parameters of the crystalline phase of three brands of polylactide have been studied. It was found that annealing increases the melting temperature by 2–3°C and increases the degree of crystallinity by 2–6%. X-Ray analysis showed the possibility of formation of crystal structures of the α and β modifications in polylactide. The change in correlation time of radical rotation in amorphous regions of polylactide as a function of the history of thermal pretreatment of the samples was shown via the electron paramagnetic resonance method.

Photo-oxidative degradation of poly-3-hydroxybutyrate and polyethylene based films

The photo-oxidative degradation of films based on polyethylene and poly-3-hydroxybutyrate (PHB) is studied. Application of infrared spectroscopy, differential scanning calorimetry, mechanical strength analysis, and oxygen uptake measurements to studying photoinduced aging shows that the rates of oxidative and photo-oxidative degradation increase with the concentration of PHB in the mixture. It is found that PHB acts as an initiator of the photo-oxidation of polyethylene in the mixture. The greater the surface area of the interphase boundary in the polymer mixture, the more intense oxidation occurs at the initial stage.

Thermal oxidation and degradation of poly-3-hydroxybutyrate nonwoven materials

Studies of the thermal degradation of poly-3-hydroxybutyrate samples in the presence and absence of oxygen demonstrate that, in the first case, the degradation begins sooner, but the decomposition temperature (maximum of degradation peak) changes only slightly for two different types of samples. It is shown that the activation energy for the thermal degradation of samples without access of oxygen is higher. According to the oxygen uptake curves at T = 150°C and an oxygen pressure of p = 600 Torr, the longest induction period is observed for film samples, whereas the maximum rate of oxidation, for fine nonwoven fiber samples. The kinetics of water uptake is investigated, which shows that the thermophysical characteristics of the samples alter after exposure to an aquatic environment.

Thermal oxidation and structure of polylactide–polyethylene blends

The thermal oxidation of polylactide–low-density polyethylene mixtures with additives of oxidized polyethylene as an analogue of recyclable materials is studied. It is found that the polylactide is oxidized more slowly than polyethylene, whereas the introduction of up to 30 wt % of oxidized polyethylene accelerates the thermal oxidation of the mixtures, with the physical and mechanical properties of the resultant materials remaining suitable for practical use. It is established that the presence of oxidized polyethylene has virtually no effect on the melting point of polylactide and polyethylene, somewhat increasing, however, the degree of crystallinity of the components of the blend.

Specific structural features of crystalline regions in biodegradable composites of poly-3-hydroxybutyrate with chitosan

Differential scanning calorimetry and X-ray diffraction at wide and small angles were used to examine the biodegradable composites of poly-3-hydroxybutyrate with chitosan, produced by mixing of these polymers in a rotor disperser at 150°C. Samples of individual polymers and composites with 80, 40, and 20 wt % poly- 3-hydroxybutyrate were studied. It was found that the presence of chitosan in the composites leads to a change in the crystallite size of poly-3-hydroxybutyrate and to an increase in the large period in this polymer. Mixing of poly-3-hydroxybutyrate with chitosan affects the structural rearrangement in crystalline regions of poly-3-hydroxybutyrate under a high-temperature treatment. The effect of a high-temperature treatment of the composites via alternation of melting–crystallization cycles in the nonisothermal mode, when a sample is heated and cooled at the same constant rate of 8 deg min–1 in the range from 20 to 200°C and is annealed at a temperature of 150°C, was analyzed. This analysis suggests that, in composites of this kind, the intermolecular interaction between the components is a factor strongly affecting the structure of the crystalline regions and the mechanism of their rearrangement in the course of annealing. The mechanism of this interaction is discussed.

Effect of the Concentration of the Spinning Solution on the Morphology and Properties of Nonwoven Poly-3-Hydroxybutyrate Fibers

The nonwoven fibrous materials of poly-3-hydroxybutyrate obtained by electrospinning were studied. The average diameter of the fibers was correlated with the polymer concentration in solution. As the concentration of poly-3-hydroxybutyrate in the spinning solution increased from 5 to 9 wt %, its crystallinity in the fibrous material increased by 4–5%, and the melting temperature changed insignificantly. A paramagnetic resonance study showed that the density of the amorphous phase of the fibers increased with the polymer concentration in solution. The resistance of the fibrous materials to aggressive environmental factors also increased.

Composite Materials Based on Polylactide and Poly-3-hydroxybutyrate “Green” Polymers

Blends of polylactide with low-density polyethylene and of poly-3-hydroxybutyrate with synthetic ethylene–propylene rubber with the component weight ratios of 30 : 70, 50 : 50, and 70 : 30 were prepared and studied in comparison with the pure components. The thermal characteristics of these blends were determined by differential scanning calorimetry. The melting point of polyhydroxybutyrate and polylactide in the blends changes insignificantly, by 1–2°C. The dependence of the morphology on the composition for both polymer systems was examined by scanning electron microscopy. The physicomechanical properties of the samples are determined by the major phase. The blends undergo biodegradation in soil at 20 ± 3°С. The process occurs faster for blends of polyhydroxybutyrate with ethylene–propylene rubber of all the compositions studied.