L. S. Shibryaeva

MORPHOLOGICALLY SPECIAL FEATURES OF POLY(3-HYDROXYBUTYRATE)/LOW-DENSITY POLYETHYLENE BLENDS

In an effort to investigate the morphology of biodegradable films, the combination of differential scanning calorimetry, scanning electron microscopy, and Fourier transform infrared polarization spectroscopy methods are used. The methods enable one to examine the structural and morphological peculiarities of extruded blend compositions on the base of low-density polyethylene (LDPE) and poly(3-hydroxybutyrate) (PHB) at concentrations of the latter ranges from 0 to 32 wt%. The blend components are thermodynamically incompatible and form the proper morphological elements with good visible interfaces between the disperse phase (PHB) and the continuous matrix LDPE. For film extrusion, blend components affect each other, as is seen by the crystallinity drop for both PHB and LDPE. The dichroism measurements show that the axes of LDPE and PHB molecules are presumably located at right angles, therewith the largest axes of the PHB crystallites are oriented along the extrusion direction. The matrices at all blend ratios, besides 32 wt% composition, are reinforced by alternative bandlike and cylinderlike fibriles of PHB. The architecture of such morphological elements is carefully studied by the SEM method.

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.

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.

Influence of different factors on the destruction of films based on polylactic acid and oxidized polyethylene

Influence of different environmental factors on the degradation of film samples based on polylactic acid and low density polyethylene with the addition of oxidized polyethylene was studied in this work. Different methods were used to find the relationship between degradation and ultraviolet, moisture, oxygen. It was found that the addition of oxidized polyethylene, used as a model of recycled polyethylene, promotes the degradation of blends.

Structural Effects in Oxidation of Polypropylene

Structural rearrangements occurring in the course of oxidation of isotropic and oriented samples of isotactic polypropylene were studied. The mechanisms of structural rearrangement in intercrystallite regions of isotropic and oriented samples were examined. The character of relaxation transitions in oriented polypropylene was studied in relation to the structures of the initial fibrils and of interfibrillar and intrafibrillar regions.

Morphological Features of Poly (3-Hydroxybutyrate)/Low Density Polyethylene Blends

Abstract In an effort to investigate the morphology of biodegradable films, the combination of DSC, SEM and FTIR polarization spectroscopy methods are used. The methods enable us to examine the structural and morphological peculiarities of extruded blend compositions on the base of PELD and poly(3-hydroxybutyrate) (PHB) at concentration of the latter ranges from 0 to 32 wt%. The blend components are thermodynamically incompatible and form morphological elements with good visible interfaces between disperse phase (PHB) and continuous matrix (LDPE). For film extrusion, blend components affect each other that is seen as the crystallinity drop for both PHB and LDPE. The dichroism measurements show that the axes of LDPE and PHB molecules are presumably located at right angle, therewith, the biggest axes of the PHB crysrlallites are oriented along the extrusion direction. The matrices at all blend ratios, besides 32wt% composition, are reinforced by alternative band and cylinder-like fibriles of PHB. The architecture of such morphological elements is carefully studied by SEM method.

Thermooxidation and Biodegradation of Nonwoven Biopolymer Fibrous Materials

This paper studies water absorption and processes of thermooxidative destruction and biodegradation of film and nonwoven fibrous materials based on the natural polymers polylactide and polyhydroxybutyrate. Nonwoven fibrous materials were obtained by electrospinning, and film fibrous materials were obtained by watering onto the glass surface. It was determined that fibrous materials have high water absorption and a high oxidation rate in comparison with film materials, which significantly accelerates (by about five times) the processes of biodegradation under environmental conditions. Fibrous nonwoven material from biodegradable polymers is an important development as a disposable soil mulching material and a covering material that has a service life of less than 1.5 months under natural conditions.

PRESOWING TREATMENT OF SEEDS OF SPRING WHEAT WITH LOW-FREQUENCY ELECTROMAGNETIC FIELD

Seeking for effective natural stimulants that enhance crop productivity is relevant to ensure high quality yield production. The influence of physical factors (e.g. electric and magnetic fields, ultraviolet, infrared, laser irradiation) on seeds which contributes to an increase in sowing properties, plant photosynthetic activity, survival and yield is in the focus for researchers. However, a more detailed study of the mechanism of energy influence on the internal seed structure, plant growth and development sill remained relevant. Besides, it is necessary to develop effective, simple, reliable and low cost devices for agrophysical stimulation. The Federal Scientific Agroengineering Center VIM together with the Kazakh National Agrarian University has developed low frequency electromagnetic radiation construct which is mounted directly on combine-harvester to expose seeds to electromagnetic field during harvesting. The purpose of this study is to assess the sowing qualities of seeds and biometric indicators of the derived plants of spring wheat (Triticum aestivum L.) variety Omskaya 18, as influenced by low frequency electromagnetic fields depending on intensity and time of irradiation. The seeds were harvested in September 2015 (Republic of Kazakhstan). The construct used was developed on the basis of the magnetotherapy apparatus Almag-02, placed on a combine-harvester Enisey 1200 NM (Russia). We compared different modes of seed exposure. These were flow treatment (a dynamic mode) at magnetic induction B = 6 mT and frequency f = 10 Hz; static treatment for 3, 6, and 9 min at 6 mT and 3 Hz/16 Hz, and flow treatment at 6 mT and 3 Hz/16 Hz. Irradiated and non-irradiated seeds (control) were used in further studies. Seed germination parameters were estimated in laboratory tests. The seeds were germinated on filter paper in Petri dishes in darkness in a thermostat LP-113 (Labor Muszeripari Muvek Esztergom, Hungary). To assess the growth and development of seedlings and plants we used a phytotron Vic-Terra (FSAC VIM, Russia). Treatment with low frequency electromagnetic field for 9 min in static mode increased seed germination energy and germination rate by 12-13 %. When irradiating seed flow, germination was below the control, e.g. at 6 mТ, 10 Hz this parameter decreased by 4.3 % in the laboratory test and by 3.5 % in the phytotron. Plant weight and height were higher in the irradiated samples. Under static irradiation for 9 min at 6 mТ, 3 Hz and 16 Hz the plant weight was 0.56 and 0.59 g, respectively. The smallest weight (0.46 g per plant) resulted from flow treatment at 6 mТ, 16 Hz. After storage of treated seeds at laboratory conditions for 3 and 7 months the indicators (germination energy and germination rate) remained satisfactory. The best result was noted for seeds, processed in static mode for 9 min at 6 mТ, 3 Hz/16 Hz. A decline in sowing properties did not exceed 6 %, indicating the preserving effect of the electromagnetic field.