Thermoplastics in the recycling process are characterized by mechanical and thermo-oxidative degradation, which leads to deterioration of the operational properties of finished plastic products. A possible option for giving the secondary raw material optimal characteristics during processing may be the inclusion of aluminosilicate microspheres and modifiers that increase the fluidity of the melt. This paper presents the results of the study of rheological and physico-mechanical properties of polymer composites based on secondary polypropylene filled with aluminosilicate microspheres in the presence of stearic acid. It is shown that stearic acid increases the fluidity of the melt, improves technological performance during mechanical processing, including promotes uniform distribution of particles of aluminosilicate microspheres in the polymer volume. The optimal concentration of stearic acid is 0.5 % by weight, at which there is a maximum increase in the melt flow rate, a decrease in tensile strength of no more than 16 %, as well as an increase in resistance to dynamic impact without a significant change in the elastic modulus characterizing the stiffness of the material.

Taraxacum hybernum Steven (Asteraceae family) native to Southeast Europe is a promising rubber-bearing dandelion species. In the 1930s, several phenotypically distinct forms were described in this dandelion, such as brown-achened and pinkish-achened. More than 70 years after termination of research of temperate zone rubber-bearing plants we were able to find both forms of this species of dandelion in natural habitat. The species is still poorly studied, and there is no information about the differences in the quality and quantity of rubber between brown-achened and pinkish-achened forms. Therefore, the purpose of our study was to analyze the root morphology and yield, the rubber and inulin content, and to determine the molar mass of rubber in brown-achened and pinkish-achened T. hybernum. These two forms of T. hybernum, as well as T. kok-saghyz Rodin and T. brevicorniculatum Korol., were studied. The results show that the root shape most attractive for domestication is typical of brown-achened T. hybernum. The greatest mass of roots was gained for pinkish-achened T. hybernum. The rubber content was about 6% in T. kok-saghyz, 3% in both forms of T. hybernum, and 1.5% in T. brevicorniculatum per dry root mass. Taraxacum kok-saghyz and pinkish-achened T. hybernum turned out to be the leaders in inulin content. Of all four dandelions, the molar mass of rubber was more than 1 million g/mol only for T. kok-saghyz and pinkish-achened T. hybernum. Pinkish-achened T. hybernum is a good alternative for T. kok-saghyz and can be recommended for domestication and cultivation in the temperate zone.

For butadiene polymerization with the multicenter catalyst TiCl 4 –Al( i -C 4 H 9 ) 3 the inverse kinetic task with identification of the kinetic scheme and determination of the kinetic parameters is solved. The preliminary experimental molecular weight distribution of polybutadiene macromolecules is approximated by the superposition of Flory distributions. Polymerization is modeled by the Monte Carlo method using a novel fast “inversion” algorithm that enables the time of calculations to be reduced by two orders of magnitude compared with the classical scheme of the method. It is shown that for identification of the kinetic scheme of diene polymerization in the presence of multicenter catalysts coincidence between the experimental and calculated dependences of monomer conversion on time and the dependences of average weights (or average degrees of polymerization) on polymerization time is insufficient. Coincidence between molecular weight distributions at all polymerization times is also required.

Aluminosilicate (ASM) and hollow glass microspheres (HGM) are promising fillers for recycled polypropylene (PP) due to their high chemical resistance, cheapness and low true density, due to which it is possible to obtain lightweight and durable plastic products with the possibility of their recycling.Due to the incompatibility of polypropylene and aluminosilicate microspheres in the preparation of polymer composites, the tensile strength of the samples decreases, and therefore the purpose of this work was to study the effect of polyethylene with grafted maleic anhydride (PE MA) on the properties of secondary polypropylene containing aluminosilicate and hollow glass microspheres.

The relevance of the problem under study is due to an increase in the amount of polymer waste based on synthetic polymers, which determines the feasibility of its involvement in recycling in relation to thermoplastic polyolefins. A significant proportion of plastic waste falls on plastic products made of polypropylene, while the processed raw materials almost always contain a mixture of polypropylene with different polyethylene content. The aim of the work was to study the thermal characteristics of polymer compounds based on secondary polypropylene filled with high and low pressure polyethylene. The leading approach to the study of this problem is the use of methods of thermogravimetry and differential scanning calorimetry, which make it possible to identify patterns of changes in temperature and thermal characteristics of phase transitions, as well as thermal stability of polymer compounds. It is shown that the presence of two peaks of melting and crystallization on thermograms of differential scanning calorimetry of polypropylene-polyethylene mixtures indicates the incompatibility of polymers, while the polymer system is heterophase. In the presence of polyethylene, the crystallization rate of polypropylene changes, while its melting temperature decreases and the crystallization temperature increases compared to a pure polymer. Filling the compound with polyethylene of both low and high pressure reduces the rate of decomposition of secondary polypropylene and shifts the decomposition process of compounds to higher temperatures. The mass of the dry residue when heated to 400°C and 600°C for a polymer compound with low-pressure polyethylene is higher compared to high-pressure polyethylene. The materials of the article can be useful for the creation of polymer composites based on recycled polypropylene in the presence of polyethylene, as well as the development of technological modes of their processing.

The results of studying kinetic regularities in the process of obtaining polyisoprene in the presence of neodymium-containing catalytic systems for various technological modes of industrial production are presented. The process kinetic scheme is provided under conditions of the used catalyst monocenter, according to which a mathematical model of the process of isoprene polymerization for the process periodic and continuous modes is compiled. Kinetic approach to solving problems of chemical kinetics in combination with the method of moments was applied in the process mathematical description. To evaluate hydrodynamic influence exerted by the process implementation in a reactor cascade, the constructed kinetic model was supplemented with a macro-kinetic module that takes into account the relevant patterns. Features of the starting and static modes calculation in continuous production were determined. Numerical calculation methods were introduced to obtain dependences of alterations in the molecular parameters of the resulting product for a different number of reactors used in the continuous production system under static conditions. The hydrodynamic mode influence was shown in the reaction zone on the molecular weight distribution of the resulting product. As a result of computational experiments aimed at increasing the length of the reactor cascade, increase in the average molecular weights and approximation of the obtained values to the those characterizing the process periodic mode were noted

Polymer composites based on recycled thermoplastic polymers filled with biodegradable components of plant origin are developed. Repeated thermal and mechanical action on polymers during their processing in the presence of dispersed phase particles leads to a change in the thermophysical and strength characteristics of finished products. The patterns of change in the heat resistance of the polymer composites based on a recycled block copolymer of propylene and ethylene and rice hulls processed by injection molding and pressing are studied. It is shown that filling the recycled polymer with rice hulls leads to an increase in the heat resistance of the composites, which is characterized by an increase in the deflection temperature under load, the Vicat softening temperature, and the decomposition temperature during thermogravimetric analysis in an inert atmosphere. Compared to the injection molding method, pressing of the polymer composites makes it possible to obtain more heat-resistant plastic products. This is obviously due to the differing degrees of crystallinity of the polymer phase. The high cooling rate of the polymer composite melt during the filling of the injection mold does not provide the time necessary for the corresponding change in the conformation of macromolecules and the formation of the crystalline phase. As a consequence, an increase in the content of the amorphous phase of the recycled block copolymer of propylene and ethylene reduces the heat resistance of the prototypes.

The relevance of the study is conditioned by the fact that increased consumption of synthetic polymers leads to an increase in environmental pollution due to the long decomposition time of plastic waste. As a result, it is necessary to develop polymer composites based on a biodegradable polymer matrix, and to improve the performance properties of finished plastic products, it is necessary to purposefully select cheap and affordable inorganic fillers. Thus, the purpose of this study is to investigate the regularities in the generation of a spatially structured polymer matrix under UV irradiation of polylactide-based composites filled with aluminosilicate microspheres (ASM). The leading approach to the given problem is to melt polymer composites of various compositions and to determine the physical, mechanical, and thermophysical characteristics of the prototypes, including the supermolecular structure of the polymer matrix under the influence of ultraviolet irradiation. The study suggests that the filling of polylactide with ASM particles leads to an increase in the elastic modulus, a decrease in the strength at static rupture and resistance to dynamic destructive effects, as well as heat resistance. Small aluminosilicate microspheres, when added to polylactide, perform the function of nucleation and, even with a small content, increase the crystallinity degree by 3.7 percentage points. In the range of ASM content from 1 pph to 10 pph, the absolute value of the crystallinity degree practically does not depend on the filler concentration in the polymer composite. UV (ultraviolet) irradiation in the presence of air oxygen initiates the thermooxidative destruction of polylactide and leads to the establishment of a spatially structured polymer phase using the electrostatic intermolecular interaction of additionally formed oxygen-containing functional groups in macrochains, as well as partial intermolecular crosslinking during recombination of macroradicals. The establishment of spatial structures in the polymer matrix under UV irradiation determines an increase in the resistance of experimental samples to thermal effects. It is manifested in an increase in the bending temperature under load by 7-10 percentage points, a decrease in the crystallinity degree by 1.2-2.6 percentage points, a decrease in the fluidity of the meltage and also an increase in the glass transition and melting temperature. The materials of the study are of practical value for the development of biodegradable composites based on polylactide filled with inorganic components.

The results of studying the kinetics of the polyisoprene synthesis in the presence of neodymium-containing catalytic systems under conditions of preliminary hydrodynamic action at the stage of preparation of the catalytic complex are reported. Mathematical research methods allow expansion of the results of laboratory studies to the scale of continuous industrial production and evaluating the effect of dosages of triisobutylaluminum and diisobutylaluminum hydride on the molecular characteristics of the resulting product. The essential role of triisobutylaluminum, which is initially present in the composition of the catalytic complex, has been demonstrated in the mechanism of limiting the growth of polymer chains.

The aqueous solutions of chitosan, succinyl chitosan sodium salt, and carboxymethylcellulose sodium salt are studied by the rheological method. An increase in the polymer concentration in solution leads to a sharp increase in viscosity due to formation of the entanglement network, the transition of the polymer solution to the gel-like state, a sharp increase in the relaxation time, and the appearance of elasticity of solutions. These systems are characterized by time anomalies characterized by a hysteresis loop, the area of which depends not only on concentration but also on the rate of increase/decrease of the shear rate. Thixotropy is observed in the intermediate concentration range, where supramolecular structures are formed and the time required for their destruction is comparable to the time of the experiment. This makes it possible to regulate a number of properties of materials formed from solutions. According to DSC studies, the glass transition temperatures and the melting temperatures of films obtained from solutions of different concentrations are different. The tensile stress and the elastic modulus of film polymeric materials pass through a maximum corresponding to the polymer concentration at which the maximum degree of structuring is implemented while maintaining the fluidity.

cis-1,4-Polyisoprene was prepared under conditions of the industrial production process using small high-performance diffuser–confuser tubular turbulent apparatuses in the stage of formation of titanium, neodymium, and gadolinium Ziegler–Natta catalysts, and characteristics of the synthesized rubber were determined. The catalytic systems can be ranked in the following order with respect to the content of cis-1,4-units in the synthesized polyisoprene: titanium (96.3%)–neodymium (97.5%)–gadolinium (99%); the polyisoprene obtained on lanthanide catalysts contains no trans-1,4-units. The mean molecular masses of polyisoprene increase in the same order, whereas the polydispersity coefficient varies insignificantly. Natural rubber compared to synthetic analogs contains virtually no thermally stable compounds, is characterized by higher surface microhardness, and contains about 1% volatiles.

One of the most common ways to create polymer composites based on polypropylene is to fill it with chalk, which allows one to improve the appearance of the resulting plastic products and their performance properties. The thermoplasticity of the resulting polymer composites determines the possibility of involving retired polymer materials in reprocessing, which requires studying the laws of the influence of heating on the thermophysical properties of the polymer phase. The regularities of changes in the thermophysical parameters of polymer composites based on secondary polypropylene in the process of filling it with a chalk additive have been studied. It is shown that processing of primary polypropylene by injection molding leads to a decrease in the thermal stability of the resulting secondary polymer material without changing the melting and crystallization points of the polymer phase, but it is accompanied by a decrease in the melting enthalpy (by 9–11%) and the degree of crystallinity of the polymer (by 5.6–6.5%). Filling secondary polypropylene with chalk additionally reduces the temperature of the beginning of decomposition of the composite, while the temperature corresponding to the maximum rate of thermo-oxidative destruction is shifted by 18–25°С to the lower temperature region. The introduction of 2 wt parts chalk into polypropylene reduces the melting point by 3.6°С and increases the crystallization point of the polymer phase by 1.3°С. Filling of secondary polypropylene with a chalk additive in the amount of 5–10 wt parts reduces the degree of crystallinity of the polymer, which can lead to changes in the physical and mechanical properties of plastic products.

The effect of the method and the number of processing cycles on polypropylene thermal and physical-mechanical properties is studied. It is shown that, regardless of the processing method, the thermal stability of polypropylene, expressed by the temperature of the onset of decomposition, decreases, the content of thermally stable compounds increases, and the degree of crystallinity of the polymer decreases by 5.6–6.5%. With an increase in the number of heating-cooling cycles simulating the multiplicity of thermoplastic polypropylene processing, the temperature of the onset of decomposition decreases from 211°C to 166°C, the mass of the sample decreases due to its partial decomposition, the melting point decreases from 166°C to 158°C, the degree of crystallinity of the polymer decreases. With an increase in the number of polypropylene processing cycles by compounding in the mixing chamber of the plastograph, an increase in the load on the rotation of the screws during plasticization and in the melt flow is observed, while the strength and elongation at break of the plastic sample consistently decrease..

The effect of the method and the number of processing cycles on polypropylene thermal and physical-mechanical properties is studied. It is shown that, regardless of the processing method, the thermal stability of polypropylene, expressed by the temperature of the onset of decomposition, decreases, the content of thermally stable compounds increases, and the degree of crystallinity of the polymer decreases by 5.6–6.5%. With an increase in the number of heating-cooling cycles simulating the multiplicity of thermoplastic polypropylene processing, the temperature of the onset of decomposition decreases from 211°C to 166°C, the mass of the sample decreases due to its partial decomposition, the melting point decreases from 166°C to 158°C, the degree of crystallinity of the polymer decreases. With an increase in the number of polypropylene processing cycles by compounding in the mixing chamber of the plastograph, an increase in the load on the rotation of the screws during plasticization and in the melt flow is observed, while the strength and elongation at break of the plastic sample consistently decrease..

A model of isoprene polymerization kinetics in the presence of the catalytic system TiCl4–Al(i-C4H9)3 has been developed. The feature of the model is its ability to forecast molecular-mass characteristics of polyisoprene on the basis of particle sizes of the catalytic system. It allows one to select such sizes which provide necessary fluidity for the use of polyisoprene as a component of vulcanized sealant.

When processing and operating polymer materials under the influence of environmental factors (ultraviolet radiation, moisture, oxygen, ozone, etc.), a change in their properties is often observed. This research is devoted to the study of the effect of chalk additives on morphology and topography, as well as the physical and mechanical properties of samples based on recycled polypropylene raw materials after exposure to UV radiation in air. In order to confirm the occurrence of photo oxidative processes, the data of two methods were used: modified iodometric analysis and IR spectroscopy. The physical and mechanical properties of polymer composites before and after photo aging were determined on standard 1 mm thick blades. To study the surface changes of experimental polymer composites under the influence of ultraviolet radiation, atomic force microscopy was used. The result of the experiment is the proof that the chalk additive interferes with the intensive course of photo-oxidative degradation. In general, the introduction of a chalk additive in a small amount (2 to 10 weight parts) allows maintaining the strength characteristics of composites based on recycled polypropylene raw materials after exposure to UV radiation in air, probably because of crosslinking of macromolecules due to the intermolecular interaction of hydro peroxide groups accumulated by the polymer, as well as involving only surface layers of composite samples in the photo oxidation process. Moreover, the analysis of AFM images of samples subjected to ultraviolet irradiation for 18 hours shows that the surface becomes smoother. This is confirmed by the calculation of the root mean square roughness and the maximum height of the roughness. Further irradiation for additional 18 hours leads to an increase in roughness, which indicates a change in the supra molecular structure in the surface layers of polypropylene as a result of photo oxidative transformations. Therefore, from the obtained composites, one can expect the maintenance of operational characteristics during the period of consumption, followed by decomposition under the influence of environmental factors.