Oxidative destruction of anionite AV-17×8 using the Fenton reaction

The kinetic studies of AV-17×8 strongly basic anionite’s oxidative destruction using the Fenton reaction have been carried out. The effect of the process’s temperature and the concentration of catalysts of iron(II) sulfate or copper(II) sulfate on the oxidation of anion-exchange resin with hydrogen peroxide is estimated. With an increase in temperature in the range of 323–348 K, a regular increase in the effective rate constant of oxidative anionite destruction is observed when using iron(II) sulfate by 1.5 times, and when using copper(II) sulfate – by 22 times. It was found that the obtained values of the activation energy of the anion exchanger’s oxidation with the addition of copper(II) sulfate are 124.3–115.7 kJ/mol and are characteristic of the process proceeding in the kinetic region. The nature of the change in the surface morphology of the anionite granules in the process of oxidative decomposition has been revealed.

MECHANODESTRUCTION OF ISOPRENE RUBBER. PART 3. KINETICS OF OXIDATIVE DESTRUCTION

Continuation of studies of changes in molecular parameters, in particular, the molecular weight (MM) during the plasticization (P) of SKI-3 isoprene rubber. The kinetics of oxidative destruction (OD) in the temperature range (T) 30-130 °C and time (t) 30–600 s were studied in detail. Plasticization of rubber, as before, was carried out in a laboratory rubber mixer of the company «NFM», and gel chromatographic studies were carried out on a gel chromatograph of the company «Waters». The speed constant OD K0 decreases in absolute value with a decrease in T and an increase in t. The calculated effective activation energy of OD Eeff decreases from 24,4 to 13 kJ/mol in the studied t range. The influence of the oxygen diffusion process on the kinetic features of the OD of SKI-3 at Р is pointed out.

Thermo-Oxidative Destruction and Biodegradation of Nanomaterials from Composites of Poly(3-hydroxybutyrate) and Chitosan

A complex of structure-sensitive methods of morphology analysis was applied to study film materials obtained from blends of poly(3-hydroxybutyrate) (PHB) and chitosan (CHT) by pouring from a solution, and nonwoven fibrous materials obtained by the method of electrospinning (ES). It was found that with the addition of CHT to PHB, a heterophase system with a nonequilibrium stressed structure at the interface was formed. This system, if undergone accelerated oxidation and hydrolysis, contributed to the intensification of the growth of microorganisms. On the other hand, the antimicrobial properties of CHT led to inhibition of the biodegradation process. Nonwoven nanofiber materials, since having a large specific surface area of contact with an aggressive agent, demonstrated an increased ability to be thermo-oxidative and for biological degradation in comparison with film materials.

Synthesis and study of aroylethyl(ethyl)-xanthates as stabilizers of polymeric materials

The number of aroylethyl (ethyl)xanthates have been synthesized by the reaction of the exchange decomposition of β-dimethylaminopropiophenone hydrochlorides with potassium xanthate containing several functional groups (C=O, C=S, C–OH), which determine the use of these xanthates as stabilizers with internal synergy to polymeric materials. It was shown that the thermal stability of the compounds, depending on the nature of the substituent in the benzene ring of the molecule was observed in the temperature range of 149–196 °C. It was revealed that aroylethyl(ethyl)xanthates had a stabilizing effect due to the suppression of thermo-oxidative destruction of polyethylene; they increased the induction period of polyethylene oxidation by 2–6 times, and the oxidation rate was reduced by about 3–9 times. Among the studied compounds, 4-hydroxybenzoylethyl (ethyl)xanthate had the greatest stabilizing effect. The study of the mechanism of the stabilizing action of the compounds showed that xanthates react with cumene hydroperoxide (CHP), which proceeded through the stage of formation of an intermediate product that actively decomposed CHP, i.e., the oxidation chain was terminated by the decomposition of the CHP not by the initial xanthates but by their transformation products.

SIMULATION OF KINETIC CURVES OF THERMO-OXIDATIVE DESTRUCTION OF PROLIMERS USING DIFFERENTIAL EQUATIONS OF FRACTIONAL ORDER

In the paper it is proposed to consider fractal kinetics equations for process of thermo-oxidative destruction of melt polymers in the form of differential equations of fractional order, equaling to fraction of reactant groups of polymer, which are not subjected to destruction, with order of reaction n > 1. Small νd characterize the autoslowed-down type of reaction, and at big νd <1 - the autoaccelerated thermooxidation type with an decreasing speed of oxidation reaction, respectively much more smaller and close to an integer derivative on time of the first order. Comparative analysis of calculation results with corresponding results obtained by differential equations of integer order and degree of their matching with experimental data is given. Keywords: Fractal analysis, thermo-oxidative destruction, auto-slow and auto-accelerated type of thermal oxidation, differential equations of type and fractional orders.

Oxidative Destruction of Vulcanized by Changing the Dispersion Composition of Oxidized Vulcanized

The aim of the present work is to study the processes of oxidative destruction of waste vulcanizates (flakes) with nitric acid. The composition of the particles of the main reaction product was determined (oxidized vulcanized). The IR spectra of hexane and acetone extracts of the oxidized vulcanizates are also presented. It was found that the rubber component of the vulcanizates undergoes deep structural changes leading to the formation of products characterized by chemical heterogeneity

Mechanodestruction of Isoprene Rubber. Part 1. Process Kinetics

A method is proposed that allows us to obtain the values of the rate constants (CR) of the processes of mechanodestruction (mechanical cracking) of kм, oxidative destruction of kо, and recombination of kр macromolecules, as well as the mass fractions of the corresponding fractions of φм, φо, and φр,r involved in the plasticization process (P) of SKI-3 isoprene rubber. The method is based on the selection of the values of these parameters that correspond to the previously obtained experimental data, using the previously obtained recurrent equations and a specially developed program. The dependences of the CR on the time P at 30oC are obtained, which allows us to describe the kinetics of the processes accompanying P at this temperature, and the changes in molecular mass (MM) in this process. It is shown that constant values of CR are established at large times of P. Refined explanations of the nature of the kinetics of the CR change at P are proposed. The MM value of SKI-3 macromolecules that have not undergone destruction is calculated, depending on the time of plasticization.

INVESTIGATION OF THE INFLUENCE OF THE THERMAL REGIME OF FDM PRINTING ON THE STRUCTURING AND WARPING OF POLYETHYLENE SAMPLES

The study of the influence of the temperature of polyethylene printing on the dimensional stability of samples obtained by the method of FDM printing has been carried out. It is shown that a change in the temperature of the nozzle from 200 to 260 °C leads to a decrease in the deviation from the plane by a factor of eight. In this case, the tensile strength remains practically unchanged, and the elongation increases by 30 %. It has been established by the methods of rheological and microstructural studies that the observed effect is associated with a change in the structure of polyethylene, which is initiated by an increased temperature of the printer's extruder head. It has been suggested that the likely reason for the change in the structure of polyethylene is a change in the course of the crystallization process due to partial thermal oxidative destruction of the polymer matrix in the extruder head of a 3D printer.

A mitochondria-targeted BODIPY-Ir(III) conjugate as a photoinduced ROS generator for the oxidative destruction of triple-negative breast cancer cells

Photodynamic therapy (PDT) provides an alternative option to root out localized Triple-negative breast cancer (TNBC) and has been experiencing a surge of research interest over recent years. In this study,...