Polymer Science, Series D最新文献

The different effects of chemical elements (carbon, oxygen, hydrogen, nitrogen, iron, etc.) on mechanical and performance properties of titanium-based alloy have been established. The optimal composition of alloying elements (carbon, oxygen, hydrogen, nitrogen, iron, etc.) of titanium for the production of dental implants with high performance properties has been established. The samples of the CONMET, Astra Tech Implant, and Alpha Bio implant systems, as well as implants of domestic production by NIITOP, have been selected for the research. The chemical composition of the samples was determined on an X-Met7500 X-ray fluorescence spectrometer (Oxford Instruments). The results of the research indicate that the distinctive features of all the implants under study, the reliability of which is proven by durability and failure-free operation, are a composition containing from 0.66 to 1.27% iron and from 0.012 to 0.058% nickel in the titanium-based alloy, as well as a minimal content of nitrogen, oxygen, and hydrogen compared to domestic VT brands.

The influence of test temperature, aging, and modification of bitumen PG58-28 with active powder of discretely devulcanized rubber on damage accumulation rate curves; fatigue parameters N_f, FREI, and F; and postpeak slope of the τ(γ) curve is analyzed on the basis of processing of experimental data of the linear amplitude sweep test using three models based on the VECD theory, five destruction (failure) criteria, and two variants of calculating the α parameter (19 variants in total). It is shown that, at small deformations, parameter N_f decreases with decreasing temperature, but increases after operational aging, while parameters FREI and F change in the same direction with aging and decreasing test temperature—parameter F increases, and parameter FREI decreases. The modification resulted in a decrease in F, an increase in FREI, and a decrease in the slope of the F and FREI curves versus temperature, as well as a decrease in the postpeak slope of the τ(γ) curve.

Using polyurethane ureas as a basis for protective coatings materials with high wear resistance and strength margin can be prepared. It has been shown that cycloaliphatic diisocyanates, such as 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate and 4,4'-diisocyanatodicyclohexylmethane, impart transparency to polyurethane urea-based coatings due to formation of a single-phase structure. The possibility of optimizing the content of antifogging surfactants in these coatings has been investigated.

This paper reviews the results of research in the field of photopolymerization of cyanoacrylate monomers and compositions based on them. Various methods and mechanisms of photopolymerization are considered. Examples are provided to illustrate the use of photopolymerization processes in various fields of engineering and medicine.

The paper presents a formula relating the hydrogen atom radius to the external pressure exerted on it. The formula only contains the fundamental constants. The possibility of hydrogen atom destruction and the temperature appearance is discussed. A criterion is proposed for the atom destruction.

A series of composites based on plasticized cellulose acetate and ground hay of meadow grasses with cellulose acetobutyrate, ethyl cellulose, and corn starch additives was prepared. The main physicomechanical characteristics and the degree of biodegradation during exposure in active soil for 60 days were determined for the obtained composites. The regularities of influence of the content of modifying additives on the properties of the materials were established.

The influence of various additives on the adhesive characteristics of compositions based on nitrile–butadiene rubber (NBR) and thiokol mixtures was studied. Indene-coumarone resin, pine rosin, highly chlorinated polyethylene resin, oil-polymer resin, product “Pavolan,” the copolymer of maleic anhydride with α-olefins C₁₂–C₁₄, and a low-molecular-weight polymer (LMWP-1), a complex of isoprene oligomers, were used as additives. It was shown that the best adhesive properties are exhibited by the compositions based on the nitrile–butadiene rubber and thiokol containing 5 parts of weight of rosin. The adhesive strength of the compositions containing rosin increases many times relative to that of the control sample. It was found that the adhesive strength of the compositions based on the NBR–thiokol mixture does not depend on the substrate type and testing method, which is typical for “pressure-sensitive” adhesives. It was demonstrated that in these compositions the used modifiers act not as adhesive additives influencing the intensity of interfacial interaction between an adhesive and a substrate but in a different way, affecting factors determining the performance of pressure-sensitive adhesives.

The work is related to the study of the strength and radiation resistance of carbon–carbon composite material used in the manufacture of medical products for traumatology and orthopedics. Composite cylindrical rods can be successfully used in transosseous osteosynthesis devices for the treatment of fractures and limb reconstruction. The studied material has the property of radiotransparency, which allows comfortable carrying out any radiographic studies necessary for monitoring the treatment process. Various mechanical tests are carried out on the samples pre-exposed to γ irradiation in a wide range of doses in open atmosphere.

Polymer composite materials based on ethylene–vinyl-acetate copolymer modified with various petroleum polymer resins applied to steel substrates were investigated. In the process of measuring the surface-energy characteristics by wetting with test liquids and calculating them using the Owens–Wendt and Van Oss–Chaudhury–Good equations, it was found that modification with resins increases the acidic (according to Lewis) properties of compositions—the free surface energy’s acid–base component and the acid parameter. The cathodic disbondment method was used to estimate the adhesive strength of modified coatings on steel, which agrees with the defect diameter in the coating after an 8-h experiment. Experimental results obtained in this work are confirmed by theoretical calculations, as a result of which the dependences were found between the defect diameter after cathodic disbondment and such surface-energy characteristics as the acid–base component of the free surface energy of polymer composites, the reduced acidity parameter, and the thermodynamic work of adhesion. Dependences obtained have a decreasing exponential nature. Based on the conducted research, a conclusion was made about the correspondence of the adhesive strength of modified polymer coatings on steel assessed under cathodic polarization conditions, as well as the thermodynamic characteristics of the materials being joined.

The review summarizes in brief literature data addressing the use of biomass components (stems, leaves, fibers, seed shells) of cultivated hemp (Cannabis sativa L.) and products based on them (felt cloth) as sorption materials for the removal of various metal ions (Ag⁺, Al³⁺, Cd²⁺, Co²⁺, Cr(III), Cr(VI), Cu²⁺, Fe³⁺, Mn(II), Ni²⁺, Pb²⁺, and U(VI)) from aqueous media. Brief information is provided on the content of chemical compounds in hemp biomass components. The review presents parameters of the adsorption processes of the considered pollutants by Cannabis sativa biomass components and processing waste. It has been shown that treatment of the latter with various chemical reagents improves sorption characteristics for metal ions. It has been revealed that the adsorption isotherms are most often described by the Langmuir model and the kinetics of the process in most cases corresponds to the pseudo-second order model.