Polymer Science, Series D最新文献

The article reviews and systematizes information sources in the field of creating pressure-sensitive adhesives based on natural and synthetic rubbers and self-adhesive materials based on them, intended for use in the aviation industry, medicine, construction, and other areas of technology and the national economy. The article presents the results of domestic and foreign studies aimed at finding ways to modify the composition of pressure-sensitive adhesives in order to improve their adhesive, cohesive, and technological properties in self-adhesive materials. Examples of practical application of adhesive tapes based on pressure-sensitive adhesives and self-adhesive materials based on them are presented.

The work presents the results of studying the electrical characteristics of a sealing composition based on a tetraethoxysilane-modified epoxy resin filled with boron nitride. The dependence of the electrical resistance, as well as the permittivity and dielectric losses of the material in the microwave range on the content of tetraethoxysilane and boron nitride in concentrations that allow maintaining acceptable rheological characteristics for use as a potting compound is established.

A model for the assessment of the kinetics of desorption of dioctyl phthalate from polyvinylchloride films with a coating based on polyurethanes with various compositions into human blood and simulation fluids is proposed. The approach to the modeling of the kinetics of desorption of the plasticizer is based on the equations describing the kinetic dependences of desorption in the system of coordinates of the square root from the time of the process. The proposed model provides determination of the dependence of the kinetics of desorption of the plasticizer on the composition of polyurethane. The delay time of the process of desorption is found and a parameter determining the ratio between the processes of desorption into simulation fluids and blood is proposed.

The results of measuring the glass transition temperature of amorphous regions of three variants of partially crystalline polyamide-11 tubes after aging at elevated temperature, thermal cycling and in a thermal-humidity environment are presented. It is shown that, with an increase in the glass transition temperature from 4 to 56°C, the shape of the tensile-strain curves changes, the peculiarity of which is the appearance of a yield region. The difference between the upper and lower yield points increases with an increase in the difference between the glass transition temperature and the temperature of deformation loading.

Based on the literature data, a two-factor model has been developed for predicting the rate of the extraction of dioctyl phthalate from a poly(ethylene terephthalate) film with a silica-based protective coating of different thicknesses. Using the proposed approach to developing the model, the process of plasticizer desorption has been divided into two stages, which differs in the rates of transfer of an ingredient. The coating thickness affects both the desorption rate at the first stage and the plasticizer content, the desorption of which results in the transition to the second stage of the process. A numerical solution of the equation has been performed to obtain the dependence of the content of desorbed dioctyl phthalate on the protective coating thickness and on the extractant temperature.

Hot-melt adhesives are widely used for the production of disposable soft medical equipment (e.g., surgical linen, plasters) and sanitary and hygienic products (diapers, napkins, etc.). The paper presents the results of studies of the effect of butyl rubber (BR) and styrene–ethylene–butylene–styrene (SEBS) hot-melt adhesives on the properties of such compositions. It has been established that the use of SEBS starting from 30 pts wt leads to a significant increase in the strength of the compositions. However, for compositions containing SEBS, a decrease in the relative elongation under tension and adhesion to lavsan film and to nonwoven material based on polypropylene is observed. Nevertheless, the stickiness of the compositions increases. For compositions containing butyl rubber in the range from 10 to 40 pts wt, with an increase in the BR, adhesion to lavsan film and steel increases, good adhesion to nonwoven material is observed, but a decrease in relative elongation occurs, while the tensile strength of the adhesive compositions does not change.

The change in the properties of ethylene–propylene SKEPT-40- and SKEPT-50-based rubbers under thermocycling in air and a medium of DOT-4 brake fluid within a temperature range from –50 to +50°C has been studied. It has been shown that SKEPT-40-based rubber specimens have a higher degree of retaining the strength characteristics, whereas SKEPT-50-based specimens have a higher degree of retaining the hardness and relative elongation. The frost resistance of ethylene–propylene rubbers in DOT-4 medium is much better preserved as compare to exposure in the air medium due to their good stability in this medium and its plasticizing effect. The contribution of ultra-high-molecular-weight polyethylene (UHMWP) to the stabilization of both the physicomechanical properties and frost resistance of ethylene–propylene rubbers has been established.

The influence of stability conditions, processes of preventing stratification in epoxy polymers, optimal ratios between polymer matrices and flame retardants, and curing rheology on the possibility of providing the necessary level of fire safety and physicomechanical characteristics for epoxy polymers has been determined. The effect of flame-retardant fillers, such as aluminum and magnesium hydroxides and antimony(III) oxide, has been considered. It has been established that the simultaneous application of these flame retardants has a positive effect not only on the performability of filled epoxy compositions, but also on the efficiency in reducing the combustibility of an epoxy polymer due to an essential increase in the inflammation temperature. It has been shown that stability in inhibiting the precipitation of aluminum and magnesium hydroxides with a dispersity less than 10 μm in a lowly viscous epoxy anhydride composition is provided by adding 2–4 wt pts of antimony(III) oxide with a dispersity of 6–8 μm. This technological method, at an optimal aluminum and magnesium hydroxides/antimony(III) oxide ratio of 2.5 : 1, provides a rather high level of fire safety characteristics: an inflammation temperature up to 400–410°C with retention of a high level of physicomechanical properties. It has been revealed that the addition of the aforementioned flame retardants (Al(OH)₃, Mg(OH)₂, and Sb₂O₃) at quantities less than 5 wt pts has no significant effect on a decrease in the level of important physicomechanical characteristics, such as Charpy fracture toughness and ultimate tensile stress. This provides a broader application of epoxy adhesives at higher temperatures to be especially relevant in high-energy industry branches, where the use of epoxy polymers was limited earlier due to their increased combustibility. The ability of antimony(III) oxide to reduce the stratification of hydroxides in a polymer matrix due to the probable implementation of rather strong intermolecular interaction and the formation of a network of physical bonds in epoxy compositions has been confirmed.

Studies on obtaining anatase with a developed pore system of particles by hydrothermal synthesis of titanium (IV) sulfate solution with different concentrations and acidities with a change in the process temperature of 125–150°C were carried out. The precipitates formed under the above conditions correspond to the formula—TiO₂⋅nH₂O (n = 0.3–1.5). The kinetic characteristics of the process of heat treatment of precipitates with a change in temperature of 110–800°C were determined. Analysis of the diffraction patterns of the samples indicates that the formation of the anatase structure occurs due to dehydration and its gradual ordering, which is accompanied by compaction of structural bonds and increases the degree of crystallinity. Morphological properties are reduced. Conditions for the synthesis of titanium dioxide are proposed, allowing anatase with a sufficiently developed surface and high purity to be obtained, using a technical product in the form of ammonium titanyl sulfate isolated from titanite—a technogenic waste of apatite–nepheline ore enrichment.

A kinetic model is used to theoretically describe the relationship between the curing rate of methyl methacrylate adhesive and the mole fraction of syndiotactic triads in polymethyl methacrylate formed during adhesive curing with the synthesis conditions and the composition of macroinitiator used for curing. A macroinitiator was obtained by radical coordination polymerization in the presence of a peroxide or hydroperoxide initiator and zirconocene dichloride. It is shown that an increase in the initial concentration ratio of zirconocene dichloride to the initiator’s initial concentration during the macroinitiator synthesis [Mc]₀/[I]₀ in the range from 0.1 to 10 (at [I]₀ = 1 mmol/L) increases the concentration of coordination active centers in the macroinitiator by at least an order of magnitude, which increases the adhesive curing rate. At the same time, the mole fraction of syndiotactic triads in the polymethyl methacrylate formed during adhesive curing decreases. An increase in the macroinitiator synthesis’s temperature in the range of 323–343 K has a significantly weaker effect on the concentrations of active centers than a change in [Mc]₀/[I]₀ in the range of 0.1–10, which results in a weaker effect of temperature of the macroinitiator synthesis on the adhesive’s curing rate and the molar fraction of syndiotactic triads in the composition of polymethyl methacrylate.