Polymer Science, Series D最新文献

There are many ways to improve the quality of wood (including little-used wood, in particular aspen), one of which is thermochemical modification. Modification of wood with a urea solution is associated with the polycondensation of urea, lignin, and readily available fractions of hemicelluloses. Urea reacts with the hydroxyl groups of wood components to form hydrogen bonds. When treating wood with urea solutions, chemical interaction of urea with wood occurs, lignin condenses with amides at hydroxyl groups, both aliphatic and phenolic. The aim of the work is to study the strength and water resistance of adhesive joints (made from thermochemically modified aspen wood) based on polyvinyl-acetate dispersions for further use in joinery and construction production, corresponding to DIN EN 204 and DIN EN 205 standards. These standards describe the test methodology and the required values for determining the shear strength of wood along the fibers. To determine the strength and water resistance of adhesive joints, glue based on polyvinyl-acetate dispersion was used. The formation of an adhesive joint based on PVA glue with modified wood occurs due to the chemical interaction between the hydroxyl groups of cellulose macromolecules and the methoxyl groups of urea with the formation of esters. As a result of the tests, the strength and water resistance of adhesive joints of aspen wood (modified with urea) were determined; Rhenocoll Super W/DW glue complies with the DIN EN 204–2003 class D3 standard in terms of average strength and water resistance.

The methods of trimethylolpropane trimethacrylate synthesis by methacrylic acid esterification and methyl methacrylate transesterification with trimethylolpropane are considered. For each method, the influence of process conditions, as well as catalyst nature and concentration on the yield and quality of the target product, is described. Options for isolating trimethylolpropane trimethacrylate from reaction mixtures, as well as additional purification of the monomer, are considered.

For purposes of research, we used a stand for wear testing under low climatic temperatures. We investigated the operating temperature establishing process of the “powder coating–counterbody” friction unit. By means of the profilometric method, under sliding friction, we studied the surfaces of powder coatings and metal counterbodies under low climatic temperature conditions.

Accelerated laboratory tests of tubes made of Polyamide 11 with three compositions for the action of elevated temperature, thermal cycles, relative humidity, and an aqueous solution of salts for 200–3000 h are conducted. To find out the effects of aging, the weight of the samples, ultimate strength, Young modulus, and tensile elongation as well as rigidity of the tubes upon compression are measured. A clearly pronounced decrease in the weight of the tubes is found under all the conditions of accelerated tests which is induced by the removal of monomer residues, antioxidants, and plasticizers from the bulk of the samples. A result of thermal and thermal-cycle action on the tubes turns out to be an increase in their strength and rigidity accompanied by a simultaneous decrease in tensile elongation. Exposure at increased relative humidity only partially compensates embrittlement of Polyamide 11 as a result of the plasticizing action of sorbed moisture. Out of all the studied modes of aging, only exposure of the tubes in a solution of salts induces plasticization under the action of water molecules, as a result of which mechanical indicators of the polymer unsubstantially change. The performed tests show high resistance of Polyamide 11 to accelerated aging.

Studies have been conducted on the chemical resistance of various binders based on ED-20 resin and IMTGFA, KhT-152 B, and Etal-45M hardeners, as well as a binder based on modified Etal-370 epoxy resin and Etal-450 hardener. The composition based on ED-20 and KhT-152 B showed high chemical resistance in such media as water, 10% NaOH solution, concentrated hydrochloric acid, and 3.5% sea salt solution. The binder based on Etal-370 and Etal-450 has better chemical resistance to concentrated sulfuric acid. All the binder compositions studied in this work have high chemical resistance to concentrated hydrochloric acid.

Adhesion indices of adhesives based on copolymers of acrylamide and sodium acrylate to silicate glass and paper products were determined depending on the ratio of monomer units in macromolecule. An optimum ratio of units in the copolymer was established for gluing substrates.

Analysis is carried out of layer formation from a surfactant dissolved in a polar liquid (water) flowing over the layer formed on the metal surface of the nozzle channel of a waterjet cutting machine. The analysis is based on continuum models of a liquid medium, the classical theory of viscous liquids, and the theory of micropolar liquid media, as well as a nonlocal model of adhesive interactions. The mechanism of surfactant layer formation on the metal surface of the nozzle wall is determined by affecting surfactant particles by adhesion forces generated near the surface owing to a nonuniform electric field.

The current development trend in clothing production and design, namely, the processing of used items into new textile materials, is discussed in the paper. Foreign and domestic experience in recycling synthetic textiles and plastic waste into new clothing products with improved ergonomic and aesthetic characteristics for various target consumer groups has been analyzed. The prospects of the technology under consideration lie in the responsible approach of the designer to the task of reducing the level of environmental pollution by recycling waste accumulating on the planet.

Ethylbenzene hydroperoxide (EBOOH) is used as an initiator of polymerization of anaerobic adhesives. It was experimentally established that the complex of dibenzo-18-crown-6 ether with CaCl₂ (Ca²⁺∙DBC) accelerates the ethylbenzene oxidation. Based on quantum-chemical modeling by the PBEPBE-GD3/def2TZVP method, it was revealed that the formation of the catalyst’s intermediate adducts with the reaction system’s components is possible and energetically favorable. The O–O bond strength decreases both in α-EBOOH and in β-EBOOH in the adduct EBOOH∙Ca²⁺∙DBC. However, the adduct α-EBOOH∙Ca²⁺∙DBC promotes a more rapid decomposition of ethylbenzene hydroperoxide into radicals.

The results of investigation of the influence of fibrous basalt, sulphur and dicumyl peroxide content on thermomechanical properties of composites based on high density polyethylene are presented. A compatibilizer, a copolymer of high density polyethylene with maleic anhydride, was used to improve the compatibility of the blended components of the mixture. Derivatographic analysis of basalt containing plastics has shown that only at the filler content of more than 15 wt % some decrease of melting temperature of composites is observed.