Using self-foaming dispenser, wet aqueous foams were prepared from isoviscous solutions of sodium lauryl sulfate (SLS) with chemically distinct polymer stabilizers. Contribution of coalescence and Ostwald ripening to the foam decay was examined from photos and video data. The bubble coarsening was estimated by dispersion analysis using the Lifshitz–Slezov–Wagner equation. Water-soluble polymers were selected from typical thickeners and suspending agents. Xanthan gum, hydroxyethyl cellulose, polyacrylamide, cross-linked sodium polyacrylate, cross-linked and hydrophobically modified (meth)acrylate copolymers were tried as foam stabilizers. By the same way, xanthan gum and submicron bentonite particles were used as foam stabilizers. Stability of the foams containing mentioned polymers as well as xanthan plus bentonite studied by the photographs and dispersion analysis. The polymers characterize by their efficacy to stabilize the wet foam. Possible reasons for poor stabilization of the foam containing cross-linked polyacrylates, both hydrophilic and hydrophobically modified, are given. The behavior of polymer-containing foams and joint stabilizing action of xanthan and bentonite are explained by variations in the structure of foam films. Graphical Abstract

The dispersity, specific surface area, porosity, and pore size distribution are determined for samples of colloidal silica and calcium o-phosphate, toothpaste constituents. The results obtained show...

Один из видов повреждения материала — пластическая деформация, которая может нарушить нормальную работу конструкции. В связи с этим разработана методика оценки степени повреждаемости металла. Для ее реализации изготовлен корсетный образец на растяжение из алюминиевого сплава системы Al – Zn – Mg – Cu. Из-за переменного поперечного сечения рабочей зоны образца при растяжении в нем возникало неоднородное напряженное состояние, для моделирования которого использован конечно-элементный комплекс ANSYS. Сначала измеряли твердость корсетного образца, затем его испытывали на растяжение до момента начала образования шейки и падения нагрузки на диаграмме деформирования. После разгрузки образца вдоль его рабочей зоны измеряли твердость по методу Бринелля и шероховатость поверхности. Результаты измерений твердости показали, что в зонах образца, где напряжения при растяжении ниже условного предела текучести материала, она соответствовала твердости исходного материала. В области образца, где при растяжении напряжения выше условного предела текучести, твердость повышалась и достигала максимума в центре образца, зоне минимального поперечного сечения. Таким образом, определяя изменение твердости и шероховатости поверхности по длине образца, связывали его с повреждаемостью материала. По результатам инструментального сферического индентирования разработана методика оценки механических характеристик материала. Она заключалась в испытании одного образца на твердость и на растяжение. По полученным экспериментальным результатам строили корреляционные зависимости нагрузок при растяжении и индентировании. Эти зависимости позволили по диаграммам вдавливания исследуемого материала получать расчетные диаграммы растяжения.

Objectives. To develop a method to obtain a hydrosol of the salt of chitosan with sulfuric acid—chitosanium sulfate (ChS) hydrosol—and to study the effect of various water-soluble polysaccharides on its stability over time, as well as its resistance to indifferent and non-indifferent electrolytes.Methods. κ-Carrageenan, sodium alginate (SA), and xanthan were used as polymers which perform the function of colloidal protection for ChS nanoparticles. Capillary viscometry was used to study the viscosity of polymer solutions, their molecular weight, and their adsorption on ChS. The stability of the sols over time and their resistance to indifferent and non-indifferent electrolytes were evaluated photometrically. The hydrosol particle size was determined by means of dynamic light scattering.Results. On the surface of ChS, κ-carrageenan is adsorbed most strongly over a wide range of concentrations. The graphs of the dependencies of the relative change in the turbidity of sols with the addition of various polysaccharides on their weight concentration at a sol lifetime of 2 days have the shape of curves with a maximum. Sols with the addition of 0.0125% SA and κ-carrageenan in the range of 0.04% have the greatest stability over time. According to dynamic light scattering data, the average particle size of freshly prepared sols with the addition of the polymers to ensure their greatest stability over time are 10.8 nm and 14.6 nm, respectively. For freshly prepared sols without polysaccharides, this size is 24.8 nm. The hydrosol coagulation threshold with an indifferent electrolyte (NaCl) is 9.3 times higher than that with a non-indifferent electrolyte (Na₂SO₄). κ-Carrageenan and SA protect the hydrosol from coagulation with an indifferent electrolyte (NaCl) at all their used amounts. At the same polymer concentrations, no protection from coagulation with a non-indifferent electrolyte (Na₂SO₄) was observed.Conclusions. A method was developed to obtain ChS hydrosol with a positive particle charge. The stability of ChS sols over time was studied both without and with the addition of SA, κ-carrageenan, and xanthan. Sol coagulation thresholds with indifferent and non-indifferent electrolytes, as well as the protective numbers for κ-carrageenan and SA against the coagulation of hydrosols with these electrolytes, were established. The mechanism of stability of sols at certain concentrations of water-soluble polysaccharides was explained using data on the adsorption of these polysaccharides on the surface of chitosan treated with a solution of sulfuric acid. Based on the results of the work, it can be concluded that SA and κ-carrageenan can be used for the efficient stabilization of ChS hydrosols over time and for the colloidal protection of ChS from coagulation with sodium chloride.