Gelation in polyacrylonitrile fiber precursor during spinning from a polymer solution was examined. One of the assumptions during the study was that gelation was examined only as a diffusion phenomenon in the polymer-solvent-precipitant system and; correspondingly, a change in the concentrations of these components. A system of equations for gelation in the polymer solution having an analytical solution that could be calculated without using a computer and numerical methods was given. An analytical mathematical model of gelation with algebraic expressions for calculating the time of complete gelation and the gel thickness was obtained. The values obtained at the start of the study agreed satisfactorily with the experimental results.

The effect of the degree of water vapor sorption on mechanical properties of needle-punched nonwoven fabric based on a blend of polyethylene terephthalate (PET) fibers with 0.33 and 1.7 tex linear densities in 45:55 % ratio is investigated. The fabric strength is estimated by nominal breaking stress. A parameter expressing the ratio between nominal stress and relative tensile elongation in the first stage of the process is proposed for estimation of tensile strength. The structure of the fabric based on fibers with various linear densities is studied and the mechanism of its elongation and breaking is proposed. Increase of tensile strength and strength of moistened fabric in longitudinal and transverse directions is observed at sorption degrees ranging from 0 to 4.5-5.0 kg/kg.

A numerical model of natural convection in packages of materials with organized ventilated air gaps is presented. The results of thermal calculations of packages of materials with ventilated air gaps are considered on the example of clothing for greenhouse workers.

The mechanism of permeation of liquid ingredients of printing inks and technological fluids used in polygraphy into the layered structure of multi-layer composite sheets reinforced by fibers is established. A rubber-cloth plate used in polygraphy is used as an example to develop a method for rapid evaluation of the chemical stability of multi-layer composite sheets. The ability to protect the end sections from permeation of solvents by applying emulsions and/or solutions of film-forming polymers is demonstrated.

The article is devoted to the problem of creating composite combinations of materials for upholstered furniture of reduced fire hazard, as well as the development of proposals for improving the test methodology and fire safety requirements for upholstered furniture in public buildings with a mass stay of people. The results of assessing the characteristics of the fire hazard of materials that make up the elements of upholstered furniture are presented; an analysis of the current regulatory requirements for the fire-safe use of upholstered furniture is carried out and proposals are developed to ensure its fire-safe use.

This paper considers the problem of reliable determination of the volume of cellulose fiber and its active surface to estimate or predict the properties of the paper or cardboard manufactured on its basis. To that end, we construct a 3D model of paper or cardboard fiber using contemporary methods of sample preparation for electron microscopy along with a professional powerful graphical editor. The 3D modeling included preparation of a series of microstructure paper slices with a step of at least 10 μm followed by their transformation into a 3D body. In the Object Properties section, the vector format graphic software sets the volume of fiber material, its surface and weight. Provided that the 3D body is correctly scaled, i.e., in accordance with the dimensions specified in microscopic images, the Object Properties section generates the required parameters. The obtained 3D fiber model also enables the force direction of interfiber interaction to be determined in the 3D coordinate system. Until now, the absence of a 3D fiber model in real dimensions has impeded evaluation of the actual value of interfiber bonding forces. These forces, as vector quantities, are characterized by not only numerical values, but also directionality.

The effect of density of main punching on mechanical properties of fabric is investigated. A parameter is proposed for determining resistance to initial stretching of fabric. It is shown that the best mechanical properties are achieved at punch density of 220-300 cm-2. The effect of punch density on formation of fabric structure and fabric stretching and breakup process is examined.

A technique for determining the shear strength at the fiber–matrix interface was developed. The experiments used the copolymer of para-aramid fiber Rusar C (Termotex SPC) and a polymer composite based on KDA epoxide resin. The limiting strength was found to be 105.2 MPa. The dependence of the strength of single filaments on the clamping length, thread strength, and strength of a microplastic fabricated from this thread were used as the input information.

Issues with mathematical modeling of relaxation processes of polymeric textile materials are discussed. Application of an optimality criterion of the mathematical modeling of the viscoelasticity allows the accuracy of determining the relaxation characteristics and the reliability of predicting the relaxation processes to be controlled. The proposed method allows the problem of the technological direction of choosing materials with the optimal relaxation characteristics to be solved with respect to the operational properties.

Mathematical modeling and computer prediction of elastic, viscoelastic, and plastic deformations of polymeric textile materials are examined. Division of full deformation of polymeric textile materials into components helps solve the problem of determination of their functional properties.

The paper considers deformation operational modes of polymer fibrous materials and their mathematical modeling, representing the base for predicting the operational processes of various complexity in these materials, ranging from the simple relaxation and creep to complex deformation-recovery and reverse relaxation with the alternation of loading and unloading.

From the results of a survey of employees of a construction complex it was concluded that special work outfits used at present do not meet the requirements of protection of employees from injurious and hazardous factors that arise at the construction site. It is proposed to use synthetic fabrics for making outfits that have better performance characteristics and additional protective properties compared to blend fabrics.

The article is devoted to the development of accurate theoretical methods for predicting the pressure of compression shells on the human body. A mathematical model based on numerical methods has been developed. The software script is available for embedding as a 3D-CAD module for designing compression clothing.

The dependence of relative elongation of needle-punched nonwovens of various structures on the impact of a constant load is studied. The major stretching occurs in the first 20 seconds and then 5-10 % more until a constant value is attained in 30 minutes. Relative elongation under a constant load depends on the direction of cutting of the samples and surface density of the fabrics. Fabric stretching under constant load is determined by straightening crimped fibers in the punching process and stretching in the longitudinal direction depends on the reorientation of the fibers from the transverse to the longitudinaldirection.

The article is devoted to determination of parameters of constitution, structure, and characteristics of mechanical properties of polypropylene fabric (PPF) with due account of the number of measurements. The experimental data are processed by standard methods of the state system to ensure uniformity of measurements. The investigations made it possible to evaluate the tensile parameters and characteristics of the PPF with confidence error limits. Analytical dependencies of evaluation and confidence error limits on the number of measurements are constructed.

Determination of irreversible deformations of geotechnical nonwoven materials that have significant importance for increasing accuracy of prediction of deformation-functional processes of these materials is discussed. The noted increase of accuracy of prediction of functional processes is achieved by introducing an appropriate correction for irreversibility of deformation into integral determining equations for these processes.

Global manufacturers of high-strength high-modulus fiberglasses are analyzed. Scientific and technical information on sizing packages for fiberglasses used for reinforcement of heavy-duty fiberglasses is analyzed. Data on the adhesive strength of epoxide and polyester fiberglasses based on fibers treated with promising commercial brands of organosilicon finishes are reported.

Methods of digital prediction of deformation modes of functioning of polymer fiber materials are reviewed. Such prediction is based on mathematical modeling of functional processes of any complexity ranging from simple relaxation and simple creep processes to complex deformation-recovery processes.

The effect of the technology of roll calender processing of nonwoven needle-punched fabric based on a blend of polymer and bicomponent fibers on the correlation between the decrease of porosity and the tensile strength of the processed materials is investigated. The characteristics of fabric processing on roll calender are studied. A method is proposed for loading the calender, in which the time of contact of the fabric with the heated rollers increases. The porosity of the fabric decreases steadily with decrease of the gap between the rollers, whereupon the tensile strength of the material reaches the maximum at a particular gap between the rollers.

The article proposes a version of the mathematical model of deformation properties of polymer textile threads. Based on it, the operational processes of various complexities (from simple relaxation processes and simple creep to complex deformation and recovery processes and reverse relaxation processes with alternating loads) are predicted.