It was found that in filtration, the initial average fractional composition of the particles of a contaminant varies from 9 to 18 μm in the filtrate, while the content of particles under 4 μm in size decreases from 50 to 3-5%, which indicates the high efficiency of filtration of particles with nap-raised nonwoven materials. The efficiency of filtration of solid particles with nap-raised materials with a surface density of 400 g/m 2 and needle-punch cloth with a surface density of 700 g/m 2 is close, which results in a more than 40% savings in fibre.Effective filtration of contaminated gases and liquids using needle-punch nonwovens is attained at a relatively high surface density, greater than 600 g/m 2 [1], which significantly increases the cost of the materials and deceases their competitiveness in comparison to other materials with similar applications. When nap-raised materials are used for these purposes, high filtration efficiency is combined with an increase in the working time of the filter materials without periodic treatment to remove accumulated sediment. Increasing the working life of treatment devices is a pressing problem whose importance increases in recovery of polydisperse particles.Increasing the duration of continuous operation of treatment devices using nap-raised materials for filtration is the consequence of the structural features of such materials, in particular, the existence of a density gradient over the thickness. The gradual increase in the density of the materials as the gases or liquids move (from the side of the nap-forming layer) results in selective filtration of trapped particles of different nature. A rapid increase in the air resistance or pressure loss of the filter materials is eliminated in such filtration conditions, which makes it necessary to remove the residue of solid particles from their surface.Nap-raised materials made from natural fibres (wool, cotton, flax, etc.) with textile processing technology are now used. These materials have important drawbacks: low chemical stability, low light fastness, heat resistance, and weatherproofing. Since natural fibres have a developed surface, solid particles strongly adhere to the fabric. In addition, the increase in the cost of natural fabrics is casting doubt on the expediency of using them for industrial purposes.The drawbacks of natural fibres are leveled by utilizing synthetic fibres (polyester, polypropylene, polyamide, etc.) in nonwovens manufacturing technology. High chemical resistance of the materials to both climatic factors and different media has been attained. The smooth surface of synthetic fibres facilitates removal of trapped particle residue from the surface of the materials [2].We determined the effect of the nap, type of fibre blends, and process parameters on the filtering properties of napraised nonwovens.Low resistance of the nap to the mechanical effect of the filtered gas or liquid stream is a common problem in using napraised needle-punch materials as filters. Increasing the resistance of the nap while ...

In processing the experimental data, an equation was obtained that can be used for predicting the change in the nap height of materials undergoing heat treatment and with a known bicomponent fibre content under the effect of mechanical loads. The optimum duration of heat treatment of nap-raised materials is 1-2 min and the temperature is 175°C.Nap-raised materials of different composition and methods of fabrication have performance characteristics that ensure their effective use. Their wide use as heat-and sound-insulating materials is due to the structural and functional features such as the density gradient over the thickness and the presence of an important proportion of pseudoimmobilized air in the napraised part. Preservation of these characteristics in time is basically a function of the resistance of the nap to mechanical loads.Nap-raised materials from synthetic fibres are fabricated with technology for production of needle-punch nonwovens [1, 2]. The process scheme for fabricating them includes forming fibre webs from polyester fibre, strengthening them by needle-punching, and napping on special equipment that ensures one-sided needle-punching with crown needles. The existing methods of napping of needle-punch cloth provide for precise regulation of the height and density of the nap, which increases the related performance characteristics. Nevertheless, increasing the resistance of the nap to mechanical loads of different natures remains a pressing problem.Another possible direction in use of materials with stable nap is using them as bases for application of polymer coatings. The developed surface of the nap-raised part of the materials increases the area of contact with the polymer binders, and this increases adhesion between the polymer layers.The resistance of the nap to the effect of a mechanical load is a function of the mechanical characteristics of the fibres, which can increase with heat treatment. At the same time, shrinkage and an increase in the density are consequences of heat treatment of the materials. The nap resistance can be increased and the density of the materials can be preserved or insignificantly altered by using a blend of fibres with different behavior on heating. The effectiveness of using materials made of blends of polyester and bicomponent fibres followed by treatment with heated air has been established in many studies [3, 4] for solving such problems.We examined the effect of the conditions of heat treatment of blended nonwovens on the resistance of the nap to mechanical loads.Nap-raised nonwovens based on a blend of polyester fibres with a linear density of 0.33 tex (TU 6-13-02204077-95-91) and 0.44 tex bicomponent fibres (South Korea) in different ratios were investigated. The structure of the bicomponent fibre consisted of a poly(ethylene terephthalate) core and a polypropylene shell. The nonwoven material was made by the mechanical method of forming a fibre web on a Spinbau unit (Germany) followed by needle-punching at a punching density of 160 cm -2 . Napping was con...