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The pore structure of heat-treated nonwoven materials is determined by the conditions of heating and cooling them. The effect of the shrinkage properties of a bicomponent fibre on the pore structure of the materials is manifested at a treatment temperature above the melting point of polypropylene.The effectiveness of using nonwoven materials for filtration and as fibrous sorbents is basically determined by their pore structure. At the same time, the mechanical properties of these materials should ensure resistance to development of deformation. The comprehensive requirements imposed on filtering materials and fibrous sorbents have made it necessary to combine mutually exclusive characteristics such as low density and high mechanical strength.One possible method of obtaining highly porous and strong materials involves to addition of shrinkable fibres to the nonwovens and conducting heat treatment in the final stage of production. The proposed methods of formula and process modification of nonwovens can affect their pore structure. In studying the formation of the pore structure in nonwovens containing polypropylene fibres in [1], it was previously shown that this process takes place in conditions of significant shrinkage over the area of the material and changes in the initial structure formed in the needle-punching stage. The change in the structure of the materials causes the formation of closed pores unavailable for transfer of gases and liquids in the bulk of the materials.We investigated pore structure formation in nonwovens containing bicomponent fibres treated with heat at different temperatures. Nonwovens made of a blend of polyester fibres with a linear density of 0.33 tex (TU 6-13-0204077-95-91) and 0.44 tex bicomponent fibre with an outer polypropylene shell and a poly(ethylene terephthalate) core (South Korea) were investigated. The materials contained 20 and 40 wt. % bicomponent fibres. The samples of the nonwoven material were made by the mechanical method of spinning the fibre web followed by needle-punching at a punching density of 160 p./cm 2 .The real (V r ) and apparent (V a ) pore volumes of samples with an area of 100 cm 2 , determined with the following equations [2], were used as the pore structure characteristics of the initial and thermostated materials:where V 1 is the volume of the sample, cm 3 (according to GOST 3811-72); m 1 is the weight of the sample, g; ρ is the density of the fibre blend determined pyknometrically and equal to 1.21 g/cm 3 ; m 2 is the weight of the sample after holding in water, g; ρ w is the density of the liquid (water), g/cm 3 .To determine the apparent pore volume, the disk-shaped samples were placed in distilled water for two days. After removal from the water, the samples were placed on a screen and left there until all of the liquid had drained. The samples were weighed in a plastic container of known weight, which excluded losses of water in handling the samples during the experiment.The dependence of the real and apparent pore volumes of the materials on t...

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