A method for dyeing thermostable PMA fibre with disperse and cationic dyes using a swelling agent is developed. The effect of the duration of treatment in the swelling agent and the concentration of dye in the dye bath on the colors obtained and their resistance to physicochemical effects are established. Dyeing of PMA fibre with the method developed does not significantly decrease its fundamental physicomechanical indexes. No changes are found in the structure of the dyed PMA fibre by x-ray diffraction.Thermostable fibres have a special place in dyeing of textiles, since dyeing them involves great difficulties caused by the chemical structure of these fibres, such as the high degree of orientation of the macromolecules in the polymer chain, high crystallinity and density of the structure, and the pronounced intrinsic coloring.Studies on development of a dyeing process for thermostable fibres using traditional technologies are continuously being conducted all over the world. The number of methods of dyeing these fibres is relatively large, but each one is usually oriented toward a certain fibre, which limits their use or makes it impossible to use them with fibres of different structure. For this reason, the conditions of obtaining stable, saturated color are individual for each of the existing fibres.There is also no universal method of dyeing aramid fibres except for bulk dyeing. In most of the proposed methods, the fibre is processed to reversibly loosen its structure, followed by incorporation of a dye or substance with active groups and capable of binding with the dye. There is a method of dyeing polyaramid fibres (Nomex, Kevlar) with anionic dyes by providing these fibres with active sites capable of reacting with the anionic groups in the dyes [1]. The fibres are first treated with a composition containing a solvent, aliphatic or aromatic amine, and a wetting agent. They are then returned to the unswollen state, for example by drying, and dyed with cationic dyes using traditional technology.Russian researchers suggest using a composition containing 0.2-0.5 g/liter of sodium alkyl sulfate and a cationic dye for dyeing polyhetereoarylene (PHA) fibres [2]. Dyeing after preliminary treatment of the fibres in an alkyl sulfate solution is also possible.A method for continuous dyeing of poly-m-phenylene isophthalamide fibres with acid, active, cationic, direct, and disperse dyes and pigments is described in [3]. With this method, the fibre is processed in a mixture containing a solvent, neutral agent, and dye at a 70-90% concentration of solvent and temperature of 18.3-93.3°C.The meta/para-aramid (MPA) fibre studied in [4] is almost undyeable with any of the existing classes of dyes in ordinary conditions. The fibre itself has a pronounced yellow-green color which creates additional difficulties in dyeing. Developing a process for dyeing MPA fibres or articles made from them in conditions of limited swelling is a fundamental problem. It is necessary to preserve the basic performance characteristics: heat resistan...

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