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There are several types of carbon fibre materials (CFM) fabricated by carbonization of hydrated cellulose (HC) fibres. In particular, the following brands of CFM are manufactured at Khimvolokno Scientific and Industrial Association: UVK, Uglen, UUT-2, Ural (Viskum), etc. [ 1, 2]. These materials not only differ in textile form, but also in the final heat treatment temperature (HTT). Thermal decomposition of HC fibre raw material in the presence of a catalytic additive, which significantly affects the physicomechanical characteristics of the f'mal product (CFM), is the basic technology for their production.The analysis of the published data on thermal decomposition of HC fibres in the presence of different additives [3][4][5][6][7] suggests that when they are correctly selected, the yield of CFM can be increased to 28-30 wt. %, the physicomechanical characteristics of the CFM can be improved, and the duration of the heat treatment stage, and formation of active groups in the structure of the CFM can be decreased, etc. In this respect, we considered studies of the effect of inorganic additives on thermal decomposition of HC fibres to be urgent and of scientific and practical interest.We investigated the features of thermal decomposition of HC fibres in the presence of sodium triphosphate in the 20-900"C temperature region and with different concentrations (0.05-0.1 M) of additives by physicochemical methods. The advantages of using triphosphates as additives in thermal decomposition of polymer fibres consist of the following: Triphosphates, also known as tripolyphosphates, are nontoxic, do not degrade fibres of any type, are incombustible, and do not corrode the equipment used for carbonization.HC twist fibre from Mogilev Khimvolokno Industrial Association was used for our studies, and sodium triphosphate was used as the inorganic additive. The samples of HC fibre were impregnated with aqueous solutions of Na5P3010 of different concentration for 0.5 and 1 h, then the excess solution was squeezed out and the samples were dried in air. The dried samples of HC fibres were carbonized in the setup shown in the diagram in Fig. 1. The reaction of thermal decomposition was conducted in a quartz reaction vessel 2 in helium medium with a temperature elevation rate of 2~ to 400~ The temperature was subsequently increased to the given temperature at the rate of 3.3 ~The sample was then raised to the top of the reaction vessel, cooled to 80-90~ and the yield and strength characteristics of the f'mal product were determined [81.The temperatures in furnace 1 were monitored with chromel alumel thermocouple 3, and the temperature elevation rate was regulated with a RIF-107 instrument. The derivatograms were made on a Q-1500D instrument. Calcined aluminum oxide was used with ethanol. The reaction of thermal decomposition of samples of HC was conducted in a current according to the following method: weighed portions of samples of HC fibres (--0.25 g) were taken and placed in a platinum crucible, and the temperature was raised at the ...

The expansion of the areas of application of carbon fibre materials (CFM) made it necessary to create new varieties with a number of valuable properties [1][2][3][4][5][6][7][8]. These properties of CFM allow using them in different areas of modern technology and in some cases, forr example, in creating construction materials, severe requirements are imposed on the physicomechanical indexes, while in other cases, the strength is not of decisive importance, but the adsorption [5][6][7][8], ion-exchange [9], or catalytic properties [10] are the most important. It is preferable to use less expensive CFM for manufacturing new CFM, so-called sorption-active materials (SCFM) [4,5]. However, there has recently been a trend toward sharply rising prices and a shortage of primary stock. The importance of using secondary resources of some textile products, for example, wastes from the flaxprocessing industry, has increased for this reason. In our opinion, the use of secondary stock (tow) from the flax-processing industry for manufacture of SCFM can be 2-3 times more efficient than using hydrated cellulose or polyacrylonitrile fibre materials. In addition, the study of thermal transformations of natural cellulose fibres is of both theoretical and applied importance, since it predetermines the possibility of regulating the processes of their thermooxidation.It should be noted that the effect of chemicaI reagents on pyrolysis of natural cellulose, wood in particular, has been the subject of many studies whose results are most completely summarized in [11][12][13][14]. As these studies showed, chemical reagents alter the temperature region of active pyrolysis of wood or polymer fibres, accelerate the process at lower temperatures, and change the activation energy of thermal reactions. The degree of the effect of the reagents is most frequently determined by the nature and to a lesser degree, the concentration of the additives.However, the effect of reagents in pyrolysis of natural cellulose is not limited to their effect on the parameters of pyrolysis alone. The quantitative and sometimes also the qualitative composition of the final product changes most frequently in carbonization of cellulose in the presence of inorganic, usually phnsphorus-containing additives [14]. The density and degree of order of the carbon matrix of the fibre simultaneously increases and its reactivity in subsequent treatments decreases [14,15].In the study examined below, carbonization and subsequent activation of natural cellulose fibre stock, in particular flax tow, were investigated by derivatographic, structural-sorption, and adsorption methods.Flax cloth (sarp cloth), nonwoven needle-punching material (NM), and flax sewing thread (GOST 11970.2-76) were used as the initial stock and NaH2PO 4, KH2PO4, and K2HPO 4 were selected as the inorganic additives. The criteria for selection of the phosphorus-containing additives were not only their effectiveness and availability, but also the technological effectiveness of their use for manufacturing CFM and ...