677.17.494Flame-resistant PAN fibre was obtained by impregnating the finished fibre with solutions of flame retardants (FR) in different ratios of components. The oxygen index of the modified samples increased to 34.5 vol. %. The presence of a reaction between the PAN fibre and the FR due to both chemical and van der Waals and hydrogen bonds was established by calculating the effectiveness factor of the sorption reaction. The effect of FR on pyrolysis of the modified fibres was investigated. Cyclization processes began in the modified fibre at lower temperatures than for the initial PAN fibre, took place at a lower rate, and were accompanied by a high yield of coke residue.The combustibility is one of the criteria that determine the possibility of using polymers in many branches of industry. Reducing their fire hazard is one of the most important scientific and practical problems. This is confirmed by the law "On Fire Safety" passed in the Russian Federation. Problems of reducing the combustibility of textile materials remain the center of attention in research. This is indicated by the projected increase in production of fireproof textile materials.Great attention is focused on surface treatment of fabrics and fibres with flame retardants (FR) or flame retardant systems (FRS) in modern methods of reducing the combustibility of polyacrylonitrile (PAN) fibre.Note that few FR are effective in reducing the combustibility of PAN fibres, so that modification of PAN fibres using synergistic systems consisting of Pyrofix (PF) and diamidomethylphosphate (T-2) were examined here. Urea (UR) and polysaccharides (PS) were used to fix the FR in the structure of the fibre and preserve the fireproofing effect.Modification, conducted in previously selected conditions [1], included the following stages: impregnation of the finished fibre with solutions of FR with a different ratio of components at 20°C for 60 sec and bath ratio of 5; drying to a constant weight at 25±5°C; heat treatment at 150°C for 10 min for the FR to react with the fibre; washing at 40°C to remove unreacted preparation; drying.Calculation of the effectiveness factor of the sorption reaction of the fibre with the FR, which characterizes retention of the FR in the fibre after laundering, showed that the greatest increase in the effectiveness of the sorption reaction was attained by incorporation of UR, which can form inclusion compounds with both organic and inorganic substances in the modifying bath (Table 1).Since PAN fibre passes into the devitrified state at high temperatures, the effect of these conditions on the effectiveness of the reaction of the FR with the fibre was determined in the studies.In modification with the FR and FRS investigated, the high efficacy of treatment of the fibre with a bath containing mixed FR, (T-2 + PF) + PS, was established (Fig. 1). This effect persisted with all methods of modification. Moreover, it should be noted that preliminary heat treatment of unmodified PAN fibre at 100°C and impregnation with the bath at 85°C insigni...

The structural changes in standard and as-spun PAN gel fibres in modification with flame retardants were investigated using dynamic isothermal heating, thermogravimetric, and x-ray structural analysis. The characteristics of thermooxidative degradation of the fibres in predominance of structure formation over degradation were established. Modified PAN gel fibres have an OI of 40 vol. % and are resistant to wet treatment with a fireproofing effect.A number of requirements is imposed on modern industrial textile materials that determine their use in severe, sometimes extreme conditions, for example, with high mechanical loads and high temperatures. They are primarily fireproof materials with elevated performance properties for different branches of industry and flameproof work clothing.We investigated standard polyacrylonitrile (PAN) fibre manufactured on the industrial scale from the ternary copolymer of PAN (93 wt. %), acrylonitrile, 5.7 wt. % acrylonitrile, and 1.3% itaconic acid) and substandard PAN fibre from the intermediate stage of the manufacturing process -as-spun fibre which had not gone through all manufacturing processing stages and was a friable, oriented, nonequilibrium gel. The substandard fibre was characterized by a developed internal surface and high number of open pores (50-60% of the volume).A synergistic system consisting of Pyrofix (PF), diamidomethylphosphate (T-2) was used as flame retardants (FR), and flame retardant fixatives in the structure of the fibre that preserve the fireproofing effect -urea (UR) and polysaccharides (PS ) -were used as fixatives.The characteristics of pyrolysis of modified standard PAN fibres were previously [1, 2] investigated by thermogravimetric analysis (TGA). The resutls of the analysis of as-spun PAN gel fibres with this method of pyrolysis showed predominance of depolymerization processes over cyclization processes (Figs. 1 and 2).The effect of FR on cyclization was confirmed by the decrease in the intensity of the exothermic reaction and the lower weight losses during pyrolysis, and the high yield of coke residue in the modified fibres (see Fig. 1). The coke formed was characterized by higher thermal stability, as indicated by the lower weight losses at temperatures above 500°C. This was characteristic of all modifying bath compositions.The effect of modification on the structure of PAN fibres was investigated by isometric heating of the sample in the unloaded state. The essence of the method consists of recording the internal stresses that arise in gradual heating of the sample with constant tensile deformation. The temperature elevation rate is high.The shape of the diagram is also significantly dependent on the conditions of drawing the initial fibre: ratio, rate, temperature. The initial state of the PAN fibre is determined by the structure of the polymer. PAN copolymer is a highly oriented, amorphous-crystalline polymer, the crystal lattice of the PAN fibre is hexagonal, and the degree of crystallinity is 39%.The isometric heating diagram (IHD) of PAN ...

No abstract

No abstract

The possibility of modifying viscose fibre with hybrid systems containing flame retardants was demonstrated. The effect of the flame retardants on the physicomechanical properties of the fibres was determined. Bath compositions and modification parameters that ensure the sorption-diffusion reaction of the flame retardant and fibre and production of material with a high oxygen index (greater than 70%) were developed.A great deal of work has been done to create fibres with reduced combustibility. Different flame retardants (FR) are used to give fibres fireproof properties. Multicomponent systems that simultaneously contain several kinds of flame retardants (FR) have recently been used. These so-called hybrid compositions have a synergistic effect due to the combustion inhibitors they contain -phosphorus and nitrogen.We previously selected the FR and determined the temperature and duration of modification of viscose fibres [1] with hybrid systems. The FR Pyrofax (PF), diamidomethylphosphate (T-2), and methazine (MTZ) were incorporated in the hybrid systems and the following sequence of manufacturing operations was established; impregnation, heat treatment, washing, drying. We investigated the effect of the composition of the modifying systems on the properties of the viscose fibres.The viscose fibres were modified from water baths containing 20 and 30 wt. % mixtures of FR consisting of T-2, PF, MTZ, and phosphoric acid (PA). In addition, all components of the modifying bath containing phosphorus and nitrogen affected thermooxidative degradation and combustion of the fibre; methazine held the FR in the fibre, and PA played the role of a catalyst that accelerates the reaction of the reactive groups in FR and the fibre. Based on previous studies on sorption of FR, the duration of impregnation with a solution of FR of 20% concentration was 60 sec, and it was 30 sec for the 30% concentration.The amount of sorbed flame retardants increased both with an increase in their content in the bath from 20 to 30 wt. % and with a change in the ratio of methazine and phosphoric acid in it (Fig. 1). The weight losses in heat treatment and washing were lower in the fibres modified in a bath with a high content of MTZ and PA.The efficiency of the reaction (E r , %) of FR with viscose fibre [2] was determined with the equationwhere ω la , ω im are the amount of FR retained by the fibre after laundering and impregnation, respectively.Simultaneously increasing the content of both MTZ and PA in the modifying bath increased the effectiveness of the reaction and the content of FR in the fibre (Table 1). Simultaneously increasing the content of both MTZ and PA in the bath gave the fibre higher resistance to wet treatments and increased E r by 6-16%.Since the fibres were modified from water baths and viscose fibre is hydrophilic, the effect of the modification conditions on the deformation-strength properties of the fibre is natural.The studies established a correlation between the ratio of the components in the bath and the properties of the ...