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With an adequate mathematical model, it is possible to study the effect of the most important technological parameters on the fibre formation process and to optimize it with consideration of the equipment, spinning conditions, and linear density of the fibre. The promise of regulating the spinning process by addition of a precipitator to the spinning solution was demonstrated.Spinning of polyacrylonitrile (PAN) fibre has been relatively widely described in the international literature [1][2][3], but as always in the study of complex, multiparameter technological processes, there are still a number of important factors which it is difficult for the human mind to grasp without using computers and mathematical models. Regulation of the technical and economic parameters of the technology and the properties of the fibre by varying the conditions of fibre formation is such a factor in the technology of production of PAN fibre by the water-dimethylformamide method. We will assign the parameters which have the greatest effect on the spinning process to such conditions: the temperature of the spinning solution and spinning bath, the concentration of precipitator in the spinning bath and spinning solution, and the duration of the process. The latest mathematical model of this process accounts for all of these parameters. The model, its substantiation, and verification of the adequacy were published previously [4][5][6][7].In contrast to the previously developed models of this process, the model accounts for heat exchange and phase transition processes. The equilibrium and heat exchange conditions will naturally undergo some changes during fibre formation under the effect of rheological factors. Unfortunately, this model does not yet take into consideration the rheological factor, but based on previous experimental testing of the model, it is poss~le to perform calculations of the fibre-formation process with sufficient certainty (from the technological point of view).Obtaining a gel-like (totally coagulated) fibre with a def'med structure of the gel at the outlet of the spinning bath is the basic problem of fibre formation. If gelation is not terminated in the spinning bath, spinning becomes unstable and the quality of the fibre becomes inhomogeneous, which is usually undesirable. For this reason, the time of total gelation (solidification) of the spinning solution in the spinning bath is one of the basic parameters in fibre fabrication technology.Let us consider the effect of the above parameters -temperature of the spinning solution tsp and spinning bath tsb, concentration of water in the spinning bath Csb and spinning solution Css on the gelation time ~-g.The research described here was conducted by the classic method. The total gelation time was determined by setting the fibre formation parameters, except for one, at a constant level, only varying one parameter, with a computer, model, and appropriate software.One of the simplest methods of changing the gelation time of the spinning solution in the spinning bath is to ...

The thermal properties of the aromatic fibres Arselon, Arselon-C, Arimid, and Armos, as-spun and heattreated are investigated using methods of thermomechanical and dynamic thermogravimetric analysis and differential scanning calorimetry. According to the TMA data, Arselon, Arselon-C, Arimid, and heat-treated Armos fibres retain size stability up to 400°C. Shrinkage is no more than 1-2%. As-spun Armos fibres lengthen insignificantly (under 7%). The temperature characteristics of aromatic fibres obtained by TGA and DSC show that thermooxidative degradation markedly begins only at temperatures above 390-400°C.Thermostable aromatic fibres and the textiles made from them are widely used in manufacture of articles for occupational protection: special clothing for rescuers, firemen, metallurgists, workers in the petroleum and petrochemical industry, and for manufacture of thermostable filter materials, thermal and electrical insulation, and other articles [1][2][3][4][5][6][7][8].During manufacture, processing, and use, thermostable fibres, fibre materials, and articles made from them are exposed to intensive thermal effects which alter their structure and properties as a function of the temperature, duration of exposure, composition of the environment, and other factors. The occurrence of these changes is correlated with the temperature characteristics of the materials: temperatures of relaxation and phase transitions, thermochemical transformations.The thermal characteristics of para-aramid fibres were analyzed in [2,3,9]. Thermal degradation of Oxalon polyoxazole fibres is examined in [10]. These and other studies were conducted by different methods, so that in many cases, the results obtained differ significantly, and there is no published comparative analysis of the thermal characteristics of different thermostable fibres/thread using the same instruments and methods.The manufacturing processes for thermostable fibres are improving, and new modifications of thermostable fibres are appearing.