The effect of the content of active co-monomer, itaconic acid (IA), in PAN fiber on the thermal chemical transformations of the fiber during oxidation was studied. It was shown that the temperature for the start of the exotherm decreased as the IA content increased to 1. 8-1.9% and remained constant at 182°C as the content was increased further. A study of the effect of the degree of oxidation on the change of thermochemical characteristics of PAN fiber found that two successive exothermic processes occurred. The difference in their mechanisms was explained by the effect of autocatalysis that was due to catalytically active centers of the macromolecules that arose during the oxidation and contained polyconjugated bonds.The process for producing carbon fibers from fibers based on acrylonitrile copolymers includes two basic steps that differ in their reaction conditions. In the initial step (oxidation), polyacrylonitrile (PAN) fiber is subjected to relatively lengthy (60-100 min) gradient heating in air. The oxidized PAN fiber is subjected to further heat treatment (carbonization) that is carried out in a non-oxidizing gas, Ar or high-purity N 2 .Two principal processes, structuring of PAN fiber and destruction of the polymer, occur during the course of the oxidation. The term structuring means the rearrangement of linear PAN macromolecules into molecules with a staircase structure that contain polyconjugated systems [1]. This process can be viewed as the initial step in the transformation of the polymer structure into a graphitic one. Two principal reactions, oxidative dehydrogenation of the PAN macromolecule hydrocarbon chain and polymerization of nitrile groups to form naphthyridine heterocycles, occur during the structuring. Conditions such as heating, which favor preferential occurrence of structuring and minimize destructive processes, make it possible to convert PAN fiber into carbon fiber.One of the most important features of the oxidation of PAN fiber, which is characteristic of the oxidation of any organic compound, is its exothermicity. If the process heating regime is not followed, the heat released as a result of the reaction can increase uncontrollably and lead to destruction as a result of the predominance of destructive processes. Therefore, one of the main methods for investigating the oxidation of PAN fiber is to study the heat releases accompanying this process.The kinetics of thermal oxidation of PAN fiber are rather complicated and depend on the heating conditions. Published results of numerous investigations of this process were based on a study of fiber samples that were oxidized under laboratory conditions and did not correspond with heating regimes under industrial conditions. These conditions can be considered only to approximate those of the actual industrial process for producing conditioned carbon fiber. However, it is impossible to measure directly heat releases during continuous heat treatment of PAN fiber under conditions close to the industrial ones.Herein thermal effects observed ...

The process of carbon fibre finishing by various finishing agents is studied. Analysis of the obtained data show that the test finishing agents, vis-à-vis the standard one, improve the properties of the fibre and the fibreglass based on it. The strength of monofilaments containing the finishing agent is slightly lower than that of thread containing a standard finishing agent, but the degree of attainment of the strength in fibreglass and, consequently, the value of the attained strength is much higher when the test finishing agents are used. The test finishing agents of 2 and 3 type increase the abrasion resistance of carbon tows by 80%.High-strength, high-modulus carbon fibres are nowadays the most effective reinforcing fillers of composite materials. Most commonly, epoxy resins are used as a binder in such composites. The activity of nonpolar surface of carbon fibres submitted to heat treatment at about 1500°C in nonoxidizing medium for its manufacture leads to weak reaction with polar groups of epoxy resins.Two methods are employed to intensify their reaction. The surface of the carbon fibres are activated (oxidized), which increases the specific surface of the fibre and facilitates formation of surface oxygen-bearing groups, and a thin layer of oligomers, generally containing active epoxy or amino groups, is laid on the surface. Such a layer markedly increases adhesive interaction between the active groups of the carbon fibre and the functional groups of the binder.The function of the finishing agent, however, is not merely to promote adhesion between the filler and the binder in the composite. Since carbon fibres are highly brittle and wear out on abrasion easily, their protection against breaking in subsequent treatment processes (weaving, producing prepreg, winding, etc.) acquires special importance. The finishing agents for carbon fibres must therefore have affinity to the fibre and the binder as well as high lubricating properties. Further, the finishing agents must reduce stresses developed on the fibrematrix interface under dynamic loads due to the difference in the deformation properties of these components of the composite. Finishing agents consisting of epoxy resins have been used in Russia so far to produce carbon fibres. After drying, a layer of such resins, in spite of its small thickness, remains brittle and transmits this brittleness to the fibres without enhancing the ability of the fibre to undergo subsequent treatment.In this work, for finishing carbon fibres we used a mixed composition containing aqueous dispersions of epoxy resins and polyurethane and aqueous solution of trialkoxysilane. Polyurethane was used to stabilize the dispersion and enhance the elasticity of the finished fibre, and trialkoxysilane played the part of elastic cross-linking of the finishing agent molecules and for imparting the properties of the lubricant to it. As a result of preliminary studies of various versions of finishing agent preparations from a number of starting compounds, the basic compositions that ensure...