Aspects on interaction between multistage stabilization of polyacrylonitrile precursor and mechanical properties of carbon fibers

Abstract

SYNOPSISThe progression of polyacrylonitrile (PAN) fibers on multistage stabilization stage has been monitored by following the variations in density, elemental composition, morphological aspect, and mechanical properties. The effects of various processing conditions during the multistage stabilization on the mechanical properties of final carbon fibers were evaluated in detail. To achieve an optimal extent of stabilization of PAN fibers is critical as the final mechanical properties of carbon fibers are concerned. This aim can be realized by adjusting and matching the temperatures in each step and the processing rates during multistage stabilization. Imposing stretching on multistage stabilization is beneficial to mechanical properties of carbon fibers. I NTRODU CTlO N Carbon fibers as reinforcements in the composites have gained wide range of applications from sports products to items used by the areospace industry. Among the many precursors for making carbon fibers, polyacrylonitrile fibers (PAN) have been established as a most suitable precursor for producing high-performance carbon fibers.'-5 The conversion of PAN fibers to carbon fibers usually include: (a) a low-temperature oxidative stabilization to yield a cyclized ladder structure, (b) higher temperature carbonization in inert environment to produce a graphitelike structure, and (c) an alternative "graphitization" treatment to improve the orientation of the carbon basal planes and the stiffness of fibers. Since the low-temperature stabilization (ZOO-300°C) step is usually time consuming and has significant effect on not only the mechanical properties but also the manufacturing cost of carbon fibers, tremendous efforts have been accumulated to understand the complex transformations during this intermediate step and to choose optimal processing conditions on

Influence of processing parameters on the properties of carbon fibres – an overview

“…Because of different mass and heat transport phenomena, the results cannot be directly transferred to a continuous conversion of fibres . Additionally, process investigations have been performed partly for batch and partly for continuous processes . This kind of process control leads to varying processes differing for instance in stabilisation (stepwise temperature treatment in continuous processes and linear change of temperature in batch processes) and can therefore hardly be compared.…”

UV‐induced crosslinking and cyclization of solution‐cast polyacrylonitrile copolymer

“…Thermo-oxidative stabilization typically involves the heating of the polymer precursor fibers in the range between 200 and 300 C in air or in another oxidizing atmosphere. 7,8 The thermo-oxidative reactions in PAN are highly exothermic. 6 This is considered the most critical step during the production of carbon fibers because it determines the final structure and mechanical properties of the resulting carbon fibers.…”

“…15 In addition, polymerization and stabilization reactions are known to proceed at lower temperatures when initiated by UV radiation. 8,[18][19][20] Alternatively, the incorporation of this UV-based preoxidation step may lead to a reduction of the time required for thermal stabilization process while maintaining the properties of resulting fibers. 8,[18][19][20] Alternatively, the incorporation of this UV-based preoxidation step may lead to a reduction of the time required for thermal stabilization process while maintaining the properties of resulting fibers.…”

UV-Based Dual Mechanism for Crosslinking and Stabilization of PAN-Based Carbon-Fiber Precursors

“…These tensile properties of the PAN fibers are consistent with those reported in the literature for commercial and experimental grade PAN-based fibers: 0.3-2.5% for the breaking strain, 0.1-6.5 GPa for strength, and 30-500 GPa for tensile modulus. 2,6,9,15,30,54 Tensile-testing results shown in Table 13.4 indicate that, at 95% confidence, there are significant differences in the breaking strain and ultimate tensile strength between pure control and pure UV-treated fibers. The UV treatment reduces the elongation capabilities of the pure fibers and the ultimate tensile strength by approximately one third.…”

“…7 This is considered the most critical step during the production of carbon fibers because it determines the final structure and mechanical properties of the resulting carbon fibers. 8,9 The thermo-oxidative reactions in PAN are highly exothermic. 1,8 Further, the thermal conductivity of PAN precursor (like other polymers) is relatively small (B0.26 W m À1 K À1 ).…”