Abstract
Viscosity and specific electrical conductivity of polyacrylonitrile (PAN) in N,N-dimethylformamide (DMF) medium are studied in the presence and absence of anionic surfactants as sodium oleate, sodium dodecyl sulfate and palmitic. Critical micelle concentrations of these surfactants are determined in DMF medium. Thermodynamic functions (\({\Delta H^{\circ}_{\rm m},\,\Delta G^{\circ}_{\rm m}}\) and \({\Delta S^{\circ}_{\rm m}}\)) of micelle formation of sodium dodecylbenzene sulfonate and sodium dodecyl sulfate are determined. Curves of X-ray diffraction and differential thermal analysis showed that the PAN samples containing SDS lead to the development of the crystalline structure of PAN, and the initiation temperature decreases of the cyclization reaction of nitrile groups of PAN by 8.5 °C, respectively.
Highlights
Since the invention of PAN-based carbon fibers in the 1950s by Shindo and Watt have attracted the world’s attention as high-performance materials [1]
The mechanical and structural properties of polymeric solutions are strongly affected in the presence of surfactants; because the effectiveness of interactions between macromolecules themselves is significantly affected by these substances
PAN solutions are prepared in the presence of surfactant and its absence, poured in Petri dishes, put in dryer at 50 ◦C until the complete vaporization of DMF, where solid samples are obtained, these samples are examined by X-ray diffraction (XRD) and differential thermal analysis (DTA)
Summary
Since the invention of PAN-based carbon fibers in the 1950s by Shindo and Watt have attracted the world’s attention as high-performance materials [1]. Viscosity of PAN solution plays a significant role in the studying of mechanical and structural properties of produced fiber. A study of the relationship between viscosity of PAN solutions and concentration in DMF medium shows strong associations of PAN molecules, and this is because of the interactions between dipoles [5,6,7]. The mechanical and structural properties of polymeric solutions are strongly affected in the presence of surfactants; because the effectiveness of interactions between macromolecules themselves is significantly affected by these substances. These surfactants affect the shape and dimensions of crystals being formed, and the conditions under which they grow. The new of this research is a study the properties of PAN at different concentrations and temperatures, the colloidal properties of different types of surfactants in DMF medium and interactions between PAN and surfactants
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