Structure and properties of oxidatively stabilized viscose rayon fibers impregnated with boric acid and phosphoric acid
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Structure and properties of oxidatively stabilized viscose rayon fibers impregnated with boric acid and phosphoric acid prior to carbonization and activation steps Ismail Karacan • Taner Soy
Received: 1 August 2012 / Accepted: 16 October 2012 / Published online: 27 October 2012 Ó Springer Science+Business Media New York 2012
Abstract The role of boric acid–phosphoric acid (BA– PA) impregnation and oxidation on the structure and properties of viscose rayon fibers was examined in air at temperatures ranging from 150 to 250 °C. The results obtained from the measurements of fiber thickness, linear density, X-ray diffraction, thermal analysis (DSC and TGA), and infrared spectroscopy demonstrated that oxidation temperature had a significant influence on the structure and properties of oxidized viscose rayon fibers. Physical transformations were characterized by fiber thickness and linear density values together with color variations and improved burning behavior with progressing oxidation temperature. The DSC analysis showed that BA– PA impregnation enhanced thermal stability and prevented the evolution of volatile by-products by blocking the primary hydroxyl groups. TGA thermograms revealed an enhancement in the char yields. X-ray diffraction analysis showed the loss of cellulose II crystalline structure caused by the decrystallization process initiated by the gradual loss of intermolecular hydrogen bonds. Analysis of IR spectra revealed gradual and continuous loss of intramolecular and intermolecular hydrogen bonding as part of the simultaneously occurring dehydrogenation and dehydration reactions. Analysis of IR data also demonstrated the disturbance of the cellulose II crystalline structure with increasing oxidation temperature in agreement with the results obtained from X-ray diffraction measurements. The formation of C=C bonds attributed to the crosslinked ladder-like structure was also confirmed by the IR spectra.
I. Karacan (&) T. Soy Department of Textile Engineering, Erciyes University, Kayseri, Turkey e-mail: [email protected]
Introduction Conventionally produced activated carbons were found to be unsatisfactory for the needs of environmental protection, medical care, and defense sectors. Poor performance of activated carbons with small specific surface area (BET less than 1000 m2/g) led to the development of activated carbon fibers (ACFs) with a larger specific surface area (BET more than 1500 m2/g) [1]. The structure and properties of ACF have been investigated thoroughly and manufactured on a commercial scale for several decades now since its commercial introduction in the 1960s. It has also played a major role in the development of adsorption technology due to its porous structure and excellent absorption and desorption characteristics [2]. Viscose rayon [2], polyacrylonitrile [3], phenolic resin [4], polyvinyl alcohol [5], sisal [6], hemp [7], flax [8], and quite recently aromatic polyamide fibers [9–13] were used for the production of ACFs as potential replacements for granular and powder ba
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