Enhancement of oxidative stabilization of viscose rayon fibers impregnated with ammonium sulfate prior to carbonization and activation steps

Abstract

The oxidative thermal stability of microcrystalline plant-based viscose rayon cellulose fiber was improved in the presence of an ammonium sulfate solution. The structural characterization of the oxidized samples was carried out using a combination of fiber thickness, linear density, burning test, X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and infrared (IR) spectroscopy measurements. Oxidized viscose rayon fibers showed physical and chemical transformations with increasing oxidation temperature and were characterized by a reduction in fiber diameter and linear density values together with color changes with increasing oxidation temperature. The results obtained from XRD analysis showed the loss of crystallinity due to the amorphization processes. XRD analysis also showed increasing conversion to a highly crosslinked and cyclized structure with progressing temperature. The DSC and TGA measurements indicated that there was an improvement in thermal stability. The results obtained from IR spectra showed the progress of dehydrogenation and dehydration reactions. IR spectra in the 2000-800 cm À1 region showed a loss of crystalline structure confirming the results of XRD. The IR spectra of the oxidized samples also showed the conversion of primary hydroxyl (OH) groups to carbonyl (C¼ ¼O) groups and the presence of C¼ ¼C double bonds arising from the formation of a cyclized and crosslinked structure.

Effect of boric acid on the stabilisation of cellulose-lignin filaments as precursors for carbon fibres

“…Typically performed by applying these flame retardants to a precursor by passing the tow through a solution in water before drying (Morgan 2005), Karacan et al showed that rayon fibres treated with a mixture of phosphorus and boric acid significantly improved oxidative stability while reducing the evolution of volatile compounds. However, no specific details in regards to the stabilisation mechanism, carbon yield or stabilisation rate was discussed (Karacan and Soy 2013). Byrne et al treated regenerated cellulose samples with a phosphorus-based ionic liquid showing a significant improvement in the carbon yield (50% remaining after carbonisation at 500°C).…”

Enhancing the carbon yield of cellulose based carbon fibres with ionic liquid impregnates

“…10 Indeed ILs have themselves been shown to be excellent carbon precursors. 11,12 Typically impregnate chemicals are based on nitrogen, sulfur and phosphorus 9,13 containing compounds as such we have focused our attention on the following ILs: triethylammonium phosphate [TEA]H 2 PO 4 , triethylammonium hydrogen sulphate [TEA]HSO 4 , 1-methyl imidazolium phosphate [HMIM]H 2 PO 4 , 1-methyl imidazolium hydrogen sulfate [HMIM]HSO 4 and cholineH 2 PO 4 . We also included 2 phosphonium ILs, tributyl(ethyl)phosphonium diethylphosphate CYPHOS IL 169 and tributyl(methyl)phosphonium methylsulfate, CYPHOS IL 108 since the thermal degradation temperature of these ILs is better than the imidazolium ILs.…”

“…Fig. 3a shows the 13 C NMR spectra and Fig. 3b shows the XRD spectra of the carbonized samples impregnated with [TEA]-H 2 PO 4 , [HMIM]H 2 PO 4 and cholineH 2 PO 4 , respectively.…”

Molecular Motions Aided Thermally Responsive Biocompatible Textile Pads

“…[26] The modifi cation of NWVR with PPy forms a hydrogen bond with hydroxyl group (as discussed before) will make a selective decrystallisation (amorphisation) of (1I -0) plane, which will cause the decrease in the intensity in the (1I -0) plane. [27] The gradual decrease in intensity at (1I -0) plane upon increase in PPy concentrations is observed and it indicates the increase in this selective amoprhistion due to polymerisation ( Figure S6A). To fi nd the temperature effect on crystallographic structure, we performed XRD analysis for preheated (analysis performed immediately after 5 mins heating) samples.…”