M. M. Abdel Moteleb

Dielectric investigation of the effect of ferric chloride on viscose fibres

Measurements of the dielectric constant and the dielectric loss, at frequencies of 0.05-10 kHz over a temperature range of 10–60 °C, were carried out on viscose fibres, viscose with iron adsorbed and with iron removed. The results obtained show that: (i) a relaxation process is observed in the low-frequency region only in the case of the viscose-iron complex, and (ii) the variation of the dielectric constant with temperature showed a transition at about 30 °C with the untreated fibres, and the transition disappeared when the fibres were treated with ferric chloride. These results, together with changes in hydrogen bonding obtained from infrared spectra for these samples are discussed. Oxidation and adsorption of ferric ions can modify the dielectric properties of viscose fibres.Measurements of the dielectric constant and the dielectric loss, at frequencies of 0.05-10 kHz over a temperature range of 10–60 °C, were carried out on viscose fibres, viscose with iron adsorbed and with iron removed. The results obtained show that: (i) a relaxation process is observed in the low-frequency region only in the case of the viscose-iron complex, and (ii) the variation of the dielectric constant with temperature showed a transition at about 30 °C with the untreated fibres, and the transition disappeared when the fibres were treated with ferric chloride. These results, together with changes in hydrogen bonding obtained from infrared spectra for these samples are discussed. Oxidation and adsorption of ferric ions can modify the dielectric properties of viscose fibres.

The effects of preheating on the dielectric relaxation, and of temperature on the ‘static’ dielectric constant, of cellulose acetate fibers

Abstract The effect of preheating at 140°C and 180°C on the dielectric relaxation of cellulose acetate of degree of substitution 1·90 has been investigated, together with the dependence on temperature over the range 80–200°C of the ‘static’ dielectric constant of variously acetylated cellulose samples. The results obtained are discussed in terms of progressive gain of compact structure, together with the initiation of crystallization at a temperature governed by the acetyl content in the fiber. Phase changes involving discontinuity in the first variation of the ‘static’ dielectric constant on heating, and irreversibility of the temperature dependence path on cooling are thus observed.

Dielectric investigation of some hydroviscoses and oxyhydroviscoses

Abstract Hydroviscose was found to resist oxidation with either hydrogen peroxide or potassium dichromate in oxalic acid, but changes in its fine structure took place, whereas nitric acid or periodate were found to cause oxidation and produced oxyhydroviscoses. The dielectric properties of hydroviscoses and oxyhydroviscoses were investigated. In the case of hydrogen peroxide, potassium dichromate in oxalic acid and periodate, a β-dielectric relaxation corresponding to the methylol groups in non-crystalline regions was observed, but in the case of nitric acid oxidation such relaxation disappeared. A new dielectric relaxation process β′ at high temperatures and frequencies was found in the case of dichromate/oxalic acid treatment.

Effect of acid hydrolysis on the apparent specific volume of viscose rayon

Abstract The apparent specific volumes of viscose rayon and its hydrolysis residues, prepared by the action of 0·2 and 1 N HCl at 100°, were measured dilatometrically in the range 5–50° using toluene as displacement medium. The variation of the specific volume at 20° with the progress of hydrolysis showed a characteristic minimum, dependent on the hydrolytic conditions. These results, with those previously obtained from i.r. studies showed that the crystallinity of the fibre increased till 2·5% dissolution, and then decreased. Also, it was found that the second order transition of viscose rayon is primarily a function of its accessibility rather than its DP.