Effect of electric heating on ripening of viscose

Ripening of viscose in heating with an industrial-frequency electric current was investigated. It was shown that an effect of homogenization of the viscose is obtained with the electric current. It was found that when viscose was heated with an electric current, in contrast to use of heat exchangers, the minimum viscosity and concentration of gel particles was preserved during the time required for deaeration and filtration. This will allow obtaining a spinning solution with optimum physicochemical properties for spinning.Siberian Institute of Technology, Krasnoyarsk. Translated from Khimicheskie Volokna, Vol. 25, No. 1, pp. 18–19, January–February, 1993.     

Light scattering studies of hi-impact polystyrene

Small-angle light scattering techniques have been used to evaluate the factors controlling the transparency of two hi-impact polystyrene films. These factors were found to include surface smoothness, volume fraction of the phases in the system, the difference of the refractive indices of the phases, and the sizes of the phases. The elongation of the rubber phase during processing was also determined.     

Effect of carbonyl-containing compounds on the dynamics of ripening of viscose

The effect on the dynamics of ripening of viscose in the presence of carbonyl-containing compounds: hexamethylenetetramine (urotropin), sodium sulfoxylate (Rongalite C), and dimethylolurea, was investigated. A hypothesis was advanced concerning the possibility of formation of mixed cellulose xanthate methylol derivatives whose presence alters the chemistry and kinetics of hydrolysis of cellulose esters in the spinning bath.     

Light scattering studies on crystallization in polyethylene terephthalate

The light scattering from the spherulites of polyethylene terephthalate grown near the glass transition temperature has been investigated. The Hv scattering profiles can be reproduced by the sum of the ideal spherulite scattering with the distribution of spherulite radius and the isotropic scattering from randomly oriented crystallites. The ratio of optical anisotropies in the isotropic scattering to the ideal spherulite scattering is obtained by the method established to eliminate the effects of the number density of spherulites and the coefficient depending on the experimental conditions. It is found that the anisotropy ratio is almost independent of the crystallization time and of temperature above 106 °C, while it is larger at a crystallization temperature of 103 °C. The spherulitic structure is discussed in terms of the anisotropy ratio.     

Light scattering studies of the stability of liquid fuels

Storage stabilities of upgraded coal-derived liquids (H-coal and SRC-II), JP-5 jet fuels derived from petroleum and oil shale, and a petroleum-derived diesel fuel were compared using laser light scattering measurements. The most severely hydrotreated coal-derived liquids have stability characteristics comparable to the jet fuels derived from petroleum and oil shale. Fuel degradation was monitored in the presence of added specific heteroatomic compounds. Very pronounced enhancement of light scattering intensity has been observed for coal-derived liquids containing the following additives: 1. phenol + pyridine + Cu; 2. 2,6-di-tertbutylphenol (DTBP) + pyridine + Cu; 3. phenol + dimethylquinoline, (DMQ) + (Cu; and 4. 2,5-dimethylpyrrole (DMP) + thiophenol. Previous studies have shown that phenolic oxidative coupling is an important reaction responsible for the ageing of coal-derived liquids and this observation is confirmed here. Pyridine and DMQ complexed with Cu are shown to be effective catalysts for oxidative coupling. DMP by itself is deleterious to fuel stability, in that it promotes sediment formation and light scattering. During accelerated ageing of upgraded H-coal in the presence of DMP a sediment formed with empirical formula C₇H₈NO_1.3, which was further characterized by solid-state C 13 n.m.r. and X-ray photoelectron spectroscopy.     

Light and neutron scattering studies of excess low-angle scattering in moderately concentrated polystyrene solutions

The light scattering (LS) and small-angle neutron scattering (SANS) behaviour of semi-dilute solutions of polystyrene has been determined in both ‘good’ and ‘theta’ solvents. Above a critical concentration related to chain overlap, an excess small-angle scattering component is in evidence for scattering vectors, q, such that qR_g < 1. Application of a number of recent solution scattering theories fails to account for the small-angle scattering observed. The inter- and intramolecular scattering functions are measured experimentally through characterization of the SANS behaviour of solutions containing mixtures of polystyrene and perdeuteropolystyrene. The resultant intermolecular scattering functions depend on the fraction of labelled chains, indicating clearly that the solutions contain large scale fluctuations. LS studies support this hypothesis and further show that the presence of these fluctuations is reproducible, yet dependent on the solution preparation procedure. Similar behaviour is observed in screening length measurements. The excess low-angle scattering is well characterized by the Debye—Bueche random two-phase model, which is subsequently used to estimate the characteristic dimensions of the long-range fluctuations.     

Dynamic light scattering studies on random cross-linking of polystyrene in semi-dilute solution

The random cross-linking of appropriately functionalized polystyrene in semi-dilute toluene solution (c = 0.01–0.05 g/mL) was studied by time-dependent measurements of dynamic light scattering. Macroscopic gelation occurred from concentrations as low as 0.02 g/mL. The gelation time, determined from the first appearance of fluctuations of the scattering intensity and the initial amplitude of the intensity correlation function (ICF), decreases markedly from about 100 min to 10 min with an increase of polymer concentration or cross-linker content. After the gel point, the ICFs display a characteristic power-law decay. The power-law exponent, n = 0.75 ± 0.06, does not change with (i) extent of reaction, (ii) polymer concentration, and (iii) cross-linker concentration, within the inspected ranges. This universal behavior is traced back to the fact that gelation took place as a result of random cross-linking of existent macromolecules, whose state of solution does not change markedly during conversion.     

Intensification of ripening of viscose with the aid of an optimization equation for the process

Conclusions It has been shown that in the intensification of the ripening process of viscose the optimum temperature curve, which allows viscose to be obtained prior to spinning with certain values of ripeness and rate of its change, there are two periods corresponding to heating and cooling of the viscose. A method has been described for determining the optimum temperature curve with the help of an ACM. We have dealt with a definite production situation for which tables have been calculated and formulae obtained, which for certain initial and final values of the ripeness and temperature of the viscose allow a determination of the optimum temperature—time conditions for the ripening process to be made.All-Union Synthetic Fibre Research Institute (VNIIV). Moscow Institute of Chemical Machinery (MIKhM). Translated from Khimicheskie Volokna, No. 3, pp. 22–24, May–June, 1969.     

Light scattering study on the dynamic behaviour of cellulose inclusion complex in LiOH/urea aqueous solution

In our previous study, the rapid dissolution of cellulose in alkali/urea aqueous solution at low temperature induced by a dynamic self-assembly process has been demonstrated [1]. The cellulose solution was meta-stable, and its stability could be influenced by system fluctuations (temperature, concentration or time). In the present work, cellulose dissolved in 4.6wt% LiOH/15.0wt% urea aqueous solution pre-cooled to −12 °C was studied by means of dynamic light scattering (DLS). The results revealed that cellulose existed as single inclusion complexes (ICs) associated with LiOH and urea hydrate which could surround the ICs at their surface. And the ICs were stiff, as revealed by results from transmission electron microscopy (TEM) and light scattering (LS). When there was a system fluctuation, the self-association of cellulose with each other took place, resulted from the destruction of the urea shell, and leading to the aggregation of the ICs. For that reason, the ICs stability could be evaluated by the aggregation behaviour. In our findings, the hydrodynamic radius (R_h,app) for the cellulose dispersion in dilute solution shifted to higher values with an increase of the temperature, the concentration or the storage time, indicating an IC aggregation phenomenon.