The Physico-chemical Hydrodynamics of Dyeing

Meetings of the Leeds Junior Section, held in the Department of Colour Chemistry and Dyeing, University of Leeds, on 11 November 1969, Mr K. R. F. Cockett in the chair; and of the Manchester Region, held at the Literary and Philosophical Society, Manchester, on 20 November 1969, Mr H. R. Hadfield in the chair Films of methoxymethylnylon 6.6 have been inserted into a stream of dye-liquor. The rates of dyeing of an acid dye at different points down the film were measured. Under some conditions of dyeing, the rate was shown to be controlled by the diffusion in the liquid phase. Values of the thickness of the diffusional boundary layer were calculated from the flux and shown to agree with theory. Modifications of the dyeing conditions, e.g. by increasing the pH or lowering thedyebath concentration, reduced the diffusion coefficient of the dye in the film, and the rate of dyeing became dependent on diffusion both in the film and in the liquid.     

Crystallization phenomena in some polyester — urethanes

A density balance has been used to measure the crystallization isotherms of poly(ethylene adipate) and copolymers which were prepared by extending the polyester with four different diisocyanates. The occurrence of extensive secondary crystallization processes precluded satisfactory interpretation in terms of the Avrami theory and further analysis could only be based on the half-time for crystallization. This parameter has the advantage that it is determined directly and is independent of any theoretical analysis. The presence of very small concentrations of diisocyanate units can have a profound effect on the rate of crystallization if they are very different structurally from the parent polyester, e.g. a molar concentration of about 5% of 2,4-tolylene diisocyanate increases the half-time by a factor of 20 whereas the same concentration of hexamethylene diisocyanate has an insignificant effect. The temperature dependence of the half-times is discussed in relation to several theories of crystallization.     

INTERFEROMETER MEASUREMENTS OF THE THERMAL DILATATION OF GLAZED WARE1

The network of fine cracks often seen in the surface of glazed products not only mars the surface but shortens the life and lowers the price of the ware. Since the relative expansivity of the glaze and body is a very important factor in controlling this condition reliable measurements of both are of the utmost importance. Until recently the difficulty has been that the expansivity of the glaze has been measured on specimens of the material melted to glass and drawn into rods or cast in molds of sufficient length. Owing to the difference between this treatment and that received by the material when spread on the ware, it was realized that these methods might lead to unavoidable errors. By the interference method, specimens 0.2 mm. in length can be measured with sufficient accuracy. Therefore in measuring glazes the samples may be taken directly from the finished ware. In this paper the thermal expansion of glaze materials prepared in the form of drawn glass or cast rods is compared with that of the same material taken from the finished ware. From the measurements, the expected divergence is found to be as much as 20% in the case of drawn glass specimens, and 10% for cast specimens.