Foam application from a closed system – a study of machine and foam parameters
An attempt has been made to gain a greater insight into the interaction between foam and a moving textile substrate. The effects of changing wet pick–up, fabric velocity, liquid viscosity, foam density and mode of application on penetration have been studied. Application from a closed system makes it possible to apply an exact amount of liquid, and reflectance measurements revealed that between 10 and 60% wet pick–up the actual level of wet pick–up is of major importance. The amount of liquid available determines the likelihood of capillary transport. The results obtained in terms of fabric speed and foam density still leave questions to be answered on the mechanisms of foam flow and degradation in the textile.
The flow properties of foam
The rheological behaviour of foam, prepared from an aqueous solution with lauryl sulphate as surfactant, has been measured with a viscometer as a function of the blow ratio, bubble diameter distribution and concentration of the thickener used. The influence of wall slip and of hysteresis effects on the rheological behaviour have been determined. Calculations and measurements pertaining to the pressure drop in pipes have been performed, in which the foam was considered as a compressible pseudoplastic whose rheology depended on blow ratio. The distribution of the foam passing through a closed distribution unit has been studied. This distribution unit consisted of a pipe and a cross-head distribution slit. Complementary measurements of the flow of foam through narrow slits have been made. The design of a closed foam distribution unit is discussed. The consequences of the choice of several design parameters are examined.
Foam Finishing of Wool and Wool-Blend Fabrics
Foam application of finishing chemicals can yield reduced water add-on and energy savings in fabric-finishing operations. Initial work in a study of foam application of chemicals to wool and wool-blend fabrics is reported. The foam application system used is the Foam Finishing Technology (FFT) System developed by Union Carbide Corporation. It was found that the finishing chemicals could be suitably foamed and applied to the fabrics on lab-scale equipment. Laboratory applications of chemicals for shrinkage resistance and water/oil repellency were made on five fabrics (wool or wool blend) at wet pick-ups from 15 to 30%. Wet-on-wet applications were made as well as applications to dry fabrics. Test results on treated fabrics indicate that foam applications of finishing chemicals by FFT to fabrics of this type are feasible.