Use of the ultrasonic cavitation in wool dyeing process: Effect of the dye-bath temperature

Abstract

The present work aims to study the effect of the liquid temperature on the performance of ultrasounds (US) in a dyeing process. The approach was both theoretical and experimental. In the theoretical part the simplified model of a single bubble implosion is used to demonstrate that the "maximum implosion pressure" calculated with the well known Rayleigh-Plesset equation for a single bubble can be correlated with the cavitation intensity experimentally measured with an Ultrasonic Energy Meter (by PPB Megasonics). In particular the model was used to study the influence of the fluid temperature on the cavitation intensity. The "relative" theoretical data calculated from the implosion pressure were satisfactorily correlated with the experimental ones and evidence a zone, between 50 and 60°C, were the cavitation intensity is almost constant and still sufficiently high. Hence an experimental part of wool dyeing was carried out both to validate the previous results and to verify the dyeing quality at low temperatures (40-70°C) in presence of US. A prototype dyeing equipment able to treat textile samples with US system of 600W power, was used. The dyeing performances in the presence and absence of US were verified by measuring ΔE (colour variation), R (reflectance percentage), K/S (colour strength) and colour fastness. The US tests performed in the temperature range of 40-70°C were compared with the conventional wool dyeing at 98°C. The obtained results show that a temperature close to 60°C should be chosen as the recommended US dyeing condition, being a compromise between the cavitation intensity and the kinetics which rules the dyestuff diffusion within the fibres.

Selective Modifications of Sheep Wool Usable in Non-Textile Applications

“…Valuable information on the influence of US bath temperature on the wool dyeing process was provided by the study of Actis Grande et al [13]. It used both theoretical and experimental approaches and their comparison applied a simplified mathematical model of the implosion of a simple bubble.…”

“…Summary of the topics covered. Effect of US scouring on color strength of dyed wool Pan et al[9] Effect of US scouring on color strength of dyed wool Nasmul Islam et al[10] Comparison of the scouring using US bath with and without detergent and using Soxhlet dichlomethane extraction Braniša et al[11] Two-phase scouring; gross impurities in water bath and US bath with detergent, alkali soap, and sodium carbonate.Czaplicki et al [12]Effect of US bath temperature on dyeing Grande et al[13] Effect of US bath on wool morphology, physico-mechanical characteristics, and dyeability Pan et al[14] Use of immobilized thermophilic lipase to remove the lipid layer Taleb et al[15] …”

Determinig the parameters of the acoustic system for the primary treatment of wool

“…Every bowl had its working pump and the tank. Such a machine had the same disadvantages as machines from Australia [11].…”

“…Formulae (11), (12), based on the assigned material parameters of wool with an aqueous solution and geometrical parameters of the gratings of transporters, make it possible to calculate coefficients of reflection and passage for the exciting acoustic wave.…”