Optimisation of process parameters of Alpaca wool printing with Juglans regia natural dye

Abstract

AbstractThe aim of this research study was to optimise the process parameters of Alpaca wool hand‐knitted samples screen‐printing with Juglans regia natural dye and to set the optimal conditions regarding colour yield, colour fastness and colouristic properties of printed samples. An extensive preliminary examination of the Alpaca woollen yarn and hand‐knitted samples characteristics, the characteristics of suitable thickeners and the optimisation of the printing paste composition, was performed. A starch‐based thickener, British Gum, with a dry matter content of 4% was selected due to its rheological properties responding to properties of the Alpaca yarn and knitwear. It was determined that the fluidity increases while the viscosity and the elasticity decrease in acidic pH, so a pH of 4 was set for the thickener preparation. The thickener of lower viscosity and higher fluidity assures easier pressing of printing paste through the screen, giving uniform colour yield on the substrate, contributing to easier absorption of dyes into the fibre. A 45‐minute fixing process at 105°C by steaming delivered the best results of printing quality. Iron sulphate was used as the mordanting agent. The colour fastness to washing, dry and wet rubbing, and to light, was tested for samples with and without mordanting. The highest light and washing fastness were obtained with the iron sulphate mordanting agent printed in acid (pH 4) with paste containing 4% dry matter‐based thickener. The rubbing fastness was satisfactory for samples with iron sulphate printed with paste containing 4% dry matter thickener, fixed for 45 minutes, regardless of the pH.