FEATURED ARTICLE Digital Laser Dyeing & Dyeing Properties of Wool for Textile Design The Effect of CO2 BY LAURA MORGAN
A digital laser dyeing technique for woolen textiles has been developed at Loughborough University. The technique was developed to explore potential sustainable design techniques using laser technology. The research examined the effect of laser irradiation as a pre-treatment to dyeing 100 percent wool and the potential to use this as a design tool for textile processing.
The textiles and clothing sector represents the second biggest area of global economic activity in terms of intensity of trade with an economic value of over one trillion US Dollars, so the sector’s environmental impacts are hugely significant. The consumption of water, energy and chemicals used in current dyeing and finishing processes in the textile industry pose significant environmental concern and have been identified as key challenges to sustainability within the industry. By offering alternative solutions to traditional textile wet processing through laser technology, there is potential to increase environmental sustainability through significant reduction in energy and wastewater effluent.
Current industry standards for dyeing woolen textiles use high temperatures and long processing times to aid dye diffusion through the hydrophobic cuticle layers of wool fibers. Chemical pre-processing such as chlorination is regularly required for an optimum dye reaction to take place.
To examine the effect of laser treatment on the surface properties of wool, laser irradiation at increasing power outputs was performed prior to dying the wool with reactive dyestuffs. The laser system used for the study was a Synrad carbon dioxide source laser that operated at a wavelength of 10.6 µm in the far infrared spectrum with a maximum power of 100 W. Dyeing of the laser treated wool was performed in an Ahiba Infrared Dye Machine. In the machine, each fabric sample occupied its own airtight vessel where temperature and agitation could be controlled and maintained throughout the dyeing process.
The morphology of the irradiated surfaces was examined by scanning electron microscopy (SEM). SEM was carried out on an area of the wool fabric that had been subject to laser irradiation. The micrograph in Figure 1 shows the woolen fibers after laser irradiation. Two particular fiber strands of note,
12 LIATODAY FOCUS: LASERS IN MANUFACTURING JULY/AUGUST 2015 Figure 1. SEM Micrograph Laser Irradiated Wool
labeled A and B can be clearly seen. The characteristic scales of a natural wool fiber can be seen on Strand A, this strand had not been subject to laser irradiation. On Strand B however, the scales on the surface of the fiber appear less pronounced; they have been ablated by laser irradiation.
This laser modification of the outer cuticles of wool fibers, was found to remove and disrupt the hydrophobic surface. Removal of the scales, not only removes the covalently bond fatty layer of lipids to give a less hydrophobic surface, but also exposes more of the underlying hydrophilic cortex.
An increased rate of diffusion when dyeing may be
expected, which has potential to be used as an alternative to wet, chlorination processes with the added advantages of the laser allowing accurate and targeted processing.
Figure 2 shows the schematic for dyeing wool. The red line shows standard optimal dyeing conditions used for
Laser Irradiation on Surface
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