Najua Tulos and colleagues of the Faculty of Applied Sciences, UiTM, Shah Alam studied the potential of chitosan to dye polyester fabric. They found that dyed polyester has an excellent colourfastness to washing.
Looking back, human began to wear clothes for protection against harsh weather. The clothes came in a form of pieces of woven fibres like reed or cotton which were strapped on chest or loins. Then wool, silk, gold and silver threads followed. The wealthy fascinated themselves with richly decorated dyed garments. Then in the 20th century, technology took its place to change clothing; it discovered polyester.
Polyester is now one of the man-made fibres that are extensively produced in factories for garments and home furnishing. This new material has taken the world by storm; its wide use reflects its range of pleasing properties such as high resilience, stretch and recovery, and good strength. It also has dimensional stability and is highly wrinkle-resistant.
However, it is not easy to dye polyester. Polyester fibres have definitive hydro-phobic character and high degree of crystallinity, a barrier to dye penetration. Disperse dye is the only effective one for polyester, which is usually done at high temperature (130ºC). At temperatures above 1000C and being under pressure, the heat generates a very large amount of energy that allows a better dye uptake.
Thereby, this research studied the potential of chitosan to dye polyester in low temperature. In particular, it investigated the possibility of chitosan as surface treatment to dye with a reactive dye. The effect of lower temperature on dyeing was also tested.
In the test, the white polyester fabric surface was treated with chitosan by exhaustion, pad-dry-cure and ultrasound. The treated fabrics were then dyed with reactive dyes at low temperature. The colourfastness to washing, colourfastness to perspiration, colourfastness to rubbing/crocking and colourfastness to light were evaluated to measure the colour change and staining.
It was found that the dyed polyester had excellent colourfastness to washing with a colour change rating between 4/5 and 5, and staining 4/5 and 5. This was made possible as the surface of polyester was treated with chitosan solution. The chitosan made it dyeable even under lower temperature. Hence news for fabric industry, reactive dyes have a higher affinity for polyester fibres.
News for us too, we will be strutting in brighter clothes.