3.1 Wet processing systems Flashcards
Grey (Greige) goods:
An unfinished fabric as it comes off the weaving or knitting machine
Tentering:
A mechanical straightening of wet woven or knitted fabrics under tension and heat
Textile wet processing operations generally involve some form of wet treatment. These operations include three distinct types of processes:
1 preparationprocesses: scouring bleaching, and heat setting
2 colourationprocesses: dyeing and printing
3 finishingprocess: repellency treatments and handle modifications
3.1.1 Open-width processing
In the open-width system, the fabric is prepared, coloured or finished with the fabric opened to its full width. Open-width is also used for most fabric drying and heat setting operations. In these operations, the fabric is stretched out on a tenter frame. Clips or pins hold on to the selvages of the fabric. The tiny marks or holes can often be seen in the selvage of a fabric. If, during tentering, the fabric is pulled in such a way that the warp and the filling yarns are not perpendicular to each other, the fabric will be distorted or skewed. A fabric that has been heat set or set by chemicals in this distorted shape will usually remain skewed even after washing and straightening.
3.1.2 Rope processing
The fabric is not spread open but finished in a loosely bunched rope.
3.1.3 Continuous systems
In a continuous system, the fabric moves without interruption from one process to another. Fabrics from different looms can be sewn end to end to make one long continuous length of fabric. Fibres (eg loose-stock dyeing), slivers (eg wool shrink-proofing) and yarns (eg yarn dyeing) can also be processed in continuous systems.
3.1.4 Batch systems
In the batch system, short lengths of fabric or smaller batches of yarn are processed as separate, individual units. A batch system is therefore the opposite of a continuous system. Fibres and slivers can also be processed in batches. When a continuous and a batch proc- ess are combined, it is known as a semicontinuous process (eg pad-batch dyeing).
3.1.5 Garment systems
Garments are first constructed and then finished or dyed. This system is extremely popular with firms such as Benetton. Its main advantage is that garments can be made from grey goods and only then dyed when sales indicate which colours will be popular during a particular season.
3.1.6 Solvent systems
In many wet processes, water is replaced with chemical solvents. This reduces water pollution and energy consumption. The solvents are more expensive than water and are therefore recovered, cleaned and reused.
3.1.7 Foam systems
Some dyes and finishes can be applied in a foam form. This reduces water consumption, and therefore also energy consumption, water pollution, chemical consumption, labour costs and the time required to dry the fabric.
