From the traditional function of dressing people, textiles now provide wearer comfort and protection in dangerous environments.

The most important requirements for protective wear are barrier effectiveness and thermo-physiological comfort for the wearer. Our textile industry is constantly trying to innovate production techniques to improve the product quality.

We use "finishing chemicals" to convert a textile material into a technical textile with functional properties. It is very important that these products are developed in an environmental friendly way.

We always hear that technical textiles will continue to increase every year because of the modification of regular textiles using some innovative finishes which make them more functional. There are different types of functional finishes and the right type of finish should be selected depending on the fibre type of the textile substrate and the desired end use.

Now let's understand the general requirements of chemical finishes.

Primary effects of the finishes are :

1. High effect level at low cost for products and application,
2. Possible effect design, adaptation to customer wishes, article demands and favoured use.

Desired secondary effects are :

1. Usable for all kind of fibres and all textile forms, as yarn, woven or knit fabric, garment, nonwovens.
2. High permanence for washing and dry cleaning for garments and most household textiles.
3. No loss of important textile qualities such as tear strength and abrasion resistance, comfort, appearance, hand.
4. No yellowing of undyed fabrics, no shade change of coloured ones, no reduced colour fastness.
5. Easy and safe handling, non-flammable.
6. Simple application, preferably with several standard methods and equipment at low cost.
7. High stability under storage and application conditions (temperature, pH, mechanical stress).
8. Even distribution, either on the fibre or fabric surface or inside the fabric. 
9. Compatibility with other finishes.
10. Synergistic effects, no reduction of effect of other finishes.
11. Easy correction of finishing faults such as removal of finish or stains. 
12. No environmental problems, non-toxic, biodegradable, no volatile organic compounds.

In Part 2, I talked about 4 important functional finishes and in this blog I will talk about 2 more finishes.

Shrinkage Control,

It is the ability of fabrics to maintain their dimensions, whether the fabric is used in apparel or home furnishings. Shrinkage is a reduction in fabric length or width while growth is a term used for an increase in a fabric dimension.

Dimensionally stable fabrics will never shrink or grow.

Controlling shrinkage is the goal of every textile manufacturer. Putting fabric in conditions such as moisture or heat that might induce shrinkage before it is sewn into garments is common.

High moisture absorbent fabrics made out of cotton, linen, rayon and wool are most susceptible to shrinkage during laundering. Synthetic fabrics made out of polyester, nylon, acrylic etc. do not absorb water to a great extent and have higher dimensional stability. Manufacturing of woven or knitted fabrics imposes stresses in the materials as they are stretched during process. When the tension is removed and these fabrics are subjected to wetting during laundering, the yarns relax, moving closer together. The amount of relaxation depends on the degree of stretching the fibres underwent during manufacturing and the propensity of the fibres to absorb water and to stretch. Wool and rayon are more extensible than many other fibres and therefore shrink more. Wool has a further problem in that the fibres are covered with scales that can catch and lock together, entangling under conditions of moisture, mechanical action, and heat. This is called felting shrinkage and is the primary reason wool fabrics are not normally washable.

Compressive shrinkage, the most general control method, is appropriate for 100% cotton, linen, or rayon fabrics. In the process, the fabric is dampened and placed on a thick woolen or felt blanket that travels around a small roller. The wet fabric is stretched as it moves around the contour of the roller and then compresses and squeezes as it enters a straight area. Heat is applied to set in the compressed structure. Sanforized and Sanfor-set are trade names for this type of shrinkage-control treatment.

Wool fabrics require special treatments to inhibit both relaxation and felting shrinkage. Synthetic fibres, which are sensitive to heat, can shrink when heat is applied. This phenomenon is apparent when synthetic-fibre fabrics are ironed at too high a temperature. The tendency for heat shrinking can be controlled in finishing by heat setting the fabric at a temperature that allows the molecules in the fibres to relax somewhat. They are therefore less likely to relax further and shrink during the use and care of the textile product.

Hand building finishes,

One of the oldest in textile industry which is also one of the very important finish. Variety of hand effects are imposed on fabrics using different kinds of natural and synthetic polymers. Fabric hand is the quality of the fabric assessed by the reaction obtained from our sense of touch. It's a person's estimation when feeling fabrics between our fingers and thumb.

Finishes that add firmness to fabric hand are often called hand builders. These finishes are also used to increase the weight of fabrics that are below weight specifications. Hand builders are roughly divided into two groups depending on the major effect on fabric hand. One is which adds fullness, i.e., the feeling of increased bulk or weight. Another one is which provides stiffness or a resistance to bending. Even the mix of both is also possible using various chemical compositions.

After laundering of shirts, blouses and table cloths, starch is used for stiffening them. Fabrics with low warp and fill densities like lining fabrics, suit and costume fabrics, overcoat poplins, pile fabrics like corduroy are often increased with fullness. Some stiffness and fullness effects are necessary for laces and knitted dress fabrics. Even greater stiffness is usual for selected denim articles, work clothes and industrial uniforms, such as some jeans, overalls, aprons and lab coats. A full and stiff hand is demanded for mattress duck, tapestries and awning fabrics. Fabrics for window treatments like blinds and curtains require a measure of stiffness. Many textiles receive a non-durable stiffening finish for ease in cutting and processing. Some durable hand builders are also used as pigment binders, binders for non-wovens, finishes for carpet backings, coatings for glass fibre fabrics and as additives (for example adhesives) for other specialty finishes.

Let us see few more functional finishes in my next article … Part 4…

By moving to a Semi-Integrated process route, we can save up to Rs.10 per kg on the fabric costs. This in turn leads to a reduction of 1.5 - 2% cost in a Rs.100 T-shirt. That’s a big impact on cost. After all a rupee saved is a rupee earned.

RELATED TOPICS:#apparel industry,Finishes,BestFinishes,Satheesh Kumar