The Rupp Report: Physiological Apparel Part V: The Right Finish For Perfect Functions
Jürg Rupp, Executive Editor
Possibly the most important factor of all jobs to be done downstream in the physiological and functional apparel production chain is the finishing of the fabric. The right finish for a defined end product and its requirements provides the ultimate opportunity to give the fabric the desired properties. In the fifth round of its physiological apparel series, the Rupp Report highlights some fundamental characteristics and requirements of appropriate finishing.
Finished fabrics for physiological and functional apparel have to fulfill many requirements and desired characteristics. The recent Rupp Reports have shown quite clearly that it is not possible to produce one single fabric for every end-use. It is the other way around: Appropriate finishing improves the properties of the fabric for the desired end product. If one takes into consideration how many performance characteristics and requirements have to be and can be checked, everyone can see this is not an easy task. Just to name a few requirements, there are lightfastness, colorfastness to water, fastness to perspiration and rub resistance.
Furthermore, many other factors have to be examined if physical and physiological aspects of the apparel are the focal point of the fabric to be produced: waterproofness; spray test; rain test; air permeability; water vapor permeability; abrasion test; crease angle; tensile strength; tear strength; seam slippage; and recovery to washing at 30° C.
Main Treatments And Finishes
Some of the main finishes for functional fabrics used for correct physiological apparel are:
- water-repellent finishes — impregnation with silicone or fluorocarbon resin, not applicable for microfiber fabrics;
- fine coatings — acrylic resin, polyurethane elastomer and silicone coatings with weights under 30 grams per square meter (g/m2), resulting in a low water density of about 30 millibars, however, with sufficient water vapor transmission resistance.
- microporous coatings — a well-known and popular method. A very fine coating is applied, usually via a series of strokes. Pore diameter is slightly larger than Teflon®, about 0.3 microns;
- calendering and chintzing —thermal and mechanical dry finishes that can increase the water- and wind-repellent properties considerably and very inexpensively; and
- brushing — a mechanical and dry treatment that is mainly used on the inside of fabrics for sweatshirts and similar products to improve the insulation properties — the more air between the fibers, the better the insulation properties.
One of the most important factors is waterproofness. The scale unit for waterproofness is millimeter (mm) water column, for example, 250 mm/hg (mercury). Among the many components that affect the waterproofness, or water density, are yarn or filament fineness, type of texturing, weave density, calender treatments, impregnation. washing process, thermal treatments and coatings.
As one can see, it is a great deal to combine all these requirements in one piece of fabric for tailor-made physiological apparel. However, if the desired properties are defined, other factors must match too. Here is an opportunity for clever technicians and engineers of all textile faculties.
Dyeing And Finishing
Coatings are the most compromising solution to fulfill the desired properties of the finished apparel or the corresponding end-use. On the one hand, fabrics for protective apparel can be easily produced and made waterproof, but breathability is zero. On the other hand, fabrics with high air permeability are lacking in water-repellent properties. This list of compromises can be extended.
There are many ways to improve fabrics by all kinds of finishing treatments. Luckily, the textile finishers, the machinery manufacturers and the chemical industry are very much aware of all the requirements about aspects of physiologically correct apparel. All three sectors are constantly working to improve their treatments, machinery and chemicals. In the last decade, microporous coatings, which are breathable, in particular have made a lot of positive noise. The trend is clearly moving away from the traditional treatment and closer to the characteristics caused by the proper choice of the yarns and the design — that is, the construction — of the fabric.
As mentioned in the last Rupp Report, many people think they have an allergy caused by textile products, when their apparel — mainly made of man-made fibers — has direct contact with the skin. In almost 100 percent of cases, it is a simple skin irritation, not an allergy. These sensations can be avoided through proper material design. Allergies to man-made fiber materials are extremely rare. However, Table 1 below shows a lot of factors that provoke skin irritation or even allergies:
|Material||Factors To Provoke Skin Irritation|
|Fibers||Animal, natural vegetal, man-made|
|Dyestuff||Azo dyes, anthraquinone dyes|
|Finishing material||Formaldehyde, optical brightners|
|Foreign fibers||Rubber components, elastomer (spandex)|
|Contamination||In manufacturig, while wearing|
|Cleaning||Residues, cleaning agents|
|Additives||Spinning preparations, special additives, preservatives|
|Unwanted components||Broken glass, iron, metal and such|
|Non-physiological||Tight apparel, ventilation problems|
|Accessories||Zippers, sewing thread and such|
All these factors have nothing to do with man-made fibers. A lot of irritation is caused by cheap washing agents in the household. Especially detergents or cleaning agents for hand washing in a sink are particularly aggressive, noticeable on a relatively sensitive skin. It is more about mechanical action that causes mechanical problems on the outermost skin layer, the epidermis. Some marathon runners put a plaster on their nipples to protect them against mechanical actions by a scratching T-shirt.
Forget about the old wives’ tales of allergy-causing chemical fiber — it is simply not true. There can be many reasons for skin irritation, but the fiber material is not one. Even surgeons are using monofilament man-made fibers in the operating theater, definitely not cotton or other natural fibers. A perfect fabric for sportswear is piqué, which has only a small direct contact with the skin. Between this material and the skin there is “room” for the air, allowing better ventilation and convection. Wet sportswear is unpleasant when it sticks to the skin. The less the material touches the skin; the better is the wicking action. And forget about the odor from wearing apparel made of man-made fibers. Everyone should have a shower after sports activities.
The next and final Rupp Report about physiological apparel will describe some important points about cut and sew, making-up, and washing and care of functional apparel.
August 26, 2014