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The Rupp Report

The Rupp Report: Physiological Apparel Part II: Fundamental Requirements

Jürg Rupp, Executive Editor

In this second article about physiological apparel, the Rupp Report will highlight the fundamental requirements of functional fabrics and sports apparel.
Four Basic Needs
Fabrics and apparel with functional and sports characteristics must fulfill four basic specifications:

  • protection;
  • insulation;
  • transpiration; and
  • elasticity.
Protection will prevent the wearer from wind, water and very cold to very hot weather conditions.
Insulation is the next step and, obviously, is very close to protection, as it will protect the wearer from cold weather conditions.
Transpiration is one of the key points for every functional fabric and apparel: It must ensure that the fabric acts like a wick and the body moisture can penetrate, or diffuse, through all apparel layers to the outside.
And, last, but not least, elasticity provides the comfortable feeling and a perfect fit during sports activities.
Consequently, functionally correct apparel has to meet the following major requirements:
  • pleasant microclimate, in terms of temperature, and moisture for the skin sensory range, in terms of the direct contact of the fabric with the skin;
  • good moisture absorption and moisture transportation (wicking) properties;
  • no unpleasant odor from sweat;
  • sufficient compatibility — in terms of tolerance and agreeability — with the skin;
  • good elongation properties without any limits of movement;
  • perfect fit;
  • low weight without impairment of the physical performance; and
  • largely water-and dust-repellent behavior of the fabric.
What should be considered when it comes to functional fabrics and sports apparel?
At first sight, physiological apparel seems to be quite complex, but for true textile professionals, it isn’t that difficult. However, if one takes a look at the many test methods and results from various research institutes, it is indisputable that some important issues must be mentioned and taken into consideration:
  • The thermal insulation and the moisture resistance of an apparel system can be influenced by the cut and make-up of the individual piece of apparel as well as the characteristics of the yarns and fabrics.
  • The thicker the encased air layers in the apparel, the greater the thermal insulation and moisture resistance.
  • Virtually, the real heat insulator of the apparel is the encased air.
  • Water-repellent fabric layers within an apparel system must be as thin as possible to allow sufficient moisture diffusion through the layers.
  • Air permeability of fabrics does not necessarily imply good moisture permeability.
  • The field of application will increase if there are no slim fit textiles close to the skin.
Functions And Design
For functional fabrics and sports apparel, good design includes perfect functionality. It is well known that sports apparel is not always perfectly functional. That’s why today in many cases these products are called technical or fashionable sportswear. However, in the first place, apparel should be sustainable and easy-care, and visually should look nice. As mentioned in the last Rupp Report: the body produces heat, which in fact is dependent on the wearer’s activity or workload. To make sure that the wearer does not leave the so-called comfort zone, the heat must be transferred simultaneously through the layers to the outside. A sweat output of a half, or a full liter per hour, is not a problem for the body if high humidity in the environment and the flow, or throughput, resistance of the apparel do not prevent it. If these two factors are present, the consequence will be the previously described heat accumulation.
Here is an example to explain this rather complex issue: You make fine Italian pasta, let’s say spaghetti. After cooking, the noodles are “dried” in a sieve. If the holes of the sieve are clogged and not able to let the water through, the pasta remains wet. This is somewhat how the body behaves wearing apparel that is not functional in terms of wicking: The body moisture has too much flow resistance, and the body is and remains wet; consequently, the wearer feels uncomfortable. The insulation behavior of the fabric increases this effect significantly. The thermal insulation and moisture flow resistance are therefore the determinant factors of the apparel.
User Value — And Material Testing
State institutions, such as the Switzerland-based EMPA and others, can precisely check performance characteristics and requirements for the fabrics. Main properties to be examined are lightfastness, waterfastness or colorfastness, fastness to perspiration, and abrasion resistance.
On top of that, many other criteria are examined because physical and physiological aspects of the apparel are more and more in the foreground and have become the main issue of modern apparel. Some of the tests for these criteria are:
  • waterproofness;
  • spray;
  • rain;
  • air permeability;
  • moisture permeability;
  • abrasion;
  • crease angle;
  • tensile strength;
  • tear strength;
  • seam slippage; and
  • recovery after washing at 30° C.
One of the most discussed issues in modern functional apparel is waterproofness. The unit to measure water density is millimeters (mm) of water column, for example 250 mm/hg (mercury). There are many components that affect the water density; here are the most important ones:
  • yarn, or fineness of filaments;
  • type of texturizing;
  • weave density;
  • calendering;
  • impregnation;
  • Washing process
  • thermal treatment; and
  • coatings.
Some important necessities and reasons for functional fabrics and sports apparel are now identified. Of course, it is not easy to combine all the desired requirements perfectly. If the desired properties are defined, many other factors must match, which requires experienced textile technicians and engineers. They handle mainly yarns, fabric constructions, cutting and making-up, as well as finishing. In the next issue of the Rupp Report, you will read about these influences on production of the perfect functional fabrics and sports apparel.
July 22, 2014