Gore-Tex
GORE-TEX is a waterproof/breathable fabric and a registered trademark of W.L. Gore & Associates. It was co-invented by Wilbert L. Gore (1912-1986), Rowena Taylor, and Gore's son, Robert W. Gore. Robert Gore was granted U.S. patent 3,953,566 on April 27, 1976, for a porous form of polytetrafluoroethylene with a micro-structure characterized by nodes interconnected by fibrils. Robert Gore, Rowena Taylor, and Samuel Allen were granted U.S. patent 4,194,041 on 18 March 1980 for a "waterproof laminate." For its invention, Robert W. Gore was inducted into the National Inventors Hall of Fame in 2006.
Company
Worldwide sales of all W.L. Gore Ltd's products totalled $2 billion in 2007.
The company employs 8000 workers and is privately held.
WL Gore and Associates has consistently been placed in the Fortune magazine top 100 companies to work for worldwide.
As well as the fabrics for outdoor clothing it is best known for, the company also manufactures products for "electronic signal transmission; medical implants; as well as membrane, filtration, sealant, and fibers technologies for diverse industries." [1]
Design
Gore-Tex materials are typically based on thermo-mechanically expanded polytetrafluoroethylene (PTFE) and other fluoropolymer products. They are used in a wide variety of applications such as high performance fabrics, medical implants, filter media, insulation for wires and cables, gaskets, and sealants. But Goretex is best known for its use in protective rain wear.
The simplest sort of rain wear is a two layer sandwich. The outer layer is typically nylon or polyester and provides strength. The inner one is polyurethane, aka PU, and provides water resistance, at the cost of breathability.
Early Goretex fabric replaced the inner layer of PU with a thin, porous fluoropolymer membrane (Teflon) with a polyurethane coating that is bonded to a fabric, usually nylon or polyester. This membrane had about 9 billion pores per square inch (around 1.4 billion pores per square centimeter), each of which is approximately 20,000 times smaller than a water droplet, making it impenetrable to liquid water while still allowing the smaller sized water vapour to pass through.
However it was found that when used in clothing the exposed Teflon membrane layer was easily damaged, as well as being compromised by exposure to the wearer's own sweat. As a result a third layer was added - a coating of PU on the inside of the fabric to protect the membrane. [2] This final design has been criticized as offering greatly reduced performance and more marketing benefits than performance ones. [3]
More recent fabrics such as eVent and Epic avoid the need for this inner PU coating [4] and have been shown to have have higher breathability as a result, while still being rainproof. [5]
Use in outdoor clothing
The best known application for GORE-TEX fabrics is in outdoor activity clothing.
High breathability in rain wear for users performing physically demanding activities can be a matter of life and death. Removing sweat can be critical to survival in harsh conditions: trapped sweat makes insulating layers less effective and rob the body of heat through evaporative cooling, thus leading to hypothermia. [6] This is especially the case if vigorous exercise is followed by a period of being stationary in the cold and the wet.
It is important to understand that Goretex is not perfectly breathable, although it is more breathable than some alternative materials [7] - although less breathable than others. Thus exertion may still deposit sweat potentially causing hypothermia. For this reason it is vital that layers worn underneath Goretex (or any similar material) for activities such as hiking should be made of fabrics such as wool or fleece that maintain their warmth while wet rather than, say, cotton, which does not. Additionally, an adequate balance between the activity level and venting should be maintained, and the removal of insulating layers should be considered if sweat is building up. See Layering (clothing).
Performance and comparison with other breathable fabrics
The suitability of Goretex for high performance clothes for outdoor aerobic activities such as hiking, cross country skiing, and cycling, etc, has been particularly questioned:
The problem with Gore-Tex in warm weather is precisely that the quantity of sweat vapor it can pass is extremely limited. Without true breathability, the heat and then the humidity inside the suit rises quickly to the saturation point, turning sweat vapor into wet, liquid sweat at the Gore-Tex barrier...
In colder weather.. an athlete will be wearing some form of underclothing which will ordinarily absorb some of his sweat, both as liquid and as vapor. This is undesirable because it means the underclothing traps the very heat load the body is trying to rid itself of. Worse yet, after the exercise is over, evaporation of damp underclothing may cause over-cooling of a fatigued athlete, already cold from cessation of activity...
...As clothing, Gore-Tex does its thing best in hot, dry air—precisely when it would be least desirable because of the enormous heat load it would cause. In cool, wet weather it works best when the user is not exercising vigorously. The ubiquitous tan raincoat seen on every commuter who ever wore a white collar would seem to be a perfect, huge market. So would the market for golf jackets, car coats and wind breakers when these products are used for casual activities such as walking and spectating. [8]
The latest version of the US Army's ECWCS system corresponds to the above by using the more breathable Epic fabric in its combat smocks, designed to be worn while very active, and Goretex in the system's parka, designed to be donned over the smock during periods of relative inactivity. Epic achieves its high breathability through avoiding the use of a membrane and instead sheathing its fibres in silicone. [9][10]
According to US Army testing, the alternative fabric eVent provides up to four times the rate of moisture transfer as Goretex, depending on relative humidity inside and outside the garment - in particular it transfers moisture better at lower levels, thus allowing an equilibrium to be reached at much more comfortable (and safer) level. However, eVent is arguably not as physically tough as Goretex's premium XCR fabric, making the choice of optimum fabric dependent on activity, with eVent preferred more as activity levels rise. [11][12] However "directional" fabrics like Nikwax Analogy may be both tougher and more breathable than Goretex.
Goretex suffers reduced breathability when its pores are blocked by dirt, a problem avoided by some alternatives fabrics such as Xalt (although this fabric is less breathable than clean Goretex). [13]
Product range
The current Goretex product range for clothing includes both the tougher premium Goretex XCR, and the lighter, cheaper and more breathable Goretex Paclite. [14]
Care of Goretex fabric
- As dirt - and even human sweat - will block the pores that allow Goretex to breathe, clothing that uses it should be kept clean for performance as well as hygiene and appearance reasons.
- Both wear and cleaning will reduce the waterproofness of Goretex clothes by wearing away the Durable Water Repellent (DWR) treatment on the surface of the fabric. However this can be restored using a DWR washing additive or spray.
- See [15] for a guide to maintaining Goretex fabrics.
Other uses
GORE-TEX is also used in surgery as an implant material, patch, or membrane, such as is used in plastic surgery and heart surgery.
Gore requires that all garments made from their material have taping over the seams, to eliminate leaks. Gore's sister product, Windstopper, is similar to Gore-Tex in being windproof and breathable, but (1) has ability to stretch and (2) is not waterproof.
GORE-TEX is playing an increasing role in the conservation of illuminated manuscripts.[1]
References
- ^ Singer, Hannah. “The Conservation of Parchment Objects Using Gore-Tex Laminate.” The Paper Conservator 16, 1992: 40-45.