Velcro fastener
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The Velcro fastener is predominantly a textile fastener that can be loosened almost any number of times and is based on the principle of Velcro fruits . The bionic implementation consists in the typical form of two woven synthetic fiber strips, one of which has flexible barbed hooks and the other has loops. When pressed together, they result in a resilient, but reversibleQuick release. The woven Velcro straps are made from polyamide, polyester and polyolefin fibers. Fibers made from polyaramids are also used for special products. With hook straps, the hooks are incorporated during weaving or later. DIN EN 12242: 1999 is used to test textile Velcro fasteners. Characteristic values are the tensile shear strength, the tensile strength (front tear strength) and the peel resistance. Velcro tapes and snap fasteners can also be coated with pressure-sensitive adhesives on the back.
history
The Swiss engineer Georges de Mestral often went for nature walks with his dogs. Again and again some fruits of the great burdock ( Arctium lappa ) came into contact with the fur of the dogs and got stuck in it. He put the fruits under his microscope and discovered that they have tiny elastic hooks that do not break off even if they are forcibly removed from hair or clothes. Mestral examined their properties and saw a possibility of reversibly connecting two materials in a simple manner. He developed the textile Velcro fastener and applied for a patent for his idea in 1951 . The product was marketed for the first time under the name "Velcro", composed of the French terms velours (velvet) and crochet (hook).
sorts
In the meantime, different variants have been developed from the principle copied from nature:
- Hook and loop tape (felt tape) (typical application for clothing)
- Mushroom head tape and velor tape (stronger adhesion)
- Mushroom head tape and fleece tape (high holding forces under shear stress)
- Mushroom head band on mushroom head band (typical industrial application, with a defined pressure point, high holding forces under shear and tensile loads)
- Extruded hooks / mushrooms on knitted fabric (a diaper fastener)
Possible applications
Velcro fasteners are used, for example, on shoes and clothing, on blood pressure measuring cuffs, on baby diapers , to fix synthetic turf, carpets, tarpaulin, on rucksacks and bags, in trade fair construction , on tools, in cars, on astronauts' space suits and as cable ties .
- Application examples
Sneaker with Velcro fasteners
Velcro fastener on a bracer
Cable tie with Velcro on a power supply unit
Further development
- There have been Velcro fasteners with metal hooks and loops and a base made of Kevlar since about 1986 , which were intended for use in high-temperature areas, but were not used often because of the high price. After the Apollo disaster in 1967, caused by a cabin fire, NASA demanded an absolutely incombustible Velcro fastener made of fiberglass, which was then manufactured and used.
- There are also Velcro fasteners for fire brigade and racing driver clothing that are made entirely of Nomex and are non-flammable. Special Velcro tapes are also used in the aviation industry. For this purpose, specially impregnated Velcro strips are used, which are self-extinguishing in the event of fire.
- Since 2009 there have also been detachable connections made of punched, thin chrome-nickel sheets under the brand name Metaklett , which work on the Velcro principle. These are characterized by high holding forces and high resistance to thermal and chemical influences. The product received the steel innovation award in 2009 .
- The 3M company developed a "mushroom head" Velcro fastener that works with just one component of the Velcro fastener. Instead of hooks, the smallest hemispherical heads (26, 40, 62 or 110 knobs per cm² on a short punch) are made of polyolefins , these are arranged in a wave-like or parallel manner and ensure optimum holding power and releasability. The mushroom heads slide over each other until they are anchored into each other by pressure. The pressure lock, with a thickness of around 4 mm, can be subjected to both tension and shear. The tensile and shear strengths of the snap fasteners differ greatly and depend on the number of mushroom heads / cm² that are combined with one another. The closure is opened by a peeling movement. The thinnest version with a connection thickness of 1.7 mm is transparent and is called "Dual Lock SJ4570" by the 3M company . For closures of packaging, 0.87 mm thick combinations of a mushroom head and a loop tape are now available.
Velcro tapes can be sewn or welded onto textiles; the Velcro tapes are also stuck on stiff surfaces. For this purpose, the backs are given pressure-sensitive adhesive coatings, the shear forces of which are usually greater than the shear forces of the Velcro connections.
Trivia
In the episode Carbon Creek (2002) of the television series Enterprise , one of the volcanic companions of T'Mir (T'Pol's great-grandmother) is called Mestral. The scriptwriter saw this naming as a tribute to the inventor Georges de Mestral. At the end of the episode, T'Mir sells the Velcro fastener, which is a Vulcan invention in the series, to a company in order to finance a young man's studies. Mestral remains as the only Vulcan on earth.
At his number one hit, Thrift Shop , Macklemore had an admirer say, “Aw, he got the Velcros,” when he wore Velcro sneakers from the thrift store .
literature
- Christoph Hein: Systematic investigations into metallic Velcro connections. ISBN 978-3-89791-394-3 .
- Georg Krüger: Velcro fasteners - materials, manufacture, testing, applications. ISBN 978-3-446-43440-0 .
Web links
- Velcro patent specification. SA of March 16, 1954 (French-language PDF) (133 kB)
- Invention, history and principle of operation
Individual evidence
- ↑ Georg Krüger: Velcro fasteners - materials, production, testing, applications . Leipzig, 2013, ISBN 978-3-446-43440-0 .
- ↑ Velcro fastener. In: derkreiger.at. Retrieved April 27, 2009 .
- ↑ The steel Velcro fastener, 1 m² holds 35 tons at up to 800 ° C.
- ↑ Dual Lock