Velcro

The hooks on a piece of VELCRO brand fastener

Velcro is a brand name of fabric hook-and-loop fasteners. The term VELCRO is a registered trademark in most countries. Generic terminology for these fasteners includes "hook and loop", "burr" and "touch" fasteners. The VELCRO company headquarters is in Manchester, New Hampshire, USA.

History

The loops on a piece of VELCRO brand fastener

The hook-loop fastener was invented in 1948 by Swiss engineer, George de Mestral. The idea came to him after he took a close look at the Burdock seeds which kept sticking to his clothes and his dog's fur on their daily summer walks in the Alps. He examined their condition and saw the possibility of binding two materials reversibly in a simple fashion.^[1][2] He developed the hook and loop fastener and submitted his idea for patent in 1951. It was then granted in 1955.^[3] De Mestral named his invention "VELCRO" after the French words velours, meaning 'velvet', and crochet, or 'hook'. The uses and applications of the product are numerous. Today, the VELCRO mark is the subject of more than 300 trademark registrations in over 160 countries.

Composition

Tiny hooks on a Burdock (Arctium Lappa) (detail)

Hook and loop fasteners consist of two layers: a "hook" side, which is a piece of fabric covered with tiny plastic hooks, and a "loop" side, which is covered with even smaller and "hairier" plastic loops. There are many variations to this which include hooks on both sides, for example. When the two sides are pressed together, the hooks catch in the loops and hold the pieces together. When the layers are separated, the strips make a characteristic ripping sound.

Use

The strength of the hook and loop bond depends on how well the hooks are embedded in the loops and the nature of the force pulling it apart. If hooks and loops are used to bond two rigid surfaces, e.g. auto body panels and frame, the bond is particularly strong because any force pulling the pieces apart is spread evenly across all hooks. Also, any force pushing the pieces together is evenly applied over the entire surface, engaging more hooks and loops. Vibration can also cause rigid pieces to improve their bond.

When one or both of the pieces is flexible, e.g. a pocket flap, the pieces can be pulled apart with a peeling action which applies the force to relatively few hooks at a time. If a flexible piece is pulled parallel to the plane of the fastener surface the force is spread evenly as with very rigid pieces.

hooks (left) and loops (right).

Two ways to maximize the strength of a bond with one or more flexible pieces are:

• increase the area of the bond, e.g. long purse straps.
• ensure that the force is applied parallel to the plane of the fastener surface, e.g. bending around a corner or pulley. For example, shoe closures can resist a large force with little bonding area by wrapping a strap through a slot which reduces the force on the fastener by ensuring the force is parallel to the plane of the fastener and by halving the force on the bond by acting as a pulley system.

Applications

A shoe using hook and loop fasteners

Because it is easy to use, maintenance free, and totally safe, the hook-and-loop fasteners have been used for just about every conceivable application where a temporary bond is required. It is especially popular in clothing where it replaces buttons or zippers, and as a shoe fastener for children who have not yet learned to tie shoelaces and for those who choose hook-and-loop over laces.

A stronger version of the hook-and-loop material has even made it possible to create semi-permanent bonds (where it is extremely hard to separate the hooks from the loops), useful for higher stress applications. Hook and loop fasteners made from stainless steel are used in the automotive industry to attach parts such as bumpers. Rather than loosening the fasteners (as would happen with a bolt), the vibration of the automobile actually maintains the bond (since any hooks that come loose are more likely to re-attach due to random motion).^{[citation needed]}

The strength of a hook and loop bond depends on how much surface area is in contact with the hooks: full-body hook and loop suits have been made that can hold a person to a suitably-covered wall.

References

• VELCRO® -- Official company website

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