What Are The Hook And Loop Fasteners?

Hook and loop fasteners, touch fasteners or hook and pile fasteners have two lineal strips of fabrics that are attached opposite to each other to get fastened. The first component has tiny hooks and the second one has small loops. When both of them are pressed against one another, the hooks are caught into the loops and the two strips get fastened or banded properly. If you need to separate them, peel or pull the two strips apart. The strips will make a ripping sound.

Strength

Hook and loop Velcro comes in various strengths. The one having glass backing, polyester hooks and Teflon loops are used in space shuttles and other aerospace applications. The bond strength depends on how the hooks are being embedded in loops, how much is the surface area in contact with hooks and the type of force that is needed to pull them apart.

If hook and loop Velcro is used to bind up any two rigid surfaces like the auto frame and body panels, the bond is really strong as the force used to pull these pieces apart has to be spread evenly over all the hooks. Also if there is any force to push up the pieces together, it will disproportionately be applied over engaging hooks and loops. Vibrations could improve the strength of bonds.

In case both the pieces are flexible, like the pocket flap, the pieces could be pulled apart through a peeling action which applies the force to some new hooks during that time. If the flexible pieces are pulled in the direction parallel with the plane, the force will get spread evenly with rigid pieces.

Ways of maximizing strength in hook and loop Velcro

Increasing the bond area, i.e. using large pieces

Ensure that the force is applied in a direction parallel with the plane of fastening surfaces, like bending around the pulley or corner.

Increasing the number of loops and hooks in each unit area.

Pros and cons of hooks and loops Velcro

Hooks and loops Velcro are free of maintenance and are easy and safe to use. The effectiveness gets declined minimally only after many fastenings and unfastening. It makes a tearing noise which is very useful in the case of pickpockets.

The main deficiency that tends to come in their use is that it could accumulate fur, dust and hair in just a few months of use. The loops may become elongated or get broken after extended use. The hooks may get attached to the articles like clothing, especially loose woven items such as sweaters. The clothing could get damaged if attempted to remove, even if separated slowly. The tearing sound while unfastening could make them inappropriate to use in many applications.

Application

Due to their ease of use, hook and loop Velcro are widely used in many applications, especially in the cases where a temporary bond is required. It is popular in clothing as it replaces zippers or buttons and is used as a shoe fastener in children shoes.