Velcro ® Brand Fastening Systems: Hook & Loop

HOOK SHAPES

J Hooks – This hook style, because of its unique geometry, can be densely positioned in either an opposed direction or in a unidirectional configuration. This flexibility allows for high shear performance and the potential for directional release. Works well with non-woven and thin-knit loops.

‘Palm Tree’ Hooks – Shaped like its namesake, this high-strength hook offers about twice as much peel performance as a J hook. Within the palm family of hooks, a stiffly stemmed ‘buttressed’ palm hook provides increased peel values.

‘Mushroom’ Hooks – When you need the toughest of bonds in an application where cycle requirements are limited, this hook profile offers very high shear and peel attributes. Perfect for creating strong, near-permanent attachments.

HOOK MATERIALS

Nylon – A tough, lightweight abrasion-resistant polymer with excellent durability. Nylon performs well in high temperatures (maximum continued use temperature range of 270 to 300 degrees F) and can be sonically welded to substrates. Nylon has poor resistance to prolonged sunlight and is hydrophilic (absorbs water).

Polyester – A durable water and UV resistant polymer with a lower temperature range than nylon (-70 to 200 degrees F).

Polypropylene – Like polyester, performs well as a water and UV resistor. Temperature range is –40 to 200 degrees F. Easily heat sealed.

Polyethylene – Most commonly known as the material used for plastic bags, polyethylene is a soft, hydrophobic (resists water) polymer with good chemical resistance. This polymer is easily heat sealed. Polyethylene has a continuous use temperature of 180 degrees F.

Polyphenylene Sulfide – Often referred to as PPS, this polymer is most notable for its chemical and heat resistance. PPS has a high temperature range of 400 degrees Fahrenheit. In addition to heat, PPS also resists UV and abrasion well. These fibers don’t retain dyes and are relatively brittle.

Polyvinylchloride – PVC is commonly used in the construction industry because it’s relatively inexpensive, durable, and easy to work with. This soft resin resists sunlight and heat (upper range 350 degrees F) and is radio frequency weldable.

Nomex® – A heat and flame resistant fiber produced by DuPont, its temperature range is -70 to 330 degrees F.

Stainless Steel – For extreme high temperature needs (upper range to 800 degrees F), this hook and loop material is also chemical resistant.

OTHER HOOK INFORMATION

Permeability – Woven or knit products are porous but molded plastic hooks (HTH i.e. High Technology Hooks) are water impermeable.

Injection Molded Hooks – Hooks can be directly and integrally molded onto injection molded parts while the parts are being formed. This process eliminates the need to adhere hooks to substrates via adhesives, welding or sewing.

Environmental – Hooks can be produced from recyclable, RohS compliant materials.

LOOP TYPES

Woven – Woven loops are versatile, providing high cycle life as well as strong peel and sheer performance. Available in relatively narrow widths, loop can be woven from nylon, polyester, stainless steel, and Nomex® yarns.

Non-woven – A thin, low-profile fastener with low cycle life. Available in widths up to 120”. Non-wovens are most commonly produced from polyester or polypropylene fibers.

Knits

Warp Knit – Stable in machine direction. Wide, available in widths up to 62”. Low to medium cycle life, usually made from nylon or polyester. Applications: single use blood pressure cuffs, knee braces, disposable straps.

Circular Knit – Flexible knits, tend to stretch in both machine and cross-machine directions. Wide, available in widths up to 57”. Medium to high cycle life and commonly made from nylon and polyester yarns. Applications: buffing pads, warehouse belts.

Loop Orientation

Napped – Top loop yarns are randomly oriented for maximum peel performance.

Un-napped – Top loop yarns are oriented in an orderly configuration for maximum cycle life.

PERFORMANCE MEASURES

	Peel: the tensile strength of a hook and loop closure is measured when overlapped and engaged, held on the same end, and pulled at 180 degrees from each other.
	Shear: the tensile strength of a hook and loop closure is measured when overlapped and engaged, held on opposite ends, and pulled at 180 degrees from each other.
	Tension: the tension strength of a hook and loop closure is measured when overlapped and engaged, then pulled perpendicular to the engaged plane.
	Cycle Life: the number of times hook and loop can be engaged and disengaged before the closure strength is reduced to 50% of original values.