Velcro straps are used to secure loads in sewn fabric dunnage. Velcro, a type of mechanical fastener, is easier to open and close than cams, buckles, zippers, or other hardware. With Velcro, two layers of fabric are pressed together or pulled apart. One layer contains tiny hooks. The other layer contains tiny loops. Booth layers are usually made from nylon or polypropylene.
What Is Velcro?
VELCRO® brand is a registered trademark of a company called Velcro BVBA, but the term “Velcro” is used generically to refer to hook-and-loop fasteners. Not all hook-and-loop fasteners are made by Velcro BVBA, however, and more than one type of VELCRO® brand strap is available. For example, some straps provide greater elasticity. Others support both indoor and outdoor use.
Dunnage Design Decisions
For designers of sewn fabric dunnage, deciding whether to use Velcro straps isn’t a simple yes-or-no decision. Packaging engineers need to understand the complete application environment in order to choose the best strap material. Design considerations include peel strength, the use of batting, and the number of times (cycles) that the Velcro will be opened and closed.
Velcro straps can be made of nylon or polypropylene. Nylon is fine for general-purpose use, but this synthetic polymer can’t withstand prolonged exposure to ultraviolet (UV) light from the sun. Polypropylene looks like nylon, but has better sunlight and moisture resistance. For sewn fabric dunnage that’s stored in outdoor environments, Velcro straps made of polypropylene are a better choice.
Peel strength is the average load required to separate bonded materials where the angle of separation is 180°. In layman’s terms, peel strength testing measures bond strength. With sewn fabric dunnage, designers need to specify a Velcro strap that’s strong enough to stay together but not too difficult to pull apart. Otherwise, loads can loosen the straps, or workers may struggle to separate the Velcro.
Some Velcro straps can adhere to the batting that’s used with headliners, door panels, and other packaged parts. This is a problem for personnel who need to slide parts in and out of automotive rack bags during loading and unloading. Damage to part surfaces can occur, too. Velcro straps that won’t stick to batting are available, but they’re more expensive. Yet in the long run, these straps can reduce your true costs.
Number of Cycles
Finally, design engineers need to consider the number of times that workers will open and close the Velcro straps. This number can vary considerably, and may require the use of a high-cycle material. It’s also important to remember that Velcro tends to lose “stickiness” toward the end of its useful life. A longer-lasting strap may cost more, but can save you money by preventing damage to high-value parts.
Which Velcro Straps Do You Need?
Hold-True is a Made in the USA manufacturer of sewn fabric dunnage that can help you to select the right Velcro strap for your rack bag application. We recommend UV-resistant polypropylene for the strap material and offer a choice of Velcro based on the number of cycles that you need. Our experienced team is ready to talk to you about batting and peel strength, too. To get started, contact us.