How to Bond Foams with Hot Melt Adhesive
Foam substrates provide a level of protection that other standard packaging materials don’t, offering a buffer between the product and the hazards it may encounter during the packaging, shipping and delivery process, and ensuring it arrives intact to the end user. However, when you’re using hot melt equipment to work with foam substrates, finding the right hot melt adhesive for your needs can be tricky. Thankfully, by making informed adhesive choices, you’ll be able to effectively use hot melts even when you’re working with foam. Here’s how.
If you’ve ever tried to use a standard hot glue gun on a foam substrate, you probably discovered rather quickly that the two don’t play nicely together. Using a too-hot adhesive on a foam substrate is more likely to lead to a sticky, stinky mess than a suitable bond.
With this in mind, if you’re using foam in your packaging materials, you’ll need to do some research on lower temperature hot melt adhesives. While many hot melt adhesives are applied at temperatures of up to 400 degrees Fahrenheit, there are a range of lower-temperature hot melt adhesives that are designed to be applied at temperatures less than 350 degrees Fahrenheit. Using one of these lower-temperature adhesives in your hot melt equipment may help you avoid many issues related to melting.
If you think of a cardboard substrate like a slice of cheddar, then, a foam substrate is much more similar to a piece of Swiss cheese with many holes in it. Many types of foam substrates have open cell construction.
Due to the way that foam is constructed, foam substrates like those can absorb adhesive into the material without offering any benefits to the bonding process. In these situations, using a roll coater is ill advised, as it will likely push hot melt adhesive into open cells and lead to large amounts of adhesive waste. Instead, consider using swirl/spray adhesive techniques which apply a light coating of adhesive to the surface of the foam, creating better bonding.
Additionally, swirl/spray applications also reduce the overall temperature of the adhesive eliminating heat sensitive foam degradation. Rather than applying a hot, highly concentrated bead of adhesive to a particular spot on the foam substrate, you’re distributing the same amount of hot melt over a much greater surface area. This can also accelerate the bonding speed, driving the temperature out of the hot melt, and promoting fast tack.
If you’ve avoided using foam in your packaging process because of concerns about melting or ineffective bonds, it may be time for you to reconsider your decision. Today, there are lower-temperature hot melt adhesives that can create solid bonds without turning your foam substrates into a melted mess. Additionally, hot melt systems that allow you to swirl/spray the adhesive onto the foam create a greater bond without leading to a lot of wasted adhesive. By making smart adhesive choices, you’ll be able to enjoy all of the benefits that foam offers without having to sacrifice the quality of your packaging bonds.
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