By Will Cannon, Industrial National Accounts Manager for Glue Dots International
Both pre-formed Pressure Sensitive Adhesives (PSAs) and traditional hot melt glues have beneficial attributes dependent on the surface application and the environment in which it is applied and stored. For deep penetration of a surface, some packaging operations prefer to use hot melt to secure product packaging made from heavy-duty materials. However, traditional hot melt isn’t always the best option for securing packaging.
Hot melt, which is typically applied at 250 to 350 F, can cause serious injuries. According to a 2016 report from American Burn Association data on burn incident treatment in the U.S., scalding or thermal burns accounted for 34 percent of all burn types – second only to flame burns (43 percent). Of all burn center admissions, occupational burns numbered 8 percent. Although specific data related to workplace thermal burns does not appear to be collected by the Occupational Safety and Health Administration (OSHA), workplace burns are a real risk.
For packaging companies that use hot melt, a large portion of employee training time can be spent on burn prevention and learning how to maintain the equipment used for hot melt application. If an accident occurs, the costs associated with worker’s compensation claims and lost labor time can add up.
The safety of pre-formed PSAs is a big draw for packagers looking to reduce injuries and training time spent on a somewhat transient workforce. While safety is a primary benefit of using pre-formed PSAs, there are many other points of differentiation that simply make pre-formed PSAs the best match for specific substrates. How can packagers determine if a safer PSA will be effective in their operation? Surface by surface, what follows are six substrates where a pre-formed PSA pattern can be a better adhesive option than traditional hot melt, and why.
Foam is a perfect example of a surface to which PSAs are appropriately matched. Foam is affected by heat. Sometimes, applying hot melt to a solid foam surface will cause the material to cavitate, literally burning or etching into the foam’s surface. Pre-formed PSA patterns do not produce that effect because they sit on the surface of the foam. This allows the PSA patterns to create strong adhesion versus irreparable damage to the foam material incurred through melting.
When working with metals, the laws of thermodynamics come into play. For instance, when applying a hot melt to metal, the metal will act like a heat sink. Essentially, this means that the metal is going to draw heat out of the adhesive rapidly. As this occurs, the adhesive will cool more quickly requiring the bonding process to be completed much faster. There is less time to complete a bonding or assembly process. Depending on the type of metal being applied to, and the density of it, hot melt will have varying degrees of adhesion times. In this situation, room temperature PSAs will demonstrate consistency by providing equally effective adhesion across all metal surfaces.
Chipboard, or cardstock, is especially conducive for use with PSAs and the two are commonly used together. Chipboard and pre-formed PSA patterns can form a strong bond, yet tearing is avoided with the correct adhesive selection. The two materials together create an aesthetically appealing look. Application is easy, very fast and no angel hair is left on the package, as a hot melt has the potential to do. It is a great option for adhering two chipboard cartons together such as a Buy One Get One (BOGO) twin pack, or a “free sample with product” presentation, like a trial-size cereal box with a full-size box of cereal.
Some packaging scenarios are more critical, extending far beyond aesthetics. For example, on a product box with printed instructions, those printed portions need to remain intact. If the instructions get damaged, consumers are unable to read them, creating the possibility the product gets used incorrectly and possibly leading to injuries. It could be a liability. A hot melt may dive into the fibers a bit deeper, causing an opportunity for fiber-tearing through printed materials. With pre-formed PSA patterns, the adhesive can be entirely removed without compromising the printed information.
Plastic film surfaces are also well suited for pre-formed PSA use. Most films are affected by heat, which can distort the film or melt it. Pre-formed PSAs are much less prone to damaging this type of surface because they can be applied at whatever ambient temperature is. Distortion is no longer a concern once heat application of adhesives is ruled out.
With glass surfaces, pre-formed PSAs provide great bonding when pairing a glass item with another glass item, or a glass item with non-glass material. In either instance, high-profile, pre-formed PSAs have the properties needed to create a cushion or gap between two products, like adhesive shock absorbers. The PSA acts like a bumper, preventing products from becoming damaged. This shock-absorption effect is extremely hard to attain with traditional hot melt. The problem with hot melt in this scenario is that to obtain that cushion, the hot melt would have to be built up thickly on the surface of the glass. Not only would this prove to be messy, but It would be very difficult to build hot melt up to the level of thickness required for that bumper-like effect.
Choosing the right adhesive for a surface application may seem daunting. Pre-formed pressure sensitive adhesives are effective adhesives when matched properly to the target substrate, making sure the effects of adhesion are aligned with the needs of the final packaged product. With minimal training and equipment costs and absolutely no burn risks, pre-formed PSA patterns can be readily adopted for their advantage with specific substrates, as well as their speed of application and ease of use.
Will Cannon is an industrial national accounts manager for Glue Dots International.