Food Packaging: Adhering Hard-to-Bond Surfaces

May 6, 2015 Off Comments in Food Packaging by
Food Packaging: Adhering Hard-to-Bond Surfaces

The food packaging industry is home to a wide variety of packaging, from high glosses to gain appeal on a store shelf to wax boxes that increase functionality of packaging. While these unique packaging materials offer a competitive edge in the food industry, they are much more difficult to adhere and often require specialized adhesives.

Without the right adhesive, you may face pop-opens and other adhesion failures, increasing the amount of money and time spent on rework and scrap.

In this four-part series, we’ll discuss the different types of hard-to-bond paper stocks you might be working with in food packaging, and how we can help you bond them.

Part 1: Wax
Wax is curtain coated or impregnated into various paper stocks to act as a moisture barrier between the paper fibers and food product. In curtain coated boxes, the wax is concentrated only on the surface of the paper stock, making it difficult for an adhesive to penetrate to the fibers and form a bond.

Wax impregnated boxes contain wax throughout their fibers. Although these boxes have a higher wax content, the wax is not as concentrated on the top layer, making it slightly easier to bond.

For these types of packaging, we would recommend an adhesive with a long open time, enabling it to penetrate through the wax and form a full fiber-tearing bond.

Part 2: Recycled
Did you know that corrugated is the most-recycled packaging material on earth? In fact, the average corrugated box consists of 46 percent recycled fiber.

Just about every product under the sun is shipped using corrugated packaging. It’s rare to find corrugated that isn’t recycled, especially with the prominence of sustainable packaging. Although good for the environment, recycled fibers are more difficult to bond than virgin.

Recycled corrugated is manufactured by breaking down previously used paper and corrugated into pulp, removing contaminants, and then reforming into new boxes. The break down process means recycled fibers are shorter and more compact than the original fibers, making it harder for adhesives to penetrate and form a good mechanical bond.

Virgin corrugated is less dense due to the longer interwoven fibers allowing adhesive to better wet out and form a bond. Like a tree growing roots in clay versus aerated soil, adhesives can form their “roots” easier on virgin fibers, than on dense recycled fibers.

More commonly, we are seeing adhesive users working with their adhesive suppliers to ensure the right type of adhesive is being applied according to the recycled content of their corrugated packaging.

Part 3: High Gloss
Walking through the grocery store aisle, there are many types of packaging—some more appealing than others. You may even be compelled to purchase a product over another due to its packaging. What is it that makes it more appealing?

High gloss, colorful packaging tends to stand out on store shelves and is eye-catching to consumers. Although this type of packaging attracts shoppers and differentiates itself from competitors, its high gloss surface (whether it is polyethylene, polypropylene, metallized, etc.) is difficult to bond, often requiring a specialized adhesive.

The smoothness and often low surface energy of a high gloss carton makes it difficult for adhesives to “wet out” and penetrate the surface. Unlike traditional corrugated adhesion, the hot melt doesn’t bond like a tree forming roots in the ground; rather, the chemical bond behaves more like a magnet. The two materials are attracted to each other because of their chemical make-up, not the mechanical adhesion of a root.

When adhering a high gloss paper stock, we recommend working closely with your adhesive supplier since this particular application requires a specific hot melt with the ability to form a chemical bond to the surface of these high gloss paper stocks.

Part 4: Clay Coatings
Consider which logo would stand out more—the one printed on plain, recycled brown paper stock, or the logo on white, clay coated paper stock? Often the latter, clay coatings improve brightness and tend to really give any printed design that extra “pop,” so that the overall packaging appeals to customers.

Printing on a clay coated paper stock also reduces the amount of ink used since it does not readily absorb it, unlike an uncoated paper stock. This very same concept of resisting absorption is what makes adhesion to this surface difficult. Just as clay coated paper stock doesn’t absorb ink, it doesn’t allow adhesive to easily penetrate its surface, making it difficult to form a bond.

Adhering clay coated paper stocks requires a specialized hot melt that has the ability to “wet out” on the surface of the coating. This will allow the adhesive to “bite” through the surface and achieve an excellent, fiber-tearing bond.

As with all of the hard-to-bond coatings we’ve previously discussed, we cannot stress enough the importance of working with your adhesive supplier to help you find the right solution that will work for your specific application, whether it is bonding wax boxes, recycled corrugated, high gloss or clay coated paper stock. Having the foundation of a trusting relationship with your adhesive supplier will go a long way in optimizing your overall packaging process.

Worry-Free Production
At RS Industrial, we carry a line of specialized adhesives to ensure you get the best bonds for your specific food packaging application. By performing on-site testing at your facility or our internal lab, we can quickly recommend an adhesive solution that fits your specific food packaging application.

To learn more about how we can help decrease your chances of pop-opens and increase your production, contact us at 1-800-844-1740 or info@rsindustrial.com. Let us take the guesswork out of your adhesive process!

 

*Check this spot for a weekly update—we’ll be adding a new paper stock each Wednesday!*
Wax-4/15/15
Recycled Stock-4/22/15 (Earth Day!)
High Gloss-4/29/15
Clay Coated-5/6/15