Biodegradable adhesives break down over time and revert to what they were made from. Those that aren’t biodegradable don’t, which can be a problem in materials like paper and packaging. These products have a short useful life, but can last far longer in the landfill or wherever else they end up.
To address this, many paper converters and packaging manufacturers have either started using biodegradable water-based adhesives in processes like laminating, or are considering do so. Here we’ll first discuss why biodegradability matters and then explain how dextrin adhesives can help.
The Importance of Biodegradability in Paper and Packaging
According to waste and recycling data from the US EPA, on average each of us produces around five pounds of trash every day. That works out to some 300 million tons per year. That trash is composed of things like lawn clippings, food and glass and plastic bottles, but the largest single category, accounting for nearly a quarter of all waste, is paper and paperboard.
Much of that paper and paperboard gets either recycled or composted. Composting is where natural biological processes turn a material into something soil-like over a period of six months or less. It’s a relatively fast form of biodegradability. Other materials may be biodegradable but take longer to break down.
Laminating processes in paper and paperboard manufacturing employ a lot of adhesive. Using an adhesive that’s biodegradable offers two big advantages.
Satisfies customer demands for “green” products
Gives packaging manufacturers and buyers an alternative to non-biodegradable packaging
The Different Types of Water-Based Adhesive
Water-based adhesives all use the same mechanism to bond permeable, and some non-permeable surfaces: the adhesive agent is held in a water solution that spreads and penetrates. Then the water evaporates, leaving the adhesive to hold the bound items together. Those adhesive agents fall into four categories:
Latex — a form of polymer used for fabric and leather, stamps and paper
Resin or polymer acetate — these are the white PVA and EVA adhesives used for bonding paper, wood and plastic
Animal protein (casein) — with especially quick fixing and setting properties, this is used for label application in beer and wine bottling
Vegetable — this is the adhesive used in bookbinding, for wallpaper hanging, and for laminating packaging materials
Vegetable adhesives divide into those that are starch-based and those using a modified form of starch known as dextrin. Here we’re focusing on dextrin because of its use in paper laminating processes and its biodegradability.
Origins and Properties of Dextrin
Dextrin is a form of carbohydrate. If that makes it sound like bread or potatoes you’re not wrong. Dextrin is derived from starch, which comes from vegetable products like those. In practice though, most dextrin for adhesives is made from cornstarch, because it’s both cheap and plentiful.
The cornstarch is roasted with an acid that turns it into polymer molecules. When dry these form a brown powder that readily dissolves in water. Dextrin adhesive manufacturers tailor the concentration of polymer in water to vary strength and other properties of the final adhesive.
The chief “strength” of dextrin is that it forms strong bonds to porous materials, especially paper. It has good resistance to temperature extremes and is very economical. Drying is relatively slow, which is desirable in applications where careful positioning is needed, although this can be accelerated by heating the solution. It’s also, as mentioned previously, biodegradable, thanks to its vegetable origins.
The major downside of dextrin adhesives also stems from their plant origins. It’s susceptible to moisture damage. This can lead to bonds coming apart when wet and promotes mold growth. It also means these adhesives have a finite shelf life.
Applications for Dextrin Water-Based Adhesives
Dextrin adhesives have a host of applications in paper converting and packaging manufacturing. It’s used in envelopes, cartons, fiberboard cases and paper bags. A major application however is laminating. Here, the strong bonding performance, coupled with slower drying time are an economical way of achieving quality results. Furthermore, biodegradability is making dextrin laminated paper products increasingly attractive to an audience focused on recycling and composting.
Let’s Discuss Your Application
We often suggest dextrin adhesives to manufacturers looking for a biodegradable adhesive for laminated paper products. It’s a reliable yet economical choice that delivers excellent performance in many applications. However, it does have some limitations. That’s why we invite you to contact us for advice on water-based adhesives for your application.