In meetings with plant and maintenance personnel, I am often asked about the different types of adhesives. Here is an overview on industrial adhesives that could be helpful to those of you who may have questions regarding adhesives.
DEXTRIN ADHESIVES
Dextrin adhesives are starch-based products, usually derived from industrial grade corn starch. They are economical in price, and do well in bonding paper stock. These adhesives typically machine cleanly, and are easy to clean up, normally with warm water.
The major drawback for their use in most packaging sealing operations is their slow set speed. Generally over twenty seconds compression time is needed to form a good bond, which is not suited for high speed operations.
These adhesives are used typically used in paper converting operations, with point-of-purchase production being a common use. We have a unique line of products for this purpose.
RESIN EMULSIONS
These adhesives, commonly called "white glues" are petroleum-based products that replaced dextrins where increased speeds in case and carton sealing operations were required. The most common resin emulsions are based on polyvinyl acetate polymers, which exhibit clean machining and clean up with warm water since they are water soluble. They are commonly used for the glue joint in corrugated box production.
When special formulations are needed to bond less porous surfaces such as SBS/SUS carton stock or corrugated boxes with coatings, Vinyl Acetate Ethylene(VAE) polymers are used. The result is an adhesive that bonds well, but is more difficult to clean. Hot water is needed to clean these products off the equipment as these polymers are water resistant.
For non-porous surfaces, VAE polymers with certain adhesion promoters or Acrylic-based polymers are utilized to bond these surfaces.
With any of the resin emulsions, once the bond is formed, these products are stable over a very wide temperature range.
HOT MELTS
Hot melts are also petroleum-based products that are 100% solid at room temperature and become liquid when placed in hot melt applicators at raised temperatures for application to the substrate. Depending on the product and use, the application temperature can range from 225-425 degrees F.
For a high speed packaging operation, hot melts are used for carton seal or case seal due to a speed of set of as little as 1-2 seconds to form a bond. There are hot melts specifically designed to be used for these applications where the packaged product will be a freezer-grade application.
The base polymer of hot melts can be Ethylene Vinyl Acetate(EVA), polyethylene, or metallocene, with the majority of products being EVA-based when it comes to packaging or paper converting applications.
A fourth polymer type, Polyamide-based hot melts, are used where special needs arise, such as very high temperature applications or high strength needs. Polyamide hot melts also show better resistance to oils and solvents.
One other category is APAO-based polymer hot melts, which are used where long open time and good tack are needed. A typical application for these hot melts would be in mattress production.
Pressure Sensitive Hot Melts
A special class of hot melts are the ones that remain tacky even after they are cooled to room temperature. These hot melts are compounded from synthetic rubber-based polymers and can be strong with a permanent bond, or removable such as those used for name tags.
If your facility is in the states of Illnois, Michigan, Wisconsin, Minnesota, or Iowa, we would welcome the opportunity to discuss ways to optimize your adhesive usage or hold a seminar on Industrial Adhesives 101 for designated plant personnel.