Temperatures and humidity are soaring in the contiguous United States, affecting everything from the hair on your head to the glue on your shoes. When it comes to hot melt adhesives, these environmental conditions play a role in how well an adhesive will perform. To select the right adhesive for your job or product, one must take the production, storage, and distribution environments into consideration to ensure your adhesive holds up against any possible extreme temperatures and humidity.
Let’s discuss how environmental temperatures (and humidity/moisture) impact hot melt adhesives’ ability to perform properly. Problems associated with extreme temperature and humidity can be avoided with the correct adhesive. The team at Glue Machinery is here to help you find the perfect adhesive for your needs.
Overview of Hot Melts
In 1940, hot melt adhesives were invented by Paul Cope, a Procter & Gamble chemical and packaging engineer, to solve a problem: the water-based adhesives used at the time were not performing well in humid climates. Hot melt adhesives, a thermoplastic material, are 100% solid at room temperature and liquefy when heat is applied. They contain no water or solvents and form bonds, nearly instantaneously, due to rapid cooling. Each hot melt adhesive formula is unique, and while some are very simple, others can be extremely complex. In general, hot melt adhesives have four ingredients in common: polymers, tackifiers, plasticizers, and antioxidants. Each of these ingredients can be affected by exposure to extreme heat. Polymers give adhesives their strength and flexibility, tackifiers increase tack or stickiness, plasticizers give the hot melt greater flexibility and toughness, and antioxidants protect the material from degradation.
Heat, Humidity, and the Application Process
Hot melt adhesives must be applied at the correct temperature. If it is too hot, it takes too long to set and if it is too cold, it can set before the materials are bonded. Hot melt glues liquefy at temperatures ranging from 250 to 375 degrees Fahrenheit. If there is too much moisture or humidity in the air, it can prevent glue from drying and impacting bonding.
There are various types of hot melt adhesives available on the market and not all are created equal when it comes to performance in higher temperatures and humidity levels.
Different types of hot melt have different levels of heat resistance. A good general rule to follow is that as temperatures increase, the strength of a hot melt adhesive decreases. The adhesive will go through chemical changes that ultimately affect how well it will perform and can change its strength, elasticity, and stiffness.
Technical information provided by manufacturers for each type of hot melt gives insight into temperature resistance. For example, Polyethylene (PE) is temperature resistant up to 80°C (176°F) continuously and 95°C (203°F) for shorter times. Other types of hot melts, like polyurethane (PUR), offer excellent heat and chemical resistance, allowing them to be used externally. Glue Machinery carries a wide variety of hot melt adhesives for all of your needs.
Need help beating the heat? We’re here to help.
From construction projects to bookbinding, we are here for all your adhesive needs year-round. If you are unsure of what product would work best for your specific needs, our Glue Diligence® team can easily help you find the right products. Call us today at 1-866-274-7925 to get started.