Five Tips for Working with Polyurethane Reactive (PUR) Hot Melt – Hotmelt.com
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Five Tips for Working with Polyurethane Reactive (PUR) Hot Melt

Five Tips for Working with Polyurethane Reactive (PUR) Hot Melt

PUR hot melt has a hybrid chemistry designed to create and maintain a secure bond in wet environments, extreme temperatures, high-flexibility situations, and other less-than-ideal settings.

PUR hot melt combines the advantages of traditional thermoplastic technology with the performance characteristics of reactive adhesive chemistries. It is extremely strong, can be engineered for flawless application in a variety of settings, and is basically impervious to the extreme environmental conditions that would ruin most bonds.

PUR hot melt is a great match for indoor and outdoor applications that need to stand the test of time and the trials of harsh conditions. Here are a few tips to help you make the most of it, no matter the project.

Equipment You’ll Need to Work with PUR Hot Melt

We probably should have called this section “equipment you won’t need to work with PUR hot melt” because it’s surprisingly uncomplicated for such a powerful adhesive.

PUR hot melt combines the production benefits of hot melt adhesives and the bonding performance of two-part structural adhesives, yet it’s a “single system.” That means it’s easy to dispense using hot melt equipment. There is no additional metering, mixing, or curing.

And, because PUR hot melt is a 100 percent solid, there are no volatile organic compounds (VOCs) to worry about. This eliminates environmental and health concerns and reduces the extra time and energy expenditure associated with drying ovens, safety gear, and other equipment needed to work with water- and solvent-based adhesives.

repairman wood board

 

How to Apply PUR Hot Melt

PUR hot melt adhesive can be applied at temps ranging from 85°C to 140°C (185°F to 284°F), which is cooler than other hot melt varieties that can reach temps of 190°C to 230°C (375° to 450°F). This makes PUR hot melt a great candidate for substrates that are sensitive to high heat.

However, that doesn’t mean it’s any weaker than other hot melts or adhesives in general. As it cools and cures, PUR hot melt reacts with moisture in the air and the substrates to which it’s applied. This secondary bond forms a new polyurethane polymer that provides strength and flexibility unheard of in other forms of hot melt.

In addition, the viscosity of PUR hot melt can be engineered from 2,000 cPs all the way up to 60,000 cPs. At a higher viscosity, it will set and quickly become structurally rigid. This makes PUR hot melt excellent for use in line manufacturing when speed is of the essence. However, PUR hot melt can also be formulated to have an open time up to 10 minutes, allowing for a variety of application methods to match unique production requirements.

Best Applications for PUR Hot Melt

Because it is a single-system adhesive with a flexible application temperature and viscosity, PUR hot melt is used in everything from food packaging to shower wall installation.

Woodworkers find PUR hot melt affordable, efficient, and versatile for both temporary tacking and long-lasting architectural and aesthetic applications. For cabinetry and furniture makers, PUR hot melt can provide superior strength and precision over hammers and nails, making finishing work faster and that much more attractive.

When it comes to construction and remodeling, you name it, and PUR hot melt has done it—solid surface applications for kitchens and bathrooms, hard-seaming in wall cladding, vertical applications in nearly every room of the house, and more.

Because PUR hot melt will bond with nearly any substrate, can be engineered to have a long or short open time, and is a single-system product that’s immune to harsh or wet conditions, it’s a dream for almost any product assembly line.

man repairing furniture

 

How to Prolong the Shelf Life of PUR Hot Melt

Modern enterprise moves quickly and expects a lot from its tools. That means adhesives today must have a long shelf life and be able to cure quickly when dispensed. Because of its two-fold reaction that involves both heat release and moisture, when stored correctly PUR hot melt will remain solid and shelf-stable right up until the time it’s used.

If unopened, PUR hot melt should be stored in a foil pouch in a cool, dry place. To prevent premature activation, keep it from rain or any other moisture. For PUR hot melt that has been partially used, before stopping work for the day, extrude a one-inch bead of adhesive to remove all air from the tube for short-term storage. 

How to Clean Your PUR Hot Melt Equipment

There’s no way around it—working with PUR hot melt means maintaining your hot melt equipment will require thorough, regular cleaning. Keeping your equipment running smoothly pays off in several ways, including improving the longevity of your equipment, reducing waste, protecting your safety, and, of course, boosting the bottom line at your business.

PUR hot melt begins to cure into a strong, permanent bond as soon as it cools, so it’s vital you run your cleaning material immediately after you’re done dispensing adhesive, to avoid damaging your equipment.

Preserve your equipment longevity and your own safety with these easy-to-follow cleaning tips:

Step 1

Power down your machine and purge as much hot melt as possible. This will help you reduce the amount of cleaner you have to use.

Step 2

Add your cleaner of choice and bring your equipment back to heat. Turn the pressure pump on to move the cleaner through the system. Repeat this step until you’ve removed all the remaining hot melt.

Step 3

Make sure to drain all the used cleaner before refilling your tank with fresh PUR hot melt. Leftover cleaning agents can contaminate any adhesive you put in your tank and keep it from achieving its full bonding potential.

As you can see, no matter the application, there’s a PUR hot melt that will produce great results. If you need help choosing—or more tips on using—the right PUR hot melt adhesive for you, contact us for help.