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Traditional Hot Melt vs. PUR Polyurethane Hot Melt Adhesives

Traditional Hot Melt vs. PUR Polyurethane Hot Melt Adhesives
When deciding what kind of adhesive to use for your manufacturing, packaging, and labeling needs, you may consider a moisture-curing polyurethane hot melt adhesive (PUR). With their high bond strength, polyurethane hot melt can be an attractive option for many different kinds of adhesive applications. However, polyurethane hot melts are not without their disadvantages as well. Let's take a closer look at the pros and cons of using polyurethane hot melts for your particular adhesive needs.
 

Traditional Hot Melt Adhesives

There are several kinds of industrial adhesives available on the market. The most popular kind, by far, is the hot melt adhesives family. Hot melt adhesives are polymer-based, and are thermoplastic in nature, meaning they are solid at room temperature. These are generally applied as either a molten film or in a series of beads that are converted to a solid form when the materials cool and set. Because hot melt adhesives do not utilize water or solvents, they also have a very fast set time, which makes them the more popular kind of industrial adhesive. 

When to choose traditional hot melt adhesives?

Use hot melt adhesives when your budget matters more than the strength of your bond. It is no secret that PUR provides much stronger bonds than traditional hot melt, but hot melt adhesives win the budget battle. Bulk hot melt adhesives are one of the easiest ways to control the cost of your adhesive.

When not to use hot melt?

Hot melt adhesives do not provide a structural bond. This isn't to say there aren't some strong hot melt adhesives out there, this is just how the chemistry works. You should not use a traditional hot melt adhesive if the bond will be exposed to direct heat or varying weather temperatures. A hot melt is applied in a liquid state - if exposed to heat the bond will return to its original liquid state and fail.

Polyurethane (PUR) Hot Melt Adhesives

Polyurethane (PUR) hot melts are used in tons of manufacturing and product assembly applications across the world and gaining steam every year. You'll find PUR adhesives in applications that require strong bonds to wood, plastics, fabrics, leather and many other materials. PUR hot melts are becoming increasingly popular because of how versatile they are. PUR can be applied as a bead or sprayed for covering large surface areas. These adhesives also come in a wide range of open times and viscosities allowing them to cater to specific application needs. Check out our Complete Guide to Polyurethane PUR Hot Melt Adhesives.

When should I use a PUR adhesive?

Use PUR when you need a structural bond, but don't want to deal with the messy dispensing and mixing that many structural adhesives like MMAs and Epoxies are prone to. Use PUR when you want to replace fasteners, staples, nails, and screws (think woodworking and finishing work).

When not to use PUR?

Because PUR hot melt reacts with moisture in the air, it must also be protected from moisture before it is used. This means it has to be packaged in airtight cartridges or foil and cannot be exposed before use. It also means that PUR hot melt carries a shelf life of around 12 months (traditional hot melts have none).

 Comparing the Benefits of Hot Melt vs PUR

Benefits of Traditional Hot Melt:

  • Cost-effective
  • Easy-to-use
  • Formulas made for a variety of applications and materials
  • Easy to store, no shelf life
  • Excellent seal quality
  • Simple dispensing

Benefits of PUR Hot Melt: 

  • Much stronger than traditional hot melt
  • Chemical change - not just thermal bond
  • Easy to dispense - no mixing
  • Can replace more expensive structural adhesives
  • Many options for open time and viscosity


The "PUR Difference"

PUR hot melt is different from traditional hot melt. It is dispensed in very much the same way, the adhesive is heated to a liquid state and applied to your materials and cools to 'stick' them together. But... this is where PUR hot melt is special. As it cools, PUR hot melt reacts with moisture in the air and changes chemically to create an incredibly strong bond. This bond then continues to strengthen over 24-48 hours until it is fully cured and super strong.


We Are Here to Help

As always, the experts at Hotmelt.com are available to answer any questions you have on PUR hot melt adhesives. We're happy to provide product recommendations, discuss applications, or provide a custom quote based on your needs. Contact us today!