Moisture-curing polyurethane hot melt (PUR) is an option to consider when selecting an adhesive for your manufacturing, packaging, and labeling requirements. Although polyurethane hot melts offer several advantages due to their high bond strength, there are also disadvantages. We are looking at the advantages and disadvantages of polyurethane hot melts compared to traditional hot melts.
（1）Comparison of PUR hot melts and traditional hot melts:
There are many types of industrial adhesives on the market today. Hot melts are the most widely used type.
Traditional hot melts
Because they are thermoplastic and polymer-based, hot melts are solid at room temperature. They are usually applied in a bead sequence or molten film that sets as the ingredients cool and solidify. They also have a fast setting time because they do not use water or solvents.
Use traditional hot melts when cost is more important than bond strength. However, heat-curing hot melts do not form structural connections. Although there are several strong hot melts available, such hot melts are not the best choice if the bond will be exposed to direct heat or fluctuating temperatures. Applying hot melt adhesive while the material is still liquid can cause the bond to revert to its original state and fail.
PUR Hot Melt Adhesive
PUR hot melt adhesive is different from traditional hot melt adhesive. It is dispensed much like applying glue to materials after heating it to a liquid state. As the materials cool, they adhere to each other. But as it cools, it undergoes a chemical change that forms an exceptionally strong bond with moisture in the air. This bond continues to strengthen until it is fully cured after 24 to 48 hours.
Use PUR when you need structural bonding but don't want the clumsy mixing and dispensing of many adhesives. Use PUR when replacing screws, nails, staples and other fasteners. PUR is used in a variety of applications that require a strong bond to leather, textiles, wood, plastics and many other materials.
（2）Advantages of PUR vs. Traditional Hot Melt Adhesives:
PUR Hot Melt Adhesive:
Stronger than traditional hot melt adhesives
Not just a thermal bond, but a chemical change
Simple to dispense - no mixing required.
Can replace more expensive structural adhesives.
Wide choice of viscosity and open time
Traditional hot melt adhesives:
Affordable
Simple to use
Suitable for a wide range of materials and applications
Excellent sealing quality
Easy to dispense
（3）Disadvantages of PUR and traditional hot melt adhesives:
While both PUR and traditional hot melt adhesives have great advantages, they also have disadvantages.
PUR hot melt adhesives:
PUR is generally more expensive than traditional hot melt adhesives. Another disadvantage of polyurethane hot melt adhesives is that they require more storage considerations due to the way it cures with water. The product can be damaged by improper storage and exposure to moisture. Therefore, they have a shelf life of about one year, but other hot melt adhesives do not.
Traditional hot melt adhesives:
Traditional hot melt adhesives only create a thermal bond, which is one of their disadvantages. Therefore, they are weaker than PUR. If strength is your main concern, you may want to reevaluate your decision. Traditional hot melt adhesives are generally less heat resistant than PUR hot melt adhesives, which is another disadvantage.
