eptember 26, 2025
What Are Polyurethane Adhesives?
Polyurethane adhesives, sometimes referred to as PUs, are a type of adhesive made of polymer chains and urethane links. They can be two-component or one-component adhesives and can be vastly different based on this one property alone.
One-component polyurethanes cure with moisture and are known for their great elasticity but have a lower strength. Two-part polyurethane glues cure after a chemical reaction between the two components form a cross-linked polyurethane polymer. They are strong enough for structural applications.
Properties of Two-Component Polyurethane Adhesives
Two-part polyurethane-based glues are structural adhesives known for their flexibility. While every product is unique, two-part polyurethanes tend to have a higher resistance to impact and stress compared to other types of structural adhesives like epoxies or acrylics. They can also be used on various different substrate materials.
Pros
Two-part polyurethane adhesives have several benefits, including:
- Excellent flexibility and elongation
- Structural strength
- Resistance to impact and stress
- The ability to bond to various substrates
- Good chemical resistance
- Various cure times
Cons
While there are several pros of two-component polyurethanes, there are also some downfalls, including:
- Poor UV resistance
- Surface preparation is required
- Health and safety concerns
Two-Part Polyurethane Applications
Two-component polyurethane glues can bond several types of substrates and be used in a wide variety of structural bonding applications. You commonly find two-component polyurethane adhesives in:
- Building panels
- Automotive assembly and vehicle manufacturing
- Structural glazing
- Boat building
How to Choose Your Adhesive
If you are looking for a structural adhesive that has a high amount of flexibility and impact resistance, then two-component polyurethane adhesives may be the way to go. When choosing between two-part polyurethane adhesives, you should consider:
- Substrate materials
- Bonding requirements
- Cure speed
- Environmental exposure
- Budget
Because every adhesive is different, the right one for your application will depend on your specific needs. You should test the adhesive on your application first and may want to consult an adhesive expert for a personalized recommendation.
Product Examples
At Gluegun.com, we have been in the adhesives industry for over 50 years and have a wide range of knowledge when it comes to structural adhesives. To help you narrow down your choices for two-component polyurethanes, we are sharing a few of the products we recommend.
Bostik is one such brand that is trusted in the industry, and their Pliogrip™ 7700 series is a great choice of two-part structural polyurethane adhesives. This series is primarily used with plastic but may also be suitable for composites, metals, and wood. These adhesives are also sag-resistant, sandable, and paintable with gap-filling capabilities, so they can be used in a wide range of applications.
The series comes with a selection of different working times to better meet people's needs. If you are looking for a shorter work time, try the Pliogrip 7771 adhesive. It has a working time of about one and a half minutes. For a medium work time of around eight to ten minutes, try the Pliogrip 7779 polyurethane. If you are in need of a longer working time, there is the Pliogrip 7770. It has a working time of around 35 to 40 minutes and reaches handling strength in around 90 to 120 minutes.
Looking for More Insight?
Choosing the best adhesive for your application can be a challenge. If you have any questions about two-part polyurethane adhesives or are looking for a recommendation, we are here to assist you. Just reach out.
