What are one-component polyurethane adhesives and sealants?
Polyurethanes (PURs) were invented in the 1930s and have found multiple industrial applications. Polyurethane has been used in adhesives since the 1950s. They are classified as one- or two-component polyurethane adhesives, and each category contains several different types of adhesives. Reactive one-component polyurethane adhesives have isocyanate functions, which react with atmospheric moisture, or moisture in the substrate. One-component polyurethane adhesives do not require pre-mixing before application, unlike two-component polyurethane adhesives.
They offer superior elasticity that enables less shrinkage deformation during curing and better absorption of external pressure from vibrations and impacts, high mechanical performances, and adhesion to a wide variety of substrates. As a result, one-component polyurethanes are a great option for flexible lamination, building and construction, transportation, and assembly applications.
Types of one-component polyurethane adhesives
Bostik’s one-component polyurethane adhesives can be reactive, amorphous or crystalline.
Liquid Polyurethane Adhesives
Bostik proposes a complete range of liquid polyurethane adhesives providing high strength for a stong bond, fast curing for fast production, and washing resistance fo a reliable adhesive force, even in humid environments. Liquid polyurethane adhesives can be used in sandwich panels for construction and transport, flexible packaging for paper lid laminates, agglomeration of corks, scrubs, and others.
Hot Melt Polyurethanes Adhesives (HMPUR)
PUR is a "reactive" adhesive because a chemical reaction is required for the strong adhesive bond to work. Reactive hot-melt polyurethane adhesive (HMPUR) is a 100 % solids content, solvent-free adhesive. It is appreciated for its high green strength, good weather resistance, wide range of adhesion to various materials, high production speed capabilities, and others. Within the family of HMPUR, there are amorphous and crystalline one-component polyurethane adhesives.
o Amorphous polyurethane becomes more viscous and tacky when cooling and has excellent adhesion on difficult substrates like fluorocarbon-treated textiles or membranes but remains soft. This makes it ideal for textile lamination, especially for low-temperature applications for thin breathable membranes.
o Crystalline polyurethane adhesives can be used in the automotive industry for rigid bonding surfaces (automotive plastic, carpet, etc.). These adhesives are heat, cold, and moisture resistant. Crystalline polyurethane becomes solid while keeping a good stiffness when the temperature goes below its melting point.
Polyurethane sealant is famous for its good toughness and simple preparation. It can also adapt to the expansion and deformation of joints or cracks caused by temperature changes. However, Silyl Modified Polymers adhesives are increasingly replacing polyurethane sealants because they require a low primer, have less impact on health and the environment, and have better UV resistance. Polyurethane bonding and sealing are used in transportation (bus, train, marine) building, construction, and others.
Benefits of one-component polyurethane adhesives and sealants
Among the many advantages brought by one-component polyurethane adhesives, we can mention the following features:
- Improved mechanical performance with high bonding strength
- Enhanced versatility due to multi-substrate adhesion, including to polar substrates
- Increased design possibilities with compatibility to post-bonding treatments like painting, and bonding dissimilar substrates
- Extended durability due to good chemical and thermal resistance.
- Heightened ease of application with no mixing requirement
- Reduced environmental impact due to low monomer emissions
Contact us if you want to know more about our sustainable one-component polyurethane innovations, if you have technical questions or if you need advice.
Applications of single component polyurethanes adhesives and sealants
One-component polyurethane is dedicated to paper (and board) applications.
These adhesives react with the moisture of the substrates. Only paper contains enough moisture to make the adhesive react (compared to plastic or metallic substrates).
The main application in flexible packaging is yogurt pot lids (paper to plastic film lamination).
In building materials, liquid one-component polyurethane adhesive can be used to bond panels with plaster, polystyrene, or other materials. PU sealants can be used for window or door sealing, for example. Amorphous polyurethane hot melt adhesive can be used to make roofing membrane insulation lamination.
Hot Melt Polyurethane is appreciated in transportation for its very high green strength, short setting time, and good adhesion to a variety of rigid substrates. One-component moisture-curing PU is used for bonding door trim, instrumental panels, joining steel frames to glass windshields, steel to side glass windows, etc.
Cork Bottle Caps
You can also use one-component polyurethane for cork agglomeration. In this case, the adhesive is solvent and filler-free. It is mixed with cork and inserted into an oven to start the crosslink.
One-component Polyurethane adhesives can be used for textile lamination to manufacture two-layer textiles and are appreciated for their excellent resilience, elasticity, heat cold, and water resistance. Hot melt polyurethane adhesive has good adhesion to textile, polyester, cotton, blended fabric, TPU, PVC, PC / ABS.