What Are One-Component Polyurethane Adhesives: Everything You Need To Know

Introduction

One-component polyurethane adhesives are adhesives that cure by reacting with moisture in the air to form a strong, long-lasting bond. Unlike two-component systems that need to be mixed before application, one-component adhesives are more convenient to use and reduce the possibility of mixing errors.
This article will provide a comprehensive overview of one-component polyurethane adhesives. By understanding their chemical composition, physical properties, and different types, you can understand the benefits of these adhesives. And it will compare with two-component systems to provide insight into why one-component polyurethane adhesives may be a better choice for specific needs.

What Are One-component Polyurethane Adhesives

One-component polyurethane adhesives are mainly formulated with isocyanate groups and polyols. When the adhesive is exposed to air, it can react with airborne water to form a strong sealant. This process is often referred to as moisture curing. Whilst it is convenient to use a single component adhesive, it is slow to cure and produces air bubbles during the curing process, which results in a reduction in bond strength.
As far as physical properties are concerned, these adhesives are available in a wide range of viscosities from liquid to paste and are suitable for a variety of applications. Highly elastic, they can absorb shock and vibration without breaking the bond. Ready to use without mixing and with a longer shelf life than two-component polyurethane adhesives, the unique chemistry and curing process make one-component polyurethane adhesives the preferred choice for more industrial applications.

Types Of One-component Polyurethane Adhesives

One-component polyurethane adhesives can be divided into two categories, reactive and non-reactive, according to the type of reaction.

Reactive One-component Polyurethane Adhesives

Reactive one-component polyurethane adhesives cure by a chemical reaction with moisture. The cured adhesive is resistant to moisture, heat and chemicals.

Reactive one-component polyurethane adhesives are classified according to their specific chemical formulation and curing mechanism:

——Moisture Cured Polyurethane Adhesives
Cure on exposure to atmospheric moisture, which triggers a chemical reaction that changes the adhesive from a liquid or paste to a solid. High bonding strength, good flexibility, good water resistance and heat resistance.

• Commonly used in construction sealing and bonding, automotive assembly and woodworking.

——Heat Cured Polyurethane Adhesives
Heat-cured polyurethane adhesives require heat to initiate the curing process. When heated, they undergo a chemical reaction that cures the adhesive. Provides a strong, durable bond and can withstand high temperatures and stress.

• Typically used in industrial environments where heat can be controlled, such as automotive and aerospace manufacturing.

——UV Cured Polyurethane Adhesives
UV cured polyurethane adhesives cure under ultraviolet (UV) light. The UV light triggers a polymerisation reaction that hardens the adhesive. It has a fast cure time, precise application and low heat generation.

• It is suitable for electronics, medical devices and optical components where precise control of the curing process is required.

Non-reactive One-component Polyurethane Adhesives

Non-reactive one-component polyurethane adhesives, on the other hand, do not rely on a chemical reaction with moisture to cure. Instead, they cure by physical processes such as drying or cooling. This is the case, for example, in the packaging and textile industries, as they can be bonded quickly without the need for moisture. Non-reactive adhesives have faster processing times and are less dependent on ambient humidity.

Non-reactive one-component polyurethane adhesives can be further divided into:

——Solvent-based Polyurethane Adhesives
These adhesives contain solvents that evaporate after use, leaving a solid layer of adhesive. It has a shorter drying time, strong initial tack and is easier to use.

• It is mainly used for flexible packaging, laminated textiles and assembled consumer goods.

—— Hot Melt Polyurethane Adhesives
These adhesives are applied in a molten state and cured on cooling. No chemical curing process is involved. It is fast curing and easy to use and has a strong bond to a wide range of substrates.

• Commonly used in packaging, bookbinding and furniture assembly.

—— Pressure-sensitive polyurethane adhesives
These adhesives require no curing or drying. Once pressure is applied, the adhesive forms instantly, is easy to apply, and in some cases removes without leaving a residue.

• Typical applications are tapes, labels and surface protection films.

Benefits Of One-component Polyurethane Adhesives

1. One-component polyurethane adhesives have excellent mechanical properties and provide a strong, durable bond that can withstand high stresses and strains.

2. One-component polyurethane adhesives enhance versatility by bonding a wide range of materials such as metals, plastics, wood and ceramics.

3. One-component polyurethane adhesives have a strong bonding capability that allows for innovative and complex designs that cannot be achieved with other adhesives, increasing design possibilities.

4. One-component polyurethane adhesives offer longer durability, making them a durable solution for bonding needs.

5. Ease of application eliminates the need for mixing or preparation.

6. One-component polyurethane adhesives are formulated to emit low levels of volatile organic compounds (VOCs), reducing the environmental impact.

Applications Of One-Component Polyurethane Adhesives

Flexible Packaging
One-component polyurethane adhesives are widely used in the flexible packaging industry. Their strong bonding capabilities ensure that different layers of packaging materials, such as plastics, foils, and papers, adhere securely. These adhesives provide excellent resistance to moisture, chemicals, and temperature variations, ensuring that the packaging remains intact during storage and transportation.

Building Materials
In the construction industry, one-component polyurethane adhesives are used to fix insulation panels, seal joints and bond flooring materials. These adhesives provide a strong and durable bond that can withstand the pressure and movement that buildings are subjected to over time. They are also resistant to environmental factors such as humidity, heat and UV rays that are common in the built environment.

Transportation
One-component polyurethane adhesives are used in the assembly and repair of vehicles such as cars, trucks, buses and even aircraft. Capable of bonding a wide range of materials used in vehicle manufacturing, such as metals, plastics and composites. With the ability to absorb vibration and shock, the adhesives are also resistant to fuels, oils and other automotive fluids, helping to maintain the durability and performance of bonded parts under harsh operating conditions.

Cork Bottle Caps
In the beverage industry, one-component polyurethane adhesives bond to cork bottle caps, ensuring that the stopper is firmly bonded to the cap, preventing leakage and maintaining the quality of the beverage. The adhesive’s strong bonding properties, moisture and chemical resistance, and the fact that the adhesive is non-toxic, make it safe for use in food and beverage packaging, ensuring that it does not affect the flavour or safety of the product.

Textile Lamination
Textile lamination is another area where one-component polyurethane adhesives are widely used. These adhesives bond different layers of fabrics and textiles to create laminates for apparel, upholstery and technical textiles. One-component polyurethane adhesives provide strong, flexible bonds that stand up to repeated use and washing. They also improve the durability and performance of laminated textiles and have a fast cure time, making the lamination process efficient and reliable.

Comparison With One And Two-Component Polyurethane Adhesives

When comparing one-component polyurethane adhesives to two-component polyurethane adhesives, it is clear that one-component adhesives can be used without mixing, simplifying the application process and reducing the potential for error. In contrast, two-component polyurethane adhesives require precise mixing of resins and hardeners, which is not only time-consuming but also prone to errors if not done properly. In addition, cure time is another critical factor. One-component adhesives are typically cured by exposure to moisture, heat or UV light, with cure times ranging from minutes to hours, depending on the specific formulation. Two-component polyurethane adhesives typically cure much faster after mixing, so they need to be applied quickly after opening.

In terms of performance, both types provide a strong and durable bond, but there are subtle differences. Two-component polyurethane adhesives typically have higher strength and chemical resistance, making them ideal for high-stress applications. One-component polyurethane adhesives are slightly less strong, but still offer excellent flexibility and durability, making them suitable for a variety of uses.

Conclusion

One-component polyurethane adhesives are versatile adhesives that are widely used in a variety of industries due to their ease of use. Unlike two-component adhesives, which require mixing prior to use, one-component polyurethane adhesives are ready-to-use and do not require precise mixing ratios, which reduces waste. They cure when exposed to atmospheric moisture, making them ideal for bonding a wide range of materials such as wood, plastics, metals and composites. Their ability to form long-lasting bonds in both indoor and outdoor environments also makes them suitable for use in construction, automotive assembly, furniture production and other manufacturing industries that require strong, flexible bonds.

As technology advances and formulations are updated, modern one-component polyurethane adhesives improve environmental sustainability, reduce emissions and enhance performance characteristics to meet specific industry needs. Understanding their curing mechanisms, application techniques and compatibility with different substrates is essential to maximise their efficiency and ensure optimum bonding performance.

Related referenceIntroduction to one-component polyurethane adhesives and sealants
Product description of one-component polyurethane adhesives
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