What are Two-Component Reactive Polyurethane Adhesives?

Two component polyurethane adhesives typically consist of hydroxyl components (polyols, polyamines, or mixtures with fillers, etc.) as the A component and NCO containing components (curing agents) as the B component, which can be isocyanate monomers or end NCO polyurethane prepolymers.

Properties of Two-Component Polyurethane Adhesives

1. This is a reactive adhesive that offers excellent elasticity, toughness, heat resistance, low-temperature resistance, and resistance to various media.

2. During preparation, the composition of the raw materials and the molecular weight can be adjusted to ensure that the two components have an appropriate viscosity at room temperature.

3. It typically cures at room temperature, though curing can be accelerated by heating.
4. The ratio of the two components can be adjusted within a certain range, and there is generally a degree of tolerance.

Solvent-Based Two-Component Polyurethane Adhesives

Solvent-based polyurethane adhesives offer excellent initial tack, ease of use, high bond strength, and good flexibility. To further enhance performance, a two-component system can be used to increase bond strength and heat resistance.

General-Purpose Two-Component Polyurethane Adhesives

The general universal two-component polyurethane film is strong, impact resistant, and vibration resistant, with excellent oil and low temperature resistance, and can withstand water, oil, dilute acid, and other media. However, due to the poor long-term hydrolysis resistance of polyester, it is particularly not resistant to alkaline water, especially for adhesives with low B-group distribution ratios. As the cross-linking degree of the adhesive layer is not high, it is not suitable for long-term use in humid environments with high temperatures. Can be applied to bonding metals, nonmetals, and bonding between different materials.

Two-Component Polyurethane Adhesives for Laminated Films

When the main component of solvent-based polyurethane adhesive for composite films is adipic acid based polyester polyol, the strength is high. When polyether based polyurethane polyol is used as the main component, the cost is relatively low, and the adhesive strength is usually not high. However, it can be used to produce packaging composite films for dry food or other items.
The main resin components of steam resistant polyurethane adhesives are mostly aromatic polyester polyols or isocyanate modified aromatic polyester polyols. They not only have high bonding strength to plastic films and aluminum foils but also have high temperature resistance in the adhesive layer and have high bonding strength at high temperatures.

Formulation Example 1

Prepare a light yellow transparent viscous liquid with a solid content of 75%, an NCO mass fraction of 13% to 14%, and a viscosity of ~1500 to ~2500 mPa·s.
The adhesive is recommended to be prepared with a mass ratio of component A to component B of 10/1.

Formulation Example 2

Apply the adhesive at a dry coating rate of 3 g/m² onto polyester film and composite it with nylon film at 50°C and 0.07 MPa. After curing for 3 days, the peel strength of the composite film can reach 8.8N/15mm.

Formulation Example 3

Solvent-Based Two-Component Polyurethane Adhesives for Footwear

Two-component polyurethane adhesives for footwear are characterized by high viscosity and low solids content. They crystallize and cure rapidly after solvent evaporation. Used in cold-bonding processes for footwear materials, they offer a simpler application process compared to single-component solvent-evaporating polyurethane adhesives, while providing superior durability and strength.

Formulation Example 1

Formulation Example 2

Formulation Example 3

The trend in solvent-based polyurethane shoe adhesives is toward water-based two-component polyurethane shoe adhesives. Similar to solvent-based adhesives, these contain crystalline segments in the main chain, which ensures good initial tack after the water evaporates, while the crosslinking agent provides the adhesive layer with excellent water resistance, heat resistance, and durability.