In the manufacturing process of polyurethane adhesives, in addition to the basic raw materials, isocyanates and polyols, the addition of various additives is also very important. Additives can adjust the production process, improve adhesive application processes, enhance product quality, and expand the application range.
Tertiary Amine Catalysts:
Tertiary amine catalysts are particularly effective in promoting the reaction between isocyanates and water. They are generally used for the preparation of polyurethane plastics. They are also used in foaming polyurethane adhesives, low-temperature curing, and moisture-curing polyurethane adhesives.
Chain Extenders and Crosslinkers:
Low molecular weight compounds containing hydroxyl or amine groups are used together with isocyanates as chain extenders and crosslinkers. They affect the ratio of hard and soft segments in polyurethane, directly influencing the properties of polyurethane adhesives. Chain extenders can react with excess isocyanates to form crosslinkers.
Stabilizers:
Polyurethane adhesives are susceptible to aging, mainly due to thermal oxidation, photopolymerization, and hydrolysis. To address this issue, stabilizers such as antioxidants, UV stabilizers, and hydrolysis stabilizers are added to improve the adhesive’s resistance to aging.
Polycarbodiimide is a vital additive in polyurethane adhesives, functioning as both a hydrolysis stabilizer and a crosslinker. It protects against moisture damage and enhances adhesive strength and durability. It forms a stable barrier against hydrolysis and creates a strong, interconnected network within the adhesive, improving mechanical strength and resistance to deformation. Polycarbodiimide is crucial for long-lasting, high-performance polyurethane adhesives used in various industries.
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Fillers and Thixotropic Agents:
Adding suitable fillers to the composition of polyurethane adhesives is mainly to improve their physical properties. Fillers can reinforce the adhesive, enhance its mechanical properties, reduce shrinkage stress and thermal stress, improve thermal stability, and lower the coefficient of thermal expansion. Additionally, fillers can adjust the adhesive’s viscosity and reduce costs. Thixotropic agents are added to control the fluidity of the adhesive during the curing process, especially for materials with strong absorption, such as leather, textiles, or concrete.
