PUR hot melt adhesive, fully known as moisture-curing reactive polyurethane hot melt adhesive, combines the ease of application, rapid curing, and high initial tack of hot melt adhesives with the high bonding strength and excellent heat resistance of reactive adhesives. It is widely used for hot melt bonding in industries such as woodworking, textiles, furniture, home appliances, and packaging. The unique feature of PUR is that it cures through moisture in the air, forming an ultra-strong bond that does not remelt. Polyurethane reactive adhesives (PUR adhesives) are single-component formulations that combine the initial speed of hot melt adhesives with the strength of structural adhesives.
Bonding occurs in two stages: when the adhesive cools and solidifies like a hot melt adhesive, it achieves handling strength, followed by a moisture-curing reaction over the next 24-48 hours to reach final structural strength. These adhesives are resistant to extreme temperatures and flexible, providing vibration and impact resistance.
(1) Hot melt Pur adhesives have the following characteristics:
High bond strength:
They have the high initial bond strength inherent in hot melt adhesives, which can achieve increased productivity. They are also reactive (moisture cure, UV cure), so they have excellent bonding characteristics and durability. They are solid at room temperature, similar to other thermoplastic polymer hot melt adhesives such as ethylene vinyl acetate (EVA), polyalphaolefin (PAO), polyester and polyamide.
Wide Temperature Range:
The adhesive is melted using a specially designed premelter and then applied to the items to be bonded. The melted application temperature ranges from 85°C to 140°C (185°F to 284°F), which is lower than typical thermoplastic hot melt adhesive products. Depending on the specific requirements, the viscosity at application temperature can be designed to range from 2,000 to 60,000 cPs.
Rapid Curing:
The open time of hot melt adhesives ranges from 10 seconds to 10 minutes to meet application requirements.
Excellent Adhesion to Challenging Substrates:
Compared to thermoplastic hot melt adhesives, hot melt PUR adhesives offer unique performance advantages, as they cure to form a heat-resistant thermosetting material. This curing process involves a reaction with moisture in the air or on typical substrates, resulting in a strong, durable, and high-temperature-resistant adhesive.
（2）Some of these advantages include:
Heat Resistance:
The polyurethane structure effectively crosslinks the adhesive, preventing it from remelting or dissolving, which can occur with standard thermoplastic hot melt adhesives. The cured adhesive exhibits excellent high-temperature resistance and environmental durability. Many hot melt PUR adhesives can withstand temperatures ranging from -40°F to +200°F while maintaining strong bonding performance.
Flexibility:
Due to controllable curing times and rapid development of initial strength, these products can be designed to require minimal fixturing. They are typically applied through methods such as roll coating, slot die coating, gravure printing, screen printing, or spraying (swirling or fiberization), followed by brief clamping or pressing to provide a bond with handling strength. Final curing and ultimate strength can be achieved within hours to days, depending on the adhesive, substrate, and factory conditions.
Low VOC Emissions:
Hot melt adhesives can be designed and developed with a wide range of properties to meet specific application requirements. Hot melt adhesives are 100% solids, meaning they contain no volatile organic compounds (VOCs) and do not require drying ovens. This eliminates many environmental concerns associated with solvent-based adhesives, as well as the energy demands of drying water-based and solvent-based products.
(3) Applications:
● Digital
● Textile
● Home appliances
● Home decoration
● Automobile
● Shoemaking
● New energy
Due to its high strength, durability and fast setting time, PUR is very suitable for various applications such as digital, textile, home appliances, home decoration, automobile, shoemaking, new energy and other industries.
