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                                                                   What is the curing mechanism of PUR hot melt adhesive?

What is the curing mechanism of PUR hot melt adhesive? There are two types of moisture-curing polyurethane hot-melt adhesives and closed-type polyurethane hot-melt adhesives. These two types of glue can achieve product bonding, fixing, waterproofing, and sealing. The hot-melt glue dispenser first heats and melts to form a fluid, then applies glue and then fits another piece. The PUR hot-melt glue is cooled and solidified to achieve product bonding. So what is the curing mechanism of the PUR hot-melt glue?

Moisture-curing polyurethane hot-melt adhesive is made of isocyanate-terminated-NCO-based prepolymer as the base material, with fillers and additives such as thermoplastic resins and tackifying resins that do not react with isocyanate groups. The curing of moisture-curing PUR hot-melt adhesive after sizing is in the cooling process. PUR hot-melt adhesive absorbs moisture in the air, trace moisture in the adhered substrate and other compounds containing active hydrogen, and NCO The group undergoes a chemical reaction to form a polymer with a cross-linked structure and high cohesion, which further enhances the adhesive force and realizes the strong bonding of the product.

The closed polyurethane hot melt adhesive is to protect the end-NCO group in the polyurethane prepolymer with a blocking agent (oxime, phenol, alcohol sodium bisulfite, etc.) under certain conditions to form a closed prepolymer. body. Such PUR hot melt glue is not reactive at room temperature. When heated to a certain temperature, the sealing agent decomposes, releasing the active -NCO group, and then reacts with compounds containing active hydrogen such as moisture in the air. Forms a high-viscosity polymer that achieves a strong bond to the product.