Polyurethane glue, also called PU glue, is a type of adhesive that is versatile and offers strong bonding properties. The production process of polyurethane glue involves the reaction between polyols and isocyanates.
1. Raw Materials Preparation
Polyols: Polyols are compounds with multiple hydroxyl groups. Common examples include polyether polyols and polyester polyols.
Isocyanates: Isocyanates are compounds with one or more isocyanate functional groups. Common examples inculde toluene diisocyanate and methylene diphenyl diisocyanate.
Additives: Various additives such as catalysts, surfactants, and stabilizers may be included to enhance specific properties of polyurethane glue.
2. Prepolymer Formation
The polyol and isocyanate react to form a prepolymer. This is typically done by mixing the two components in specific ratios. The reaction is exothermic and produces a semi-liquid or viscous prepolymer.
3. Chain Extension
Prepolymer is then mixed with additional polyol to extend the polymer chains. This step is known as chain extension and is often catalyzed by specific catalysts.
4. Additives and Modifiers
Various additives, such as catalysts, surfactant, and stabilizers, are incorporated to fine-tune the properties of polyurethane glue. These additives may influence curing time, viscosity, flexibility and other characteristics.
5. Solvent Removal
In some cases, solvents may be used to adjust the viscosity of polyurethane glue. If solvents are employed, they need to be removed from the final product through processes like evaporation or vacuum stripping.
6. QC and Packaging
Polyurethane glue undergoes rigorous quality control checks to ensure it meets specificed standards. This includes testing for viscosity, adhesion strength, curing time and other relevant properties. Then polyurethane glue is packaged into containers suitable for distribution and use.