What is two-component polyurethane adhesive?
Two component polyurethane adhesive is one of the most important categories of polyurethane adhesives. It is widely used and used in large quantities. Usually consists of a, B and two components, the two components are separately packaged, before use, according to a certain proportion can be prepared. The first component (the main agent) as hydroxyl component, component B (curing agent) for free isocyanate component. Some main agent for polyurethane pre terminated NCO prepolymer, curing agent for low molecular weight polyols or amine group, and component B are mixed according to a certain proportion to produce polyurethane resin.
(1) reactive adhesives, after mixing two components, react with each other to produce a cured product.(2) when preparing, the composition and molecular weight of the two components can be adjusted so that they have proper viscosity at room temperature and can be made into a solid or solvent-free two-component adhesive.(3) it can be cured at room temperature at ordinary times. The curing speed can be reduced by selecting the raw material of the adhesive or adding catalyst. In general, two component polyurethane adhesive has greater initial adhesive force, which is called heating and curing. The final adhesive strength is greater than that of single component adhesive, which can meet the requirements of structural adhesive.
The amount of the two components can be adjusted in a certain range, generally there is a certain tolerance. The two components of the NCO / OH ratio is greater than or equal to L in general, when the curing time, curing reaction of a part of the NCO group to participate in the production of chemical glue, adhesive force, the excess of the NC0 group in the heat curing, can also produce allophanate, shrinkage of two urea, increase the crosslinking degree, high the adhesive cohesive strength and heat resistance. The solvent-free two-component polyurethane adhesive, because each component of initial molecular weight is generally equal to or slightly greater than NCO / OH molar ratio of L to completely cured, especially in adhesive seal, NCO component can be too much too much. The solvent based two-component adhesive, the main agent of high molecular weight and viscosity of good performance, the two components of the amount can be adjusted in a large range, NCO / OH molar ratio of less than 1 or greater than 1 times. When the NCO component (curing agent) over more occasions, a polyisocyanate adhesive layer is formed from poly tough, adhesive suitable for hard materials; NCO components in less occasions, it can be used for bonding adhesive soft, leather, fabric and other soft materials.
