Recently, the two-component polyurethane structure glue due to its high elasticity, good adhesion and the popularity of people, the breadth and depth of the use in the industry is increasing. A two-component pu structural adhesives for its formula of short adjustable performance design and room temperature curing and no solvent pollution, can heat cure, can also be room temperature curing, bonding process is simple, operation performance is good, after curing two-component polyurethane adhesive with high intensity, abrasion resistance, water resistance, oil resistance, solvent resistance, good chemical resistance, ozone resistance, become the focus of current adhesive development research topic.
Structure of a two-component polyurethane adhesive with significant advantage features in the adhesive, two-component polyurethane adhesive has excellent impact resistance, durability, low temperature resistance, fatigue resistance, and good construction performance. Usually consists of two components, a and b, and the two components are separately packaged and prepared in a certain proportion before use. Group a (main agent) is hydroxyl component, and group b (curing agent) is the component of the group that contains the cyanate group. Some main agents are polyurethane prepolymers of end-based NCO, and the curing agent is low molecular weight polyol or polyamine, and group a and group b are mixed to produce polyurethane resin in a certain proportion.
The two-component polyurethane structure adhesive has the following characteristics:
(1) the reactive adhesives, after mixing the two components, are cross-linked to produce the solidified product.
(2) when preparing, the raw material composition and molecular weight of the two components can be adjusted to make it suitable for viscosity at room temperature, and can be made into high solid content or solvent-free two-component adhesive.
(3) it can be cured at room temperature, and the curing speed can be cured by selecting the raw material of the adhesive or adding the catalyst. In general, the two-component polyurethane adhesive has a large initial adhesion, which is called heating curing, and its final adhesion strength is larger than that of single component adhesive, which can meet the requirements of structural adhesive.
(4) the amount of two components can be adjusted in a certain range, and there is a certain tolerance. Two components of NCO/OH mole ratio is greater than or equal to l in the general case, when curing, part of NCO group participate in the curing reaction of adhesive, produce chemical cohesiveness, redundant NC0 groups when heat curing, also can produce urea formate and biuret, increase the degree of crosslinking, improves the cohesive strength and heat resistance of rubber. For solvent-free two-component polyurethane adhesive for initial molecular weight of components is not big, in general the NCO/OH mole ratio equal to or slightly greater than l, beneficial to cure completely, especially in the bonded seals, pay attention to the NCO components can not be too much too much. For solvent-based two-component adhesive, its main agent molecular weight is bigger, can better initial adhesion, the dosage of the two components can be adjusted in a wide range of NCO/OH mole ratio can be several times of less than 1 or greater than 1. When the NCO component (curing agent) is excessive, the polyisocyanate can form a tough adhesive layer, which is suitable for the adhesion of hard materials. In the case of small amount of NCO component, the rubber layer is soft, which can be used for the adhesion of soft materials such as leather and fabric.
With the expanding of synthetic adhesives market demand, the structure of two-component polyurethane adhesive will with its superior performance and environmental safety, become the most varieties, production is the biggest in the polyurethane adhesive products.