Single component
Single component material: it is composed of a single liquid material, which is applied by brushing, scraping or spraying, and then evaporated or cured by reaction to form a certain thickness on the base surface, which is called single component material;
Single component · insufficient
The isocyanate group in the material system reacts with the moisture in the air to form the primary amine group and carbon dioxide, and the primary amine group can react with the remaining isocyanate group in the system rapidly to crosslink and solidify. Because the surface material of the coating contacts with the moisture in the air, the surface layer begins to solidify. When the surface layer solidifies, it is difficult for the carbon dioxide produced in the inner layer to escape, leading to blistering.
Two component
Two component material: the two liquid materials of group A and group B are mixed according to a certain proportion, which are applied by brushing, scraping or spraying, and then cured by reaction to form a certain thickness of material on the base surface, which is called two-component material;
(reactive)
Bicomponent · properties
(curing mechanism)
The desiccant added in the two-component material system has the characteristics of targeting, which can quickly catalyze the reaction between the isocyanate group of group A and the hydroxyl group and chain extender of group B, prevent the reaction between the isocyanate group of group A and moisture to produce CO2, and effectively avoid the disadvantages such as bulge. When the isocyanate of group A is mixed with hydroxyl group of group B and chain extender for one minute, the surface layer and inner layer can start to catalyze one reaction and solidify one reaction almost at the same time. Therefore, the two-component material can be thick coated at one time without bulging.
Two component · difficulty
(need precise ratio)
Group A and group B of two-component materials must be mixed evenly according to the proportion before they can be filled and solidified into glue, because group B materials cannot be solidified alone, and they must be crosslinked with isocyanate of group a before they can be cured. Once the active groups of group B are not completely reacted, the whole material will be sticky and non gelled, which is called raw meal. The ratio of group A and group B is generally derived from the molar ratio of active functional groups. Generally, the ratio of NCO group of group A to hydroxyl group of group B and amino group of chain extender is between 1.1 and 1.3:1. Too high is easy to bulge, too low material strength is very poor.
