A latent curing agent is primarily meant for usage in different types of coatings, adhesives, and sealant applications. The reason why they are immensely used is they tend to be very powerful in situations that feature high build properties. For example, waterproof coatings and construction sealants. Oxazolidines is majorly used as a latent curing agent and can be used in both one and two component PU systems.
In case of one component PU system, these latent curing agents are generally used with aliphatic prepolymers. They promote fast through-cure with leaving no space for carbon dioxide gas evolution. On being come into contact with moisture, these agents get hydrolysed, resulting into reactive amine and hydroxyl functional groups.
The unrivaled properties of this latent curing agent is majorly distinguished by the curing mechanism, which is entirely different from the traditional “moisture cure” reaction. During this process, moisture reacts directly with the terminal isocyanate of the prepolymer emissioning gaseous carbon dioxide. It results into blisters and bubbles in the coating film.
Moisture heavily reacts with the oxazolidines rather than with the prepolymer’s terminal isocyanate groups. The fundamental process of hydrolysis and ring opening of the oxazolidine generates amine and hydroxyl groups. These amine and hydroxyl groups then subsequently react with the isocyanate of the prepolymer without the evolution of carbon dioxide gas.
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