What type of adhesive is described as one component that remains liquid while exposed to air?

The type of adhesive that is one component and remains liquid while exposed to air is classified as a type known as anaerobics. Anaerobic adhesives are unique because they cure in the absence of air, typically when trapped between closely fitted surfaces. This means that as long as they are exposed to air, they remain in a liquid state, which allows for easy application and positioning before they set.

Anaerobic adhesives are commonly used in applications such as thread locking and bonding mechanical assemblies, where the adhesive is confined in small gaps without exposure to air after the components are brought together. This property is particularly beneficial as it allows for adjustments before the adhesive cures, ensuring that parts can be aligned correctly.

In contrast, cyanoacrylates cure rapidly when exposed to moisture in the air, and epoxies generally require a hardener to start the curing process, becoming solid upon mixing. Modified phenolics also involve a curing process, often requiring heat. Given these characteristics, anaerobics stand out as remaining liquid until they are in an environment that prevents air from interacting with them, which makes them ideal for specific industrial and mechanical applications.