Seal coats are a mixture of liquids and small particle solids (like grains of sand, dissolved asphalt, polymer additives, and other mineral fillers) and are applied by spray or squeegee.
Once it is applied to the surface of an asphalt pavement, oils in the sealcoat flow down and help restore asphalt oils that have dried up over time.
At the same time, the tiny asphalt, sand, and mineral particles fill in small cracks and gaps. With the oils restored, and the cracks and gaps filled in, the asphalt pavement surface now becomes even and looks like a new pavement.
Acid rain, U.V.rays, and other chemicals when introduced into asphalt degrades the materials that bind the asphalt, resulting in deterioration.