The Cause of Headlight Deterioration

In the 1990s, car manufacturers transitioned the material headlights where manufactured from glass to poly-carbonate. While lighter and more impact-resistant, poly-carbonate has a critical weakness: it degrades over time. The clearcoat they come with to protect them often fails. This can result in hazy, white or yellowed lenses that dramatically alters the light output . The primary cause of lens deterioration is oxidation. This occurs when chemicals in the plastic react with oxygen in the air, causing it to degrade over time. Ultraviolet B (UVB) light from the sun accelerates this process, breaking down the plastic, making it brittle, and leading to further deterioration. Dirt, road chemicals, and debris can also embed into the poly carbonate lens, while small pitting and scratches from road damage can worsen the clarity, further impairing visibility. Manufactures clear coat typically fail first and once it does the deterioration speeds up.