Why Do Road Markings Turn Yellow? The Role of UV & Resin Weathering
Road marking yellowing is primarily caused by UV degradation and resin weathering, compromising visibility and safety. Here’s how they interact:
1. UV Damage
Sunlight’s ultraviolet (UV) rays break down chemical bonds in marking materials. For thermoplastic markings, UV exposure oxidizes resins (e.g., C5 petroleum resin), forming yellow chromophores. White markings with low titanium dioxide (TiO₂) content lose whiteness faster, as TiO₂ shields against UV but degrades over time.
2. Resin Weathering
Thermoplastic resins soften at high temperatures (180–230°C), accelerating oxidation. Overheating during application or prolonged sun exposure speeds up resin degradation, leading to yellowing.
Aromatic TPU resins (used in some coatings) are prone to UV-induced yellowing due to benzene ring structures, unlike more stable aliphatic TPU.
Solutions
Add UV absorbers (e.g., benzotriazole compounds) to resins, blocking 270–380nm UV rays.
Use high-purity resins and sufficient TiO₂ (≥18%) to enhance UV resistance.
Control Application temperature (180–200°C) to prevent thermal degradation.
By addressing UV and resin stability, road markings can retain color and performance longer.
