Repurposing Waste LDPE as a Sustainable Coating for CFRP With Emphasis on UV Durability and Performance

This study investigates the potential of utilizing waste low‐density polyethylene (LDPE) as a protective coating against UV exposure for carbon fiber reinforced polymer (CFRP). The LDPE and epoxy‐coated CFRP samples were subjected to accelerated UV‐aging of up to 2000 h. This work simulates the open environment conditions where degradation products remain trapped in the polymer matrix and accelerate photo‐oxidation, thereby revealing the true extent of UV‐induced damage. Thermogravimetric analysis (TGA) analyses revealed progressive thermal degradation, with epoxy showing a delayed onset of decomposition and LDPE exhibiting decomposition onset after 500 h of UV‐aging. LDPE‐coated CFRP composites exhibited a steady decline in mechanical properties but retained more than 50% of their initial tensile strength up to 1000 h of UV‐aging. Morphological analysis of aged samples revealed increasing surface fragmentation and embrittlement in LDPE‐coated samples after 1000 h of UV‐aging. The carbonyl index calculated from Fourier Transform Infrared (FTIR) spectra reached ~0.6 after 1000 h of UV‐aging, suggesting the onset of extensive photo‐oxidative degradation. The results highlight that waste LDPE can serve as a low‐cost, moderate‐performance alternative coating for CFRP in non‐critical construction applications, offering a sustainable route for plastic waste reuse.