Institute for Color Science and Technology (ICST) Progress in Color, Colorants and Coatings 2008-2134 20 2 2027 05 01 Enhancing Automotive Bumper Performance through Advanced Materials, Surface Treatments, and Design Optimization 159 170 82197 10.30509/pccc.2026.167726.1475 EN M. Zarei Department of Polymer Engineering, SR.C., Islamic Azad University, P.O. Box: 11365/4435, Tehran, Iran R. Soltani Department of Polymer Engineering, SR.C., Islamic Azad University, P.O. Box: 11365/4435, Tehran, Iran M. Ataeefard Department of Printing Science and Technology, Institute for Color Science and Technology, P.O. Box: 16765-654, Tehran, Iran Journal Article 2025 11 18 A<em>utomotive bumpers play a critical role in vehicle safety by absorbing impact energy. Polypropylene (PP) composites reinforced with ethylene propylene diene monomer (EPDM) rubber are widely used for their flexibility and impact resistance. However, low surface energy limits coating adhesion. In this study, flame treatment was systematically optimized using Box-Behnken design and Response Surface Methodology (RSM) to enhance surface and adhesion performance of PP/EPDM bumpers. Effects of air pressure inside the cabin, flame gas pressure, flame/surface gap, and treatment time were evaluated for surface tension, adhesion strength, moisture and immersion resistance, and high-pressure wash durability. Results indicated that flame/surface gap, treatment time, and flame gas pressure were the most influential factors. The optimal conditions—10 cm gap, 120 s treatment, and 200-220 mbar flame pressure—simultaneously improved physical and chemical responses. These findings provide a practical guideline for industrial applications, improving coating durability and bumper performance through controlled surface modification and design optimization.</em> https://pccc.icrc.ac.ir/article_82197_aadf7a0eb3e69fdf4681f47ba6001d8e.pdf