Surface modification of polypropylene composites for enhanced adhesion with polyurethane in-mold coatings

Polypropylene (PP) composites, widely used in industrial applications, face significant challenges in achieving strong adhesion with polyurethane (PU) in-mold coatings due to their non-polar nature. This study investigates surface modification of PP composites to improve adhesion with PU in-mold coatings. The surface treatment agent is used to enhance both mechanical interlocking and chemical bonding between PP and PU coating. The agent swells the PP surface, creating protrusions that improve mechanical interlocking, while introducing chlorine and oxygen-containing groups (-COOH) to form bonds with PU. The modified PP composites show significantly improved interfacial adhesion to PU coatings compared to traditional flame treatment. The agent-treated PP/PU interface also demonstrates excellent high-temperature and chemical resistance, with well orange peel, meeting industrial coating requirements. This method enhances both the durability and appearance of the components, overcoming common issues like talc powder or whiskers defects seen with flame treatment. The findings provide a promising, environmentally-friendly solution for manufacturing industrial parts with improved adhesion and aesthetics.