Waterborne polyurethane composite films using castor oil‐based polyol and graphene nanoplatelets: synthesis, characterization and antibacterial applications

Abstract Recent advancements in sustainable synthetic methodologies have prioritized using non‐edible vegetable oils as polyols in polyurethane (PU) production, offering an eco‐friendly alternative to traditional processes. Replacing petroleum‐derived polymers with bio‐based counterparts demonstrates significant potential in lowering environmental impact and conserving non‐renewable resources. In this context, we synthesized waterborne PU polymers (WPUs) using castor oil (CO) as a polyol along with isophorone diisocyanate, dimethylolpropionic acid as an internal emulsifier and triethylamine as a neutralizing agent. Various CO‐based WPU composite (GCWPU) films were also prepared through the incorporation of graphene nanoplatelets (GNP) (1, 5 and 10 mg) using a cationic surfactant, cetyltrimethylammonium bromide, in the WPU dispersions via ultrasonic‐assisted solution mixing. Further, the physicochemical, structural, chemical, thermal and mechanical properties of the synthesized GCWPU films were investigated. All the synthesized PU composite films were characterized using various techniques. The GCWPU films exhibited a significant improvement in terms of their thermal, mechanical and antibacterial properties. The antibacterial properties of synthesized GCWPU films were tested against S. aureus and E. coli using the colony‐counting method. As per our findings, the GCWPU films showed antibacterial activity against S. aureus and E. coli with an increase in GNP content. In conclusion, it was found that the GCWPU composite films developed in this work could be effective antibacterial material for food and packaging applications. © 2025 Society of Chemical Industry.