Design of curcumin-activated antioxidant-barrier bilayer polymer systems incorporating post-industrial recycled polypropylene

• Bilayer design enables at least 20% recycled PP integration. • 37% stiffness and 34% strength increase via structural design. • Non-release active material with 1% curcumin achieves 50% hydroxyl radical scavenging. • Coupled barrier-antioxidant functionality in scalable bilayers. The development of multifunctional polymer architectures incorporating recycled flexible polymers while mitigating oxidation-driven product deterioration through a non-release mechanism is a key challenge in sustainable materials design. Flexible polypropylene is rarely recycled due to a lack of appropriate recycling technologies. In this work, a material design strategy is proposed for developing non-release and antioxidant-barrier bilayer polymer systems incorporating post-industrial recycled polypropylene (rPP) behind a curcumin-activated copolymer layer capable of scavenging hydroxyl radicals for high-value applications. The structure-properties relationship of multifunctional active polymeric systems was systematically evaluated. Their scavenging capacity, along with their structural, thermal, mechanical, overall migration, heat sealability, and permeability properties, were evaluated under the effects of rPP incorporation, active-layer inclusion, and curcumin content. rPP exhibited poor barrier/mechanical properties and high overall migration, but the designed multifunctional bilayer systems containing 20% rPP met the migration limit in a fatty simulant. The 1% curcumin-activated bilayers had the highest antioxidant activity, with 50% greater hydroxyl radical-scavenging than the non-active systems. The results demonstrated that non-release curcumin-activated bilayer materials with moderate enhancement of mechanical resistance, combining barrier and radical-scavenging functionalities within a scalable architecture, can incorporate rPP, and potentially be used in multilayers to preserve products, such as dry fatty foods.