Sustainable approach for recycling metal–polymer composites using foaming technology

• Bubble nucleation-induced interfacial delamination was studied for Aluminum and 40% glass fiber-reinforced polycarbonate (PCGF40). • A physical foaming process using CO 2 gas and subsequent heating was employed to generate gas bubbles at the interface. • X-ray CT was used to visualize gas bubbles, while tensile lap-shear tests measured the maximum load during Al–PCGF40 separation. • An optimal balance of minimal separation load and high-purity metal and polymer recovery was achieved by tuning the saturation conditions. The separation of metal–polymer composites poses significant challenges in industries such as automotive, aerospace, and electronics. To address this, we propose a separation method utilizing CO 2 -induced bubble nucleation at the metal–polymer interface for effective delamination. While this method has demonstrated success under specific conditions, further optimization of saturation parameters is required for complete delamination. A lap-shear specimen comprising an aluminum (Al) alloy bonded to 40 % glass fiber-reinforced polycarbonate (PCGF40) was impregnated with CO 2 gas at saturation pressures ranging from 5 to 15 MPa at a constant temperature of 80 °C for 24 h. Subsequently, specimens were heated at 130 °C for 3 min to induce bubble nucleation at the interface. Differential scanning calorimetry (DSC) analysis indicated an increase in crystallinity with rising saturation pressures. The maximum separation load between the metal and polymer was determined using tensile lap-shear strength tests according to ISO 19095-3 fixture standards. Results showed that heating at 130 °C significantly reduced the separation load as the saturation pressure increased up to 13 MPa due to bubble nucleation and cracking, as confirmed by X-ray computed tomography (X-ray CT) imaging. However, at pressures of 14 and 15 MPa, crystallinity reached a constant level, and the increased lamellar thickness resulted in higher separation loads. Additionally, lower saturation temperatures (50 °C and 60 °C) led to reduced crystallinity rates. At 12.5 MPa and 60 °C, followed by heating at 130 °C, minimal residual resin content and the lowest separation load were achieved. These findings establish optimal saturation conditions, promoting efficient composite recycling and high-purity material recovery.