Flexible Polyimide Foam Fabricated by Emulsion-Templating Technique Toward Sound Absorption and Heat Insulation

A flexible polyimide (fPI) foam, created using an emulsion-templating technique, is introduced. By adjusting the internal phase volume fraction (ɸ _in) and surfactant content, the foam's porous structure, density (0.065–0.125 g cm⁻³), and porosity are controlled. The foam exhibits an open-cell structure with a compressive modulus of 0.07–0.28 MPa, tensile modulus of 0.61–3.67 MPa, and elongation at break of 15.6%–19.8%. It also shows exceptional thermal insulation, with a thermal conductivity of 44.2 mW (m K)⁻¹ at 30°C, and maintains a top surface temperature of 79.2°C after 30 min on a 200°C hot plate. The foam demonstrates high heat resistance, with T ₅ decomposition temperatures of 503°C in air and 524°C in N₂. Additionally, it achieves a noise reduction coefficient (NRC) of 0.49–0.54, outperforming commercial foams like polyurethane (NRC = 0.38). This study highlights the emulsion-templating technique as an effective method for producing open-cell fPI foams with superior thermal and acoustic insulation properties, making them ideal for harsh environments.