Preparation of Open-Cell Rigid Polyimide Foam via Nonaqueous High Internal Phase Emulsion-Templating Technique

Rigid PI foams with highly interconnected open-cell structures are successfully prepared by an oil-in-oil emulsion-templating strategy. The physical properties, such as microstructure, density, and porosity, of the foams are tailored by simply tuning either the internal phase volume fraction or surfactant content of the emulsion-template. The density of PI foam is varied between 0.056 and 0.138 g·cm–3 with an open rate up to 100%. The PI foam has a high compressive modulus, ranging from 2.6 to 17.0 MPa. The PI foam exhibits excellent thermal insulation over a broad temperature range with thermal conductivity as low as 38.9 mW·(m·K)−1 at 30 °C, and 44.9 mW·(m·K)−1 at 200 °C. The PI foam is high heat-resistant with its T5 of 507 °C in air and 528 °C in N2. The sound absorption test shows that the PI foam has a high noise reduction coefficient (NRC, 0.385–0.386), much higher than the 0.2 required as a sound-absorbing material, reflecting its promising practical application in acoustic material. Generally, the emulsion-templating technique is first proved to be an effective way to prepare open-cell rigid PI foams. The PI foam shows a high comprehensive performance, suggesting its great potential application in a lightweight structural material for sound absorption and heat insulation in a harsh environment.