Facile fabrication of polyimide foam sheets with millimeter thickness: Processing, morphology, and properties

Abstract

ABSTRACTA series of polyimide foam sheets (PIFSs) with thickness of 0.5 mm using 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA), 3,4′‐oxydianiline (3,4′‐ODA), and polyaryl polymethylene isocyanate (PAPI) as main materials were first fabricated by liquid foaming and compression molding technology. The effects of different PAPI contents and 3,4′‐ODA contents on the structures and properties of PIFSs were investigated. The results indicated that PIFSs exhibited a structure that front surface displayed closed cells made of damaged cell walls and membranes, while internal cells were open, and elliptic vacancies were flatted in the thickness direction from the cross section. The average cellular diameter increased with increasing PAPI loading. In addition, the introduction of 3,4′‐ODA increased the average cell size of PIFSs. Further, PIFSs had density of 0.087–0.239 g/cm3, elongation at break of 3.75–8.01% and tensile toughness of 3.46 × 10−2−13.87 × 10−2 J/cm3. Notably, they exhibited higher tensile strength of 1.89–5.42 MPa and lower thermal conductivity of 14.727–19.25 mW/m •K at 24°C, compared to the polyimide foams reported earlier. The sound absorption coefficients (α) of samples with different PAPI contents increased and then decreased with increasing PAPI content. At low frequencies, a certain content of 3,4′‐ ODA allowed an improvement of the acoustical behavior of PIFSs, and the α increased and then decreased with increasing density. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39881.