Research on rapid preparation and performance of polymethacrylimide foams

A high‐performance polymethacrylimide (PMI) foam was prepared from the reactive monomers of acrylonitrile (AN) and methacrylic acid (MAA) via ultrasonic combined with thermal initiation radical bulk copolymerization and free heat foaming. The reaction progress of cyano and carboxyl groups were tracked by Fourier transform infrared (FTIR) spectroscopy and X‐ray Photoelectron Spectroscopy, and the results indicated that the imide groups were formed and cyano groups gradually decreased during foaming and thermal treatment. The cell morphologies of the PMI foams were characterized by scanning electron microscopy, and the results showed the PMI foams were consisted of the honeycomb structure. The thermostability of the prepared PMI foam was evaluated by thermogravimetric analysis (TGA), and the results revealed that the PMI foam possessed excellent thermal stability and char forming capability. The mechanical properties of PMI foams were measured by tensile, flexural, and compressive strength, and the responding values for the PMI foams with the density of 32.30 kg m^?3 were 0.71, 0.86, and 1.49 MPa, respectively, which demonstrated the obtained PMI foams presented superior mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44959.