The epoxy foam material filled with an absorbing agent effectively absorbs electromagnetic waves. In this study, epoxy resin was used as the matrix, and acetylene carbon black was used as the magnetic absorbing agent to prepare an absorbing foam material (epoxy/CB). The microstructure of acetylene carbon black (CB) and its distribution in epoxy resin, as well as the effects of pre-polymerization time and CB content on the foam structure, were systematically characterized. Additionally, two dispersion methods, the hot-melt in situ stirring dispersion method and the three-roll milling dispersion method, were studied for their effects on the foaming process and absorbing properties of epoxy/CB. The results showed that with the prolongation of pre-polymerization time, the pore size decreased from 1.02 mm to 0.4 mm, leading to a more uniform pore distribution. Compared to the hot-melt in situ stirring dispersion method, the three-roll milling dispersion method effectively improved the dispersion of CB in epoxy resin, reducing the aggregate size from 300-400 nm to 70-80 nm. The pore diameter also decreased from 0.453 mm to 0.311 mm, improving the uniformity of particle size distribution. However, the absorbing material prepared with the three-roll milling dispersion method exhibited unsatisfactory absorption performance, with values close to 0 dB at mid-low frequencies and around -1 dB at high frequencies. In contrast, the absorbing material prepared with the hot-melt in situ stirring dispersion method showed better absorption performance at high frequencies, reaching around -9 dB.
Keywords: acetylene carbon black; epoxy; foam; wave absorption.