Morphologies and properties of epoxy/multi-walled carbon nanotube nanocomposite foams prepared through the free-foaming and limited-foaming process

Abstract Microcellular epoxy/multi-walled carbon nanotube (EP/MWCNT) composite foams loaded with 2 wt% (mass fraction) of MWCNT were prepared through the free-foaming process (Fre-foam) and limited-foaming process (Lim-foam) using chemical foaming agent (CFA), respectively. The morphologies of EP/MWCNT composite foams with different densities were analyzed by scanning electron microscopy (SEM). It was found that the cell size of both Fre-foam and Lim-foam decreased with increasing the density, while Lim-foam exhibited a smaller cell size and a higher cell density in contrast to those of Fre-foam at similar density. In addition, the dynamic mechanical properties, thermal stability, and electrically and thermal conductive properties of the EP/MWCNT foams in the density range of 0.278 g/cm3–1.108 g/cm3 were investigated and the difference in performances between Fre-foam and Lim-foam was analyzed. Lim-foam had an obviously lower crosslink density than that of Fre-foam due to the effect of compressed gas, which was clearly reflected in the results of gel fraction, glass transition temperature (Tg), molecular weight between crosslinks (Mc), and initial thermal decomposition temperature. Compared with Fre-foam, Lim-foam had superior thermal conductive property and exhibited weak electrically conductive property, indicating the conductive pathway was affected by the foaming process.