“…S1, the IR spectrum of MW 100 exhibits extremely low absorption baseline characteristic of high carbon content materials [27]. The drastic decrease of the absorption bands in the region 500e700 cm À1 , which are characteristic of the intercalated species in expandable graphite (e.g., H 2 SO 4 , SO 3 and SO 2 ) [25,28,29], is a further evidence of their release upon the expansion process. Moreover, the elemental analysis (EA) performed at each step of the process (see Table 1) confirms the elimination of the intercalated species and the achievement of high carbon content (i.e.…”