Thermal analysis of organically modified Ca2+-montmorillonite using DSC and TSC techniques

Thermal analysis on organically modified Ca2+-montmorillonite (OMON) and its source materials—octadecylamine (ODA) and Ca2+-montmorillonite (Ca2+-Mon)—was studied using thermally stimulated current (TSC) technique. The appearance of ρ MON peak with the T max = 75 °C shows the ability of the developed TSC system to demonstrate the relaxation effects of dehydration in Ca2+-Mon. It appeared within the temperature range of DSC endothermic peak (30–100 °C) where the T mMON = 58 °C. Segmental motions of ODA chains and structural disruptions in the modifier agent compound produced TSC α ODA, ρ ODA and ρ 1ODA peaks that are comparable to thermal transition and endothermic peaks in DSC profile (T gODA, T m1ODA and T m2ODA). The effect of localized motion in ODA chains as revealed by the TSC βOMON peak (T max = −23 °C), however, is absent in the DSC profile of OMON. It shows TSC technique has high sensitivity in detecting various relaxation behaviors at molecular level. More evidences are demonstrated by the ρ OMON (T max = 86 °C) and ρ 1OMON (T max = 105 °C) peak originated from the ODA chains structures. These peaks also confirm the intercalation of the modifier cations inside the Ca2+-Mon gallery.