Macro- vs Microcrystalline Wax: Interplay of Evaporation and Decomposition under Pressure Variation

Thermal behavior of two principally different wax materials (viz., paraffin Russian grade P-2 and microcrystalline Sasol 0907) has been investigated using thermogravimetry and differential scanning calorimetry at atmospheric and elevated pressure. The variation of experimental conditions during thermoanalytical studies highly affects the kinetics and highlights the interplay between evaporation and decomposition processes. It is revealed that vaporization kinetics is defined by the amount of the linear and branched hydrocarbons and under low confinement takes place with an enthalpy of δHev(298 K) = 79 ± 7 kJ mol-1. In turn, thermal decomposition with the activation energy equal to 236 ± 4 kJ mol-1 is shown to follow the random-scission reaction mechanism. The simultaneous consideration of obtained kinetic data reveals the general kinetic compensation trend and elucidates the unified underlying nature of the wax thermal response.