Phase behavior, conformations, thermodynamic properties, and molecular motion of multicomponent paraffin waxes: A Raman spectroscopy study

Variable-temperature (72-20 degrees C) studies of Raman spectra (3100-800 cm(-1)) and thermal analysis of multicomponent paraffin wax have been carried out. The disorder-order transition under liquid-solid transition was observed and their temperature ranges were obtained through the S-lateral order parameter as a function of temperature. From 56 to 43 degrees C, the paraffin undergoes a conformational state transition of non-extended chain state (NECS) to extended chain state (ECS). The enthalpy and entropy change for the transition obtained by van't Hoff analysis were 214.286 +/- 21 kJ/ mol and 0.661 +/- 0.066 kJ/mol/K, respectively. The enthalpy determined by differential scanning calorimetry (DSC) was 52.165 +/- 5.2 kJ/mol, which is smaller than the van't Hoff enthalpy due to larger effective non-extended chain state. The variation of Raman spectra with decreasing temperature presents the structure evolution and molecular motion during the crystallization of paraffin wax. (c) 2005 Elsevier B.V. All rights reserved.Chemistry, AnalyticalChemistry, PhysicalSpectroscopySCI(E)EI0ARTICLE2219-2244