Ageing of two petroleum waxes

The effect of ageing at different storage conditions on the microstructure and melting properties of two petroleum waxes, petrolatum and microcrystalline wax, were investigated. The two waxes were stored for a maximum of 50 weeks at different temperatures. Samples were analysed before storage and removed from storage and analysed after different storage times. The effect of storage time and temperature was analysed with confocal laser scanning microscopy and modulated differential scanning calorimetry. Some alteration in the microstructure occurred with longer storage time. The amount of fine and irregular structures seen in the initial petrolatum samples decreased with storage time, and some shadowy, grey areas appeared. The microstructure of the microcrystalline wax stored at 23 °C became more diffuse and more, shadowy, grey areas appeared with time compared to samples stored at 50 °C. These showed coarser crystalline structures and fewer shadowy, grey areas. The results of confocal laser scanning microscopy and modulated differential scanning calorimetry analyses indicated that recrystallization occurred in both waxes during storage. The proposed recrystallization processes taking place during storage were most likely the same in all samples, but the recrystallization occurred to a greater extent in the microcrystalline wax samples stored at 50 °C.