The crystallisation properties and penetration-temperature-behaviour of several micro-crystalline waxes (including petrolatum) were compared with macro-crystalline and intermediate paraffin waxes. Micro-crystalline waxes mainly show two DSC-peaks analogous to macro crystalline paraffin waxes. One peak is located in the range of the melting/congealing points and a second peak is located at lower temperatures. Only one crystallisation peak is recognizable in intermediate paraffin waxes. This products lie, concerning to the mean C-number, between micro and macro paraffin waxes. The penetration-temperature behaviour of the micro waxes is, nevertheless, sooner comparable with that of the intermediate paraffin waxes. The second peak of micro waxes is frequently interpreted as solid-solid transition below the congealing point. Nevertheless, it was shown that, in contrast to macro-crystalline waxes, the hardness of the micro waxes does not markedly decrease in the temperature range of this peak. During the solvent de-oiling of petrolatum to micro wax it becomes clear that the additional peak is caused by low melting, good soluble iso and cyclo alkanes. Thus well de-oiled, hard micro waxes only show small or no additional crystallisation peaks. The thermal behaviour of micro waxes is, therefore, mainly determined by the degree of de-oiling and not by changes of the crystal structure in the solid state.

This article, written by Dr. Gernot Meyer, Manager Emulsions- & Technology-Development, has been published in the recent issue of SOFW journal.

The complete article can be downloaded here.