Thermal analysis of ground dolomite, confirmation of results using an X-ray powder diffraction methodology

Grinding is one of the most widely used unit processes in industry. The application of grinding to the pharmaceutical industry is investigated in detail. The process of grinding finds wide application because it leads to surface activation and particle size reduction. This objective is achieved by the application of energy. A lot of the applied energy is dissipated as heat. A number of pharmaceutical solids are known to be heat labile. Thus, the milling operation is a high-energy process, which could lead to detrimental effects on the structural pattern of the material being ground. This could be either due to the heat involved in the milling process or simply because of the high-energy impact of the milling medium. To investigate if grinding had detrimental effects, a detailed study was carried out using dolomite as the material to be ground. The unit cell of dolomite remained intact even after 24 h of grinding in a high-energy vibrating mill. This fact was confirmed using an X-ray powder diffraction methodology. It was found that although grinding did not deform the structural pattern of the dolomitic unit cell, a strain was however introduced in the structure. This strain appeared as a third peak in both the DTG and OTA curves This indicated the possible hazards of prolonged grinding and use of high-energy grinding equipment on the material exposed to the grinding process.