EVALUATION OF PERMITTIVITY AND SURFACE TENSION OF ORGANIC AND SYNTHETIC LUBRICATED AND COOLING LIQUIDS

Abstract

Lubricants and cooling liquids (LCL) are among the components providing for the quality of the end products in the metal-working industry. During the operation it is observed a lack of balance in the ratio between the LCL components as well as contamination (semination) by the microflora – bacteria, mold fungi and microalgae. These factors result in low quality of metalworking. The methods, which are currently applied for evaluation of the state of LCL quality do not always provide for a proper recording of the above changes, and the process of detection of the above changes takes much time. The microwave dielectrometry allows evaluation of the structural and functional condition of a biological system in the real time scale at the frequencies of the free water permittivity dispersion on the basis of variation of the amount of bonded water on the structures of macromolecular complexes, as well as of the same changes in the free water. The objective of this paper is in determining the efficiency of controlling biological contamination of the organic and synthetic LCL on the basis of evaluation of their permittivity and surface tension taking into consideration the structural and functional features of the microflora. The measurements of permittivity and surface tension of organic and synthetic LCL both freshly prepared (the reference ones) and used (the test) samples were performed by means of microwave dielectrometry within the framework of this paper. Biological analysis of morphological particularities of the microflora was executed by calculation of the colonies forming units with a subsequent microscopic examination. The experiments showed an increase of the bonded water within the 'used LCL – microflora' system as compared with the freshly prepared samples. Comparative analysis of the obtained experimental data related to the permittivity and surface tension of the used LCL revealed decreased values of the above parameters in the synthetic emulsion probably due to contamination of the LCL by gram-positive non-sporeforming bacteria. According to the curried out measurements the LCL quality testing can be used as a marker for a timely replacement of low-quality LCL at various stages of the metal-working process and for decreasing the percentage of defective end products.