IR-SPECTROSCOPY INVESTIGATION OF PARAFFIN LUBRICANT SAMPLES OF VARIOUS THICKNESS ON A METAL-SUPPORT AT ROOM AND ELEVATED-TEMPERATURES

IR spectra of vaseline and ceresine lubricant samples of various thick ness (similar to 15-0.5 mu m) on an aluminum support are investigated at room temperature and similar to 90 degrees C. Dependences of the ha lf-widths of stretching CH vibrational bands on the sample layer thick ness are studied. Based on the obtained results a conclusion is drawn that the mean lengths of the regular hans-sequences in alkane molecule s increase and that lubricant samples are compressed as the layer thic kness diminishes. An analysis of the behavior of ''crystalline'' IR ba nds of lubricants with changing the layer thickness has shown that in thin layers crystallites formed by molecules of different length are s eparated into smaller ones and more homogeneous in their composition. An increase of the valence angles in CH2 groups of alkane molecules in melted samples is revealed. This finding is accounted for by enhancem ent of compression of the lubricant layer with melted crystallites due to wetting the rhetal support.