Abstract: The phase diagram of the system of dodecyl carboxylic diethanolamine (DCD)/n-butanol (C₄H₉OH)/paraffin oil(LP)/water has been investigated. The phase structures of two points chosen from the liquid crystal phase region were determined by ²H NMR spectroscopy and polarized light microscope. The wear scar widths and the vertical loads of the two samples on the surface of aluminium alloy were measured and compared with those of water, paraffin oil, n-butanol, paraffin oil +2% n-butanol, paraffin oil+2%diethanolamine and lithium grease. The results indicate that the frictional force of the lamellar liquid crystal in the direction parallel to the surface of the alloy aluminium is very small, and the lamellar liquid crystal appear to be a good lubricant.

Key words: dodecyl carboxylic diethanolamine, butanol, paraffin oil, water, lyotropic liquid crystal, lubrication