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Acid soap and phase behavior of stearic acid and triethanolamine stearate
S Zhu1, M Heppenstall-Butler, M F Butler
1Corporate Research, Unilever R & D, Colworth Lab, Bedford, MK44 1LQ, UK. shiping.zhu@unilever.com
Abstract:
Crystals of partially neutralized stearic acid with triethanolamine (TEA) were prepared by mixing these two materials above 80 degrees C and then cooling. The crystalline composition and the structure and melting behavior of the resultant products were characterized with small-angle and wide-angle X-ray diffraction, thermal analysis, microscopy, and infrared spectroscopy. It was discovered that an acid-soap complex of 2:1 fixed stoichiometric ratio exists between stearic acid and TEA stearate. A binary phase diagram of stearic acid and TEA soap is built based on the experimental results; this is the first published record of a binary phase diagram for amine-based soap. Its behavior is significantly different from that of binary systems of fatty acid and alkali soap.
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