Abstract
Viscosity of aluminum stearate in benzene solution was measured for the specimens treated thermally under various conditions. When the disoap was heated at 110°, the viscosity of its solution increased with the weight loss of the soap, and when it was heated at 150° the viscosity initially increased and then decreased. When the monosoap was heated at a temperature higher than 110°, the viscosity of its solution decreased with the weight loss of the soap.
Infrared absorption and X-ray diffraction of aluminum stearate were measured. The absorption band due to the Al-O linkage vanished in the infrared spectrum of the heated monosoap and the X-ray diffraction patterns of the disoap tended to that of monosoap with a thermal treatment.
It was concluded that the structural change of St-Al-(OH)2 to St-Al=O occurs in the monosoap with heating. The molecular weight of disoap increases with heating at 110° because of the coordination of another disoap molecule to the position where the terminal molecule has been lost from the disoap molecule by the thermal treatment. At 150°, the chain of disoap is broken by the separation of one molecule of water from the two monomer units or one molecule of stearic acid from one monomer unit, resulting in the decrease of the molecular weight.
