Abstract
Shear creep properties of oily gelatinous preparations were studied using a double-sandwich type apparatus. The specimens were the pasty stuffs obtained by cooling hot solutions of liquid petrolatum(LP) and solid stearic acid(SA).The instantaneous compliance (Jg)and the equilibrium compliance (Je) first decrease with the increase of temperature, and then after passing through a minimum, increase again.The compliances change in proportion to the reciprocal of 2.8 th power of the SA concentration, and this behavior was interpreted with van Dongen's model.Temperature dependence of the creep viscosity was examined and the activation energy of flow was calculated from the data as a function of SA concentration.The initial anomalous decrease of J, that is the apparent hardening of the substance, with the increase of temperature, was interpreted as an effect of voids contained in the system. ' The voids are gradually replaced by the thermally expanded LP. The scaffolding structure of SA crystals is impregnated with viscous and incompressible LP and hardened to gel.The proposed idea was tested by the examination of the thermal expansion behavior of LP, SA, gels, etc.
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