2013 Volume 41 Issue 4 Pages 195-202
It is very important for product engineers in the field of cosmetics and toiletry industry to guarantee consumers to keep the constant quality and feeling of the products during the home use. This study aims at establishing technology for property control of toiletry products containing a long-chain alcohol and surfactants. Internal structure of cosmetic and toiletry products such as a self-assembly comprising cetyltrimethylammonium chloride (C16CA), cetyl alcohol (C16OH) and water was examined by electron microscopy et al. Rheological behaviors of the self-assembly were also observed to clarify the internal structure change during aging. It was confirmed that the self-assembly prepared at higher temperature involves multilamellar vesicles dispersed in continuous phase and also that semi translucent lamella was formed when self-assembly was prepared at room temperature. Phase transition of self-assembly from multilamellar vesicles to lamellae was confirmed on aging. Shear flow tests described showed that self-assembly is shear thinning with a hysteresis at higher shear rate and the maximum apparent viscosity made a steep and linear increase in a few days after preparation, followed by a gradual increase on further aging. Based on the creep test, a mechanical model for self-assembly was presented by 6 elements. The dependence of dynamic modulus (G') and loss modulus (G") on frequency (ω) was obtained. The Cole-Cole plots were combination of 2 arcs, indicating coexistence of 2 different relaxation mechanisms. They are attributed to the formation of the networks of vesicles and of lamellae. The change in the relaxation mechanisms also corresponds to the phase transition in self-assembly. In conclusion, this study unveiled the internal structure of the self-assembly comprising surfactants as a main component and showed its close relation with rheological behaviors.