Rheological and thermal characterization of peloids made of selected Portuguese geological materials

Abstract Tailored peloids are prepared by the maturation of selected clay minerals mixed with thermo-mineral waters. These dispersions are topically applied to the skin to treat different ailments because of their unique rheological and thermal properties. Colloidal dimensions of the dispersed clay mineral particles yielded stable and viscous dispersions capable of flowing when spread and stand in the area to be treated without flowing away. To be easily handled and cause a pleasant sensation during application, the clay mineral dispersions must have good consistency and cause no abrasion. As thermotherapeutic agents, these systems are heated before application being important to ensure that the clay paste has heat retention capacity and adequate cooling kinetics. On the basis of a previous detailed characterization of Portuguese clayey materials for medical hydrology applications, six clay raw materials were selected as candidates to be used in the preparation of tailored peloids. This study aims to obtain tailored peloids with suitable technical, rheological and thermal properties. Samples from “Serra de Dentro” and “Barracao Clays” formations exhibited adequate abrasivity and consistency. Regarding sedimentation volume and apparent viscosity, the majority of samples showed some difficulties as they were coagulated in the absence of a dispersing agent. Specific heat and cooling rate were adequate in samples from “Serra de Dentro” and “Luz Clays” formations.