WITH Matos2, TM
SUSTAINABLE Filho3, LP
BRAZILIAN`S CLAY. JQ MA Guillen1, Marques4, MM MA Almeida1, CR LIMA1, AR JR Baby1, EM Kaneko1, Batistela4,
Mercuri3, MV Velasco1. Faculty of Pharmaceutical Science University of São Paulo, São Paulo, Brazil. 2 Chemistry Institute – University of São Paulo, São Paulo, Brazil. 3 Federal University of São Paulo, São Paulo, Brazil. 4 Vital Especialidades, Brazil.
In a recent study on the color make-up market, Euromonitor said mineral make-up was spearheading growth in the category because it provides natural sunscreen, long-lasting coverage and is suitable for use on sensitive skin (PITMAN,2008). A new generation of Brazilian’s clay have been developed for mineral make up and it is differentiated beyond of the beauty in the colors, in the micronizing process that consists in transforming the mesh to a very small size, which on average is 5.5 m without loss the properties and its presents safety for skin (ADDOR, 2006). Although most of the physicochemical properties of clay dispersions have been studied, specific aspects concerning the physicochemical stability of mineral make up with clay remain unclear(ZAGUE,2007). The thermal analysis methods have been used in cosmetic area for quality control, preformulation and stability studies. It refers to a group of techniques in which a physical property of a substance and its reaction product is measured as a function of a controlled temperature program. (SILVA et al, 2007). The present work aims the development and stability study of sunscreen with brazilian`s clay as a mineral make up, employing the techniques of differential scanning calorimetry (DSC) and thermogravimetry (TG).
METHODS: Differential Scanning Calorimetry (DSC): for DSC measurements, the sample evaluated were: black clay, gold clay, red clay, sunscreen, a mixture of clays (Table I), and sunscreen with 10% of the mixture of clays (63,50% gold, 1,50% black, 15,00% red) as a mineral make up. The DSC measurements were performed on a Shimadzu DSC-60 cell. Approximately 5 mg of samples were weighted and placed in a sealed aluminum pan. The temperature range tested was from 25 to 1000 C and heating rate of 5 C/min in dynamic nitrogen atmosphere with the flow rate of 50 mL/min.Thermogravimetric analysis (TG): for TG measurements, the sample evaluated were: black clay, gold clay, red clay, sunscreen, a mixture of clays (Table I), sunscreen and sunscreen with 10% of the mixture of clays as a mineral make up. The TG curve was measured on a Shimadzu thermobalance TGA50.Approximately 5.0 mg of sample was used in a platinum pan, in a temperature range from 25 C to 1000 C with dynamic nitrogen atmosphere at a flow rate of 50mL/min and heating rate of 5 C/min. The decomposition was monitored as a function of temperature and weight loss.
Analysis of Clays
1) Black Clay
The figure 1 shows the thermal behavior of black clay. The first weight loss observed in TG/DTG curves might be the water liberation once this type of material has water in its composition. The subsequent weight losses are related with the thermal decomposition of this material. Black clay decomposes in three consecutive weight losses and has a residue with 74,51% of initial mass. This high percentage of mass obtained in the end of analysis can be associated with the high percentage of inorganic substances in its composition like SiO2, Fe2O3 and Al2O3. The DSC curve of black clay shows an endothermic event in the temperature range of 25-180ºC which corroborates with TG/DTG data for the material dehydration. The second weight loss is exothermic and the third is endothermic.
Heat Flow (mW∙mg )
m/t (mg∙min )
Weight Loss (%)
-0.60 -0 200 400 600 800