RESUMEN
In the presented work the influence of different 3MgO·4SiO2·H2O (talc) contents in polypropylene samples on the structure, hardness, elasticity, and friction of the surface layer was investigated. The talc content ranged from 0 to 25 wt.%, and all the samples were obtained in the same conditions by the injection molding process. The analysis of the microstructure was performed by X-ray diffraction. Changes in the hardness and elasticity were determined for three different depths (300, 800, and 4000 nm) using an ultra nano tester. For the purpose of the examination of the friction properties of the obtained compounds, a nano-scratch tester was applied. Increasing the talc content caused growth in the indentation modulus and hardness values. Simultaneously, an effect of decreasing hardness and elastic modulus with increasing indentation depth was observed. The smallest effect size was observed for 25 wt.% talc content, which might suggest that talc addition increased the homogeneity of the observed composites. Scratch tests showed increasing scratch resistance along with increasing talc content for both constant and progressive loads. The growth in talc concentration led to a decrease in the degree of the polypropylene (PP) crystallinity of the surface layer. The exfoliation process occurred in PP composites.
RESUMEN
Alterations in the structure and mechanical properties of teeth in adult Wistar rats exposed to cadmium were investigated. Analyses were conducted on two sets of incisors from female and male specimens, that were intoxicated with cadmium (n = 12) or belonged to the control (n = 12). The cadmium group was administered with CdCl2 dissolved in drinking water with a dose of 4mg/kgbw for 10 weeks. The oral intake of cadmium by adult rats led to the range of structural changes in enamel morphology and its mechanical features. A significant increase of cadmium levels in the teeth in comparison to the control, a slight shift in the colour and reduction of pigmented enamel length, higher surface irregularity, a decrease of hydroxyapatite crystals size in the c-axis and simultaneous increase in pigmented enamel hardness were observed. The extent of these changes was sex-dependent and was more pronounced in males.