Staniša Stojiljković

The influence of the addition of polymers on the physico-chemical properties of bentonite suspensions

Bentonite clays have many applications in industries ranging from construction to cosmetics. Addition of polymers can profoundly influence the properties of bentonite suspensions and we now describe the influence of a range of different polymers. Whereas polyvinyl pyrolidone and soy isolate only slightly influenced the pH and the electrical conductivity of bentonite polymers in suspension, Carbopol solution caused decreases in both pH and electrical conductivity. As expected, strong electrolytes like sodium chloride caused big changes in the electrical conductivity of the suspensions. When the temperature of the bentonite suspensions was increased, the pH was almost unchanged, but the electrical conductivity increased. Bentonite treated with polymer suspensions can be used in purifying polluted water; for example, our results suggest that high pH caused by phosphorous salts can be addressed using bentonite modified with Carbopol.

The influence of montmorillonite modification on the properties of composite material based on poly(methacrylic acid)

In this work a new class of functional composites was prepared based on the organically modificated montmorillonite and methacrylic acid. In the first step, the native montmorillonite was mixed with poly(ethylenimine) monomer to promote the intercalation process. In the second step, the methacrylic acid and initiator (potassium persulfate) were added and polymerization was carried out at 80°C for 2 hours. Characterization of the obtained composite material was performed by Fourier transform infrared spectroscopy. The change in interlamellar spacing of montmorillonite after polymer composite preparation was determined by X-ray diffraction. In prepared composite samples the existence of two crystalline phases was estimated by X-ray measurements. In the first, the poly(methacrylic acid) chains are intercalated within the montmorillonite layers, and in the second, they are dispersed in the polymer matrix. The influence of montmorillonite on the thermal properties of the obtained composites was measured using the combined thermogravimetry and differential scanning calorimetry method. The porosity of the prepared samples was determined by isotherm adsorption and the desorption of nitrogen (Brunauer–Emmett–Teller method). It was assessed that a certain amount of polymer is deposited on the montmorillonite and thus covering of the micropores and partially covering of the mesopores was achieved.

Study of Water Vapor Resistance of Co/PES Fabrics Properties During Maintenance

The goal of this study was to investigate the interlinkages of physical, mechanical and thermophysiological properties of fabrics. Changes of a thermophysiological property – water vapor resistance (Ret) during washing of six fabrics used for making clothing assemblies (for particular conditions of application) were also examined. Human thermal comfort depends on the combination of clothes, climate conditions and physical activity. Clothing maintenance by washing affects its diffusion and thermal properties. Water vapor permeability and thermal resistance of clothing are key parameter for wearing comfort. Standard methods were applied for examining physical and mechanical properties of fabrics, whereas hot plate measurements were used for testing water vapor resistance (Ret). The obtained results indicated that certain yarns properties used in the production of fabrics and constructional characteristics of fabrics significantly affect the water vapor resistance and its changes during washing. The results were used in order to establish a mathematical model for predicting the behavior of the fabrics during washing that are used for a particular clothing assembly in the phase of exploitation – wearing.

Thermal Energy Storage of Composite Materials Based on Clay, Stearic Acid, Paraffin and Glauber’s Salt as Phase Change Materials

Thermal protection and insulation are important problems in many fields such as industry, agriculture and medicine. New composite materials with good thermal storage capacities have become important in the last few decades. The role of these materials is reflected in their ability to store energy and allow it to be reused in some other thermal systems. The aim of this study was to create a new material based on the basically activated bentonite clay. First, the clay was basically activated, resulting in a thick gel. Afterwards, stearic acid, Glauber’s salt and active carbon were added, and a heterogeneous gel was obtained as a finished final product. In order to obtain the best heterogeneous gel with satisfactory storage properties, the amount of stearic acid and Glauber’s salt was varied. The characterization of the resulting heterogeneous gel was performed by measuring the cooling rate of the gel samples. Compared with stearic acid, Glauber’s proved to be more effective. Heterogeneous gel cooling tests have shown that there was a certain proportional dependence between the concentration of stearic acid and the Glauber salt. However, it has been noticed the reduction in the cooling rate. Namely, the increase in stearic acid and Glauber’s salt concentration lead to slowing down the cooling rate of the gel. Adding active carbon to the heterogeneous gel also reduced the cooling rate, which indicated that the presence of active carbon in the heterogeneous gel should not be excluded in the future. The advantage of this system is the improvement of the gel thermal characteristics by the presence of water and clay. The gel was reversibly cooled and heated up to 100 °C without changing the homogeneous structure. This system can be used as a heat recovery pad, due to its flexible body pillow. It can be very quickly warmed up in a microwave oven if it is packaged in polyethylene packaging.

Application of Bentonite Clay for Human Use

Clay minerals can be beneficial to human health by serving as active principles or excipients in pharmaceutical preparations, in spas, and in beauty therapy medicine. Since prehistoric times, man used the clay in nutrition and therapeutic purposes. The use of medicinal earths in Mesopotamia and Ancient Egypt has also been proven. The use of Nubian earth as an anti-inflammatory or the use of mud materials for mummification of cadavers can be cited as examples [2, 22]. In the Ancient Greek period, mud materials (Lemnos Earth) were used as antiseptic cataplasms to cure skin afflictions, as cicatrisers or as a cure for snake bites. Both Hippocrates and Aristotle, among others, produced classifications of medicinal earths. Most of these materials are clays, given different names depending on their origins or on the differences in their mineralogical composition and properties. Some poorly known implications of clay uses are mentioned, such as the effects of organic compounds in the transdermal migration of elements and the effective simulation of the digestion, that is in balance between chemical leaching and adsorptive effect of clays. From the standpoint of thermodynamics, the exchange of minerals in the body whether it is oral or transdermal process, define the character of the wearer. This is as emulsions, gels, suspensions or heterogeneous systems. Clay materials have emulsifying power, ion exchange, adsorption, gelation, which is typical of its living matter. It should be noted electrical properties of clay. It usually negatively charged very effectively bind metal cations positive charges or protein. Historically in most developed civilizations demonstrated activity alumino silicate clay in the exchange minerals and trace elements in the body [16].