Study of the Chemical, Climatic and Thermal Resistance of Epoxy Coatings Filled with Natural and Synthetic Wollastonite

The article shows that synthetic wollastonite, obtained on the basis of a mixture of calcium oxide and silicon oxide, as well as calcium carbonate and silicon dioxide, increases the thermal stability of epoxy materials filled with it. The chemical and atmospheric resistance of epoxy films filled with wollastonite is on average 0.2 – 0.3% lower than that of the base composition, which is probably due to the porosity of both synthetic and natural wollastonite. The phase composition of synthetic wollastonite does not significantly affect chemical resistance of epoxy materials filled with it. The chemical resistance of epoxy compositions, regardless of their composition, is lower in weakly acidic solutions and water, in comparison with weakly alkaline and saline solutions.

PRODUCTION OF SYNTHETIC WOLLASTONITE BASED ON PHOSPHORIC SLAG AND AMORPHOUS SILICA PRODUCED BY "SOLAR" SILICON

В статье приведены результаты исследований по получению синтетического волластонита на основе фосфорного шлаке и аморфного кремнезема от производства солнечного кремния. Установлено, что корректировка электротермофосфорного шлака аморфным кремнеземом от производства «солнечного» кремния облегчает процесс волластонитообразования, смещая его в область более низких температур 800-950оС и минимизирует количество примесных фаз при температурах 1000-1050оС устойчивого существования игольчатого волластонита. The article presents the results of research on the production of synthetic wollastonite based on phosphoric slag and amorphous silica from the production of solar silicon. It is established that the correction of electrothermophosphoric slag with amorphous silica from the production of "solar" silicon facilitates the process of wollastonite formation, shifting it to the region of lower temperatures of 800-950oC and minimizes the number of impurity phases at temperatures of 1000-1050oC for the stable existence of needle wollastonite.

UHMWPE/CaSiO3 Nanocomposite: Mechanical and Tribological Properties

This paper studied the effect of additives of 0.5–20 wt.% synthetic CaSiO3 wollastonite on the thermodynamic, mechanical, and tribological characteristics and structure of polymer composite materials (PCM) based on ultra-high-molecular weight polyethylene (UHMWPE). Using thermogravimetric analysis, X-ray fluorescence, scanning electron microscope, and laser light diffraction methods, it was shown that autoclave synthesis in the multicomponent system CaSO4·2H2O–SiO2·nH2O–KOH–H2O allows one to obtain neeindle-shaped nanosized CaSiO3 particles. It was shown that synthetic wollastonite is an effective filler of UHMWPE, which can significantly increase the deformation-strength and tribological characteristics of PCM. The active participation of wollastonite in tribochemical reactions occurring during friction of PCM by infrared spectroscopy was detected: new peaks related to oxygen-containing functional groups (hydroxyl and carbonyl) appeared. The developed UHMWPE/CaSiO3 materials have high wear resistance and can be used as triboengineering materials.

WEAR RESISTANCE OF EPOXY COATINGS FILLED WITH SYNTHETIC WOLLASTONITE BASED ON RICE HUSK

The extraction of natural wollastonite in the world is limited, so it is relevant to synthesize it on the basis of available calcium and silicon-containing raw materials, and it is promising to use rice husks as a source of silicon dioxide, as a waste of rice processing. Due to the needle shape of the particles, natural wollastonite increases the wear resistance of epoxy coatings, which arouses interest to study the influence of the phase composition and properties of synthetic wollastonite on this property. The calcium silicate synthesized by authors contains β-wollastonite, which is the target component. Its maximum content is achieved at a synthesis temperature not higher than 950 °C, approximately at the level of natural Mivall 10–97. Larnite is found as an impurity in the composition of synthetic wollastonite, it is an island silicate with a chain structure and therefore cannot provide such a modifying effect as fillers with anisodiametric particle shape. The nature of the particle size distribution curves of both natural and synthetic volastonite has two maxima, regardless of the filler synthesis temperature, with the exception of calcium silicate obtained at 900 °C, the particle distribution is narrower than in synthesized fillers, and they are smaller. The wear resistance of epoxy compositions, when filled with both natural and synthetic wollastonite, increases. The greatest increase in this indicator is achieved when using synthetic wollastonite, obtained at a ratio of calcium oxide and silicon dioxide 1: 1 and temperatures of 900-1000 °C. Thus, epoxy materials filled with both natural and synthetic wollastonium obtained at optimal ratios of the initial components and synthesis temperatures can be effectively and economically used as wear-resistant coatings.

Production of Synthetic Wollastonite Using Gypsum Technogenic Raw Materials

The paper analyzes the literature in the field of synthetic wollastonite production using gypsum technogenic raw materials. Using the example of the complex processing of boric acid production wastes the possibility of obtaining synthetic wollastonite at different modes of waste processing is shown. Possible areas of the practical application of the obtained wollastonite are analyzed. Keywords: gypsum technogenic raw materials, borogypsum, wollastonite, technogenic waste, concrete fillers, polymeric composite materials.

Optimization of the temperature for the production of synthetic wollastonite based on rice husk

Every year around the world, as a result of rice threshing, about 600 million tons of rice husk waste are generated. They pollute the environment, since rice husks do not disintegrate in the ground, due to the presence of silicon dioxide in its composition. Silicon dioxide from rice husk ash differs from other known types of silicon-containing raw materials in that it is in an amorphous state, contains less metal impurities and is chemically more active. At the same time, this amorphous silica can be effectively used in combination with limestone for the synthesis of promising types of fillers for polymer materials, in particular, wollastonite. Based on the results of X-ray analysis, the phase composition of the synthesized filler samples was determined. It was shown that synthetic wollastonite, regardless of the synthesis temperature and the ratio of silicon dioxide and calcium carbonate in its composition, contains mainly β-wollastonite and larnite as impurities. A higher content of β-wollastonite in the composition of the synthesized filler samples is achieved at temperatures of their preparation in the range from 800 to 900 °C. At the same time, in the case of wollastonite with a ratio of silicon dioxide and calcium carbonate 1:1, the synthesis temperature has a greater effect on its composition. Filling epoxy compositions, both natural and synthetic wollastonite, significantly increases their wear resistance. This effect is associated with the anisodiametric shape of the filler particles and is approximately the same when using natural and synthetic wollastonite, with a similar content of β-wollastonite in their composition.