Development of heat-and impact-resistant coatings for main pipelines
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DEVELOPMENT OF HEAT- AND IMPACT-RESISTANT COATINGS FOR MAIN PIPELINES I. P. Gnyp,1 M. V. Neprila,2 and B. K. Hanulych 2
UDC 669.018–419.8:620.198.7:658.584
We have developed composite layered temperature-resistant silicon-organic sandwich-type coatings with thin polyurethane silicon-organic interlayers. We used the following materials as binding components: KO 921 silicon-organic lacquer with addition of ÉD-20 epoxy resin for prime coat, the same lacquer with addition of PZ 1040 S polyurethane elastomer for thin soft interlayers, and only KO 921 lacquer for thick hard layers. The mineral filler represented a mixture of coal ash and omiacarb in proportion 70 / 30 mass %. We have manufactured and tested laboratory specimens with two hard layers and two interlayers as well as with three hard layers and two thin interlayers. We have established that the developed composite layered coatings exceed, in their basic characteristics, the requirements of the State Standard Committee of Ukraine and foreign normative documents for the rust protection of steel main pipelines. Our coatings possess high impact strength, heightened elasticity and adhesion strength and, as to their electrical insulating characteristics, exceed these requirements by an order of magnitude. We note the complexity of the technology of applying layered composite coatings and the necessity of its improvement.
To protect pipeline sections adjoining gas-compressor stations, where the temperature reaches 150°C, it was customary to use heat-resistant silicon-organic coatings [1], containing a silicon-organic prime coat, modified by an epoxy oligomer, and three layers of a silicon-organic paint, filled with coal ash [2, 3]. The total thickness of such coatings did not exceed 450 μm with an impact strength of 5 J, which met standard requirements [4]. As the requirements for the quality of such coatings at sections adjoining gas-compressor and booster compressor stations became more rigid, in particular, their thickness increased to 1000 ± 50 μm and impact strength to 8 J [5], it became necessary to improve the existing silicon-organic compositions [2, 3]. After modification of such composition with coal ash by addition of omiacarb [6], we succeeded in enhancing its impact strength to 8 J. However, with increase in the thickness of the coating to 1000 μm, this characteristic falls sharply (to 1.5 – 2 J) due to the growth of residual tensile stresses and high hardness and brittleness of the composition. Modifying a silicon-organic composition, filled with a mixture of coal ash with omiacarb, by PZ 1040 S polyurethane elastomer, we can enhance the elasticity of the coating and increase its thickness to 1000 μm, but, in this case, the impact strength is not more than 4 to 5 J. Hence, it is necessary to develop new, in principle, temperature-resistant compositions that would meet the present-day requirements for the coatings for main pipelines in the zone of action of elevated temperatures [5]. The aim of the present work is to give a scientific substantiation o
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