Effect of silazane catalysts on properties of organosilicone lacquer coatings

Abstract

We study the influence of silazane catalysts on the structurizing and formation of organosilicon coatings based on lacquer KO-921. These catalysts guarantee the curing of coatings at temperatures of (20 + 2)~ The catalytic mechanism of the action of silazanes is confirmed by the IR spectra of cured composites. The improvement in their chemical and thermal stability is substantiated by the physicochemical parameters determined experimentally.In the practice of corrosion protection of pipelines, metal structures, and technological equipment, organosilicon coatings based on polymethylphenylsiloxane lacquers and enamels are extensively used. They combine well the thermal stability of the silicon-oxygen skeleton and satisfactory physicomechanical properties of organic polymers [1][2][3]. The indicated characteristics as well as insulating and corrosion-resisting parameters of the coatings increase substantially after modification of the organosilicon matrix based on lacquer KO-921 (GOST 16508-70) with mineral fillers of the oxide and oxide-silicate types [4,5] and with polymers, specifically epoxy and furan resins [3,6].Generally, organosilicon composites cure at temperatures of 180-220~ which makes it possible to obtain high-quality heat-resistant insulating coatings. However, this complicates considerably the technological process of protection of metal products and metal structures. This is why, to lower the structurization temperature of organosilicone composites down to 20-30~ curing catalysts and reactive cross-linking agents are added to them [1][2][3][4][5][6][7]. Previous investigations of the effect of curing agents on the formation of coatings based on polymethyl-phenylsiloxane lacquer showed that the addition of silazane catalysts into compositions is promising, since, on air drying, polysilazanes can form hard protective films.In the present work, studying the properties of composite materials based on organosilicon (lacquer KO-921), we used saturated, unsaturated, and organoboron silazanes, namely, polymethylsilazane MSN-7 (TU 6-02-991-75), polymethylvinylsilazane KT-30 (TU 6-02-486-74), and methylphenylborosilazane MFSN-B (TU 6-02-862-74), as curing agents. The content of fillers in the original compositions was 2 mass %. Samples 200-300 jam thick were obtained by a familiar procedure at a temperature of (20 + 2)~ [8]. The lifetime of the composites did not exceed 2h.The degree of cross-linking of polymeric films was determined by the content of a gel fraction by extracting low-molecular constituents with toluene in a Soxhlet apparatus. The relative hardness was measured with a pendulum apparatus M-3. The chemical resistance in 5% aqueous solutions of HC1 and NaOH was evaluated by the mass method. Thermal-oxidative destruction was studied by the methods of complex differential thermal analysis and thermogravimetry on a derivatograph of the "Paulik, Paulik, Erdey" firm in air (heating rate was 10~ min-1, sensitivity of measurements was 500 units, and temperature range was 20-800~The energy of activatio...

Transparent and Thermally Stable Urushiol Films by Fast Thiol–ene Curing

“…Moreover, it is claimed that due to the poor heat-resistance, the characteristic black luster and flexibility of the urushiol film will be damaged when used above 200 °C. 9 Many attempts have been performed to address these problems including the hydrogenation of the urushiol unsaturated alkyl chain, 10 the introduction of renewable comonomers such as tung oil 11 or specialized initiators, 8 or the addition of silazane 12 or amine 13 as stabilizers, but the film shrinkage still remains a main problem. 8 Moreover, the remaining double bonds and phenolic functions decrease the aging, alkali and UV light resistance of the coatings.…”

A new organosilicon adhesive based on polysiloxane and polysilazane

“…20 PSNs were also proved as the most efficient catalysts and curing agents to increase the hardness, chemical stability, and thermal stability of organosilicon lacquer coatings. 21 Although the effect of PSN in improving the properties of PSO has been recognized, to our surprise, the number of reported PSNs used for the above-mentioned purpose is still very limited. 22,23 Little attention has been paid to the adhesive properties of such PSN-containing systems at elevated temperatures.…”