PSI - Issue 25

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Sergey Smirnov et al. / Procedia Structural Integrity 25 (2020) 209–213 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 2. The values of HM (a) and the values of (b) as dependent on the number of thermocycling cycles for samples of epoxy lacquers of different compositions being lower than the initial hardness value. A similar situation is observed for , i.e. the elastic modulus is initially 8.4 GPa to become 6 GPa after 5 cycles and 7.9 GPa after 10 cycles. This behavior clearly demonstrates material structuring as a result of afterpolymerization of the epoxy groups and orientation of macromolecules in the course of their adsorption/desorption on the filler particles during thermocycling. The behavior of varying with holding time for all the tested samples is qualitatively identical after 5 and 10 cycles (fig. 1, b and c), with varying numerical values. For the unmodified coating, increases on the average by 20% after 5 thermocycling cycles for all the holding times; as the number of cycles increases to 10, the value of creep changes only slightly. The same behavior is observed for the coatings modified with zinc oxide and silicon dioxide, but increases within the first 5 cycles by 26% and 28%, respectively. For titanium dioxide, the creep increases on the average by 35% after 5 thermocycling cycles; however, after 10 cycles, on the contrary, the creep value decreases on the average by 7% as compared to the coating after 5 cycles. 4. Conclusion For the coatings not subjected to thermocycling, doping with titanium dioxide increases Martens hardness by 5% as compared to that of the unmodified lacquer, whereas doping with zinc oxide and silicon dioxide reduces Martens hardness by 4% and 5.5%, respectively. The normal elastic modulus for the epoxy lacquer containing titanium dioxide exceeds that of the unmodified lacquer by 15%. For the coating containing zinc oxide, the modulus values remain even with those of the unmodified lacquer, while they are 6% lower than for the coatings with silicon dioxide. On the whole, cyclic thermal action smoothly decreases the elastic modulus and hardness of the pure epoxy lacquer and those modified with SiO 2 and ZnO. Thermal action has the greatest effect on the characteristics of the TiO 2 -doped epoxy lacquer coating, which manifests itself in the discontinuous variation of HM and . The creep of the loaded coatings is more attributed to the polymer base; the dopes have no significant effect on the time dependence, but they decrease . Thermocycling leaves the behavior of the time dependence unchanged, but it increases the value of creep. Acknowledgements The experimental procedures for studying polymer coatings were developed according to the work plan of IES UB RAS, theme AAAA-A18-118020790145-0. The Russian Scientific Foundation financially supported (project 19-19-00571) the purchase of the test materials and the study the effect of thermocycling on the