Using scanning electron microscopy, x-ray diffraction and IR spectroscopy to study the ageing of intumescent fire-proof coatings

Introduction. The fire protection of metal structures is a relevant present-day problem; its solution implies better fire resistance performance of structures attainable through the application of intumescent fire-proof coatings whose service life expectancy is limited.

Goals and objectives. Comprehensive studies of domestically made coating samples were performed to analyze the changes in the chemical composition of intumescent coatings containing ammonium polyphosphate, melamine, and pentaerythritol. The samples were exposed to artificial climatic ageing (3, 6, and 9 years). Methods. Optical and scanning electron microscopies were used to study the appearance of samples, the morphology of inclusions and the surface microstructure. X-ray diffraction and IR spectroscopy were employed to study the phase and structural states of samples, and the swelling ratio of fire-proof coatings was also examined.

Results and discussion. It’s been found out that the swelling ratio of samples goes down to a significant extent as the time progresses, and when the residual life of a coating reaches 30 %, the fire resistance limit of the structure goes down. Sample ageing is the reason for gradual phase composition changes due to the melamine content reduction by 40 %, ammonium polyphosphate content reduction by 15 % and redistribution of other components that change the microstructure of coatings, as well as their fire retarding properties.

Conclusions. The changes, influencing the ability of a coating to maintain its fire retarding efficiency as declared by the manufacturer, take place in the course of operation of a coating exposed to external factors. The regularities, identified by virtue of this research, can be used to study the samples taken at fire-proofed facilities to identify deviations from the initial condition of a coating and to forecast its actual service life.

1. Leonova D.I. A comparative analysis of the toxicity of the main groups of flame retardants (literature review). Actual problems of transport medicine. 2008; 3(13):117-128. (rus.).

2. Troitzsch J. Plastics flammability handbook: Principles, regulations, testing, and approval. 3rd ed. Munich, Carl Hanser Verlag, 2004; 718.

3. Fire retardant materials / Ed. by A.R. Horrocks, D. Price. New York, CRC Press, 2001; 276.

4. Vakhitova L.N., Taran N.A., Lapushkin M.P., Rybak V.V., Dridzh V.L., Burdina Y.F. The effect of the amine structure on the flame retardant efficiency of the ammonium polyphosphate / pentaerythritol / amine system. Science praci DonNTU. Seria: Chemistry and chemical technology. 2014; 1(22):142-149. URL: http://ea.donntu.edu.ua/bitstream/123456789/25983/1/17.pdf (rus.).

5. Khalturinsky N.A., Rudakova T.A. The mechanism of formation of fire protective intumescent coatings. News SFU. Technical science. 2013; 8(145):220-227. URL: https://www.elibrary.ru/item.asp?id=20214782 (rus.).

6. Korotkov A.S., Gravit M. 3D-map modelling for the melting points prediction of intumescent flame-retardant coatings. SAR and QSAR in Environmental Research. 2017; 28(8):677-689. DOI: 10.1080/1062936X.2017.1370725

7. Silnikov M.V., Gravit M.V., Zybina O.A. Thermoanalytical study of various grades of ammonium polyphosphate for intumescent flame-retardant compositions. Questions of defense equipment. Scientific and technical journal. Series 16. Technical means of countering terrorism. 2016; 9-10(99-100):76-79. URL: https://www.elibrary.ru/item.asp?id=27170060 (rus.).

8. Rudakova T.A., Yevtushenko Yu.M., Grigoriev Yu.A., Batrakov A.A. Ways of reducing the temperature of foaming in the system ammonium polyphosphate – pentaerythritol in intumestsent systems. Pozharovzryvobezopasnost/Fire and Explosion Safety. 2015; 24(3):24-31. URL: https://www.fire-smi.ru/jour/article/view/371 (rus.).

9. Li G., Liang G., He T., Yang Q., Song X. Effects of EG and MoSi 2 on thermal degradation of intumescent coating. Polymer Degradation and Stability. 2007; 92(4):569-579.

10. Study on preparation and fire-retardant mechanism analysis of intumescent flame-retardant coatings / Gu J., Zhang G., Dong S., Zhang Q., Kong J. // Surface and Coatings Technology. 2007; 201(I):18:7835-7841. DOI: 10.1016/j.surfcoat.2007.03.020

11. Nenakhov S.A., Pimenova V.P. Dynamics of foaming of fire-retardant coatings based on organo-inorganic compounds. Pozharovzryvobezopasnost/Fire and Explosion Safety. 2011; 20(8):17-20. URL: https://www.elibrary.ru/item.asp?id=16903009 (rus.).

12. Gu L., Qiu J., Yao Y., Sakai E., Yang L. Functionalized MWCNTs modified flame retardant PLA nanocomposites and cold rolling process for improving mechanical properties. Composites Science and Technology. 2018; 161:39-49. DOI: 10.1016/j.compscitech.2018.03.033.

13. Vahabi H., Gholami F., Karaseva V., Laoutid F., Mangin R., Sonnier R. et al. Novel nanocomposites based on poly (ethylene-co-vinyl acetate) for coating applications: The complementary actions of hydroxyapatite, MWCNTs and ammonium polyphosphate on flame retardancy. Progress in Organic Coatings. 2017; 113:207-217. DOI: 10.1016/j.porgcoat.2017.08.009

14. Li Y., Gao Y., Cao Y., Li H. Electrochemical sensor for bisphenol A determination based on MWCNT/melamine complex modified GCE. Sensors and Actuators B: Chemical. 2012; 171-172:726-733. DOI: 10.1016/j.snb.2012.05.063

15. Guo Z., Xu X.-F., Li J., Liu Y.-W., Zhang J., Yang C. Ordered mesoporous carbon as electrode modification material for selective and sensitive electrochemical sensing of melamine. Sensors and Actuators B: Chemical. 2014; 200:101-108. DOI: 10.1016/j.snb.2014.04.031

16. Bezaponnaya O.V., Golovina E.V., Akulov A.Yu. Identification control of fire-protective compositions of the intumescent type by the methods of thermal analysis. Tekhnosfernaya bezopasnost’/Technosphere safety. 2019; 1(22):52-57. URL: https://www.elibrary.ru/item.asp?id=37134622 (rus.).

17. Borovik S.I., Trofimova L.A. Analysis of methods for assessing the impact of operational factors on fire retardant coatings for metal structures. Research: theory, methodology and practice : mat. III Int. scientific-practical conf. (Cheboksary, November 19, 2017). In 2 volumes. Vol. 2. Cheboksary, Central nervous system “Interactive plus” Publ., 2017; 18-21. URL: https://www.elibrary.ru/item.asp?id=32334776 (rus.).

18. Andronov V.A., Danchenko Yu.M., Bukhman O.M. Approaches to determining the life of flame retardant polymer coatings. Collection of scientific papers. Vol. 31. Kharkiv, NUTSZU, 2012; 10-18. URL: http://repositsc.nuczu.edu.ua/handle/123456789/3690 (rus.).

19. Vakhitova L.N., Lapushkin M.P., Calafat K.V. The service life of fire retardant coatings intumescent type. F + S: Safety and Fire Protection Technologies. 2011; 2(50):58-61. (rus.).

20. Umrikhina M.Yu., Shorokhova T.O., Utkin S.V., Pyankova L.A., Krasnova L.Yu. Study of intumescent coatings in operation using x-ray phase and thermal analysis and IR spectroscopy. Industrial laboratory. Diagnostics of materials. 2020; 86(3):25-31. DOI: 10.26896/1028-6861-2020-86-3-25-31

21. Smirnov N.V., Duderov N.G., Bulaga S.N., Mikhailova E.D., Tolpekina N.A., Lezova M.V., Bulgakov V.V. Evaluation of the fire-retardant properties of coatings depending on their service life: methodology. 2nd ed., rev. and add. Moscow, FGBU VNIIPO EMERCOM of Russia, 2016. (rus.).

22. Teploukhov A.V., Zverev V.G., Garashchenko A.N. Methodology and results of estimation of the influence of structures long-term exploitation on basic properties of the intumescent flameretardant coatings. Pozharovzryvobezopasnost/Fire and Explosion Safety. 2016; 25(1):9-16. DOI: 10.18322/PVB.2016.25.01.9-16 (rus.).

23. Determination of heat-insulating properties of fire-protective coatings for metal : methodology. Moscow, VNIIPO, 1998; 19. (rus.).

24. Bellamy L.J. The infra-red spectra of complex molecules. London : Methuen & Co., 1954; 300.

25. Reference tables of basic spectroscopic data (IR, UV, NMR spectroscopy and mass spectrometry). Minsk, 2001; 43. (rus.).

26. Ding Z., Lu G.Q., Greenfield P.F. Role of the Crystallite Phase of TiO 2 in Heterogeneous Photocatalysis for Phenol Oxidation in Water. The Journal of Physical Chemistry B. 2000; 104:4815-4820. DOI: 10.1021/jp993819b