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This article is devoted to the study of an organomineral thermal insulation composite based on a rigid polyurethane foam (PUF) matrix and a flammability-reducing silicate component-sodium metasilicate pentahydrate (Na2SiO3•5H2O, 0.9-1.25 mm fraction). The physicochemical regularities of the interaction between the silicate component and isocyanate, the fire-retardant mechanism of the silicate component, and its effect on the thermal properties and flammability of the composite have been investigated.
A chemical interaction between the isocyanate functional groups of the reactive mixture and the water contained in the silicate component was established to occur at the phase boundary.
The fire-retardant mechanism of the silicate component consists in the endothermic release of crystallization water (70-170 ℃), which induces intumescence of the metasilicate, resulting in the formation of a porous heat-insulating barrier.
The silicate component does not alter the fundamental decomposition mechanism of the polyurethane, yet it shifts the stages of thermo-oxidative degradation to lower temperatures (by 15-85 ℃). The final residue increases up to 8.1 times (from 3.6 to 29.1 wt%), which directly corresponds to the contribution of the dehydrated silicate.
Flammability tests demonstrated that when the silicate component content exceeds 45%, the material achieves a UL 94 V 0 rating, and the limiting oxygen index (LOI) increases from 17.8 to 26.6 at a 90% silicate component loading.
The obtained results substantiate the effectiveness of using sodium silicate crystalline hydrate as a fire-retardant additive, and it can be recommended for the development of composites based on other polymer matrices.
A chemical interaction between the isocyanate functional groups of the reactive mixture and the water contained in the silicate component was established to occur at the phase boundary.
The fire-retardant mechanism of the silicate component consists in the endothermic release of crystallization water (70-170 ℃), which induces intumescence of the metasilicate, resulting in the formation of a porous heat-insulating barrier.
The silicate component does not alter the fundamental decomposition mechanism of the polyurethane, yet it shifts the stages of thermo-oxidative degradation to lower temperatures (by 15-85 ℃). The final residue increases up to 8.1 times (from 3.6 to 29.1 wt%), which directly corresponds to the contribution of the dehydrated silicate.
Flammability tests demonstrated that when the silicate component content exceeds 45%, the material achieves a UL 94 V 0 rating, and the limiting oxygen index (LOI) increases from 17.8 to 26.6 at a 90% silicate component loading.
The obtained results substantiate the effectiveness of using sodium silicate crystalline hydrate as a fire-retardant additive, and it can be recommended for the development of composites based on other polymer matrices.
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2. Feng J. et al. A Si-containing polyphosphoramide via green chemistry for fire-retardant polylactide with well-preserved mechanical and transparent properties. Chemical Engineering Journal. 2022. 431. P. 134259.
3. Pustovgar A.P., Bruyako M.G., Petunova M.D. et al. Hybrid materials based on Na-liquid glass, 2,4-toluene diisocyanate, epoxy oligomer and polyisocyanate. Polymer Science. Series A. 2018. 60 (6). P. 495 – 512. DOI: 10.1134/S230811201806007X
4. Lipka P.A., Mironova K.A., Bruyako M.G., Kozlova I.V., Samchenko S.V. Organomineral thermal insulation composite: pore structure formation. Technique and Technology of Silicates. 2026. 33 (1). P. 46 – 59. DOI: 10.62980/2076-0655-2026-46-59
5. Lipka P.A., Borisenkov N.S., Mironova K.A., Chesnokova D.S., Bruyako M.G. Thermal insulation composite material based on sodium silicate and polyurethane foam matrix. Technique and Technology of Silicates. 2026. 33 (2). P. 154 – 166. DOI: 10.62980/2076-0655-2026-154-166
6. Ishchenko S.S., Pridatko A.B., Novikova T.I., Lebedev E.V. Interaction of isocyanates with aqueous solutions of alkali metal silicates. Polymer Science. Series A. 1996. 38 (5). P. 786 – 791.
7. Kozakiewicz J., Rokicki G., Przybylski J., Pawłowski P. Water-cured poly(urethane-urea)s containing soft segments originating from siloxane/carbonate macrodiols. Polimery. 2012. 57 (11-12). P. 791 – 798. DOI: 10.14314/polimery.2012.791
8. Chemical Encyclopedia. ed. by I.L. Knunyants. Moscow.1990. 5 (2). P. 671.
9. Bugrov A.N., Gorshkova Y.E., Ivan’kova E.M., Kopitsa G.P., Pavlova A.A., Popova E.N., Smirnova V.E., Smyslov R.Y., Svetlichnyi V.M., Vaganov G.V., Vasil'ev B.V. Domain Structure, Thermal and Mechanical Properties of Polycaprolactone-Based Multiblock Polyurethane-Ureas under Control of Hard and Soft Segment Lengths. Polymers. 2022. 14 (19). P. 4145. DOI: 10.3390/polym14194145
10. Stanciu I. Study of the composition of aromatic hydrocarbons using IR spectroscopy. International Journal of Advanced Scientific Research. 2025. 10 (4). P. 138 – 139.
11. Kobelev A.A., Naganovskii Yu.K., Kruglov E.Yu., Aseeva R.M., Shapikhov E.M. Pyrolysis of hybrid polyurethane-inorganic thermal insulation: thermogravimetric analysis and FT-IR spectra. Fire and Explosion Safety. 2022. 31 (4) P. 5 – 15. DOI: 10.22227/0869-7493.2022.31.04.5-15
12. Sandjong Kuigwa L. Recherche de nouveaux solvants éco-compatibles de substitution dans le cadre de REACH. PhD thesis in Chemistry. Lyon : Université Claude Bernard – Lyon I, 2013.
13. Mel’nik I.V., Lyashenko O.V., Zub Yu.L., Chuiko A.A., Cauzzi D., Predieri G. Synthesis of alkoxysilanes as starting substances for preparation of new materials by the sol-gel procedure. Silanes with urea functional group. Russian Journal of General Chemistry. 2004. 74 (11). P. 1658 – 1664. DOI: 10.1007/s11176-005-0080-x
14. Zhuang Y., Fang Z., Yuan Z., Luo Q., Xu W. Study on the influence of raw material dosages on the production temperature of flexible polyurethane foam. Journal of Polymer Research. 2025. 32 (5). P. 181. DOI: 10.1007/s10965-025-04409-w
15. Stanciu I. Study of the composition of aromatic hydrocarbons using IR spectroscopy. International Journal of Advanced Scientific Research. 2025. 10 (4). P. 138 – 139.
16. Mandal K.K. Infrared Spectroscopy. SEM-4. CC-8. 6. PPT-12. Kolkata : St. Paul’s C. M. College, [s. a.]. P 4.
17. Gu X.H., Sung L.-P., Kidah B., Oudina M., Clerici C., Hu H. Q., Stanley D., Byrd W.E., Jean J.Y.C., Nguyen T., Martin J.W. Multiscale physical characterization of an outdoor-exposed polymeric coating system. Journal of Coatings Technology and Research. 2009. 6 (1). P. 67 – 79. DOI: 10.1007/s11998-008-9108-6
18. Duong L.D., Nam G.-Y., Oh J.-S., Park I.-K., Luong N.D., Yoon H.-K., Lee S.-H., Lee Y., Yun J., Lee C.-G., Hwang S.-H., Nam J.-D. High Molecular-Weight Thermoplastic Polymerization of Kraft Lignin Macromers with Diisocyanate. BioResources. 2014. 9 (2). P. 2359 – 2371. DOI: 10.15376/biores.9.2.2359-2371
19. Reignier J., Méchin F., Sarbu A. Chemical gradients in PIR foams as probed by ATR-FTIR analysis and consequences on fire resistance. Polymer Testing. 2021. 93. P. 106972. DOI: 10.1016/j.polymertesting.2020.106972
20. Stani C., Vaccari L., Mitri E., Birarda G. FTIR investigation of the secondary structure of type I collagen: New insight into the amide III band. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 2020. 229. P. 118006. DOI: 10.1016/j.saa.2019.118006
21. Zhang S., Ren Z., He S., Zhu Y., Zhu C. FTIR spectroscopic characterization of polyurethane-urea model hard segments (PUUMHS) based on three diamine chain extenders. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 2007. 66 (1). P. 188 – 193. DOI: 10.1016/j.saa.2006.02.041
22. Fug F., Rohe K., Vargas J., Nies C., Springborg M., Possart W. 4,4′-methylene diphenyl diisocyanate – Conformational space, normal vibrations and infrared spectra. Polymer. 2016. 99. P. 671 – 683. DOI: 10.1016/j.polymer.2016.07.075
23. Pitsevich G.A., Shundalau M.B., Ksenofontov M.A., Umreiko D.S. Vibrational analysis of 4,4'-methylene diphenyl diisocyanate. Global Journal of Analytical Chemistry. 2011. 2 (3). P. 114 – 124.
24. Torres-Carrasco M., Palomo J.G., Puertas F. Sodium silicate solutions from dissolution of glass wastes. Statistical analysis. Materiales de Construcción. 2014. 64 (314). P. e014. DOI: 10.3989/mc.2014.05213
25. Salazar Navarro A.A., Valdez Salas B. Synthesis of silica nanoparticles from sodium metasilicate. International Journal of Nanoparticles. 2022. 14 (1). P. 1 – 12. DOI: 10.1504/IJNP.2022.122939
26. Shao Z., Luo F., Cheng X., Zhang Y. Superhydrophobic sodium silicate based silica aerogel prepared by ambient pressure drying. Materials Chemistry and Physics. 2013. 141 (1). P. 570– 575. DOI: 10.1016/j.matchemphys.2013.05.064
27. Yang X., Roonasi P., Holmgren A. A study of sodium silicate in aqueous solution and sorbed by synthetic magnetite using in situ ATR-FTIR spectroscopy. Journal of Colloid and Interface Science. 2008. 328 (1). P. 41 – 47. DOI: 10.1016/j.jcis.2008.08.061
28. Modesti M., Lorenzetti A. An experimental method for evaluating isocyanate conversion and trimer formation in polyisocyanate–polyurethane foams. European Polymer Journal. 2001. 37 (5). P. 949 – 954. DOI: 10.1016/S0014-3057(00)00209-3
29. Li J., Jiang S., Ding L., Wang L. Reaction kinetics and properties of MDI base poly (urethane-isocyanurate) network polymers. Designed Monomers and Polymers. 2021. 24 (1). P. 265 – 273. DOI: 10.1080/15685551.2021.1971858
30. Duquesne S., Le Bras M., Bourbigot S., Delobel R., Camino G., Eling B., Lindsay C., Roels T. Thermal degradation of polyurethane and polyurethane/expandable graphite coatings. Polymer Degradation and Stability. 2001. 74 (3). P. 493 – 499. DOI: 10.1016/S0141-3910(01)00177-X
31. Deng Y., Dewil R., Appels L., Ansart R., Baeyens J., Kang Q. Reviewing the thermo-chemical recycling of waste polyurethane foam. Journal of Environmental Management. 2021. 278 (1). P. 111527. DOI: 10.1016/j.jenvman.2020.111527
32. He J.-J., Jiang L., Sun J.-H., Lo S. Thermal degradation study of pure rigid polyurethane in oxidative and non-oxidative atmospheres. Journal of Analytical and Applied Pyrolysis. 2016. 120. P. 269 – 283. DOI: 10.1016/j.jaap.2016.05.015
33. Rychlý J., Lattuati-Derieux A., Lavédrine B., Matisová-Rychlá L., Malíková M., Csomorová K., Janigová I. Assessing the progress of degradation in polyurethanes by chemiluminescence and thermal analysis. II. Flexible polyether- and polyester-type polyurethane foams. Polymer Degradation and Stability. 2011. 96 (4). P. 462 – 469. DOI: 10.1016/j.polymdegradstab.2011.01.012
34. Szycher M. Szycher's handbook of polyurethanes. 2nd ed. Boca Raton, FL: CRC Press. Taylor & Francis. 2013. 17. P. 1126.
35. Chattopadhyay D. K., Webster D. C. Thermal stability and flame retardancy of polyurethanes. Progress in Polymer Science. 2009. 34 (10). P. 1068 – 1133. DOI: 10.1016/j.progpolymsci.2009.06.002
36. Fabris H.J. Thermal and oxidative stability of urethanes. Advances in Urethane Science and Technology. ed. by K.C. Frisch, S.L. Reegen. Westport, Conn.: Technomic Publishing. 1976. 4. P. 89 – 111.
37. Mathur G., Kresta J.E., Frisch K.C. Stabilization of polyether-urethanes and poly(ether-urethane-urea) block copolymers. Advances in Urethane Science and Technology. ed. by K. C. Frisch S.L. Reegen. Westport: Technomic Publication. 1978. 6. P. 103 – 172.
38. Woolley W.D. Nitrogen‑containing products from the thermal decomposition of flexible polyurethane foams. British Polymer Journal. 1972. 4 (1). P. 27 – 43.
39. Ravey M., Pearce E. M. Flexible polyurethane foam. I. Thermal decomposition of a polyether‑based, water‑blown commercial type of flexible polyurethane foam. Journal of Applied Polymer Science. 1997. 63 (1). P. 47 – 74. DOI: 10.1002/(SICI)1097-4628(19970103)63:1<47:AID-APP7>3.0.CO;2-S
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