Synthesis of Cobalt Borate Compound to Confer Fire-proof Properties to Epoxy-Based Composites by Achieving Synergistic Effect with Red Phosphorus

Öz

This study investigated the synergistic effect of a cobalt borate (CoB) compound synthesized by molten-salt-assisted borothermal reduction on epoxy resins, both alone and in combination with red phosphorus (RP) flame-retardant additives, on flame-retardancy. In the first stage of the research, the CoB compound was synthesized using a molten salt-assisted borothermal method, yielding Co3B2O6 at 750°C. X-ray diffraction (XRD), scanning electron microscopy equipped with energy dispersive x-ray spectroscopy (SEM-EDX), thermogravimetric analysis (TGA), and fourier transform infrared (FTIR) spectroscopy were used to characterize the synthesized compound. The synthesized CoB compound was first tested alone at varying weight ratios to investigate its flammability. Subsequently, it was used in combination with a RP-containing flammability additive, and its synergistic interactions were evaluated using UL- 94, limiting oxygen index (LOI), and cone calorimeter tests. The flammability tests showed that the combination containing 1% CoB and 9% RP demonstrated the highest resistance to combustion. In this sample, a V0 rating was achieved in the UL-94 vertical test; LOI increased by 1.5-2.0 units compared to the additive-free epoxy, and the heat release rate (HRR) was approximately 30% lower in the calorimeter test compared to the additive-free epoxy resin.

Anahtar Kelimeler

• Epoxy resin
• Red phosphorus
• Cobalt borate
• Metal borate synthesis
• Flame retardancy

Destekleyen Kurum

Bartın University Project Technology Office

Proje Numarası

2021K12-169131/06

Etik Beyan

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper

Teşekkür

This study was financially supported by Bartın University Project Technology Office within the scope of the Regional Development Projects with project number 2021K12-169131/06

Kobalt Borat Bileşiğinin Sentezlenmesi ve Kırmızı Fosfor ile Sinerjik Etki Sağlanarak Epoksi Esaslı Kompozitlere Yanmazlık Özelliğinin Kazandırılması

Öz

Çalışma kapsamında erimiş tuz destekli borotermal indirgeme yöntemiyle sentezlenen kobalt borat bileşiğinin, epoksi reçinelerinde tek başına kullanıldığında güç tutuşurluk etkinliğine ek olarak, kırmızı fosfor yanmazlık eklentisi ile sinerjik etkinliği araştırılmıştır. Araştırmanın ilk aşamasında, kobalt borat bileşiğinin sentez işlemi, kobalt metalin tuzu ve borik asit türevleri kullanılarak sulu ortamda otoklav içinde 240oC sıcaklıkta sıcaklık-katı reaksiyonla üretilme yöntemi ile gerçekleştirilmiştir. Sentezlenen bileşiğin karakterize edilmesinde X-ışını analizi (XRD), SEM-EDX analizi, termogravimetrik analiz (TGA) ve Fourier dönüşümlü kızılötesi ışın (FTIR) spektroskopisi kullanılmıştır. Sentezi gerçekleştirilen Co3B2O6 bileşiği, öncelikle tek başına ağırlıkça değişik oranlarda kullanılarak güç tutuşurluk etkileri incelenmiş olup, daha sonraki aşamada ise kırmızı fosfor içeren güç tutuşurluk eklentisi ile birlikte kullanılarak sinerjik etkileşimleri UL-94, sınırlayıcı oksijen indisi (LOI) ve konik kalorimetre testleri ile değerlendirilmiştir. Yanmazlık testleri sonucunda, %1 oranında kobalt borat ile %9 oranında kırmızı fosfor içeren kombinasyon, yanmaya karşı direnç açısından ön plana çıkmıştır. Bu numunede, UL-94 dikey testinde V0 değerine ulaşılmış, sınırlayıcı oksijen indisi (LOI) değerinde eklentisiz epoksiye kıyasla 1,5-2,0 birim artış olup kalorimetre testinde eklentisiz epoksiye göre %30 civarında daha düşük ısı salınım miktarı (HRR) gözlenmiştir.

Anahtar Kelimeler

• Epoksi reçine
• Kırmızı fosfor
• Kobalt borat
• Metal borat sentezi
• Yanmazlık

Destekleyen Kurum

Bartın Üniversitesi Proje Teknoloji Ofisi

Proje Numarası

2021K12-169131/06

Etik Beyan

Yazarlar, bu makalede bildirilen çalışmayı etkilemiş olabilecek bilinen herhangi bir çıkar çatışması veya kişisel ilişkiye sahip olmadıklarını beyan etmektedir.

Teşekkür

Bu çalışma, Bartın Üniversitesi Proje Teknoloji Ofisi tarafından Bölgesel Kalkınma Projeleri kapsamında 2021K12-169131/06 proje numarasıyla mali olarak desteklenmiştir.

Kaynakça

1. Mouritz, A. P., & Gibson, A. G. (2006). Fire properties of polymer composite materials. Springer Dordrecht. https://doi.org/10.1007/978-1-4020-5356-6
2. Shen, K. K. (2024). Boron-containing flame retardants for epoxy thermosets and composites. In Y. Hu & X. Wang (Eds.), Non-halogenated Flame-Retardant Technology for Epoxy Thermosets and Composites, (pp. 191-207). Woodhead Publishing. https://doi. org/10.1016/B978-0-443-16046-2.00006-7
3. Morgan, A. B., & Gilman, J. W. (2013). An overview of flame retardancy of polymeric materials: application, technology, and future directions. Fire and Materials, 37(4), 259-279. https://doi.org/10.1002/fam.2128
4. Gérard, C., Fontaine, G., & Bourbigot, S. (2010). New trends in reaction and resistance to fire of fire-retardant epoxies. Materials, 3(8), 4476-4499. https:// doi.org/10.3390/ma3084476
5. Kahraman, M. V., Kayaman-Apohan, N., Arsu, N., & Güngör, A. (2004). Flame retardance of epoxy acrylate resin modified with phosphorus containing compounds. Progress in Organic Coatings, 51(3), 213-219. https:// doi.org/10.1016/j.porgcoat.2004.07.014
6. Liu, Y. L., Hsiue, G. H., Lee, R. H., & Chiu, Y. S. (1997). Phosphorus-containing epoxy for flame retardant. III: Using phosphorylated diamines as curing agents. Journal of Applied Polymer Science, 63(7), 895-901. https://doi.org/10.1002/(SICI)1097- 4628(19970214)63:7<895::AID-APP9>3.0.CO;2-L
7. Ye, G., Huo, S., Wang, C., Shi, Q., Yu, L., Liu, Z., & Wang, H. (2021). A novel hyperbranched phosphorus-boron polymer for transparent, flame-retardant, smoke-suppressive, robust yet tough epoxy resins. Composites Part B: Engineering, 227, 109395. https:// doi.org/10.1016/j.compositesb.2021.109395
8. Wu, G. M., Schartel, B., Kleemeier, M., & Hartwig, A. (2012). Flammability of layered silicate epoxy nanocomposites combined with low-melting inorganic ceepree glass. Polymer Engineering & Science, 52(3), 507-517. https://doi.org/10.1002/pen.22111

9. Von Gentzkow, W., Huber, J., Kapitza, H., & Rogler, W. (1997). Halogen-free flame-retardant plastics for electronic applications. Journal of Vinyl and Additive Technology, 3(2), 175-178. https://doi.org/10.1002/ vnl.10185
10. Toldy, A., Toth, N., Anna, P., & Marosi, G. (2006). Synthesis of phosphorus-based flame retardant systems and their use in an epoxy resin. Polymer Degradation and Stability, 91(3), 585-592. https://doi. org/10.1016/j.polymdegradstab.2005.02.025
11. Riahipour, R., Nemati, M. S., Zadehmohamad, M., Abadyan, M. R., Tehrani, M., & Baniassadi, M. (2022). Mechanical properties of an epoxy-based coating reinforced with silica aerogel and ammonium polyphosphate additives. Polymers and Polymer Composites, 30, 1-10. https://doi. org/10.1177/09673911211069019
12. Tang, S., Qian, L., Qiu, Y., & Dong, Y. (2018). Synergistic flame-retardant effect and mechanisms of boron/ phosphorus compounds on epoxy resins. Polymers for Advanced Technologies, 29(1), 641-648. https://doi. org/10.1002/pat.4174
13. Dike, A. S., Tayfun, U., & Dogan, M. (2017). Influence of zinc borate on flame retardant and thermal properties of polyurethane elastomer composites containing huntite-hydromagnesite mineral. Fire and Materials, 41(7), 890-897. https://doi.org/10.1002/fam.2428.
14. Xu, Z., Chu, Z., & Yan, L. (2018). Enhancing the flame-retardant and smoke suppression properties of transparent intumescent fire-retardant coatings by introducing boric acid as synergistic agent. Journal of Thermal Analysis and Calorimetry, 133(3), 1241-1252.
15. Erdem, A., & Doğan, M. (2023). Influence of boron bearing fillers on flame retardancy properties of huntite hydromagnesite filled ductile PLA biocomposites. Journal of Boron, 8(1), 16-24. https://doi.org/10.30728/ boron.1135702.
16. Aydın, D. Y., Gürü, M., Ayar, B., & Çakanyıldırım, Ç. (2016). Bor bileşiklerinin alev geciktirici ve yüksek sıcaklığa dayanıklı pigment olarak uygulanabilirliği. Journal of Boron, 1(1), 33-39. https://izlik.org/ JA97JB24FB
17. Le Huy, C. H., Thanh, A. T., & Nhat, H. N. (2025). Properties of epoxy polymer materials reinforced with boric acid and nano silica. Polímeros, 35(4), e20250047. https://doi.org/10.1590/0104-1428.20250032
18. Wang, M., Xiao, G., Chen, C., Wang, F., Zhong, F., Chen, C., & Zou, R. (2023). Crystallization of sodium metaborate on the surface of layered double hydroxide imparts high flame retardancy properties to epoxy coatings. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 657, 130589. https://doi. org/10.1016/j.colsurfa.2022.130589
19. Wu, K., Zhang, Y. K., Zhang, K., Shen, M. M., & Hu, Y. (2012). Effect of microencapsulation on thermal properties and flammability performance of epoxy composite. Journal of Analytical and Applied Pyrolysis, 94, 196-201. https://doi.org/10.1016/j.jaap.2011.12.009
20. Ilyas, R. A., Sapuan, S. M., Asyraf, M. R. M., Dayana, D. A. Z. N., Amelia, J. J. N., Rani, M. S. A., & Razman, M. R. (2021). Polymer composites filled with metal derivatives: A review of flame retardants. Polymers, 13(11), 1701. https://doi.org/10.3390/polym13111701
21. Weil, E. D., & Levchik, S. (2004). A review of current flame retardant systems for epoxy resins. Journal of Fire Sciences, 22(1), 25-40. https://doi. org/10.1177/0734904104038107
22. Mathews, L. D., Capricho, J. C., Salim, N., Parameswaranpillai, J., Moinuddin, K., & Hameed, N. (2023). Intrinsically modified self-extinguishing fire-retardant epoxy resin using boron-polyol complex. Journal of Polymer Research, 30(7), 271. https://doi. org/10.1007/s10965-023-03641-6
23. Gibertini, E., Carosio, F., Aykanat, K., Accogli, A., Panzeri, G., & Magagnin, L. (2021). Silica-encapsulated red phosphorus for flame retardant treatment on textile. Surfaces and Interfaces, 25, 101252. https://doi. org/10.1016/j.surfin.2021.101252
24. Savas, L. A., Deniz, T. K., Tayfun, U., & Dogan, M. (2017). Effect of microcapsulated red phosphorus on flame retardant, thermal and mechanical properties of thermoplastic polyurethane composites filled with huntite&hydromagnesite mineral. Polymer Degradation and Stability, 135, 121-129. https://doi.org/10.1016/j. polymdegradstab.2016.12.001
25. Cheng, C., Yan, J., Lu, Y., Ma, W., Li, C., & Du, S. (2021). Effect of chitosan/lignosulfonate microencapsulated red phosphorus on fire performance of epoxy resin. Thermochimica Acta, 700, 178931. https://doi. org/10.1016/j.tca.2021.178931
26. Arslan, Ç., & Doğan, M. (2023). Flame retardancy of basalt fiber-reinforced PBT composite: effect of red phosphorus and TiO2 synergism. Journal of Thermal Analysis and Calorimetry, 148(19), 10151-10161. https://doi.org/10.1007/s10973-023-12370-3
27. Yang, B., Li, X., Wang, L., Zhang, Y., Cui, J., Guo, J., & Tian, L. (2019). An efficient flame retardant for epoxy resin: preparation and pyrolytic behaviour. High Performance Polymers, 31(9-10), 1009-1019. https:// doi.org/10.1177/0954008318815730
28. Gao, M., Wu, W., & Wu, F. (2012). Thermal degradation and flame retardance of epoxy resins containing a microencapsulated flame retardant. Journal of Vinyl and Additive Technology, 18(1), 40-45. https://doi. org/10.1002/vnl.20301
29. Formicola, C., De Fenzo, A., Zarrelli, M., Giordano, M., & Antonucci, V. (2011). Zinc-based compounds as smoke suppressant agents for an aerospace epoxy matrix. Polymer International, 60(2), 304-311. https:// doi.org/10.1002/pi.2949
30. Formicola, C., De Fenzo, A., Zarrelli, M., Frache, A., Giordano, M., & Camino, G. (2009). Synergistic effects of zinc borate and aluminium trihydroxide on flammability behaviour of aerospace epoxy system. Express Polymer Letters, 3(6), 376-384. https://dx.doi. org/10.3144/expresspolymlett.2009.47
31. Kim, J., Yoo, S., Bae, J. Y., Yun, H. C., Hwang, J., & Kong, B. S. (2003). Thermal stabilities and mechanical properties of epoxy molding compounds (EMC) containing encapsulated red phosphorous. Polymer Degradation and Stability, 81(2), 207-213. https://doi. org/10.1016/S0141-3910(03)00090-9
32. Ishii, T., Kokaku, H., Nagai, A., Nishita, T., & Kakimoto, M. (2006). Calcium borate flame retardation system for epoxy molding compounds. Polymer Engineering & Science, 46(6), 799-806. https://doi.org/10.1002/ pen.20424
33. Wang, J. S., Liu, Y., Zhao, H. B., Liu, J., Wang, D. Y., Song, Y. P., & Wang, Y. Z. (2009). Metal compound-enhanced flame retardancy of intumescent epoxy resins containing ammonium polyphosphate. Polymer Degradation and Stability, 94(4), 625-631. https://doi. org/10.1016/j.polymdegradstab.2009.01.006
34. Sabet, M. (2024). Advancements in halogen-free polymers: Exploring flame retardancy, mechanical properties, sustainability, and applications. Polymer- Plastics Technology and Materials, 63(13), 1794-1818. https://doi.org/10.1080/25740881.2024.2359633
35. Unlu, M.S., Tayfun, U., Yildirim, B., & Dogan, M. (2017). Effect of boron compounds on fire protection properties of epoxy based intumescent coating. Fire and Materials, 41(1), 17-28. https://doi.org/10.1002/fam.2360
36. Zou, X., Zhang, W., Zhou, X., Song, K., Ge, X., & Zheng, W. (2022). The surface of metal boride tinted by oxygen evolution reaction for enhanced water electrolysis. Journal of Energy Chemistry, 72, 509-515. https://doi. org/10.1016/j.jechem.2022.05.039
37. Zoli, L., Galizia, P., Silvestroni, L., & Sciti, D. (2018). Synthesis of group IV and V metal diboride nanocrystals via borothermal reduction with sodium borohydride. Journal of the American Ceramic Society, 101(6), 2627- 2637. https://doi.org/10.1111/jace.15401
38. Beckett, M. A. (2016). Recent advances in crystalline hydrated borates with non-metal or transition-metal complex cations. Coordination Chemistry Reviews, 323, 2-14. https://doi.org/10.1016/j.ccr.2015.12.012
39. Dogan, M., Dogan, S. D., Savas, L. A., Ozcelik, G., & Tayfun, U. (2021). Flame retardant effect of boron compounds in polymeric materials. Composites Part B: Engineering, 222, 109088. https://doi.org/10.1016/j. compositesb.2021.109088
40. Cinausero, N., Lopez-Cuesta, J.-M., Laoutid, F., Piechaczyk, A., & Leroy, E. (2008). Synergy between nanometric alumina and organoclay in conventional fire retardant systems for ethylene-vinyl acetate check access. In T. R. Hull & B. K. Kandola (Eds.), Fire retardancy of polymers: New strategies and mechanisms (pp. 49-58). RSC Publishing. https://doi. org/10.1039/9781847559210
41. Tsai, M. C., Chen, Y. W., Kang, B. C., Wu, J. C., & Leu, L. J. (1991). Hydrodesulfurization and hydrodemetalation reactions of residue oils over cobalt-molybdenum/ aluminum borate catalysts in a trickle bed reactor. Industrial & Engineering Chemistry Research, 30(8), 1801-1810. https://doi.org/10.1021/ie00056a017
42. Rowsell, J. L. C., Taylor, N. J., & Nazar, L. F. (2003). Crystallographic investigation of the Co-B-O system. Journal of Solid State Chemistry, 174(1), 189-197. https://doi.org/10.1016/S0022-4596(03)00217-2
43. Kartal, L. (2023). Cobalt boride (Co2B) particle synthesis by one-step carbothermic reduction. Hittite Journal of Science and Engineering, 10(3), 229-235. https://doi.org/10.17350/hjse19030000311
44. Lin, H. K., Wang, C. B., Chiu, H. C., & Chien, S. H. (2003). In situ FTIR study of cobalt oxides for the oxidation of carbon monoxide. Catalysis Letters, 86(1), 63-68. https://doi.org/10.1023/A:1022659025068
45. Xiong, G., Lan, G., Wang, H., & Huang, C. (1993). Infrared reflectance and Raman spectra of lithium triborate single crystal. Journal of Raman Spectroscopy, 24(11), 785-789. https://doi.org/10.1002/jrs.1250241111
46. Gaafar, M. S., Shaarany, I., & Alharbi, T. (2014). Structural investigations on some cadmium-borotellurate glasses using ultrasonic, FT-IR and X-ray techniques. Journal of Alloys and Compounds, 616, 625-632. https://doi. org/10.1016/j.jallcom.2014.07.145
47. Abo-Naf, S. M. (2012). FTIR and UV-VIS optical absorption spectra of gamma-irradiated MoO3- doped lead borate glasses. Journal of Non-crystalline Solids, 358(2), 406-413. https://doi.org/10.1016/j. jnoncrysol.2011.10.013
48. Wen, S. J., Richardson, T. J., Ma, L., Striebel, K. A., Boss, P. N., & Cairns, E. J. (1996). FTIR spectroscopy of metal oxide insertion electrodes: A New diagnostic tool for analysis of capacity fading in secondary cells. Journal of the Electrochemical Society, 143(6), L136. https://doi.org/10.1149/1.1836902
49. Long, B., Chen, J., Sharshir, S. W., Ibrahim, L., Zhou, W., Wang, C., & Yuan, Z. (2024). The mechanism and challenges of cobalt-boron-based catalysts in the hydrolysis of sodium borohydride. Journal of Materials Chemistry A, 12(10), 5606-5625. https://doi. org/10.1039/D3TA07308D
50. Genç, A., Köse, D. A., & Şahin, O. (2023). Synthesis and characterization of transition metal complex cation heptaborate structures. Journal of Boron, 8(3), 105- 113. https://doi.org/10.30728/boron.1291141
51. Montiel, M. G., Santiago-Jacinto, P., Góngora, J. D., Reguera, E., & Rodríguez-Gattorno, G. (2011). Synthesis and thermal behavior of metallic cobalt micro and nanostructures. Nano-Micro Letters, 3(1), 12-19. https://doi.org/10.1007/BF03353646
52. Malinina, E. A., Goeva, L. V., Buzanov, G. A., Avdeeva, V. V., Efimov, N. N., Kozerozhets, I. V., & Kuznetsov, N. T. (2019). Synthesis and physicochemical properties of binary cobalt (II) borides. Thermal reduction of precursor complexes [CoL n][B10H10](L= H2O, n= 6; N2H4, n= 3). Russian Journal of Inorganic Chemistry, 64(11), 1325- 1334. https://doi.org/10.1134/S0036023619110123
53. Beckett, M. A. (2016). Recent advances in crystalline hydrated borates with non-metal or transition-metal complex cations. Coordination Chemistry Reviews, 323, 2-14. https://doi.org/10.1016/j.ccr.2015.12.012
54. Li, P., Li, L., Ji, L., Dang, L., Lan, S., & Zhu, D. (2023). Functionalized magnesium hydroxide with zinc borate and 3-aminopropyltriethoxysilane for enhanced flame retardant and smoke suppressant properties of epoxy resins. Journal of Applied Polymer Science, 140(23), e53941. https://doi.org/10.1002/app.53941
55. İpek, Y. (2021). Influence of particle size, additive ratio and chemical structure of zinc borate on thermal and mechanical properties of polyvinyl chloride. Journal of Boron, 6(4), 387-394. https://doi.org/10.30728/ boron.961843
56. Huy, C. H. L., & Thanh, A. T. (2022). Characteristics of mechanical properties and thermal behavior of epoxy nanocomposites and coatings by zinc borate, nano silica, and hardener. ACS Omega, 7(43), 38299-38310. https://doi.org/10.1021/acsomega.2c02462
57. Arada, B., Lin, S. C., & Pearce, E. M. (1979). Epoxy resins IV: The stability of the epoxy-triethanolamine borate system. International Journal of Polymeric Materials, 7(3-4), 167-184. https://doi. org/10.1080/00914037908077924
58. Ruckdäschel, H. (2022). Modeling glass transition temperatures of epoxy systems: A machine learning study. Journal of Materials Science, 57(29), 13991- 14002. https://doi.org/10.1007/s10853-022-07372-9
59. Peng, H., Wang, D., Zhang, L., Li, M., Liu, M., Wang, C., & Fu, S. (2020). Amorphous cobalt borate nanosheets grown on MoS2 nanosheet for simultaneously improving the flame retardancy and mechanical properties of polyacrylonitrile composite fiber. Composites Part B: Engineering, 201, 108298. https://doi.org/10.1016/j. compositesb.2020.108298
60. Zou, B., Qiu, S., Qian, Z., Wang, J., Zhou, Y., Xu, Z., & Xing, W. (2021). Phosphorus/nitrogen-codoped molybdenum disulfide/cobalt borate nanostructures for flame-retardant and tribological applications. ACS Applied Nano Materials, 4(10), 10495-10504. https:// doi.org/10.1021/acsanm.1c01999
61. Chen, C., Bai, X., Xiao, G., Zhong, F., Ren, B., Zhao, G., & Mou, C. (2025). Phosphorus-nitrogen doped UiO-66/cobalt-nickel borate nanoflowers combined MXene improves flame protection of waterborne epoxy coatings. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 728(2), 138667. https://doi. org/10.1016/j.colsurfa.2025.138667
62. Dogan, M., & Unlu, S. M. (2014). Flame retardant effect of boron compounds on red phosphorus containing epoxy resins. Polymer Degradation and Stability, 99, 12-17. https://doi.org/10.1016/j.polymdegradstab.2013.12.017
63. Hamciuc, C., Vlad-Bubulac, T., Serbezeanu, D., Macsim, A. M., Lisa, G., Anghel, I., & Şofran, I. E. (2022). Effects of phosphorus and boron compounds on thermal stability and flame retardancy properties of epoxy composites. Polymers, 14(19), 4005. https://doi. org/10.3390/polym14194005
64. Singh, M. K., Rangappa, S. M., Misra, M., Mohanty, A. K., & Siengchin, S. (2025). Recent advancements in nanostructured flame-retardants: Types, mechanisms, and applications in polymer composites. Nano- Structures & Nano-Objects, 42, 101468. https://doi. org/10.1016/j.nanoso.2025.101468