Synthesis of DOPO Derivatives for the Fabrication of Flame Retardant Epoxy Composites
Main Article Content
Abstract
Four flame retardant DOPO derivatives were succesfully synthesized by Pudovik reaction, including 6,6'-(([1,1'-biphenyl]-4,4'-diylbis(azanediyl))bis (thiophen-2-ylmethylene))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) 5a, 6,6'-(((sulfonylbis(4,1-phenylene))bis(azanediyl)) bis(thiophen-2-ylmethylene))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) 5b, 6,6'-((1,4-phenylenebis(azanediyl))bis(furan-2ylmethylene))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) 5c and 6,6'-((oxybis(4,1-phenylene))bis(1-(thiophen-2-yl)ethane-2,1-diyl))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) 5d. Among them, flame retardants 5a and 5d were synthesized for the first time. DOPO derivatives were combined with functionalized ammonium polyphosphate using polyethyleneimine (PEI-APP) as flame retardant systems for epoxy composites. The combination of compound 5a and PEI-APP gave the materials with the best flame retardancy. 6wt% of PEI-APP/6% of 5a promoted the composite material to V-0 rating in UL-94 vertical burning test and the limiting oxygen index reached 28.9%. The impact of flame retardants towards the mechanical and physical properties of epoxy resin was also evaluated. The combination of 5a with PEI-APP showed the least decrease in mechanical strength of epoxy composite.
Keywords:
DOPO-based flame retardant, Pudovik reaction, flame retardancy, epoxy resin, PEI-APP.
References
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Non-Halogenated Flame Retardant use, in A. B. Morgan (Ed.), Non-Halogenated Flame Retardant Handbook, Wiley, New Jersey, 2022, pp. 1-22.
[3] K. A. Salmeia, S. Gaan, An Overview of some Recent Advances in DOPO-Derivatives: Chemistry and Flame Retardant Applications, Polym, Degrad, Stab, Vol. 113, 2015, pp. 119-134, https://doi.org/10.1016/j.polymdegradstab.2014.12.014.
[4] S. Wendels, T. Chavez, M. Bonnet, K. A. Salmeia, S. Gaan, Recent Developments in Organophosphorus Flame Retardants Containing P-C Bond and Their Applications, Materials, Vol. 10, 2017, pp. 784, https://doi: 10.3390/ma10070784.
[5] X. Xu, S. Wang, S. Ma, W. Yuan, Q. Li, J. Feng, J. Zhu, Vanillin-Derived Phosphorus-Containing Compounds and Ammonium Polyphosphate as Green Fire-Resistant Systems for Epoxy Resins with Balanced Properties, Polym, Adv, Technol, Vol. 30, 2019, pp. 264-278, https://doi.org/10.1002/pat.4461.
[6] P. Wang, F. Yang, L. Li, Z. Cai, Flame-Retardant Properties and Mechanisms of Epoxy Thermosets Modified with Two Phosphorus-Containing Phenolic Amines, J. Appl, Polym, Sci, Vol. 133, 2016, pp. 43953,
https://doi.org/10.1002/app.43953.
[7] L. Li, S. Li, H. Wang, Z. Zhu, X. Yin, J. Mao, Low Flammability and Smoke Epoxy Resins with a Novel DOPO-Based Imidazolone Derivative, Polym, Adv, Technol, Vol. 32, 2021, pp. 294-303, https://doi.org/10.1002/pat.5085.
[8] H. Wang, S. Li, Z. Zhu, X. Yin, L. Wang, Y. Weng, X. Wang, A Novel DOPO-Based Flame Retardant Containing Benzimidazolone Structure with High Charring Ability Towards Low Flammability and Smoke Epoxy Resins, Polym, Degrad, Stab, Vol. 183, 2021, pp. 109426, https://doi.org/10.1016/j.polymdegradstab.2020.109426.
[9] Y. Q. Shi, T. Fu, Y. J. Xu, D. F. Li, X. L. Wang, Y. Z. Wang, Novel Phosphorus-Containing Halogen-Free Ionic Liquid Toward Fire Safety Epoxy Resin with Well-Balanced Comprehensive Performance, Chem, J. Eng, Vol. 354, 2018, pp. 208-219, https://doi.org/10.1016/j.cej.2018.08.023.
[10] Z. Yao, L. Qian, Y. Qiu, Y. Chen, B. Xu, Flame Retardant and Toughening Behaviors of Bio‐Based DOPO‐Containing Curing Agent in Epoxy Thermoset, Polym, Adv, Technol, 31, 2019, pp. 461-471,
https://doi.org/10.1002/pat.4782.
[11] D. Santiago, X. F. Francos, X. Ramis, J. M. Salla, M. Sangermano, Comparative Curing Kinetics and Thermal-Mechanical Properties of DGEBA Thermosets Cured with a Hyperbranched Poly(ethyleneimine) and an Aliphatic Triamine, Thermochim, Acta, Vol. 526, 2011, pp. 9-21, https://doi.org/10.1016/j.tca.2011.08.016.
[12] X. F. Francos, D. Santiago, F. Ferrando, X. Ramis, J. M. Salla, A. Serra, M. Sangermano, Xavier Fernández-Francos, David Santiago, Francesc Ferrando, Xavier Ramis, Josep M. Salla, Àngels Serra, Marco Sangermano, Network Structure and Thermomechanical Properties of Hybrid DGEBA Networks Cured with 1-methylimidazole and Hyperbranched Poly(ethyleneimine)s, J. Polym, Sci. B: Polym, Phys, Vol. 50, 2012, pp. 1489-1503, https://doi.org/10.1002/polb.23145.
[13] F. N. Nguyen, A. M. Saks, J. C. Berg, Use of Polyethyleneimine Dendrimer as a Novel Graded-Modulus Interphase Material in Polymeric Composites, J. Adhes, Sci. Technol, Vol. 21, 2007, pp. 1375-1393,
https://doi.org/10.1163/156856107782313610.
[14] F. N. Nguyen, J. C. Berg, Novel Core-Shell (Dendrimer) Epoxy Tougheners: Processing and Hot-Wet Performance, Compos, Part a Appl, Sci, Manuf, Vol. 39, 2008, pp. 1007-1011, https://doi.org/10.1016/j.compositesa.2008.03.005.
[15] F. G. Garcia, B. G. Soares, V. J. R. R. Pita, P. Sánchez, J. Rieumont, Mechanical Properties of Epoxy Networks Based on DGEBA and Aliphatic Amines, J. Appl, Polym, Sci, Vol. 106, 2007, pp. 2047-2055, https://doi.org/10.1002/app.24895.
[16] C. H. Lin, C. C. Feng, T. Y. Hwang, Preparation, Thermal Properties, Morphology, and Microstructure of Phosphorus-Containing Epoxy/SiO2 and Polyimide/SiO2 Nanocomposites, Eur, J. Polym, Vol. 43, 2007, pp. 725-742, https://doi.org/10.1016/j.eurpolymj.2006.12.030.
[17] S. Yang, J. Wang, S. Huo, M. Wang, J. Wang, Preparation and Flame Retardancy of a Compounded Epoxy Resin System Composed of Phosphorus/Nitrogen-Containing Active Compounds, Polym, Degrad, Stab, Vol. 121, 2015, pp. 398-406, https://doi.org/10.1016/j.polymdegradstab.2015.10.006.
[18] Y. Tan, Z. B. Shao, L. X. Yu, Y. J. Xu, W. H. Rao, L. Chen, Y. Z. Wang, Polyethyleneimine Modified Ammonium Polyphosphate Toward Polyamine-Hardener for Epoxy Resin: Thermal Stability, Flame Retardance and Smoke Suppression, Polym, Degrad, Stab, Vol. 131, 2016, pp. 62-70, https://doi.org/10.1016/j.polymdegradstab.2016.07.004.