A Dual-Functional Surfactant Strategy for High-Yield Synthesis of Epoxy-Loaded Melamine Formaldehyde Microcapsules

Document Type : Original Article

Authors

Department of Resin and Additives, Institute for Color Science and Technology, P.O. Box: 16765-654, Tehran, Iran

Abstract

The encapsulation of various healing agents can be achieved using amino resins as the shell material. For optimal encapsulation efficiency, pH adjustment is a critical parameter. In this study, epoxy resin was encapsulated via in-situ interfacial polymerization in an oil-in-water emulsion. A dual-functional surfactant featuring a quaternary ammonium moiety serving as the hydrophilic head group, combined with precise pH control, was employed. In addition to catalyzing amino resin formation at the interface, this surfactant significantly suppresses the formation of unwanted nanoparticles. Furthermore, citric acid, used for pH adjustment, also acts as a surfactant due to its structural properties, preferentially localizing at the epoxy/water interface.As a result,a high encapsulation efficiency of 92 % isachieved,which displaysan improvement of about 25 % over conventional ammonium chloride-catalyzed methods. The core-to-wall ratio was systematically optimized, with a 1:2 ratio yielding the highest encapsulation efficiency (92 %), while a 1:3 ratio led to a 15 % efficiency drop. Furthermore, stirring rate modulation enabled size control, producing capsules ranging from 1 μm (at 1100 rpm) to 2 μm (at 500 rpm). Surfactant concentration critically influenced unwanted nano particle formation and encapsulation efficiency where, using 1 wt. % of surfactant, a 92 % encapsulation efficiency was achieved, while concentrations at 10 wt. % caused a 28 % efficiency decline due to excessive aqueous-phase polymerization and capsule aggregation. This work establishes a comprehensive framework for microcapsule synthesis, enablingthe design oftailored microcapsule for high-performance self-healing applications. 

Keywords

Main Subjects

References

  1. Blaiszik B, Kramer S, Olugebefola S, Moore J, Sottos N, White S. Self-Healing Polymers and Composites. Annu Rev Mater Res. 2010;40(1):179-211. https:// doi.org/10.1146/annurev-matsci-070909-104532.
  2. Zhang MQ, Rong MZ. Self-healing Polymers and Polymer Composites. John Wiley & Sons; 2011. ISBN: 978-0-470-49712-8.
  3. Brown EN, Kessler MR, Sottos N.R , White SR. In situ poly(urea-formaldehyde) microencapsulation of dicy-clopentadiene. J Microencapsul. 2003;20(6):719-730. https://doi.org/10.1080/0265204031000154160.
  4. White SR, Sottos NR, Geubelle PH, Moore JS, Kessler MR, Sriram SR, et al. Autonomic healing of polymer composites. Nature. 2001;409(6822):794-7. https://doi. org/10.1038/35057232.
  5. Wool RP. Self-healing materials: a review. Soft Mater. 2008; 4(3):400-18. https://doi.org/10.1039/B711716G.
  6. Yuan YC, Yin T, Rong MZ, Zhang MQ. Self healing in polymers and polymer composites. concepts, realization and outlook: A review. Express Poly Lett. 2008;2(4): 238-250. https://doi.org/10.3144/expresspolymlett.2008. 29.
  7. Kessler MR. Self-healing: A new paradigm in materials design. Proceedings of the institution of mechanical engineers, Part G: J Aeros Eng. 2007;221(4):479-95. https://doi.org/10.1243/09544100JAERO172.
  8. Caruso MM, Delafuente DA, Ho V, Sottos NR, Moore JS, White SR. Solvent-promoted self-healing epoxy taterials. Macromolecules. 2007;40(25):8830-2. https:// doi.org/10.1021/MA701992Z.
  9. Yang J, Keller MW, Moore JS, White SR, Sottos NR. Microencapsulation of Isocyanates for Self-Healing Polymers. Macromolecules. 2008;41(24):9650-9655. https://doi.org/10.1021/ma801718v.
  10. Yao L, Yuan YC, Rong MZ, Zhang MQ. Self-healing linear polymers based on RAFT polymerization. Polymer. 2011;52(14):3137-45. https://doi.org/10.1016/ j.polymer.2011.05.024.
  11. Zhang C, Wang H, Zhou Q. Preparation and characterization of microcapsules based self-healing coatings containing epoxy ester as healing agent. Prog Org Coat. 2018;125:403-10. https://doi.org/10.1016/j. porgcoat. 2018.09.028
  12. Safaei F, Khorasani SN, Rahnama H, Neisiany RE, Koochaki MS. Single microcapsules containing epoxy healing agent used for development in the fabrication of cost efficient self-healing epoxy coating. Prog Org Coat. 2018;114:40-6. https://doi.org/10.1016/j.porgcoat. 2017.09.019.
  13. Altuna FI, Pettarin V, Williams RJJ. Self-healable polymer networks based on the cross-linking of epoxidised soybean oil by an aqueous citric acid solution. Green Chem. 2013;15(12):3360. https://doi. org/10.1039/C3GC41384E.
  14. Chen PW, Cadisch G, Studart AR. Encapsulation of aliphatic amines using microfluidics. Langmuir. 2014; 30(9):2346-50. https://doi.org/10.1021/la500037d.
  15. NguonO, Lagugné-Labarthet F, Brandys FA, Li J, Gillies ER. Microencapsulation byinsitu polymerization of amino resins. Poly Rev. 2018;58(2):326-375. https://doi.org/10.1080/15583724.2017.1364765.
  16. Bolimowski PA, Bond IP, Wass DF. Robust synthesis of epoxy resin-filled microcapsules for application to self-healing materials. Phil Trans R Soc A. 2016;374 (2061):20150083.https://doi.org/10.1098/rsta.2015.0083.
  17. Thakur T, Gaur B, Singha A. Bio-based epoxy/ imidoamine encapsulated microcapsules and their application for high performance self-healing coatings. Prog Org Coat. 2021;159:106436. https://doi.org/10. 1016/j.porgcoat.2021.106436.
  18. Khorasani SN, Ataei S, Neisiany RE. Micro-encapsulation of a coconut oil-based alkyd resin into poly(melamine–urea–formaldehyde) as shell for self-healing purposes. Prog Org Coa. 2017; 111:99-106. https://doi.org/10.1016/j.porgcoat.2017.05.014.
  19. Miyazaki N, Sugai Y, Sasaki K, Okamoto Y. Dual Role of citric acid as a binding inhibitor of anionic surfactant with bivalent cations and co-surfactant on bio-surfactant EOR. Abu Dhabi International Petroleum Exhibition & Conference. 2018. SPE-193277-MS. https://doi.org/10.2118/193277-MS
  20. Zotiadis C, Patrikalos I, Loukaidou V, Korres DM, Karantonis A, Vouyiouka S. Self-healing coatings based on poly(urea-formaldehyde) microcapsules: In situ polymerization, capsule properties and application. Prog Org Coat. 2021;161:106475. https://doi.org/10. 1016/j.porgcoat.2021.106475.
  21. Sharma S, Choudhary V. Poly(melamine-formal-dehyde) microcapsules filled with epoxy resin: effect of M/F ratio on the shell wall stability. Mater Res Express. 2017;4(7):075307. https://doi.org/10.1088/2053-1591/aa 7c8f.
  22. Li W, Zhu X, Zhao N, Jiang Z. Preparation and properties of melamine urea-formaldehyde micro-capsules for self-healing of cementitious materials. Materials. 2016;9(3):152. https://doi.org/10.3390/ma 9030152.
  23. Ollier RP, Alvarez VA. Synthesis of epoxy-loaded poly(melamine-formaldehyde) microcapsules: Effect of pH regulation method and emulsifier selection. Colloids Surfaces A: Physicochem Eng Aspect. 2017; 520:872-82.http://dx.doi.org/doi:10.1016/j.colsurfa.2017.02.053.
  24. Yu H, Zhang Y, Wang M, Li C. Dispersion of poly (urea-formaldehyde)-based microcapsules for self-healing and anticorrosion applications. Langmuir. 2019; 35(24):7871-8.https://doi.org/10.1021/acs.langmuir.9b 00 526.
  25. Jiang W, Zhou G, Wang C, Xue Y, Niu C. Synthesis and self-healing properties of composite microcapsule based on sodium alginate/melamine-phenol–formal-dehyde resin. Const Building Mater. 2021; 271:121541. https://doi.org/10.1016/j.conbuildmat.2020.121541.
  26. Parsaee S, Mirabedini SM, Farnood R, Alizadegan F. Development of self‐healing coatings based on urea‐formaldehyde/polyurethane microcapsules containing epoxy resin. J Appl Poly Sci. 2020;137(41): 49663. https://doi.org/10.1002/app.49663.
  27. Tong X, Zhang T, Yang M, Zhang Q. Preparation and characterization of novel melamine modified poly (urea–formaldehyde) self-repairing microcapsules. Colloids Surf A: Physicochem Eng Aspects. 2010; 371(1-3):91-7. https://doi.org/10.1016/j.colsurfa.2010.09.009.
  28. Zhang H, Wang R, Cheng F. Study on the properties and self-healing ability of asphalt and asphalt mixture containing methanol-modified melamine-formaldehyde microcapsules. Mater Today Commun. 2024;41:111 007. https://doi.org/10.1016/j.mtcomm.2024.111007.
  29. Dong B, Fang G, Ding W, Liu Y, Zhang J, Han N, et al. Self-healing features in cementitious material with urea–formaldehyde/epoxy microcapsules. Construction Building Mater. 2016; 106:608-17. https://doi.org/ 10.1016/j.conbuildmat.2015.12.140.

Files

Share

How to cite

Statistics