Microencapsulation is a widely used method for making healing agents used in self-healing composites. In this study, a novel two-stage process was used to make double-walled microcapsules. Dicyclopentadiene–urea formaldehyde (DCPD–UF) microcapsules were synthesized by in situ polymerization of oil-in-water emulsion followed by siloxane coating through ‘sol–gel process’ (DCPD–UF–siloxane microcapsules). Average diameter of microcapsules, UF shell thickness and siloxane coating thickness were found to be 300, 1.4 and 16 µm, respectively. The effect of addition of microcapsules on rheological properties of epoxy was studied. Breaking pattern of single-walled and double-walled microcapsules immersed in epoxy was analyzed by continuous monitoring of the deformation behavior through a rheometer–microscope arrangement, confirming improved mechanical properties of the double-walled microcapsules. In this study, epoxy resin cast specimens with and without microcapsules were prepared and the effect of microcapsules on mechanical properties was examined. Epoxy specimens with double-walled microcapsules were found to be having improved mechanical properties compared to those with single-walled microcapsules. Finally, healing efficiency of DCPD–UF–siloxane microcapsules in epoxy was observed to be marginally higher, and therefore, this double-walled microcapsule system is shown to be a promising candidate for further self-healing composite investigations.
Smart material Double-walled microcapsules Sol–gel process Siloxane coating Rheology Mechanical properties
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This research work was funded by a sponsored project by Dynamics and Adaptive Structures group, STTD Division—National Aerospace Laboratories (CSIR-NAL), Bangalore, India. Characterization of samples was done at Polymer Engineering and Colloidal Science (PECS) laboratory, Department of Chemical engineering, IIT Madras, India. We acknowledge Mr. Sashikumar Ramamirtham and Ms. K. A. Ramya (IIT Madras) for their technical support in carrying out the rheometer experiments. We acknowledge Mrs. R.V Lakshmi and Mr. S. Vedaprakash (CSIR-NAL, Bangalore) for their technical contribution in siloxane coating and resin casting, respectively.
White SR, Sottos NR, Geubelle PH, Moore JS, Kessler MR, Sriram SR, Brown EN, Viswanathan S (2001) Autonomic healing of polymer composites. Nature 409:794–797CrossRefGoogle Scholar
Blaiszik BJ, Kramer SLB, Olugebefola SC, Moore JS, Sottos NR, White SR (2010) Self-healing polymers and composites. Annu Rev Mater Res 20:179–211CrossRefGoogle Scholar
Hia IL, Vahedi V, Pasbakhsh P (2016) Self-healing polymer composites: prospects, challenges and applications. Polym Rev 56:225–261CrossRefGoogle Scholar
Brown EN, Kessler MR, Sottos NR, White SR (2003) In situ poly (urea-formaldehyde) microencapsulation of dicyclopentadiene. J Microencapsul Micro Nano Carr 20:719–730CrossRefGoogle Scholar
Keller MW, Sottos NR (2006) Mechanical properties of microcapsules used in a self-healing polymer. Exp Mech 46:725–733CrossRefGoogle Scholar
Blaiszik BJ, Sottos NR, White SR (2008) Nanocapsules for self-healing materials. Compos Sci Technol 68:978–986CrossRefGoogle Scholar
Kessler MR, Sottos NR, White SR (2003) Self-healing structural composite materials. Compos Part A 34:743–753CrossRefGoogle Scholar
Leyang L, Schlangen E, Yang Z, Xing F (2016) Micromechanical properties of a new polymeric microcapsule for self-healing cementitious materials. Materials 9:1025CrossRefGoogle Scholar
Chowdhury RA, Hosura MV, Nuruddin M, Narteh AT, Kumar A, Boddu V, Jeelani S (2015) Self-healing epoxy composites: preparation, characterization and healing performance. J Mater Res Technol 4:33–43CrossRefGoogle Scholar
Guadagno L, Raimondo M, Vietri U, Naddeo C, Stojanovic A, Sorrentino A, Binder WH (2016) Evaluation of the mechanical properties of microcapsule-based self-healing composites. Int J Aerosp Eng 2016, 7817962Google Scholar
Sun D, An J, Wu G, Yang J (2015) Double-layered reactive microcapsules with excellent thermal and non-polar solvent resistance for self-healing coatings. J Mater Chem A 3:4435–4444CrossRefGoogle Scholar
Caruso MM, Blaiszik BJ, Jin H, Schelkopf SR, Stradley DS, Sottos NR, White SR, Moore JS (2010) Robust, double-walled microcapsules for self-healing polymeric materials. ACS J Appl Mater Interfaces 2:1195–1199CrossRefGoogle Scholar
Jin H, Mangun CL (2014) Thermally stable autonomous healing in epoxy using a dual micro-capsule system. Adv Mater 26:282–287CrossRefGoogle Scholar
Mookhoek SD, Blaiszik BJ, Fischer HR, Sottos NR, White SR, Zwaag SV (2008) Peripherally decorated binary microcapsules containing two liquids. J Mater Chem 18:5390–5539CrossRefGoogle Scholar
Kang S, Baginska M, White SR, Sottos NR (2015) Core–shell polymeric microcapsules with superior thermal and solvent stability. ACS Appl Mater Interfaces 7:10952–10956CrossRefGoogle Scholar
Sarkar S, Kim B (2018) Facile and cost-effective synthesis of isocyanate microcapsules via polyvinyl alcohol-mediated interfacial polymerization and their application in self-healing materials. Polym Compos 39:636–644CrossRefGoogle Scholar
Rzeszutko AA, Brown EN, Sottos NR (2003) Tensile properties of self-healing epoxy. In: Proceedings of fifth annual under graduate research conference in mechanics. University of Illinois, 25th April, pp 27–33Google Scholar
Then S, Neon GS, Abu Kais NH (2011) Performance of melamine modified urea–formaldehyde microcapsules in a dental host material. J Appl Polym Sci 122:2557–2562CrossRefGoogle Scholar
Marialuigia R, Liberata G (2013) Healing efficiency of epoxy-based materials for structural applications. Polym Compos 34:1525–1532CrossRefGoogle Scholar