Title: “A Novel approach for Synthesis, Characterization and Analysis of DCPD-UF- Siloxane based Double walled Micro-capsules Used in Self-Healing Composites”
Self-Healing composites are smart materials which have the ability of self-detect and self-heal when micro-cracks propagate through the composite surface. Microencapsulation technique is more widely used compared to vascular infiltration method to make self-healing composites. In this study, a novel two-stage process was used wherein dicyclopentadiene – urea formaldehyde (DCPD-UF) micro-capsules have been synthesized by in-situ polymerization of oil-in-water emulsion followed by siloxane coating through “sol-gel process” to make double-walled micro-capsules (DCPD-UF-Siloxane). The average diameter of micro-capsules, UF shell thickness and siloxane coating thickness were found to be 300, 1.4 and 16 µm respectively. The presence of Si and O was confirmed by elemental analysis through SEM-EDAX. The effect of addition of micro-capsules on rheological properties of epoxy was studied. The breaking pattern of the single-walled and double-walled microcapsules immersed in epoxy was analyzed by continuous monitoring of the deformation behavior through a rheometer – microscope arrangement, confirming the better mechanical properties of double-walled micro-capsules. Three types of epoxy resin cast specimens with and without micro-capsules were prepared and the effect of micro-capsules on mechanical properties was examined. Epoxy specimens with double-walled micro-capsules were found to be having better mechanical properties compared to single-walled micro-capsules. This study gives inputs regarding the rheological behavior of DCPD-UF based micro-capsules and their influence on mechanical properties of the resin cast specimens. SEM analysis of broken test specimens suggests that the crack propagation of both test specimens with DCPD-UF and DCPD-UF-Siloxane micro-capsules was initiated by inter-face failure. It was also observed that the siloxane coating is compatible with the epoxy matrix. Key words: Smart material, Double-walled micro-capsules, Sol-Gel process, Siloxane coating, Rheology, Breaking load of capsules, Tensile strength, Flexural strength References: 1. E.N. Brown, M.R. Kessler, N.R. Sottos and S.R. White, In situ poly (urea-formaldehyde) microencapsulation of dicyclopentadiene, Journal of Microencapsulation: Micro and Nano Carriers, 20 (2003) 719-730. 2. M. M. Caruso, B. J. Blaiszik, H Jin, S. R. Schelkopf, D. S. Stradley, N.R. Sottos, S. R. White, and J. S. Moore, Robust, Double-Walled Microcapsules for Self-Healing Polymeric Materials, ACS Journal of Applied Materials and Interfaces, Vol-2 (2010) 1195–1199. 3. D. Sun, J. An, G. Wu and J. Yang, Double-layered reactive microcapsules with excellent thermal and non-polar solvent resistance for self-healing coatings, Journal of Materials Chemistry – A, (2015) 4435-4444.