Manufacturing of microcapsules with liquid core and their self-healing performance in epoxy for resin transfer molding
Yılmaz, Çağatay (2013) Manufacturing of microcapsules with liquid core and their self-healing performance in epoxy for resin transfer molding. [Thesis]
Microcapsules with different active core materials have been receiving a great deal of attention for developing polymer based materials with selfhealing abilities. The self-healing ability is crucial in particular for matrix materials having brittle nature such as epoxy resin. In order for abstaining from an abrupt failure of structural brittle manner polymeric materials, microcapsules can be used excellently as a viable repair agent. In this work, we present a study on the catalyst-free microcapsule based self-healing system. Microcapsules were produced by the insitu polymerization of urea-formaldehyde at the dispersed phase-water interface. Each microcapsule batches were characterized by using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analyser (TGA), Di erential Scanning Calorimetry (DSC). Characteristic peaks of urea-formaldehyde shell, core components; DGEBA, and PhCl was seen in the Mid- IR region. Characteristic thermal decomposition temperature of urea-formaldehyde wall material and DBEBA which is the main microcapsule content were determined from the TGA trace. In addition to the given thermal and spectral characterization tools, optic microscope and SEM images also ensure the formation of liquid- lled microcapsules. Although the microcapsules showed brittle behavior during the processing such as drying and sieving, incorporation of microcapsules into the epoxy matrix was achieved successfully. The healing characteristic of epoxy-microcapsule composite was assessed by the Tapered Double Cantilever Beam (TDCB) specimen at the mode-I crack opening fashion. Besides microcapsule-epoxy composite system showed a moderate healing efficiency, a significant increase in mode-I fracture toughness value was observed. Three point bending experiment was also conducted on the microcapsule-epoxy composite. It was found that microcapsules drastically decrease the flexure strength of questioned host material.
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