Charpy impact tests of epoxy matrix filled with poly(urea-formaldehyde) microcapsules for self-healing applications
Patryk A. Bolimowski, Rafał Kozera, Paulina Kozera, Anna Boczkowska
Quarterly No. 4, 2017 pages 206-210
DOI:
keywords: epoxy resin, microcapsules, composites, Charpy impact, scanning electron microscopy
abstract Smart self-healing epoxides have attracted immense interest in the industry due to their capability to prevent crack propagation and increase material service life. Self-healing can be achieved via a number of approaches, where microcapsule-based systems are deemed to be the closest to market implementation. The work presented here demonstrates the effect of polymeric microcapsules made of poly(urea-formaldehyde) on the Charpy impact resistance of a standard epoxy matrix. Poly(urea-formaldehyde) microcapsules containing epoxy resin (EPIDIAN 52) and organic solvent (Ethyl phenylacetate) were prepared using in-situ polymerisation in an oil-in-water emulsion as described in the literature. The Charpy impact tests were performed on specimens made of neat epoxy resin (EPIDIAN 52) - amine hardener (Z1) as well as for the epoxy filled with microcapsules with 1, 2.5, 5, 10 and 25 wt.%. The test results have shown that the presence of brittle and spherical additives has a detrimental effect on the mechanical properties of the polymer, resulting in a maximum 80% reduction in impact strength for the samples with the highest content of microcapsules. In addition, the fracture surfaces of the impacted specimens were investigated using a Scanning Electron Microscope (SEM). Significant differences were observed between the reference samples and those containing microcapsules, particularly when the microcapsule weight fraction is high.