Thermal mending in novel epoxy/cyclic olefin copolymer blends

In this paper, the thermal mending potential of a cyclic olefin copolymer (COC) in a thermosetting matrix was evaluated for the first time. Epoxy/COC blends were prepared by mechanically mixing a COC powder (particle size lower than 300 µm) at different concentrations (10, 20, 30 and 40 wt%) in an epoxy resin in the uncured (liquid) state. The presence of a homogenous dispersion of COC particles within the epoxy matrix after curing was confirmed by optical microscopy analysis on polished specimens. Thermogravimetric tests evidenced a positive contribution of the thermoplastic COC phase on the thermal degradation resistance of the blends. The fracture toughness of the blends (both under quasi-static and Charpy impact conditions) increased with the addition of COC. Healing tests were performed on broken samples after healing under a compressive stress of 15 MPa at 190°C for 1 hour. A significant increase of the healing efficiency with the COC content was detected, and healing efficiency values very near to 100% were obtained for a COC content of 40 wt%.