Thermal mending in novel epoxy/cyclic olefin copolymer blends

Abstract

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%.

Healable Carbon Fiber-Reinforced Epoxy/Cyclic Olefin Copolymer Composites

“…This creates a partial disruption of the fabric orientation and also increases the thickness in the laminates containing COC. This phenomenon can be also explained considering that the viscosity of the uncured resin increases with the COC concentration, as recently reported by Mahmood et al [8]. This can be verified by comparing the optical microscope pictures of EP/CF with that of the laminates containing COC (e.g., 20 wt.% or 30 wt.%), where it can be noticed that the thickness of the resin rich area is higher in the composites with an elevated COC concentration.…”

“…For example, carbon fiber reinforced composites are extensively applied in the new generation of commercial aircrafts, like Airbus A350 XWB (53 wt.%) and Boeing 787 Dreamliner (50 wt.%). A strong interest has recently arisen around the possibility to further promote the reliability and the safety of composites by introducing structural health monitoring [1][2][3][4][5] and self-healing capabilities [6][7][8][9].…”

“…Recently, Mahmood et al explored the use of cyclic olefin copolymers (COCs) as an amorphous thermoplastic healing agent in an epoxy matrix [8]. COCs are amorphous thermoplastic polymers with mechanical properties comparable with those of epoxy resins, and are available in various grades with different glass-transition temperatures [49,50].…”

Novel Poly(Caprolactone)/Epoxy Blends by Additive Manufacturing

“…PCL finds wide application in biodegradable packaging, in sutures, in adhesives, in non-woven fabrics or for the production of synthetic leather and dressings [32]. One of the most recent applications of PCL is as blending agent in epoxy system for self-healing applications [7,37,38].Self-healing capability, intended as the ability to repair damages and restoring partially or completely the lost properties and functions, has been already demonstrated in many types of polymers [39] including thermoplastics, elastomers, and thermosets [40]. Generally speaking, the self-healing mechanism can be summarized in three principal steps: actuation of self-healing feature, transportation of healing agent or chemicals in the damaged zone, final chemical or physical reparation [41].…”

“…Self-healing capability, intended as the ability to repair damages and restoring partially or completely the lost properties and functions, has been already demonstrated in many types of polymers [39] including thermoplastics, elastomers, and thermosets [40]. Generally speaking, the self-healing mechanism can be summarized in three principal steps: actuation of self-healing feature, transportation of healing agent or chemicals in the damaged zone, final chemical or physical reparation [41].…”