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Polymers and polymeric composites are widely used for various applications due to their outstanding and wide range of properties. Polyurethanes, existing in different types, are novel and versatile polymers with excellent mechanical properties. Thermosetting polyurethane resins are among the most widely used polyurethanes wherein their manufacturing and developing have been introduced during the last few years. Self-healing materials have been inspired by biological systems in which damages provoke healing responses. It is almost cost-effective to use self-healing materials in commercial applications. This study investigates a novel self-activated approach in thermosetting polyurethane resins. A tungsten (VI) chloride ( ${{\rm{WCl}}}_{6}$ ) catalyst, a co-activator (phenylacetylene) and a dissolution agent (nonylphenol) were used for the onset of ring-opening metathesis polymerization of dicyclopentadiene. Here different percentages of a catalyst in polyurethane resins were used, the impacts of which on fracture toughness and healing efficiency were also studied. To examine healing efficiency, samples with tapered double-cantilever beam geometry were prepared and using the self-activated method, the development of thermosetting polyurethane self-healing was investigated. The results showed that the concentration of catalyst affects the basic properties of the material and healing efficiency of the composite. The highest healing efficiency of 97% was obtained for a 3 wt% catalyst.

The successful invention of self-healing polymer composites a decade ago necessitated a methodology to quantify the ability of the material to heal and recover structural properties following damage. Healing efficiency was defined as the ratio of healed to virgin fracture toughness, η=K IChealed/KICvirgin . Early work took advantage of the crack length independence offered by a tapered double-cantilever beam (TDCB) fracture geometry to simplify calculation of healing efficiency to the ratio of healed to virgin critical loads, η=PChealed /PCvirgin . The current work investigates the application of the TDCB geometry and three common geometries utilized in the broader fracture literature (the compact tension (CT), single-edge notch bend (SENB), and single-edge notch tension (SENT) geometries) to the measurement of healing efficiency. While the TDCB geometry simplifies the calculation of healing efficiency because the crack lengths do not need to be accounted for, it is shown that if the virgin and healed crack lengths are not accurately accounted when using the CT, SENB, and SENT geometries, errors in calculated healing efficiency can be several hundred per cent. The TDCB geometry is reviewed at length, including the underlying theory and experimental calibration and validation of TDCB geometry. [ABSTRACT FROM PUBLISHER]

The self‐healing material under investigation is a diglycidyl ether of bisphenol A (DGEBA) epoxy matrix, which incorporates microcapsules filled with amine‐functionalized polydimethylsiloxane (PDMS‐a), as a new healing agent, combined with microcapsules filled with triethylenetetramine (TETA). The fracture toughness (KIC) and healing efficiency of these systems were measured using tapered double‐cantilever beam specimens. Fractographic analysis shows the rupture of microcapsules and release of the healing agent, inducing a change in the mirror‐like fracture plane morphology of neat epoxy and healing of cracks. It was also observed that PDMS‐a reduces the stiffness of the epoxy matrix, resulting in greater energy release rate (UIC) values. The values of self‐healing efficiency for systems healed for 48 h at room temperature varied from 0.82 to 1.0 (η, from KIC values) and from 1.0 to 1.4 (η', considering UIC values). Specimens healed at 80°C containing 2.5 wt% of microcapsules filled with PDMS‐a and TETA achieved η = 1.1 and η' = 2.0, indicating a highly efficient self‐healing process. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47627. [ABSTRACT FROM AUTHOR]