Self-healing Polymeric Materials Research Articles

Self‐Healing Materials: A Facile Strategy for Preparing Self‐Healing Polymer Composites by Incorporation of Cationic Catalyst‐Loaded Vegetable Fibers (Adv. Funct. Mater. 14/2009)

Discontinuous sisal fibers carrying extremely active (C2H5)2O·BF3 are embedded in epoxy matrix together with epoxy monomer-loaded microcapsules to fabricate self-healing composite based on the healing mechanism of cationic chain polymerization. This approach, described by D. S. Xiao et al. on page 2289, skips the encapsulation of high activity chemicals, reducing the risk of their deactivation during handling. It provides a facile strategy for making extrinsic self-healing polymeric materials.

“Click Chemistry” in Tailor-Made Polymethacrylates Bearing Reactive Furfuryl Functionality: A New Class of Self-Healing Polymeric Material

This investigation reports the effective use of the Diels-Alder (DA) reaction, a "click reaction" in the preparation of thermally amendable and self-healing polymeric materials having reactive furfuryl functionality. In this case, the DA and retro-DA (rDA) reactions were carried out between the tailor-made homo- and copolymer of furfuryl methacrylate prepared by atom-transfer radical polymerization and a bismaleimide (BM). The kinetic studies of DA and rDA reactions were carried out using Fourier transform infrared spectroscopy. The DA polymers were insoluble in toluene at room temperature. When the DA polymers were heated at 100 degrees C in toluene, it was soluble. This is because of the cleavage between furfuryl functionality and BM. The chemical cross-link density was determined by the Flory-Rehner equation. The cross-linked polymer showed much greater adhesive strength at room temperature, but the adhesive strength was quite low at higher temperature. The self-healing capability was studied by using scanning electron microscopy analysis. The thermal and dynamic mechanical properties of the thermally amendable cross-linked materials were investigated by thermogravimetric analysis and dynamic mechanical analysis.

Self-healing epoxy based on cationic chain polymerization

A two-component healing agent consisting of epoxy- and ((C 2H 5) 2O·BF 3)-loaded microcapsules was synthesized and applied to fabricate self-healing epoxy composites. Curing of epoxy healing agent catalyzed by (C 2H 5) 2O·BF 3 belongs to cationic chain polymerization, which is characterized by fast reaction at ambient temperature and low catalyst concentration. The experimental results showed that cracks in the composites containing the above healing system can be quickly re-bonded with satisfied healing efficiency. In the case of 5 wt% epoxy- and 1 wt% (C 2H 5) 2O·BF 3-loaded capsules, for example, a ∼80% recovery of impact strength was detected within 30 min at 20 °C. Because the healing capsules took effect at low content, mechanical properties of the matrix were largely retained. It is believed that the present healing system provides a possible solution to preparation of self-healing polymeric materials with practical applicability.

Thermally Self-Healing Polymeric Materials: The Next Step to Recycling Thermoset Polymers?

We developed thermally self-healing polymeric materials on the basis of furan-functionalized, alternating thermosetting polyketones (PK-furan) and bis-maleimide by using the Diels−Alder (DA) and Re...

Self-Healing Polymeric Materials Using Epoxy/Mercaptan as the Healant

A self-healing system based on conventional epoxy resin was successfully developed in this work. Epoxy and its hardener mercaptan were microencapsulated as two-component healing agent, and then the microcapsules were embedded in epoxy matrix. Attractive healing effect can be acquired at low capsule content (e.g., 43.5% healing efficiency with 1 wt % capsules and 104.5% healing efficiency with 5 wt % capsules at 20 °C for 24 h). Since only a few healant proves to be sufficient for crack repairing, a better balance between strength and toughness restoration can thus be achieved. As a result of high flowability, fast consolidation, and molecular miscibility of the released healing agent consisting of epoxy and mercaptan, self-healing was allowed to proceed rapidly offering satisfactory repair effectiveness.

Life extension of self-healing polymers with rapidly growing fatigue cracks

Self-healing polymers, based on microencapsulated dicyclopentadiene and Grubbs' catalyst embedded in the polymer matrix, are capable of responding to propagating fatigue cracks by autonomic processes that lead to higher endurance limits and life extension, or even the complete arrest of the crack growth. The amount of fatigue-life extension depends on the relative magnitude of the mechanical kinetics of crack propagation and the chemical kinetics of healing. As the healing kinetics are accelerated, greater fatigue life extension is achieved. The use of wax-protected, recrystallized Grubbs' catalyst leads to a fourfold increase in the rate of polymerization of bulk dicyclopentadiene and extends the fatigue life of a polymer specimen over 30 times longer than a comparable non-healing specimen. The fatigue life of polymers under extremely fast fatigue crack growth can be extended through the incorporation of periodic rest periods, effectively training the self-healing polymeric material to achieve higher endurance limits.