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Healing Agent (healing + agent)
Selected AbstractsA Facile Strategy for Preparing Self-Healing Polymer Composites by Incorporation of Cationic Catalyst-Loaded Vegetable FibersADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Ding Shu Xiao Abstract A two-component healing agent, consisting of epoxy-loaded microcapsules and an extremely active catalyst (boron trifluoride diethyl etherate, (C2H5)2O,·,BF3)), is incorporated into epoxy composites to provide the latter with rapid self-healing capability. To avoid deactivation of the catalyst during composite manufacturing, (C2H5)2O,·,BF3 is firstly absorbed by fibrous carriers (i.e., short sisal fibers), and then the fibers are coated with polystyrene and embedded in the epoxy matrix together with the encapsulated epoxy monomer. Because of gradual diffusion of the absorbed (C2H5)2O,·,BF3 from the sisal into the surrounding matrix, the catalyst is eventually distributed throughout the composites and acts as a latent hardener. Upon cracking of the composites, the epoxy monomer is released from the broken capsules, spreading over the cracked planes. As a result, polymerization, triggered by the dispersed (C2H5)2O,·,BF3, takes place and the damaged sites are rebonded. Since the epoxy,BF3 cure belongs to a cationic chain polymerization, the exact stoichiometric ratio of the reaction components required by other healing chemistries is no longer necessary. Only a small amount of (C2H5)2O,·,BF3 is sufficient to initiate very fast healing (e.g., a 76% recovery of impact strength is observed within 30,min at 20,°C). [source] Delivery of Two-Part Self-Healing Chemistry via Microvascular NetworksADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Kathleen S. Toohey Abstract Multiple healing cycles of a single crack in a brittle polymer coating are achieved by microvascular delivery of a two-part, epoxy-based self-healing chemistry. Epoxy resin and amine-based curing agents are transported to the crack plane through two sets of independent vascular networks embedded within a ductile polymer substrate beneath the coating. The two reactive components remain isolated and stable in the vascular networks until crack formation occurs in the coating under a mechanical load. Both healing components are wicked by capillary forces into the crack plane, where they react and effectively bond the crack faces closed. Healing efficiencies of over 60% are achieved for up to 16 intermittent healing cycles of a single crack, which represents a significant improvement over systems in which a single monomeric healing agent is delivered. [source] Embedded Shape-Memory Alloy Wires for Improved Performance of Self-Healing Polymers,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2008Eva L. Kirkby Abstract We report the first measurements of self-healing polymers with embedded shape-memory alloy (SMA) wires. The addition of SMA wires shows improvements of healed peak fracture loads by up to a factor of 1.6, approaching the performance of the virgin material. Moreover, the repairs can be achieved with reduced amounts of healing agent. The improvements in performance are due to two main effects: (i) crack closure, which reduces the total crack volume and increases the crack fill factor for a given amount of healing agent and (ii) heating of the healing agent during polymerization, which increases the degree of cure of the polymerized healing agent. [source] Coaxial Electrospinning of Self-Healing CoatingsADVANCED MATERIALS, Issue 4 2010Jeong-Ho Park Self-healing polymer coatings are formed by electrospinning bead-on-string healing agent filled capsules onto a substrate followed by infilling of a polymer matrix. Upon damage to the self-healing coating, liquid healing agents are released from the ruptured beads passivating the damaged region, preventing it from corroding as shown through microscopy, electrochemistry, and corrosion testing. [source] Self-Healing Chemistry: Delivery of Two-Part Self-Healing Chemistry via Microvascular Networks (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Mater. Microvascular self-healing of a brittle coating is accomplished by supplying fluid healing agents from an underlying network of microchannels. Dual independent networks filled with a two-part healing chemistry (epoxy resin and curing agent) that repeatedly heal damage in the coating up to 16 consecutive times are reported by K. S. Toohey et al. on page 1399. [source] Coaxial Electrospinning of Self-Healing CoatingsADVANCED MATERIALS, Issue 4 2010Jeong-Ho Park Self-healing polymer coatings are formed by electrospinning bead-on-string healing agent filled capsules onto a substrate followed by infilling of a polymer matrix. Upon damage to the self-healing coating, liquid healing agents are released from the ruptured beads passivating the damaged region, preventing it from corroding as shown through microscopy, electrochemistry, and corrosion testing. [source] Self-Healing Materials with Interpenetrating Microvascular NetworksADVANCED MATERIALS, Issue 41 2009Christopher J. Hansen Interpenetrating microvascular networks are embedded in an epoxy substrate via direct-write assembly. Each network is filled with one component of a two-part epoxy resin. This novel epoxy coating/substrate architecture enables repeated healing of at least 30 cycles of mechanical damage in the coating by independently supplying both healing agents to the damaged region(s). [source] Self-Healing Polymer CoatingsADVANCED MATERIALS, Issue 6 2009Soo Hyoun Cho Self-healing coatings that autonomically repair and prevent corrosion of the underlying substrate are created through dispersion of microencapsulated healing agents in a polymer film. Following a damage event, these healing agents are released into the damaged region, passivating the substrate. This approach to self-healing coatings is quite general, and is effective for both model and industrially important coating systems. [source] | ||||||||||