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Title:Microencapsulation of reactive amines and isocyanates and their application to self-healing systems
Author(s):McIlroy, David A.
Director of Research:Sottos, Nancy R.
Doctoral Committee Chair(s):Sottos, Nancy R.
Doctoral Committee Member(s):White, Scott R.; Braun, Paul V.; Schweizer, Kenneth S.
Department / Program:Materials Science & Engineerng
Discipline:Materials Science & Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Abstract:Microcapsule-based self-healing systems enable repair of crack damage in polymers and polymer matrix composites. Existing self-healing chemistries are limited by relatively weak chemical bonding between the matrix and the healing material, temperature stability, and side reactions that degrade the active components. We demonstrate for the first time a two-part system that incorporates a healing chemistry similar to the matrix curing chemistry, enabling chemical bonding between the healed material and the matrix material. Amine-containing microcapsules are synthesized by interfacial polymerization of a polyurea about a droplet of amine by means of suspension polymerization. Capsules are subsequently isolated and analyzed for content, and shown to contain reactive amine. The microcapsules containing reactive amine are employed in concert with microcapsules containing epoxy resin to recover fracture toughness in a cured epoxy. Both capsule types are dispersed in an epoxy resin and the resin is chemically cured. Mechanical load is applied to propagate a crack and rupture microcapsules contained within the cured resin. The average peak load at failure in a virgin specimen is recorded, and compared to the average peak load at failure in the same specimen after a healing period. Recovery of fracture toughness is limited to 15% for specimens healed at temperatures of 50 oC and below, whereas healing efficiencies of up to 60% are observed for specimens healed at temperatures above 80 oC. Control specimens where amine was not present failed to recover. Microcapsules containing isocyanate are also prepared by means of interfacial polyurea condensation. These capsules are also isolated and analyzed for content, and shown to contain reactive isocyanate. No healing was observed with these capsules, however, due to problems with bonding and long-term stability. With refinement, the isocyanate system is projected for use in polyurethane matrix materials where a moisture-cure could promote the healing reaction.
Issue Date:2011-08-26
Rights Information:Copyright 2011 David Antenen McIlroy. All rights reserved.
Date Available in IDEALS:2013-08-27
Date Deposited:2011-08

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