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A self-healing poly(dimethyl siloxane) elastomer

Posted on:2008-08-09Degree:Ph.DType:Dissertation
University:University of Illinois at Urbana-ChampaignCandidate:Keller, Michael WadeFull Text:PDF
GTID:1441390005964482Subject:Engineering
Abstract/Summary:
In this work, self-healing functionality is imparted to a poly(dimethyl siloxane) (PDMS) elastomer with low modulus and high strain-to-failure behavior. This material utilizes a two-microcapsule system to provide a mechanism for autonomic repair of damage. One microcapsule type contains a functionalized high-molecular-weight resin and organometallic catalyst compounds. The second microcapsule type contains a functional copolymer (initiator) that facilitates the crosslinking of the resin via the action of the catalyst. The healing response is triggered when damage, in the form of a tear, puncture, or crack, propagates through the material and ruptures a resin and initiator capsule. Ruptured capsules release their contents onto the crack plane, initiating polymerization. The polymerized material bonds the two crack faces together regaining much of the original strength, of the matrix material.; The mechanical behavior of the microcapsules is studied using a combination of individual microcapsule compression tests and in-situ microscopic analysis. Single-capsule compression tests are performed to extract the modulus of the capsule shell wall and to investigate the behavior of microcapsules under large deformations. The capsules are shown to survive matrix deformation in excess of 45%. Although the microcapsules are robust and endure large matrix deformations, an approaching tear does successfully rupture the capsules. A tear test protocol is adopted to assess the healing efficiency of this new material. Self-healing PDMS specimens with 5 wt% initiator and 5 wt% resin microcapsules recover 97% of the original tear strength. Complete recovery of tear strength is possible under certain conditions. Addition of microcapsules to the PDMS matrix increases the tear strength of the material by 25%. Embedded microcapsules also increase the elastic stiffness by as much as 57%.; The self-healing performance of the elastomer is also investigated under torsional fatigue loading. The microcapsule-based self-healing PDMS is capable of recovering a significant portion of the original torsional stiffness and retards dynamic crack growth rate. Depending on the matrix material, a nearly complete recovery of the original torsional stiffness is possible.
Keywords/Search Tags:Self-healing, PDMS, Material, Matrix, Original, Crack
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