Solvent-based self-healing polymeric materials

self-healing;polymers;solvent healing;microcapsules;fracture toughness;bone cement

Caruso, Mary M.

关键词: self-healing;    polymers;    solvent healing;    microcapsules;    fracture toughness;    bone cement;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/16824/Caruso_Mary.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Mechanical damage to bulk polymers typically begins as a microcrack, which can lead to eventual failure of the material if there is no method to inhibit crack growth. In living systems, this damage automatically initiates a healing response.Following the example of nature, self-healing polymers are engineered with the unique ability to extend the lifetime of materials by preventing damage propagation using various chemical mechanisms that are triggered by crack formation. The initial chemistry for self-healing materials employed a room temperature ring-opening metathesis polymerization (ROMP) using encapsulated dicyclopentadiene (DCPD) and wax-protected Grubbs’ catalyst. However the limitations of this system, including catalyst availability, cost, environmental toxicity, stability, and materials processing, motivated the search for a simpler approach to self-healing.Many chemical reactions require the use of a solvent. When an organic solvent is introduced into polymer systems, the mobility of polymer chains increases as the localized glass transition temperature is depressed. Solvent-based self-healing involves wetting of the polymer surface and resultant swelling of the bulk material, leading to interlocking of the polymer chains across a damaged crack plane to recover virgin mechanical properties. To achieve this healing in an autonomic fashion, liquid-filled microcapsules were prepared with various core components and embedded within a bulk polymer during processing. By compartmentalizing reactive fluids containing a solvent into a bulk material, in situ reactions occur upon damage in the form of a crack. A crack propagating through the polymeric material ruptures the embedded microcapsules, thus releasing solvent-based mixtures into the crack plane. The encapsulation of various solvents has been developed for use in self-healing polymers. Solvent-filled microcapsules were incorporated into thermoset matrices and thermoplastic materials such as poly(methyl methacrylate), and the healing performance is discussed in great detail. A self-healing bone cement/dental resin system based on free-radical polymerization reactions has also been studied. The development of solvent-based microcapsules led to the encapsulation of conductive materials for the repair of mechanically damaged electronic devices. Finally, additional research was carried out to examine the use of solid and protected amines for high temperature self-healing systems.