Autonomous indication of damage in epoxy coatings

Industrial coatings are applied for their aesthetic appeal and ability to protect the underlying substrate material from the environment. The indication of coating flaws for correction becomes more important for coatings operating in extreme environments. Visual indication coating damage can aid in quickly locating and repairing damage before the underlying substrate degrades or fails. In this work, fluorescent damage indication was achieved with a dual capsule system embedded in an epoxy coating. Fluorescamine, a turn-on fluorescent indicator chosen for selectivity towards primary amines, and an amine based epoxy curing agent were separately encapsulated and incorporated into an epoxy coating. When mechanical damage ruptures both capsules, fluorescamine instantly reacts with primary amines to develop a bright blue fluorescence. This dual capsule system holds the promise of creating a smart coating with damage sensing and autonomous self-healing. Clear epoxy coatings with various concentrations of indicator and amine capsules were deposited onto glass slides and scratched with a razor blade. A coating containing an even distribution of 5 wt% indicator capsules and 5 wt% amine capsules achieved the most consistent indication performance. Using the same capsule concentration, an epoxy coating with carbon black as a pigment was used to dye the epoxy matrix. Damage indication in the pigmented coating performed similarly to the clear epoxy coating. Another coating consisted of two distinct layers, where clear epoxy with embedded microcapsules was covered with an acrylic spray paint. When scratched, fluorescent indication response was considerably muted when compared to a clear epoxy coating. Indication of low velocity impact damage to glass fiber composite coupons was also achieved with this system. Fluorescence was present where the impact tup contacted the smart coating on the specimen top surface. The back surface suffered micro-cracks and delamination but did not fluoresce due to poor mixing of indicator and amine in the damage region.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Matthews, Christopher Coleman

Contributors dc:contributor

• Sottos, Nancy R.

• damage indication
• microcapsules
• smart coating
• fluorescence
• fluorescamine

Statement dc:rights

• Copyright 2015 Christopher Matthews

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/88307

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F88307