Thesis
Synthesis and characterization of UV-curable Thiol-methacrylate coatings
Washington State University
Master of Science (MS), Washington State University
07/2018
DOI:
https://doi.org/10.7273/000000078
Handle:
https://hdl.handle.net/2376/119062
Abstract
Castor oil, which is composed of 85-95% ricinoleic acid, accounts for merely 0.15% of the
world’s production of vegetable oils, but finds applications in manufacture of soaps, lubricants for
machine parts, coatings, and specialty chemicals due to it being the only source of hydroxylated
fatty acid. Ricinoleic acid has also been utilized for bio-based coating applications after
modification with reactive functional groups. This project expands on the ricinoleic acid-based
coatings research, this time by modifying it to have up to three reactive methacrylate groups and
studying its radical-mediated thiol-ene UV-curing capabilities in the presence of
trimethylolpropane tris-(3-mercaptopropionate) (TMPTMP) as the trifunctional thiol comonomer
and 2,2-Dimethoxy-2-phenylacetophenone (DMPA) as the photoinitiator to form thin films and
coatings on steel substrate. The chemical synthesis of the trimethacrylated ricinoleic ester resin
(RA3MAA) was examined and the molecular structure was characterized by proton NMR. The
photocuring behaviors were studied by FT-IR spectroscopy within the first 20-second window.
Their coating-related properties were characterized through qualitative tests such pencil hardness,
cross-hatched adhesion tape test, organic solvent resistance methyl ethyl ketone (MEK) solvent rub test in partial accordance to ASTM protocols. The surface energy of the coatings were
determined through contact angle testing, the extent of crosslinking, dynamic viscoelastic
properties and thermal stability examined by Soxhlet extraction, dynamic mechanical analysis
(DMA) and thermogravimetric analysis (TGA) in the form of films. High thiol formulations
resulted in softer and more flexible materials. Results also indicate strong correlation of increased
curing ability with higher stoichiometry of thiols and/or concentration of photoinitiator (DMPA),
with coating properties generally improving with increased UV exposure time (from 2 to 4 mins)
and higher thiol concentration due to the resistance of thiol-ene polymerizations to oxygen
inhibition. The softening and increased flexibility due to thiols were supported by DMA results
showing sharply decreasing room temperature storage modulus (E’) from ~650 MPa to ~20 MPa,
decreasing glass transition temperatures (Tg) from 43 °C to 2 °C and increasing damping
coefficient. Increasing thiol stoichiometry also very slightly and gradually decreased thermal
stability as evaluated by onset of degradation, 10% and 20% mass loss.
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Details
- Title
- Synthesis and characterization of UV-curable Thiol-methacrylate coatings
- Creators
- Harris Handoko
- Contributors
- JINWEN ZHANG (Degree Supervisor) - Washington State University, Composite Materials and Engineering CenterJUNNA XIN (Committee Member) - Washington State University, Composite Materials and Engineering CenterQIZHEN LI (Committee Member) - Washington State University, Mechanical and Materials Engineering, School of
- Awarding Institution
- Washington State University
- Academic Unit
- Mechanical and Materials Engineering, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Format
- pdf
- Number of pages
- 118
- Identifiers
- 99900590962501842
- Language
- English
- Resource Type
- Thesis