Potential of jatropha oil and derivatives as an ultraviolet curable self-healing coating

Coatings are applied at various substrates with the aim of protecting the surface and give aesthetic value. However, the coating degrades and loses its performance due to ageing and environmental factors. Therefore, self-healing coating is invented to extend the shelf-life of the protected material and hence requires less maintenance and monitoring service. This smart coating can repair damage or recover the functional performance of the coating with minimal or no intervention. In coating preparation, the strategy of using vegetable oil to replace petrochemical resin in the coating industry has been started for a few decades. However, most of the oils that have been used such as soy, linseed and sunflower are edible oils. In Malaysia, jatropha oil is a natural source with high content of the unsaturated part. This feature reflects its reactivity during chemical modification and can potentially be applied in the coating industry. Moreover, it is a nonedible oil and does not compete with the food supply. As far as it is known, no study on an ultraviolet (UV) curable self-healing coating based on jatropha oil and its derivatives has been reported. This study investigates the feasibility of jatropha oil and its derivatives as a self-healing coating using UV curing to produce the film. Following that, the microcapsule embedment technique was chosen for the preparation of the self-healing coating. The coating primer was prepared from jatropha oil-based polyurethane acrylate (JPUA), whilst the healing agent was pure jatropha oil (JO) and its derivatives were encapsulated into a microcapsule. JPUA-TDI had a higher viscosity and molar mass with a broader polydispersity index (PDI) value than JPUA-IPDI. With the addition of monomer and photoinitiator, coating formulations based on JPUA-TDI and JPUA-IPDI were developed and irradiated under UV subjected to the curing process. JPUA-TDI- and JPUA-IPDI-based films showed the best mechanical properties based on coating formulation, with a monomer to JPUA ratio of 35:65. The JPUA-TDI-based coating formulation had a lower hardness but better adhesion than the JPUA-IPDI-based coating formulation. Pure JO and JPUA-IPDI coating mixtures behaved Newtonian at 25°C, whereas JPUA-TDI coating mixtures behaved as shear thickening fluids. JO and JPUA-IPDI coating mixture were encapsulated into microcapsules by in-situ polymerisation, where polyurea formaldehyde was chosen as the shell material of the microcapsule. The variation in the agitation rate affected the morphology and the core content of the microcapsules. At the speed of 400 rpm, JO 400 (71.6 ± 2.7%) and IPDI 400 (40.0 ± 4.1%) had the highest core content. Therefore, JO 400 and IPDI 400 were chosen for self-healing coating preparation to be incorporated into the JPUA-TDI coating primer. The microcapsules were loaded into the JPUA-TDI coating primer and exposed to UV light for the curing process for film thickness variations and the percentage of the microcapsule. At a film thickness of 50 μm with 5% loading of both JO and JPUA-IPDI-based microcapsules, respectively, the prepared self-healing coating had hardness and adhesion properties that were comparable with the control sample. During the scratch test, 5% JO did not show a self-healing property with response to air. The 5% IPDI showed self-repairing action on the scratch area after exposure to UV light. Proof-of-concept of self-healing coating is offered by jatropha oil derivatives where JPUA-TDI was used as the coating primer and JPUA-IPDI coating mixture as the healing agent in response to UV light.

Text 115913.pdf Download (1MB) Official URL or Download Paper: http://ethesis.upm.edu.my/id/eprint/18254

Actions (login required)

View Item