In recent years, bio-based materials technology is developing rapidly. Bio-based materials especially vegetable oil-based materials are considered as the potential alternatives to conventional petroleum-based materials in the future. For example, vegetable oil derived polyols have been widely applied in coatings, plastic films, lubricants, rubbers, elastomers, and many other intermediate products. Although some of the petroleum-based products could be replaced by bio-based materials, many important petroleum-based materials have rarely suitable alternatives for the industrial application. Therefore, from a sustainable point, it is significant to continuously study the alternatives to petroleum-based materials for coating development.
In this work, three projects of vegetable oil-based green organic coatings were investigated. In Chapter 3, a self-healing coating contained vegetable oil-based epoxy ester as the healing agent was designed to improve the self-healing function. In Chapter 4, a waterborne polyurethane coating with improved mechanical property and corrosion resistance was synthesized from vegetable oil-based isocyanate. In Chapters 5 to 7, the fundamental structure-property relationships for non-isocyanate polyurethane (NIPU) coatings synthesized through green approaches were studied.
In Chapter 3, poly urea formaldehyde (PUF) microcapsules containing vegetable oil-based epoxy ester were successfully synthesized through in-situ polymerization. Self-healing coatings were prepared by embedding PUF epoxy ester microcapsules in the epoxy coatings. The scratched self-healing coating can provide good recovery of the corrosion resistance, compared with the neat epoxy coating. These findings demonstrated that the vegetable oil-based epoxy ester is applicable for anticorrosive smart self-healing coatings as a healing agent.
In Chapter 4, the waterborne polyurethane coatings were synthesized from dimer fatty acid diisocyanate (DDI). Previous reports showed they were challenging for the inadequate mechanical property which is due to the high flexibility of a long fatty acid chain on DDI. This problem had been solved in this study by incorporating an alkoxysilane group into vegetable oil-based waterborne polyurethane coatings. This enhancement was mainly caused by the formation of a Si-O-Si network structure from the alkoxysilane group. Additionally, the alkoxysilane modified DDI based polyurethane dispersion showed outstanding corrosion resistance due to the formation of a Si-O-Si network structure. The significantly improved mechanical property and anticorrosion property extended the potential application of DDI based material in waterborne polyurethane coatings.
In Chapter 5, green waterborne two components (2K) NIPU epoxy hybrid coatings were synthesized from renewable cyclic carbonate, fatty acid amine, amine-based internal dispersion agent, and waterborne epoxy chain extender. Then, the thermal and mechanical properties were studied. The synthesized waterborne 2K NIPU showed the excellent balance of the mechanical strength and elongation-at-break which revealed that the rigid NIPU could be tailored by introducing fatty acid amine as a soft segment. Furthermore, in Chapter 7, to develop a more effective method for the preparation of waterborne NIPU coatings, a series of the waterborne one component (1K) NIPU coatings were synthesized from the amine-based internal dispersion agent, fatty acid amine, bisphenol A diglycidyl ether (DGEBA) cyclic carbonate, and multiple epoxy resins including DGEBA, trimethylolpropane triglycidyl ether, and 4,4’-Methylenebis(N,N-diglycidylaniline). Besides, in Chapter 6, the NIPU tetraethyl orthosilicate (TEOS) hybrid coatings were successfully prepared from amine-terminated NIPU, bisphenol A (BPA) epoxy, and TEOS. The anti-corrosion performance of environmentally friendly NIPU coatings was significantly enhanced by the sol-gel chemistry of TEOS. The results revealed that the organic phase NIPU cannot provide enough compatibility for inorganic phase TEOS. Therefore, phase separation occurs at the interface between the aggregation phase and the continuous phase. As a result, incorporating TEOS into NIPU coating can be an effective approach to improve the anti-corrosion performance of NIPU coating.
In general, the successfully synthesized vegetable oil-based self-healing coating, waterborne polyurethane coating, waterborne 2K, and 1K NIPU epoxy hybrid coating are the green alternatives to conventional petroleum-based coatings. The green vegetable oil-based coatings with great performance would expand their potential industrial application and promote the replacement of petroleum materials by green materials.