Urea-phenol-formaldehyde Microcapsules Containing Linseed Oil For Self-healing Anticorrosive Coating Applications (original) (raw)
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Particuology, 2017
Micro/nanocapsules of urea-formaldehyde resin loaded with linseed oil, which are a self-healing agent in glass flake epoxy anti-corrosion paint, were prepared using a combination of ultrasonic homogenization and in-situ polymerization. The main objective of this study was to model and optimize the microencapsulation process. Five-level central composite design was used to design, model, and optimize the microencapsulation process. A quadratic model was constructed to show the dependency of the percentage of encapsulated linseed oil and capsule size, as model responses, on the studied independent variables (the rotational speed of the agitator and the power and duration of sonication). Analysis of variance showed that all of the variables have significant effects on the encapsulated linseed oil percentage, while the rotational speed of the agitator and sonication time is effective variables for controlling the capsule size. Under the determined optimum conditions, a maximum encapsulated linseed oil percentage (ELO%) of 93.9% and a minimum micro/nanocapsule size of 0.574 m were achieved at 594 rpm agitation, 350 W sonication power, and 3 min sonication time. Validation of the model was performed. The percentage relative errors between the predicted and experimental values of the ELO% and micro/nanocapsule size are 1.28% and 3.66%, respectively. The efficacy of the optimum micro/nanocapsules in healing cracks in a glass flake epoxy paint and corrosion protection was investigated by the salt spray test and Tafel polarization technique.
Progress in Organic Coatings, 2017
Linseed oil filled urea-formaldehyde microcapsules with various sizes were prepared via in-situ polymerization. To understand the healing performance of linseed oil as a healing agent and the progression of corrosion processes beneath the healed area, long term corrosion performance of scratched epoxy-based coating samples containing microcapsules was evaluated using Electrochemical Impedance Spectroscopy (EIS) as well as salt spray testing over a period of 6-days. EIS results were fitted to various equivalent circuit models and a modified model for the justification of the observed corrosion behavior was proposed. It was found that the addition of microcapsules enhances the corrosion resistance of the scratched samples, the extent of which depends on the microcapsule size and loading. At a given loading, corrosion resistance increased with increasing microcapsule size, however, the effect of microcapsule size was more significant than that of loading. Moreover, with increased exposure time to the salt solution, the corrosion behavior of scratched coated samples shifted from uniform corrosion to crevice corrosion. EIS results showed that although linseed-oil can significantly improve the corrosion performance of the damaged coating in short term however it rapidly decreases with time and hence this should be taken into account in designing of microcapsule's core composition.
Progress in Organic Coatings, 2020
In this research, polyurea-formaldehyde-based microcapsules loaded with linseed oil were synthesized by means of in-situ polymerization in an oil-in-water emulsion. The surface of the microcapsules was treated with 3aminopropyltrimethoxy silane (APS) using sol-gel procedure at pH 7.5. SEM and optical microscopy were used to characterize untreated and APS-treated microcapsules. The mechanical properties of epoxy-based nanocomposite coatings comprising different combinations of APS-treated microcapsules and nanoclay particles were evaluated by means of tensile strength measurements. The standard salt spray test, Electrochemical Impedance Spectroscopy (EIS) and SEM were utilized to study the corrosion resistance and healing performance of the samples in the presence of nanoclay. The results revealed improvement in tensile strength properties and anti-corrosion resistance by the simultaneous use of APS-treated microcapsules and nanoclay. This was attributed to the enhanced interactions between the polymer coating and the microcapsule shell and the barrier properties of intercalated nanoclay platelets. The natural salt spray test EIS results revealed enchasing corrosion resistance of the coating samples containing APS-treated microcapsule in comparison with neat epoxy samples during 7 days exposure to the conditions of the tests. The sample containing APS-treated microcapsules and nonoclay particles showed the best performance along with all samples. APS-treated microcapsules were more likely to rupture during the scratching, leading to better corrosion resistance and self-healing properties.
Progress in Organic Coatings, 2015
Core-shell microcapsules of urea-resorcinol-formaldehyde shell and linseed oil (LO) core material as paint additives for self-healing coatings were prepared. The capsules contained LO either with or without Co-octoate as drier material and/or octadecylamine (ODA) as corrosion inhibitor. The microcapsules embedded in a commercial paint were applied on sandblasted mild steel sheets. After scratching the coated surface, the inhibition efficiency of core-shell microcapsule-containing coat, dipped into corrosive media, was followed visually and evaluated numerically by electrochemical impedance spectroscopy (EIS). In separate experiments, to optimize for the self-healing process, the composition of the core material, the effect of the drier and/or the inhibitor ODA on drying process of LO films were monitored by infrared spectroscopy. Pure LO needed 6-7 days to dry completely. The drying period could be shortened (to 5 h) via application of a dryer, but the addition of the corrosion inhibitor alone increased significantly the time needed for solifidicaiton. To minimize the drying period we have found the proper combination of the ODA and the dryer of the LO. The EIS measurements, in accordance with the drying tests, resulted in the next order of selfhealing ability: LO<LO (+ODA) <LO (+Co-octoate) <LO (+ODA+Co-octoate) .
Polymer Science, Series B, Vol. 59, No. 3, 1–11, 2017
–In the field of coatings, extensive laboratory research has been conducted in the last decade. In the present work, effectiveness of epoxy resin filled micro/nanocapsules was investigated for future using in healing of cracks generated in coatings. Micro/nanocapsules were prepared by in situ polymerization of urea– formaldehyde resin to form shell over epoxy resin droplets. The optimal process parameters for synthesizing the micro/nanocapsules were selected. The as-synthesized capsules were studied by various characterizations techniques, including scanning electron microscope (SEM), particle size analyzer (PSA), Fourier transform-infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results indicate that micro/nanocapsules containing epoxy resins can be synthesized successfully. The rough outer surface of microcapsule is composed of agglomerated urea–formaldehyde nanoparticles. They basically exhibit good storage stability at room temperature, and they are chemically stable before the heating temperature is up to approximately 250°C.
Frontiers in Materials
This study focuses on the design, development, and validation of two coating systems for corrosion protection of hot dip galvanized steel substrates. The coatings consist of epoxy-based resin reinforced with core-shell microcapsules, either cerium oxide or cuprous oxide core and a polymeric shell doped with cerium ions. The effect of the modification of the epoxy resin with a liquid rubber polymer has also been studied. Corrosion studies via electrochemical impedance spectroscopy (EIS) revealed that the coatings have enhanced barrier properties. Moreover, EIS studies on coatings with artificial scribes, demonstrated an autonomous response to damage and a selfhealing effect. Heat-induced material re-flow has also been observed after exposure to temperature higher than the T g of the system, which offered an additional self-healing mechanism, partially inhibiting the underlying corrosion processes when the liquid rubber is present in the system.
Progress in Organic Coatings, 2020
This work aims at investigating the self-healing ability of epoxy coatings, modified with microcapsules containing highly reactive isocyanate in their core. Highly efficient, thermally and chemically stable isophorone diisocyanate microcapsules were prepared via emulsification followed by interfacial polymerization at the surface of oil droplets of the oil-in-water (O/W) emulsion. The microcapsules were incorporated into an epoxy coating to protect carbon steel from corrosion. Scanning Electron Microscopy (SEM) was used to assess the microcapsules̕ and coating morphology. The physico-chemical characterization of the microcapsules was studied by Fourier Transformed Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). Electrochemical Impedance Spectroscopy (EIS) was employed to evaluate the protective performance of coated steel samples and results confirmed that the barrier properties of modified coatings increased over time. The self-healing ability was studied via Localized Impedance Spectroscopy (LEIS), Scanning Vibrating Electrode Technique (SVET) and Scanning Ion-Selective Electrode Techniques (SIET) on coated steel samples containing artificial defects. This comprehensive study confirmed the ability of the capsules to heal damaged areas in the coating and to mitigate corrosion thanks to the formation of a protective polymeric barrier layer.
Preparation and Property Investigation of Epoxy/Amine Micro/Nanocapsule Based Self-healing Coatings
International Polymer Processing, No. 5, 2018
Autonomous self-healing was achieved by synthesizing epoxy coatings which contain dual micro/nanocapsules; epoxy and amine. Epoxy micro/nanocapsules were prepared by an in situ polymerization process and amine microcapsules were fabricated by vacuum infiltration of diethylenetriamine into nanoporous hollow glass microspheres. Both types of capsules were embedded into epoxy matrix. When cracks were created and started to grow in the coating, the micro/nano-capsules near the crack were ruptured and released their contents. As a result of curing reaction between released curing agents (epoxy and amine), healing of the cracked sites was completed. In this work, some properties of epoxy/amine micro/nanocapsule based self-healing coatings such as morphology of micro/nanocapsule and coating, healing and corrosion properties were studied. Also thermal stability and adhesion properties of this kind of coating were evaluated comprehensively. It was found out that optimum mass ratio of epoxy/amine capsules ratio is 1 : 1 and the highest healing efficiency was achieved for a total micro/nanocapsule concentration of 15 wt.%. Regarding thermal and adhesion behavior of coatings, it was observed that adding micro/nano-capsules to epoxy matrix did not change these properties significantly which means self-healing characteristics were achievable without deteriorating other properties.
Effect of nanoparticles on the anticorrosion and mechanical properties of epoxy coating
Surface & Coatings Technology, 2009
Homogeneous epoxy coatings containing nanoparticles of SiO 2 , Zn, Fe 2 O 3 and halloysite clay were successfully synthesized on steel substrates by room-temperature curing of a fully mixed epoxy slurry diluted by acetone. The surface morphology and mechanical properties of these coatings were characterized by scanning electron microscopy and atomic force microscopy, respectively. The effect of incorporating various nanoparticles on the corrosion resistance of epoxy-coated steel was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. The electrochemical monitoring of the coated steel over 28 days of immersion in both 0.3 wt.% and 3 wt.% NaCl solutions suggested the beneficial role of nanoparticles in significantly improving the corrosion resistance of the coated steel, with the Fe 2 O 3 and halloysite clay nanoparticles being the best. The SiO 2 nanoparticles were found to significantly improve the microstructure of the coating matrix and thus enhanced both the anticorrosive performance and Young's modulus of the epoxy coating. In addition to enhancing the coating barrier performance, at least another mechanism was at work to account for the role of the nanoparticles in improving the anticorrosive performance of these epoxy coatings.
A smart poly(aniline-formaldehyde) microcapsule based self-healing anticorrosive coating
The effectiveness of linseed oil and mercaptobenzothiazole (MBT) encapsulated poly(aniline-formaldehyde) [PAF] microcapsules was investigated for healing of cracks generated in paint/coatings. Microcapsules were prepared by in situ polymerization of aniline-formaldehyde resin to form a shell over the linseed oil and mercaptobenzothiazole. Characterizations of these capsules were studied by FTIR, TGA, and Scanning Electron Microscopy (SEM). EIS studies of the artificial defect area have shown that the coating containing microcapsules is able to protect steel in neutral media since the impedance values remained at 1.287 Â 10 8 U cm 2 even after 15 days exposure whereas the coatings without microcapsules lost their protection ability. The self healing ability of the coating containing microcapsules was studied by SVET.