Microencapsulation of epoxy resins: Optimization of synthesis conditions

In order to study the effect of healing materials viscosity on the self‐healing performance of polymer composite, mostly available epoxy resin of viscosity 10–12 Pa.s and amine hardener of viscosity 0.01–0.02 Pa.s were chosen as two different healing materials and successfully encapsulated. Effect of core to shell(c/s) ratio on the synthesis of epoxy microcapsules was investigated and 1:1 c/s ratio is suggested as an ideal ratio to synthesize epoxy capsules. Chemical structure and thermal decomposition patterns of both microcapsules and capsules reinforced composite were analyzed. Tensile strength, impact strength and fracture toughness of capsules reinforced self‐healing epoxy composite were evaluated. It was observed that the toughness of epoxy composite increased with the increase in microcapsules concentration. An optimum healing efficiency of 66% was observed with the addition of 7.5 wt% epoxy and hardener microcapsules at equal weight ratio. Stresses developed in the pure epoxy composite crack front were analyzed using Ansys V18.1.

Section: Introductionmentioning

confidence: 99%

Self‐healing performance assessment of epoxy resin and amine hardener encapsulated polymethyl methacrylate microcapsules reinforced epoxy composite

Pittala

Ben

2021

“…About 10 min later, 6.32 g formaldehyde solution (37%) was added drop-by-drop to the suspension to stabilize the emulsion. The reaction temperature was elevated up to 55 ± 1 C at 1 C/min and the reaction was continued for further 3 h. 1,34 After cooling the solution to the ambient temperature, microcapsule suspension was rinsed several times with plenty of distilled water. In the end, synthesized capsules were dried using a freeze dryer instrument (Dena Vacuum Industry Co. Iran) at −45 ± 5 C and 10 ± 2 m Pa. To examine the effect of the solvent content of the core material, additional microcapsules were prepared following a similar procedure, however; using epoxy with 30 wt% BA content.…”

Section: Preparation and Characterization Of Uf/pu Microcapsulesmentioning

confidence: 99%

“…1,46 The possible reactions for the preparation of two-component shell (UF/PU) are shown in Figure 5. 1,34 The EEW of epoxy resins is an important characteristic property for their reactivity and the performance of the final coating product. The EEW of neat and encapsulated epoxy resin was calculated in the range of 183-188 g/eq that are in agreement with information provided by the supplier (184-190 g/eq).…”

Section: Chemical Characterization Of Synthesized Microcapsulesmentioning

confidence: 99%

“…This finding also indicates that the microencapsulation process did not affect the epoxy resin. 34 Toluene and xylene are the most frequent solvents that are used for the industrial-based resins. Accordingly, the stability of prepared microcapsules in these solvents was evaluated following their dispersing in toluene and xylene and storage for 30 days.…”

Section: F I G U R E 5 Possible Reactionsmentioning

confidence: 99%

“…Epoxy resins are among the most important core materials in self-healing coatings due to their ability to react with a wide range of hardeners at different temperatures. 34 As a principle, better miscibility between the healing agents and the epoxybased coating is expected. Therefore, in this study, reactive epoxy resin was used as a core material for microencapsulation.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Development of self‐healing coatings based on urea‐formaldehyde/polyurethane microcapsules containing epoxy resin

Parsaee

Mirabedini

Farnood

et al. 2020

In this study, the synthesis of urea‐formaldehyde/polyurethane (UF/PU) microcapsules containing epoxy resin for self‐healing and anti‐corrosion coatings with good stability has been reported. Spherical microcapsules were prepared with a diameter of about 50–720 μm and a shell thickness of 0.6–0.7 μm via in situ polymerization in an oil‐in‐water emulsion using 2,4‐toluene diisocyanate‐based pre‐polymer along with the urea‐formaldehyde. Scanning electron microscopy (SEM) and optical microscopy (OM) were employed to evaluate the shape and morphology of the microcapsules. Fourier transform infrared (FTIR) spectroscopy showed the absence of free isocyanate groups within the microcapsule shell confirming the completion of shell formation reactions. OM illustrated that the microcapsules were stable over a period of 30‐days in toluene and xylene. Increasing microcapsule loading improved crack repairing and anti‐corrosion performance of the coating layer. Low‐carbon steel coupons coated with an epoxy resin containing 10 wt% microcapsules and scribed using a scalpel blade showed no visible sign of corrosion after up to 5 weeks of exposure in a standard salt spray test chamber.

Epoxy loaded poly(urea‐formaldehyde) microcapsules via in situ polymerization designated for self‐healing coatings

Tzavidi

Zotiadis

Porfyris

et al. 2020

Self‐healing systems are a next‐generation technology that can offer autonomous crack repair and increase the service lifetime of a protective coating. Polymeric microcapsules containing healing agents can be used in that perspective and exhibit significant potential. In the current study, poly(urea‐formaldehyde) microcapsules containing an epoxy healing agent as core material were successfully prepared using in situ polymerization. The effect of different process parameters was studied in respect to microcapsules' characteristics, that is, morphology, particle size, encapsulation efficiency and thermal properties. Spherical microcapsules with either smooth or rough surface were obtained with a size ranging from 90 to 165 μm, controlled by the stirring rate during the emulsification stage. The encapsulation efficiency varied between 65–77% with no significant dependence on the process conditions. Finally, the stability of the microcapsules during storage was investigated at different conditions.