Search Results (140)

Asphalt pavement cracking is an important factor affecting its service life. Under certain conditions, the self-healing behavior of asphalt itself can repair pavement cracks. However, the self-healing ability of asphalt itself is limited. In order to strengthen the self-healing ability of asphalt, the microcapsule wrapped with a repair agent is pre-mixed into the asphalt mixture. When the crack occurs and spreads to the surface of the microcapsule, the microcapsule ruptures and the healing agent flows out to realize the self-healing of the crack. Current microcapsules are mostly prepared with healing agents and bio-oil as core materials, and their high-temperature resistance to rutting is poor. While the epoxy resin contains a three-membered cyclic ether, it can undergo ring-opening polymerization to bond and repair the asphalt matrix. In addition, research on microcapsules mainly focuses on the self-healing properties of microcapsule-modified asphalt. In fact, before adding microcapsules to asphalt to improve its self-healing performance, it is necessary to ensure that the asphalt has a good road performance. On this basis, the self-healing performance of asphalt is improved, thereby extending the service life of asphalt pavement. Therefore, two-component epoxy self-healing microcapsules (E-mic and G-mic) were first prepared in this paper. Then, a temperature scanning test, rheological test of bending beams, and linear amplitude scanning test were, respectively, conducted for the microcapsule/asphalt to evaluate its road performance, including the high-temperature performance, low-temperature crack resistance, and fatigue performance. Finally, the self-healing performance of microcapsules/asphalt was tested. The results showed that the self-developed epoxy self-healing microcapsules were well encapsulated and presented as spherical micron-sized particles. The average particle size of the E-mic was approximately 23.582 μm, while the average particle size of the G-mic was approximately 22.440 μm, exhibiting a good normal distribution. In addition, they can remain intact and unbroken under high-temperature conditions. The results of road performance tests indicated that the microcapsule/asphalt mixture exhibits an excellent high-temperature resistance to permanent deformation, low-temperature crack resistance, and fatigue resistance. The self-healing test demonstrated that the microcapsule/asphalt exhibited an excellent self-healing performance. When the microcapsule content was 4%, the self-healing rate reached its optimal level of 67.8%, which was 149.2% higher than that of the base asphalt. Full article

Tung oil, as dry oil, can quickly dry and polymerize into tough and glossy waterproof coatings, with a very high application value. Tung oil was used as a core material to prepare Tung oil microcapsules coated with chitosan–Arabic gum, and the preparation process of the microcapsules was optimized. The effect of adding a UV coating on the performance of the microcapsules was explored. Under the conditions of a core–wall mass ratio of 0.5:1.0, pH value of 3.5, mass ratio of chitosan to Arabic gum of 1.0:4.0, and spray drying temperature of 130 °C, Tung oil microcapsules coated with chitosan–Arabic gum had a higher yield and coverage rate, which were 32.85% and 33.20%, respectively. With the increase of the spray drying temperature during preparation, the roughness of the coating first increased and then decreased, the visible light transmittance decreased first and then increased, and the glossiness showed an overall downward trend. The self-repairing rate decreased gradually. When the microcapsules #11 were added to the UV topcoat at 5%, the coating can obtain excellent comprehensive properties; the roughness was 0.79 μm, elongation at break was 5.04%, visible light transmittance was 77.96%, gloss loss rate was 10.95%, and self-repairing rate was 20.47%. Full article

The issue of interfacial inhomogeneity in energetic materials remains a significant challenge. In this study, fluoroelastomer F2602 was applied to HMX crystals using a water suspension granulation technique, followed by a bio-inspired coating formed via the crosslinking polymerization of polyethyleneimine (PEI) and pyrogallol (PG) on the HMX/F2602 composite. This process resulted in the formation of an HMX/F2602/PEI-PG microcapsule structure. Various characterization techniques confirmed that the chemical structure and polycrystalline morphology of the crystals were preserved throughout the coating process, maintaining the characteristic β-HMX morphology. The introduction of the PG–PEI shell significantly improved the coating coverage and minimized the exposure of crystal surfaces. Furthermore, compared to HMX/F2602, the HMX/F2602/PEI-PG composite exhibited notably enhanced thermal stability and reduced mechanical sensitivity. These improvements are attributed to the advantageous effects of the microcapsule structure formed by the bio-inspired coating on the material’s properties. Full article

Fragrance is an odorous, volatile substance. Conventionally, encapsulation is performed to improve the preservation and persistence of smells. Typical methods of fragrance encapsulation include interfacial polymerization and the sol-gel method. However, there are issues such as low encapsulation efficiency and difficulty in controlling capsule size and shell thickness. Recently, a method for generating water-in-oil-water (W/O/W)-type microcapsules using microfluidic technology was reported. This made it possible to achieve high encapsulation efficiency and excellent control of the capsule diameter and shell dimensions. However, because this method involves a preliminary dispersion process for fragrance, the production process is more complicated than that of microcapsules using general microfluidic technology. In this study, we used a method for generating oil-in-water-in-oil (O/W/O)-type microcapsules in a microchannel with partially controlled wettability and achieved the generation of monodisperse fragrance-containing microcapsules with a hydrophilic polymer shell without the need for a preliminary dispersion process. Full article

The development of self-healing coatings represents a promising approach to enhance the durability of metal substrates exposed to corrosive environments, demanding thorough in situ investigations. In this study, poly(urea–formaldehyde–melamine) (PUF) microcapsules containing linseed oil (LO) were synthesized via in situ polymerization to act as healing agents in protective coatings. The microcapsules were characterized using scanning electron microscopy (SEM), optical microscopy (OM), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The capsules exhibited a regular spherical morphology with an average diameter of 96 µm and an LO encapsulation efficiency of 81 wt%. TGA confirmed their thermal stability up to 200 °C, while FTIR verified the successful encapsulation of LO. For performance evaluation, 10 wt% of the microcapsules was incorporated into an epoxy matrix and applied to carbon steel. Corrosion resistance was evaluated using electrochemical impedance spectroscopy (EIS) in 0.1 mol/L of NaCl solution over 500 h. The coating with microcapsules exhibited a |Z|_0.01 of 10⁶ Ω·cm², higher than the 10⁴ Ω·cm² observed for the coating without microcapsules, indicating improved barrier properties. Raman spectroscopy confirmed the auto-oxidation of LO at damaged areas, evidencing the self-healing mechanism. Although full barrier recovery was not achieved, the system effectively delayed corrosion progression. Full article

Carbonyl iron powder is a widely used microwave-absorbing material due to its numerous advantages. However, carbonyl iron powder is prone to corrosion in high-salt-spray environments, reducing the service life of the composite material and limiting its applications, particularly in marine environments. In this study, we prepared polystyrene-encapsulated carbonyl iron microcapsules via in-situ polymerization and investigated their structure and properties. The results show that the coating of the polystyrene shell did not affect the crystal structure of the carbonyl iron and hardly weakened its electromagnetic properties. Compared to uncoated carbonyl iron powder, polystyrene-encapsulated carbonyl iron microcapsules exhibited superior corrosion resistance in both HCl solution and salt-spray environment. This work offers a potential solution for enhancing the durability of microwave-absorbing material in corrosive environments. With this simple, effective, and low-budget procedure, the cost of microwave-absorbing coating used in marine environments would be significantly reduced. Full article

Thermal energy storage offers a viable solution for managing intermediate energy availability challenges. Phase change materials (PCMs) have been extensively studied for their capacity to store thermal energy when available and release it when needed, maintaining a narrow temperature range. However, effective utilization of PCMs requires its proper encapsulation in most applications. In this study, microcapsules containing Rubitherm^®(RT) 21 PCM (Tpeak = 21 °C, ΔH = 140 kJ/kg), which is suitable for buildings, were synthesized using a suspension polymerization technique at different operating temperatures (45–75 °C). Two different water-insoluble thermal initiators were evaluated: 2,2-Azobis (2,4-dimethyl valeronitrile) (Azo-65) and benzoyl peroxide (BPO). The prepared microcapsules were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), particle size distribution (PSD), scanning electron microscope (SEM), and optical microscopy (OM). Additionally, the microcapsules were subjected to multiple melting and freezing cycles to assess their thermal reliability and performance stability. DSC results revealed that the microcapsules using BPO exhibited a latent heat of melting comparable to those produced with Azo-65 at an operating temperature of 75 °C. However, the onset crystallization temperature for the BPO-encapsulated PCMs was approximately 2 °C lower than that of the Azo-65-encapsulated PCMs. The greatest latent heat of melting, 107.76 J/g, was exhibited by microcapsules produced at 45 °C, representing a PCM content of 82 wt. %. On the other hand, microcapsules synthesized at 55 °C and 75 °C showed latent heats of 96.02 J/g and 95.66 J/g, respectively. The degree of supercooling for PCM microcapsules was reduced by decreasing the polymerization temperature, with the lowest supercooling observed for microcapsules synthesized at 45 °C. All microcapsules exhibited a monodisperse and narrow PSD of ~10 µm, indicating uniformity in microcapsule size and demonstrating that temperature variations had no significant impact on the particle size distribution. Future research should focus on low-temperature polymerization with extended polymerization times. Full article

The aim of this study is to develop and investigate the effect of applying microcapsules containing a melamine formaldehyde resin shell and a tannin extract as a core to form a hydrophobic coating. The microcapsules were obtained by in situ polymerization. Morphological analysis was performed by focused ion beam/scanning electron microscopy. The chemical composition of the tannin extract, the melamine formaldehyde resin, and the polymeric microcapsules with the core of the tannin extract was determined by Fourier transform infrared spectroscopy. The thermal stability of tannin, melamine formaldehyde resin, and tannin microcapsules was investigated by thermogravimetric analysis. In addition, the durability of the coating over time was tested in an environmental test chamber. The polymeric microcapsules containing tannin extract are quasi-spherical, rough, and dense, with a diameter ranging from 1 to 5 μm and a shell thickness of 50 nm. The coating exhibited a hierarchical structure with improved hydrophobic properties, resulting in a contact angle of up to 148°. Full article

Bamboo, recognized as a nutrient-dense biomass material, exhibits a high susceptibility to mold infestations, which can result in discoloration and a notable decrease in longevity, thereby posing potential health risks to humans. In this study, melamine-formaldehyde resin (MFR) was utilized to load 3-iodo-2-propargyl-butyl-carbamate (IPBC) via in situ polymerization, resulting in the preparation of microcapsules suitable for anti-mold protection of bamboo. The mold resistance of Aspergillus niger, Trichoderma viride, and Penicillium citrinum were evaluated. A scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier-transform infrared spectrometer (FTIR), and thermogravimetric analysis (TG) were used to characterize and analyze the formation process, surface morphology, structural composition, and thermal stability of the microcapsules. The effects of different surfactants (Span 80, Tween 80, SDBS, SDS, GA) on the microscopic morphology of the anti-mold microcapsules were investigated. The results show that microcapsules prepared with Tween 80 as the surfactant exhibited good mold resistance. After coating MFR with IPBC, the drug loading of I-MFR is 20%, with an encapsulation efficiency of 80%, demonstrating excellent anti-mold performance. The microcapsules show favorable anti-mold performance and have broad application prospects in bamboo protection. Full article

To address the issue of metal corrosion caused by microcracks in the coating on the steel structures of offshore drilling platforms, this study employs interfacial polymerization to prepare microcapsules with self-healing functionality for coatings. The microcapsules are fabricated through free radical polymerization between methyl methacrylate (MMA) and ammonium persulfate (APS), along with crosslinking reactions involving divinylbenzene (DVB). The particle size distribution and surface morphology of the microcapsules were optimized by adjusting process parameters using optical microscopy and scanning electron microscopy. Fourier-transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) were used to characterize the chemical structure and thermal stability of the microcapsules. The results show that when polyvinyl alcohol is used as the emulsifier, the oil–water ratio was 7.5:200, the amount of emulsifier was 1 wt%, the emulsification speed was 2500 r/min, the amount of initiator was 2 g, the core-to-wall ratio was 4:1, and the ambient temperature was 60 °C showed good sphericity, the microcapsules prepared under the optimized parameters exhibit good sphericity, a smooth surface, and an average particle size of 35.17 μm. They have a good core material encapsulation effect and thermal stability, which impart excellent self-healing properties to the epoxy coating. Such microcapsules have promising applications in mitigating the problem of metal corrosion of coatings due to microcracks and improving the service life and reliability of equipment. Full article

Acid-fracturing technology has been applied to form pathways between deep oil/gas resources and oil production pipelines. The acid fracturing fluid is required to have special slow-release performance, with no acidity at low temperatures, while steadily generating acid at high temperatures underground. At present, commercial acid systems in oilfields present problems such as the uncontrollable release effect, high costs, and significant pollution. In this research, we designed an innovative chloroformate material and investigated the release of the acid at various temperatures. This new chloroformate material reacts slowly with water at room temperature, and can completely react with water to form hydrochloric acid at high temperatures, without residual organic chlorine and other harmful substances; thus, it is suitable for use as an acid agent in oilfields. To isolate the acid-release core material from the outer water phase, we encapsulated the former with various materials, such as cross-linked polyacrylate or polystyrene, to obtain microcapsules. By slowly breaking and degrading the shell layer at a high temperature, the goal of no acid being released at low temperatures with slow acid generation at a high temperature was achieved. The microcapsules were prepared using radical polymerization and the phase separation method. Furthermore, scanning electron microscopy, differential scanning calorimetry, chemical titration analysis, and other methods were used to characterize the structure and the sustained acid release of microcapsules. The results of thermogravimetry and other experiments showed that the prepared microcapsules successfully coated the chloroformate material. In contrast to the bare material, the slow-release performance of the microcapsules was significantly improved, and the continuous acid generating time was able to reach more than 10 h. Under optimum conditions, microcapsules with a uniform particle size with a sustained-release acid core were prepared, and the encapsulation efficiency reached up to 60%. Compared with traditional acid-release systems, the new system prepared in this study has better acid-release performance at high temperatures, while the product is both clean and convenient to use. Multiple important parameters, such as microcapsule particle size, can also be controlled by varying the experimental conditions to meet the needs of different oil/gas extraction environments. In summary, we prepared a promising new and efficient slow-release acid generation system, which has unique practical significance for optimizing current oilfield acid-fracturing technology. Full article

Microcapsules are widely utilized in various applications to preserve active ingredients for prolonged durations while enabling controlled release. However, limited release of active ingredients often hampers their effectiveness in daily-use products. In this study, we demonstrated the synthesis of silica core–shell microcapsules designed for controlled fragrance release in topical formulations. The microcapsules were synthesized via the sol–gel polymerization of tetraethyl orthosilicate (TEOS) on the surface of an oil/water emulsion, leveraging the shrinkage and deformation characteristics of sol–gel-derived silica during drying. The concentrations of dipalmitoylethyl dimethylammonium chloride, a cationic emulsifier used in cosmetics, and TEOS were optimized to sustain fragrance release for up to 24 h after topical application. An additional silica coating on the microcapsules reduced the Brunauer–Emmett–Teller surface area by 76.54%, enhancing fragrance stability for long-term storage. The timed-release behavior was assessed using fragrance evaluation tests and gas chromatography–mass spectrometry. The fragrance intensity and release profiles confirmed the potential of these microcapsules in daily-use cosmetics. These findings suggest that silica microcapsules with extended-release properties have application potential in both cosmetic and pharmaceutical products. Full article

This article proposes the synthesis and characterization of (triethylene glycol dimethacrylate–N,N-dihydroxyethyl-p-toluidine) TEGDMA-DHEPT self-healing microcapsules for their inclusion in dental composite formulations. The obtaining method is the in situ emulsion polymerization of the (poly urea-formaldehyde) (PUF) coatings. The microcapsules were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), high-performance liquid chromatography (HPLC), and low-field nuclear magnetic resonance (NMR) techniques. The optimal formation of uniform microcapsules is achieved at a stirring speed of 800 rpm and centrifugation is no longer necessary. HPLC demonstrates that the microcapsules formed at 800 rpm show a better control of liquid release than the heterogeneous ones obtained at a lower stirring speed. The centrifuged samples have rounded shapes, with dimensions between 80 and 800 nm, while the non-centrifuged samples are more uniform, with a spherical shape and dimensions of approximately 800 nm. Full article

Aiming at the complex conditions of the coexistence of the explosive gases in the coal mines and the risk of spontaneous coal combustion, the effect of encapsulation, oxygen barrier and different microcapsules on methane and long-chain alkanes has been studied. A non-toxic microcapsule comprising the anti-explosion fire-extinguishing polymeric material with neutral pH value, biodegradability and full solubility in water has been developed. The fire-extinguishing platform system has been used to test and analyze the fire-extinguishing effect, explosion suppression efficiency and package efficiency of the oil-pan fires and solid stacks. It is revealed that the microcapsule fire-extinguishing technology has a strong fire-extinguishing effect and can better inhibit the methane explosion, owing to its effective enveloping effect on methane, thus making it difficult to reignite. The developed technology is of theoretical significance and has a practical application value for studying the flame retardation and fire-extinguishing behavior of combustible substances. Full article

In this work, multiwalled carbon nanotubes (MWCNTs) were melt-compounded into a novel thermal energy storage system consisting of a microencapsulated paraffin, with a melting temperature of 6 °C (M6D), dispersed within a flexible thermoplastic polyurethane (TPU) matrix. The resulting materials were then processed via Fused Filament Fabrication (FFF), and their thermo-mechanical properties were comprehensively evaluated. After an optimization of the processing parameters, good adhesion between the polymeric layers was obtained. Field-Emission Scanning Electron Microscopy (FESEM) images of the 3D-printed samples highlighted a uniform distribution of the microcapsules within the polymer matrix, without an evident MWCNT agglomeration. The thermal energy storage/release capability provided by the paraffin microcapsules, evaluated through Differential Scanning Calorimetry (DSC), was slightly lowered by the FFF process but remained at an acceptable level (i.e., >80% with respect to the neat M6D capsules). The novelty of this work lies in the successful integration of MWCNTs and PCMs into a TPU matrix, followed by 3D printing via FFF technology. This approach combines the high thermal conductivity of MWCNTs with the thermal energy storage capabilities of PCMs, creating a multifunctional nanocomposite material with unique thermal management properties. Full article