Effect Of Microcapsules Research Articles

Preparation of Healable Shellac Microcapsules and Color-Changing Microcapsules and Their Effect on Properties of Surface Coatings on Hard Broad-Leaved Wood Substrates

In order to protect the wood surface and improve the properties of coatings, microcapsules with healable and discoloration functions are produced, and their healable function is obtained using shellac, which can be cured at room temperature, as the repairing agent. In this paper, self-made shellac microcapsules and color-changing microcapsules were added to varnish in different proportions to form the composite coating on a wood board, and the color difference of the coating was measured at different temperatures to study the influence of microcapsules on the degree of surface color on the substrate. The effect of microcapsules on the healable performance of coatings on a wood board was studied by scratching the surface of the coating with a utility knife and observing the process of repair. The optimal sample was selected from the orthogonal experiment for the independent experiment. The surface roughness, hardness, infrared spectrum, and scanning electron microscopy of the optimal sample were tested, and the content in the optimal sample was further investigated. The results show that color-changing microcapsules have a color-changing effect on surface coatings based on wood boards, and shellac microcapsules inhibit the color-changing effect of color-changing microcapsules. Composite microcapsules can repair the cracks on the surface coatings of wood boards. In cases where shellac microcapsules can self-repair the coating, the color-changing effect is best when the content of color-changing powder is 15.0%.

Microencapsulated bioactive peptides from brewer's spent grain promotes antihypertensive and antidiabetogenic effects on a hypertensive and insulin-resistant rat model.

The effects of microcapsules containing brewer's spent grain (BSG) peptides were evaluated on a hypertensive/insulin-resistant rat model induced by a sucrose-rich diet (SRD) administration. Animals received for 100 days the control diet (CD), SRD, and CD and SRD diets supplemented with microencapsulated peptides (CD-P and SRD-P). During the experimental period, blood pressure was monitored. Glycemia, tissue glycogen content, nitric oxide, and the activity of enzymes related to hypertensive and diabetogenic mechanisms were determined. The consumption of SRD caused hypertensive and hyperglycemic effects compared to CD. However, the SRD-P group presented lower systolic pressure at the middle of ingestion, achieving similar values than the CD. The SRD-P rats decreased all enzymes' activities compared to the SRD reaching the values of CD, except for those of α-amylase in cecal content and DPP-IV in serum. It was possible to corroborate potential antihypertensive and antidiabetogenic in vivo effects of the microencapsulated BSG peptides. PRACTICAL APPLICATIONS: Brewer's spent grain (BSG) is the main waste obtained from brewing industry. Bioactive peptides obtained after an enzymatic hydrolysis of proteins with in vitro antihypertensive and antidiabetogenic activity have been described. However, to corroborate the action of these bioactive peptides, in vivo studies are necessary. In the present work, microcapsules containing bioactive peptides from BSG were administered on the rat model with induced hypertension and insulin-resistance, corroborating an in vivo antihypertensive and antidiabetogenic effects by inhibition of enzymes related with blood pressure regulation and glucose metabolism. This work demonstrated that microcapsules of BSG peptides could be included into functional foods formulations, or used as dietary supplement for improving health and the prevention of non-communicable diseases, adding value to the brewing process by-product.

Preparation and investigation of self-healing cementitious composite based on DMTDA - epoxy binary microcapsules system

Cement-based material are prone to cracks. Self-healing concrete appealed to extensive discussion owing to its crack-healing functions without human intervene. In this study, epoxy resin microcapsules and dimethyl thio-toluene diamine microcapsules (DMTDA microcapsules) were prepared successfully based on different mechanisms. Both of the microcapsules were spherical with favorable dispersion and good thermal stability. The effects of microcapsules on the fluidity, compressive strength and open porosity of self-healing cementitious composite were investigated, and the self-healing performance was characterized by microscopic observation of the repairable width of single cracks. It turned out that the fluidity and compressive strength of the self-healing cementitious composite decreased gradually with the increase of the concentration of microcapsules. The open porosity of self-healing cementitious composite hydrated for 28 days decreased by 19.1% when the concentration of microcapsules was 9.0% by weight. Ultimately, the single cracks with width below 40 μm could be repaired completely when self-healing cementitious composite was hydrated for 7 days.

Heat Control Effect of Phase Change Microcapsules upon Cement Slurry Applied to Hydrate-Bearing Sediment

This study aims to develop a novel low-heat cement slurry using phase change microcapsule additives to reduce the decomposition of hydrate-bearing sediments during cementing. Microcapsules were prepared by coating mixed alkanes with polymethyl methacrylate, and lipophilic-modified graphite was incorporated to enhance the thermal conductivity of microcapsules. The effects of microcapsules upon the hydration heat, pore distribution, and compressive strength of the cement slurry/stone were studied through a variety of tests. The results showed that the phase-change temperature, thermal enthalpy, and encapsulation efficiency of the microcapsules were 8.99–16.74 °C, 153.58 Jg−1, and 47.2%, respectively. The introduction of lipophilic-modified graphite reduced the initial phase-change temperature of microcapsules by 0.49 °C, indicating an improvement in their temperature sensitivity. The maximum hydration heat of cement slurry decreased by 41.3% with 7% dosage of microcapsules; the proposed microcapsules outperformed comparable low-heat additives. Moreover, the presence of microcapsules could reduce the number of large pores in (and thereby improve the compressive strength of) cement stone. The innovation of this study is that it comprehensively and intuitively confirms the feasibility of the application of low-heat cement slurry with MPCM as the key in hydrate sediments rather than just focusing on the reduction of hydration heat; furthermore, a self-made cementing device was developed to simulate the cementing process of hydrate deposition. The results show that the thermal regulation of microcapsules inhibited the temperature increase rate of the cement slurry, significantly reducing the damage caused to the hydrate. These findings should improve the safety and quality of cement in offshore oil and gas well applications.

Effect of hydrogel microcapsule on shrinkage and mechanical properties of cement mortars

Superabsorbent polymer (SAP) shows a good internal curing effect in cement-based materials, but its volume changes greatly after it releases water. This occurrence causes adverse effects on the properties of cement-based materials. Microcapsules were prepared with calcium alginate hydrogel as the shell and epoxy resin as the core material to mitigate these adverse effects. The effects of microcapsules on the shrinkage and mechanical properties of cement mortars were analysed by observing such parameters as the heat of hydration and relative humidity of the mortars, and such techniques as mercury intrusion porosimetry. The results showed that microcapsules can delay the hydration of cement and provide a superior early shrinkage reduction effect when compared with SAP. In addition, the presoaked microcapsules left pores that were smaller in diameter than those observed in the SAP mortars. As a result, the influence of microcapsules on the mortar's compressive strength was found to be less than that of SAP. Therefore, the compressive strength of the mortars containing microcapsules was essentially the same as that of the mortars containing SAP when the presoaked microcapsule content was 35 times that of the presoaked SAP content.

Investigation of Cement Prepared with Microencapsulated Microorganisms.

Cracks in underground rock masses cause gas leakage, seepage, and water inflow. To realize calcium carbonate deposition and mineralization filling in rock cracks, microencapsulated bacterial spores were prepared by an oil phase separation method. To optimize the microorganism growth conditions, the effects of microcapsules with various pHs, particle sizes, and amounts on microcrack self-healing were investigated through an orthogonal test, and the best conditions for repairing the cracks using microencapsulated Bacillus sphaericus were obtained. Infrared analysis and scanning electron microscopy were used to observe the morphological characteristics and coating performance of the microcapsules. The results showed that the microcapsules contained functional groups in the core and wall materials. The surfaces of the microcapsules prepared by the test were rough, which was beneficial for adhesion onto the fracture surface. X-ray diffraction analysis, X-ray photoelectron spectroscopy, and thermal analysis were conducted. The results showed that the microcapsules with pH = 8 and a particle size of 100 μm had the highest thermal decomposition temperature and the best thermal stability. The elements of the core and wall materials were detected in the microcapsules, and the coating had a beneficial effect. The compression and acoustic emission tests of the specimens embedding microbial capsules with different contents under different working conditions revealed that the two fractures of the specimen were due to the rupture of the microcapsule and the rupture of the rock specimen, indicating the best mechanical triggering properties and compressive properties of the microcapsule.

Effect of microcapsules doping on dielectric performance of self-healing epoxy resin composites

Effect of microcapsules doping on dielectric performance of self-healing epoxy resin composites

Effect of Microcapsules with Waterborne Coating as Core Material on Properties of Coating for Tilia Europaea and Comparison with Other Microcapsules.

Urea formaldehyde was used as wall material and waterborne coatings as a core material to prepare microcapsules. So as to explore the influence of mass ratio of core to shell, reaction temperature and standing time on the performance of microcapsules, the orthogonal test of three factors and two levels was put into effect. The orthogonal experimental results showed the mass ratio of core to shell was the most important factor. With the increase of the mass ratio of core to shell, the output and clad ratio of microcapsules increased first and then decreased. The microcapsule with the mass ratio of core to shell of 0.67:1 had better appearance, output, and encapsulation performance. The optical properties of waterborne wood coating with the microcapsules of waterborne coating as core materials did not decrease significantly, while the hardness, impact resistance, and toughness were improved. At the same time, the microcapsules have a certain self-repairing effect on coating micro-cracks. Compared with the properties of waterborne coatings with other microcapsules, the coating with waterborne coating as core material has better comprehensive performance. The results provide a new research idea for the performance enhancement and self-healing of wood waterborne coating.

Dynamic behavior of microcapsule-based self-healing concrete subjected to impact loading

This paper reports an experimental investigation on the dynamic behavior of microcapsule-based self-healing concrete subjected to impact loading. Dynamic impact tests were carried out using a Ø40-mm split Hopkinson pressure bar (SHPB) apparatus. The strain rate ranged from 30 s−1 to 200 s−1, and self-healing concrete with different mass fractions of microcapsules (0%, 2%, 5%, and 8%) was prepared. The effects of microcapsules on the dynamic compressive properties were investigated and compared with those observed in quasi-static tests. The strain rate effects on dynamic strength, failure pattern, and energy absorption were also investigated. The results show that the dynamic mechanical properties of the self-healing concrete exhibit strong strain-rate dependency. The dynamic compressive strength and strain energy density increase with increasing strain rate. Substantial differences in the post-test damage patterns are observed between the control and experimental groups. The dynamic increase factor (DIF) of the self-healing concrete increases with the strain rate in an approximately logarithmic manner, and the strain-rate sensitivity threshold occurs at 25.7 s−1. Empirical DIF relations are proposed based on the test results for predicting the material behavior of structures subjected to static and impact loading.

Preparation and properties of hydrotalcite microcapsules for coal spontaneous combustion prevention

Microcapsule materials are a new type of composite fire-extinguishing material that show good effects in preventing the spontaneous combustion of coal. In this paper, polyethylene glycol 6000 (PEG6000) was selected as the wall material, and hydrotalcite (LDHs) was selected as the core material. Microencapsulated LDHs samples with different core-to-wall ratios were prepared by melting dispersion and condensation. Scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetry/differential scanning calorimetry (TG/DSC) and other experiments were used to characterize the surface morphology, dispersion, coating, pyrolysis and other characteristics of the microcapsules. On this basis, the microcapsules were mechanically mixed with a coal sample to prepare a chemically inhibited coal sample. Based on TG/DSC experiments, the effect of microcapsules with different core-to-wall ratios on the characteristics of coal spontaneous combustion was studied. Combined with thermokinetic parameters, the inhibition mechanism of the microcapsules with different core-to-wall ratios on coal spontaneous combustion was analyzed. The results showed that LDH-PEG6000 microcapsules were successfully prepared. The thermal reactivities and inhibition mechanism of microcapsules with different core-to-wall ratios were different, and the best effect was obtained when the core-to-wall ratio was 1:5. This microcapsule material can reduce the weight loss rate and heat release of coal, increase the critical temperature and maximum weight loss rate temperature by 8.8 °C and 33.6 °C, respectively, and increase the apparent activation energy of water evaporation and gas desorption stage by 13.42 kJ/mol and the thermal decomposition stage and combustion stage by 88.64 kJ/mol. Resistance microcapsules can effectively inhibit the coal spontaneous combustion reaction In addition, this research provides new ideas for solving the problem of coal spontaneous combustion in the goaf caused by the fully mechanized top coal caving technology and enriches the technical means of fire prevention.

Effect of Microcapsules on Dielectric Properties of Self-Healing Low Density Polyethylene Insulation Composites

The polyolefin materials play important roles in transmission equipment for their advantages. However, slight damage would happen inevitably, which is difficult to detect and repair, and threatens the power supply safety. It is a new research field for realizing the self-healing ability of polyolefin insulation materials by microcapsule technology. This paper explores the preparation scheme of low density polyethylene (LDPE)/microcapsule insulation material and focuses on its dielectric properties. Based on the verification of self-healing properties, how microcapsules of different concentrations affect the LDPE dielectric properties is analyzed by the crystallinity change. The results show that the composite has evident self-healing ability, and the mechanical damage of the LDPE matrix can trigger the self-healing behavior of microcapsules timely. When the microcapsule concentration increases, the dielectric constant decreases initially and then increases, and the dielectric loss factor tends to increase. In general, the 1 wt% microcapsule composite has better crystalline, dielectric properties, and self-healing ability. In summary, microcapsules affect the crystallinity and grain size of LDPE by changing its crystallization behavior and the proportion of the amorphous region. Meanwhile, the influence of microcapsules on the crystal structure, the introduction of impurities and interfaces affect the dielectric constant and loss factor. This study not only provides a potential new self-healing insulation material, but also promotes the fusion development of new solid insulation material and self-healing.

Synthesis of Urea-Formaldehyde Microcapsule Containing Fluororesin and Its Effect on Performances of Waterborne Coatings on Wood Surface.

In order to self-repair the cracks of waterborne coatings on Basswood at room temperature, with fluororesin and waterborne coatings embedded in the shell structure of urea formaldehyde (UF) resin, the microcapsules were fabricated via in-situ polymerization, and the effect of microcapsules on the chroma, gloss, mechanics and repair effect for waterborne coatings on wood was discussed. The results indicated that the coating effect was the most significant when the ratio value of the core materials to the shell material of microcapsules in mass was 0.75, and the agglomeration of particles was the least and the surface was the smoothest when the content of microcapsules was 1.0%. It was negative between the gloss of the film and microcapsule content. The ratio value of the core materials to the shell material in mass and the amount of microcapsules had great influence on the film hardness and adhesion, but had little effect on the impact resistance. When the ratio value of the core materials to the shell material of microcapsules in mass was 0.65 and the addition amount was 4.0–10.0%, the aging resistance of the film was improved most significantly. When the ratio value of the core materials to the shell material of microcapsules in mass was 0.65 and the addition amount was 7.0%, the overall properties of topcoat film on Basswood board was the most significant. It is for the application of fluororesin microcapsules possessing self-repairing effect in waterborne coating on Basswood board that a technical groundwork is provided by this study.

Preparation and Characterization of Microcrystalline Wax/Epoxy Resin Microcapsules for Self-Healing of Cementitious Materials.

Self-healing of cracks in cementitious materials using healing agents encapsulated in microcapsules is an intelligent and effective method. In this study, microcapsules were prepared by the melt–dispersion–condensation method using microcrystalline wax as the shell and E-51 epoxy resin as the healing agent. The effects of preparation process parameters and microcrystalline wax/E-51 epoxy resin weight ratio on the core content, particle size distribution, thermal properties, morphology, and chemical composition of microcapsules were investigated. The results indicated that the optimal parameters of the microcapsule were microcrystalline wax/E-51 epoxy resin weight ratio of 1:1.2, stirring speed of 900 rpm, and preparation temperature of 105 °C. The effects of microcapsules on pore size distribution, pore structure, mechanical properties, permeability, and ultrasonic amplitude of mortar were determined, and the self-healing ability of mortar with different contents of microcapsules was evaluated. The optimal content of microcapsules in mortars was 4% of the cement weight, and the surface cracks of mortar containing microcapsules with an initial width of 0.28 mm were self-healed within three days, indicating that microcapsules have excellent self-healing ability for cementitious materials.

Corrosion Resistance Evaluation of Self-Healing Epoxy Coating Based on Dual-Component Capsules Containing Resin and Curing Agent

In this study, a self-healing epoxy coating was prepared by incorporating a dual capsule healing system including epoxy resin and its amine-based curing agent. The emulsion electrospray technique was used for encapsulating the healing agents in poly(styrene co-acrylonitrile) (SAN) as shell material. Characterizing the prepared microcapsules (MCs) by Scanning Electron Microscopy (SEM) revealed their spherical morphology with the particle size of 827 nm and 749 nm for epoxy and amine cores, respectively. Fourier Transform Infrared Spectroscopy (FT-IR) and thermogravimetric analysis (TGA) results confirmed successful encapsulation with no side chemical reaction between the encapsulated core and shell materials. The effects of embedding MCs on the physical and mechanical properties of the epoxy coating matrix were studied by pull-off adhesion, conical mandrel bending, and gloss tests. In addition, the prepared coatings’ self-healing performance was evaluated by Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization (Tafel) experiments. The results revealed that the coating sample containing 1 wt% of core-shell MCs (a mixture of epoxy and amine-containing MCs with a 50 : 50 weight ratio) showed the best corrosion performance with 99% self-healing efficiency.

Effects of Microcapsules on Self-Healing Performance of Asphalt Materials under Different Loading Modes

This study used two types of self-healing microcapsules to evaluate the healing performances of asphalt materials that contained different dosages of microcapsules under three different loading modes: shear, tension, and bending loads. The optimum dosage of the microcapsules was determined in asphalt materials. The healing performance of the asphalt materials that contained softening and bonding microcapsules under shear load was evaluated by a dynamic shear rheometer (DSR) test. The optimum dosage was determined based on the healing indexes (PDSR1 and PDSR2) of the ratio of the initial shear modulus and loading times. The healing performance of the asphalt material that contained softening microcapsules under tension load was evaluated by a low-temperature tensile (LTT) test. The optimum dosage was determined based on the healing index (PLTT) of the ratio of maximum tension. The healing performance of the asphalt materials that contained bonding microcapsules was evaluated under bending load by a semicircular bending (SCB) test. The optimum dosage was determined based on the healing index (PSCB) of the ratio of the maximum load. The results revealed that the optimum dosages of the softening microcapsules of virgin asphalt binder, aged asphalt binder, and asphalt mortar were 0.5%, 1.0%, and 2.0%, respectively. The optimum dosage of the bonding microcapsules for emulsified asphalt was 1.0% as determined by the DSR test, whereas it was less than 3.0% as determined by the SCB test.

Effect of microcapsules doping on DC flashover and trap level of self-healing epoxy resin composites

Minor physical defects can decrease the dielectric efficiency of epoxy resin and severely threaten the electrical device’s dependability. Self-healing may be considered an effective method to preserve the electrical and mechanical properties of the epoxy resin. Besides, self-healing significantly decreases the influence of small physical destruction on the power system. In this research, epoxy resin incorporated with various concentration of microcapsules was prepared. The polyurea formaldehyde (PUF) microcapsules were treated using a silane coupling agent (KH550) to enhance dispersion. Moreover, the self-healing performance of the epoxy resin incorporated with microcapsules was analyzed by FTIR, SEM, and DC Flashover in air and vacuum. In addition, trap energy and trap density were obtained from measurements of surface potential decay (ISPD). The SEM results indicate that in comparison with pure epoxy resin, the microcapsule/epoxy resin composite has an improved self-healing performance. The DC Flashover of epoxy resin in air and vacuum was found relatively higher after incorporation of microcapsules than pure epoxy resin. The distribution of trap energy and trap density measured by surface potential decay measurements confirms that 5 wt% have deeper traps and the highest trap energy levels.

Effect of Microcapsules with Different Core–Wall Ratios on Properties of Waterborne Primer Coating for European Linden

Waterborne acrylic-resin-filled urea–formaldehyde-based microcapsules with core–wall ratios of 0.42:1, 0.50:1, 0.58:1, 0.67:1, 0.75:1, 0.83:1 and 0.92:1 were prepared via in situ polymerization. Microcapsules were added into the primer to investigate the optical and mechanical properties of the coating on European linden. The results indicated that under the condition of the same core–wall ratio, chroma differences increased gradually with increasing concentration. The coating gloss decreased with increasing concentration. The hardness of 10.0–15.0% microcapsules increased more obviously, with the highest elongations at the break of the coating. At the 0.58:1 core–wall ratio and the 10.0% concentration, the coating adhesion was level 1 and the impact resistance was 10.0 kg cm. Microcapsule concentration did not affect the coating’s liquid resistance. The coating with 10.0% microcapsules added at a 0.58:1 core–wall ratio had a better self-healing property, a good stability and aging resistance. This paper lays a technical basis for the manufacturing and utilization of self-healing waterborne wood coatings.

Viability, Ultrastructure, and Migration Activity of Neutrophils after Phagocytosis of Synthetic Microcapsules

Neutrophils are the most numerous leukocyte population, which is part of the innate immunity system and provides antibacterial protection to the body. The ability of neutrophils to phagocytosis and chemotaxis make it possible to consider them for potential targeted delivery of drugs to the inflammatory foci. Loading of migrating neutrophils with encapsulated medicinal drugs makes it possible to reduce its toxic effect on the carrier cell, as well as to avoid changes in the concentration and bioactivity of the transported substance. In this work, we studied the interaction of synthetic microcapsules (potential “cargo containers”) with human neutrophils, namely, their phagocytic activity, ultrastructural changes, and capability for migration after phagocytosis. The results showed that, during short-term neutrophil cultivation with microcapsules, the cells phagocytized the microcapsules in proportion to their number in the extracellular medium. Neutrophils partially retained viability and migratory activity. However, prolonged cultivation of neutrophils in vitro with microcapsules decreased the neutrophil population and migration ability of the surviving cells, which indicated the cytotoxic effect of microcapsules. The internalization of microcapsules was accompanied by changes in the ultrastructure of neutrophils. Altered nuclear shape, plasma membrane disruption, vacuolization of the cytoplasm, and even complete destruction of individual cells were observed. Thus, neutrophils are potentially suitable for the transfer of encapsulated substances, but the development of targeted delivery systems using neutrophils and synthetic microcapsules requires optimization and further research.

Preparation and Repeated Repairability Evaluation of Sunflower Oil-Type Microencapsulated Filling Materials.

Cracks are the main challenges for asphalt pavement, which should be timely repaired. One of the most commonly used repairing methods is to fill the binding materials into cracks, but the repeated repairing ability is insufficient. The self-healing microcapsule technologies provide the potentials for enhancing the repeated repairing ability of filling materials. Therefore, the microcapsule core material was selected from sunflower oil in this study, and the capsular wall material was selected from melamine-urea-formaldehyde resin, which was used to prepare the microcapsule by using in-situ polymerization method. Three kinds of microcapsules with different particle sizes were prepared by adjusting the emulsifier dosage and core wall ratio. The microstructure, molecular structure, thermal stability, and dispersion features were further studied, and the effects of microcapsules with different particle sizes on the repeated repairability of the filling materials were evaluated via the fatiguerepair-fatigue test. In addition, the traditional regenerative microcapsules were compared to determine the optimal particle size range for sunflower oil microcapsules. According to the experimental research, it was thus concluded that the emulsion droplet size distribution was most concentrated when the emulsifier content was 0.7%; and when the core-wall ratio was 1.3:1, the microcapsules had uniform particle size and good dispersion effect. When the microcapsule emulsification rate was 900 rpm and microcapsule content was 2%, then the repeated repair effect for the microcapsule crack filling materials was optimal. The sunflower oil type microcapsule therefore meets the filling temperature requirement for the filler.

Stress-strain behaviour and pore structure of microcapsule-based self-healing cementitious composite under triaxial tests

In this study, the physical triggered self-healing cementitious composites were prepared by mixing the epoxy resin based microcapsules with the cement, and its mechanical properties and microstructure were investigated as well. The effects of the different content of the microcapsules, proportion of prepressing stress, confining pressure and curing days on the mechanical parameters and microstructure of cementitious composite were carried out by the triaxial compression test and the mercury intrusion porosimetry (MIP) tests. The results indicated that the strength, cohesion, internal friction angle of specimens gradually decreased with an increase in microcapsules content or with an increasing of preloading stress, and the deterioration degree gradually increased with an increase in the microcapsule content or the preloading stress, but peak strain increased to vary degree. The mechanical parameters of the healed samples were repaired to different degrees compared with damaged samples. Microcapsules have significant and positive influences on the healing rates and recovery rates of mechanical properties, pore structure. The healing effect of cementitious materials was improved with increasing microcapsule content. However, the effects of microcapsules on microstructure of sound samples has to be considered.