Incorporation Of Microcapsules Research Articles

Improving Self-Healing Dental-Restorative Materials with Functionalized and Reinforced Microcapsules.

Dental resin composites are widely used in clinical settings but often face longevity issues due to the development and accumulation of microcracks, which eventually lead to larger cracks and restoration failure. The incorporation of microcapsules into these resins has been explored to introduce self-healing capability, potentially extending the lifespan of the restorations. This study aims to enhance the performance of self-healing dental resins by optimizing the microcapsules-resin matrix physicochemical interactions. Poly(urea-formaldehyde) (PUF) microcapsules were reinforced with melamine and subsequently subjected to surface functionalization with 3-aminopropyltriethoxysilane (APTES) and (3-mercaptopropyl)trimethoxysilane (MPTMS). Additionally, microcapsules were functionalized with a bilayer approach, incorporating tetraethyl orthosilicate (TEOS) with either APTES or MPTMS. X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) confirmed an increased Si:C ratio from 0.006 to 0.165. The functionalization process did not adversely affect the structure of the microcapsules or their healing agent volume. Compared to PUF controls, the functionalized microcapsules demonstrated enhanced healing efficiency, with TEOS/MPTMS-functionalized microcapsules showing the highest performance, showing a toughness recovery of up to 35%. This work introduces a novel approach to functionalization of microcapsules by employing advanced silanizing agents such as APTES and MPTMS, and pioneering bilayer functionalization protocols through their combination with TEOS.

Microencapsulation of multi-component traditional Chinese herbs extracts and its application to traditional Chinese medicines loaded textiles

Extracts of traditional Chinese herbs (TCH) contain a variety of anti-allergic, anti-inflammatory and other bioactive factors. However, the defect of easy degradation or loss of active ingredients limits its application in traditional Chinese medicines (TCM) loaded textiles. In this work, TCH extracts containing different active ingredients were innovatively proposed as the core material of microcapsules. The feasibility of microencapsulation of multi-component TCH extracts in the essential oil state was initially demonstrated. Polyacrylate was also used as a binder to load the microcapsules onto the fabric to improve the durability and wash resistance of the treated fabric. Modeling the oil release of microcapsules for controlled release under different conditions may provide new possible uses for the materials. Results show that the constructed microcapsule has a smooth surface without depression and can be continuously released for over 30 days. The release behavior of microcapsules follows different release mechanisms and can be modulated by temperature and water molecules. The incorporation of microcapsules and polyacrylate does not significantly change the fabric's air permeability, water vapor transmission and hydrophilicity. The washing durability and friction properties of the microcapsule-based fabric are greatly improved, and it can withstand 30 washing tests and 200 friction tests. Moreover, the results of methyl thiazolyl tetrazolium (MTT) release assay using human dermal papilla cells (HDP) as an in vitro template confirm that the microcapsule has no toxic effects on human cells. Therefore, the successful microencapsulation of multi-component TCH extracts indicates their potential application in the field of TCM-loaded textiles.

Study on crack resistance of self-healing microcapsules in asphalt pavement by multi-scale method.

Self-healing microcapsules in the asphalt pavement must be kept intact under vehicle load to ensure there is enough rejuvenator in capsules when cracks appear in asphalt pavement. In this paper, the crack resistance of self-healing microcapsules in asphalt pavement was evaluated. Firstly, an expanding multi-scale analysis was conducted based on proposed mesoscopic mechanical models with the aim to determine the mechanical parameters for the following contracting multi-scale analysis. Secondly, the periodic boundary condition was introduced for the contracting multi-scale analysis and the stress field of the capsule wall was obtained. Finally, the effects of the design parameters of the microcapsule on its crack resistance in asphalt pavement were investigated. The results showed that the incorporation of microcapsules has almost no effect on the elastic constants of the asphalt mixture. The core could be simplified as an approximately incompressible solid with the elastic constants determined by the proposed mesoscopic mechanical model. With the increase of the modulus of the capsule wall, the mean maximum tensile stress of the capsule wall increased from 0.372 MPa to 0.465 MPa, while with the decrease of the relative radius of the capsule core, the mean maximum tensile stress of the capsule wall increased from 0.349 MPa to 0.461 MPa. The change in the mean maximum tensile stress of the capsule wall caused by the change of capsule diameter was within 5%. The relative radius of the capsule core and the elastic modulus of capsule wall were two key parameters in capsule design. Besides, the microcapsules with the wall made of resin would not crack under the vehicle load before microcracks occurred in asphalt pavement.

Evaluation of the microcapsules on the rheological and self-healing performance of asphalt

The objective of this study was to prepare microcapsules and investigate their impact on the self-healing properties of asphalt. Microcapsules with various core–shell ratios were prepared by enveloping soybean oil with Melamine-Urea-Formaldehyde (MUF) resin through an in-situ polymerization method. The laser particle size analyzer, thermogravimetric analyzer, and scanning electron microscope were utilized to character the microcapsules and determined the optimal core–shell ratio. The rheological and self-healing performance of the microcapsule-modified asphalt were examined through frequency sweep, multi stress creep and recovery (MSCR), and Fatigue-Healing-Fatigue (F-H-F) tests conducted using a dynamic shear rheometer (DSR). The results indicate that microcapsules with various core–shell ratios exhibit uniform particle distribution and excellent thermal stability. Specifically, microcapsules with a core–shell ratio of 1:2 display a smooth appearance. The incorporation of microcapsules into asphalt impedes the flow of asphalt molecules and increases the initial flow temperature. When the microcapsules rupture, the released soybean oil modifies the rheological behavior of the asphalt, leading to a decrease in stress sensitivity and rutting resistance. Simultaneously, the remaining MUF resin imparts additional elastic recovery properties to the asphalt. The self-healing performance of microcapsule-modified asphalt was significantly enhanced, with a notable improvement observed as the microcapsule dosage increased. Moreover, elevating the healing temperature and extending the healing time were found to be effective strategies for enhancing the self-healing properties of microcapsule-modified asphalt. When the healing temperature matches the initial flow temperature, the healing index HI of 5% microcapsules modified asphalt approached nearly 100% within 5 min of healing time.

Fortification of chocolate with microencapsulated fish oil: Effect of protein wall material on physicochemical properties of microcapsules and chocolate matrix

Protein stabilized fish oil microcapsules were incorporated into chocolates in order to design fortified product which could bear the nutritional claim “source of or high omega-3 fatty acids”. Protein wall material (soy, whey and potato) influenced microcapsules and chocolate performance. Soy protein resulted in the smallest microcapsules with the lowest content of surface oil. Peroxide values were low even after 14 days of microcapsules storage. Incorporation of microcapsules into chocolate led to increase in Casson viscosity and breaking force as well as decrease in melting enthalpy, due to prevalence of particle–particle over fat-fat interactions. Increase in microcapsules concentration resulted in chocolate with poorer snap and higher tendency to fat bloom formation. Whey protein microcapsules, having the largest diameter, resulted in chocolate with the lowest breaking force and melting enthalpy and the highest whitening index. In general, microcapsules addition did not require chocolate production modification and led to sensory acceptable product.

Microcapsule-Based Dose-Dependent Regulation of the Lifespan and Behavior of Adipose-Derived MSCs as a Cell-Mediated Delivery System: In Vitro Study.

The development of “biohybrid” drug delivery systems (DDS) based on mesenchymal stem/stromal cells (MSCs) is an important focus of current biotechnology research, particularly in the areas of oncotheranostics, regenerative medicine, and tissue bioengineering. However, the behavior of MSCs at sites of inflammation and tumor growth is relevant to potential tumor transformation, immunosuppression, the inhibition or stimulation of tumor growth, metastasis, and angiogenesis. Therefore, the concept was formulated to control the lifespan of MSCs for a specific time sufficient for drug delivery to the target tissue by varying the number of internalized microcontainers. The current study addressed the time-dependent in vitro assessment of the viability, migration, and division of human adipose-derived MSCs (hAMSCs) as a function of the dose of internalized polyelectrolyte microcapsules prepared using a layer-by-layer technique. Polystyrene sulfonate (PSS)—poly(allylamine hydrochloride) (PAH)-coated spherical micrometer-sized (diameter ~2−3 µm) vaterite (CaCO3) microcapsules (PAH-PSS)6 with the capping PSS layer were prepared after dissolution of the CaCO3 core template. The Cell-IQ phase contrast imaging results showed that hAMSCs internalized all (PAH-PSS)6 microcapsules saturating the intercellular medium (5−90 particles per cell). A strong (r > 0.7) linear dose-dependent and time-dependent (up to 8 days) regression was observed between the in vitro decrease in cell viability and the number of internalized microvesicles. The approximate time-to-complete-death of hAMSCs at different concentrations of microcapsules in culture was 428 h (1:5 ratio), 339 h (1:10), 252 h (1:20), 247 h (1:45), and 170 h (1:90 ratio). By varying the number of microcontainers loaded into the cells (from 1:10 to 1:90), a dose-dependent exponential decrease in both the movement rate and division rate of hAMSCs was observed. A real-time cell analysis (RTCA) of the effect of (PAH-PSS)6 microcapsules (from 1:5 to 1:20) on hAMSCs also showed a dose- and time-dependent decrease in cell longevity after a 50h study at ratios of 1:10 and 1:20. The incorporation of microcapsules (1:5, 1:20, and 1:45) resulted in a dose-dependent increase in 24−48 h secretion of GRO-α (CXCL1), MIF, and SDF-1α (CXCL12) chemokines in hAMSC culture. In turn, the normalization or inhibition of chemokine secretion occurred after 72 h, except for MIF levels below 5−20 microcapsules, which were internalized by MSCs. Thus, the proposed concept of controlling the lifespan of MSC-based DDS using a dose of internalized PAH-PSS microcapsules could be useful for biomedical applications. (PAH-PSS)6 microcapsule ratios of 1:5 and 1:10 have little effect on the lifespan of hAMSCs for a long time (up to 14−18 days), which can be recommended for regenerative therapy and tissue bioengineering associated with low oncological risk. The microcapsule ratios of 1:20 and 1:45 did not significantly restrict the migratory activity of hAMSCs-based DDS during the time interval required for tissue delivery (up to 4−5 days), followed by cell death after 10 days. Therefore, such doses of microcapsules can be used for hAMSC-based DDS in oncotheranostics.

Performance of microcapsule-based self-healing concrete under multiaxial compression with large axial strain: Mechanical properties failure mode, and pore structure

• Triaxial behavior of microcapsule-based concrete was investigated. • The effect of microcapsules on triaxial strength declined with confinement pressure. • Microcapsules improved the plastic capacity and post-peak bulk modulus of concrete. • Concrete behavior under large axial strain was controlled by granular skeletons. To promote the application of microcapsule-based self-healing concrete in engineering structures, it is important to study the mechanical behaviour under complex stress conditions. Accordingly, this study aims to investigate the mechanical behaviour of microcapsule-based self-healing concrete under the triaxial compression state with large axial strain. The self-healing concrete was prepared by mixing different dosages of UF/Epoxy microcapsules, and the influence of confinement pressure, large axial strain, and microcapsule dosage on the mechanical behaviour of concrete was investigated through uniaxial compression, conventional triaxial compression, and mercury intrusion porosimetry (MIP) test. The results show that incorporating microcapsules reduced the cohesive strength and internal friction angle of the concrete. In contrast, the influence of microcapsule dosage on triaxial strength was rapidly weakened with increasing confinement pressure. Both the incorporation of microcapsules and the application of confinement pressure can improve the plastic deformation capacity and reduce the brittleness of the specimens. In addition, microcapsules may increase the bulk modulus of the specimens in the hardening stage. It should be noted that under the action of triaxial loading with large axial strain, the ultimate strengths of specimens with different microcapsule dosages are similar, and concrete behaviour is mainly controlled by the granular skeleton.

Study of Concrete Surface Coatings Using Thermosensitive Fluorescent Microcapsules Capable of Indicating Damage.

A new type of concrete surface gel coating using thermosensitive fluorescent (TSF) microcapsules was proposed to monitor micro-cracks of cement-based materials. The gel materials can adhere other materials, and the incorporation of microcapsules into the gel coating can be cured on various structural surfaces. Zinc sulfide and phenyl acetate were encapsulated into a polymethyl methacrylate shell to prepare the TSF microcapsules by a solvent evaporation method. When micro-cracks are generated on the surface of the gel coating, the ruptured TSF microcapsules burst out, fill the damaged area, and then emit fluorescence after being excited at ambient temperature. It was found that the brightness of the fluorescence increased with increasing temperature from 80–110 °C. When the concentration of TSF microcapsules was 15% of the mass of the gel coating, the cement-based damage-sensing material had sufficient damage-indicating effects, and the fluorescence brightness of the crack location remained even after a long time. It is expected that this study will provide an effective and intuitive method for crack location detection of cement-based materials.

“Fatigue-Crack Propagation Behavior in Microcapsule-Containing Self-Healing Polymeric Networks”

Over the last years, research on the design of dental self-healing polymers has grown dramatically. It is related to the promising potential of maximizing the clinical lifespan of dental restorations that this strategy holds. In this manuscript, the microcapsule-based strategy is innovated by incorporating the high toughness component N,N-Dimethylacrylamide (DMAM) into the healing agent systems and analyzing in-depth the change in crack propagation behavior induced by the addition of microcapsules into the highly crosslinked polymeric network. In general, the addition of the hydrophilic and high vapor pressure DMAM into the healing agent systems imposed a challenge for the microencapsulation, which highlighted the importance of tailoring the properties of the capsules’ shells according to the core composition. The addition of DMAM as cushioning agent proved to be a successful strategy since it resulted in increased G’/G” crossover time from 0.06 (control) to 0.57 s and decreased storage modulus from 8.0 (control) to 0.5GPa. In addition, the incorporation of microcapsules within the polymerized networks provided obstacles to crack propagation, which translated to an overall reinforcement of the polymeric network, as evidenced by the increase in toughness up to 50 % and energy required to propagate cracks up to 100 % in systems containing DMAM at 20 wt%.

The preparation of linseed oil loaded graphene/polyaniline microcapsule via emulsion template method for self-healing anticorrosion coatings

A novel kind of graphene/polyaniline hybrid microcapsules loaded with self-healing agent (linseed oil, LO) were synthesized by Pickering emulsion template method in this work. In our strategy, graphene oxide (GO) was used as Pickering emulsifier to stabilize emulsion droplet containing aniline and linseed oil. After the polymerization of aniline, graphene/polyaniline microcapsules loaded with linseed oil (LO@GO/PANI) were prepared. By adjusting GO concentration and oil-water ratio, the size of the emulsion droplet and LO@GO/PANI microcapsule can be controlled at about 15–20 µm. The successful synthesis of LO@GO/PANI microcapsules was proved by SEM, FT-IR and TGA. The unique GO/PANI hybrid shell combined the outstanding barrier property of GO and anti-corrosion function of PANI. The solvent resistance results showed that the as-prepared microcapsules possessed stronger resistance to organic solvents. A smart coating with dual functions of anti-corrosion and self-healing was prepared by dispersing the as-prepared LO@GO/PANI microcapsule in waterborne epoxy resin. As the contents of microcapsules was 10 wt%, the scratch of the coating was completely healed after 12 h observed from the microscope images. The electrochemical impedance spectroscopy (EIS) and salt spray test all verified that the incorporation of microcapsules could significantly improve the anti-corrosion performance of the water-borne coatings. After 40 days' immersion, the low frequency modulus of the composite coating was almost 2 orders of magnitude higher than that of pure epoxy coating, and no obvious corrosion product was observed after 500 h salt spray test.

Encapsulation of Cerium Nitrate within Poly(urea-formaldehyde) Microcapsules for the Development of Self-Healing Epoxy-Based Coating

In order to study the release of cerium nitrate in a self-healing epoxy-based coating, poly (urea-formaldehyde) (PUF) microcapsules containing cerium nitrate were synthesized. The effects of healing agent concentration and weight percent of microcapsules in the epoxy resin were studied through the incorporation of microcapsules within an epoxy-based coating. The prepared microcapsules were characterized using thermogravimetric analysis and Fourier transform infrared spectroscopy and confirmed the successful encapsulation of cerium nitrate within PUF capsules. The self-healing performance of the prepared epoxy coating was investigated in 0.6 M NaCl solution using electrochemical impedance spectroscopy (EIS) tests. The EIS results indicated the successful release of encapsulated cerium nitrate from PUF microcapsules once the damage occurred in the epoxy coating, which led to effective self-healing of the epoxy-based coating. The presence of chlorine and cerium ions in the solution led to the precipitation of cerium hydroxides and oxides in the scratched area as a passive layer which hindered the corrosion in the damaged area. In addition, the EIS results showed that the healing performance of the coatings depends on the weight percent of microcapsules and the concentration of the self-healing agent. The highest self-healing performance was achieved for the maximum amount of microcapsule incorporation (10 wt %), while the increase in the microcapsule percent led to a decrease in the adhesion of the coating to the substrate.

PARACETAMOL DRUG LOADED MICROCAPSULE BASED NANOFIBER PRODUCTION

In this study, it was aimed to production and characterization of paracetamol (PCT) loaded microcapsules and microcapsule added electro spun PVA nanofibers. Eudragit RS 100 and PVA were used as the shell in the microcapsule structure, and PCT was used as the core material. First of all, the PCT loaded Eudragit RS 100/PVA microcapsules were produced by solvent evaporation method under the optimum process parameters. Then, properties such as conductivity, viscosity and surface tension of the microcapsule loaded PVA solution were measured and the effects of microcapsule concentration on the solution properties were determined. According to the solution results, while the viscosity increased with the microcapsule concentration, conductivity and surface tension did not change significantly except for the PVA-10 sample. After the electrospinning process, fibre morphology was determined by SEM and incorporation of microcapsules into the nanofibers was clearly demonstrated. It was calculated from the SEM images that average microcapsule size is 9.81μm, average fibre diameter is 550 nm and fibre diameter uniformity coefficient is 1.025. Finally, the incorporation of PCT loaded microcapsules into the nanofibers was chemically confirmed by FT-IR analysis. It is thought that the results of this study will be useful for controlled drug release, especially in medical textiles.

Gelatine Film Incorporated with Clitoria ternatea-Derived Anthocyanin Microcapsules, A Food Packaging Material Effective Against Foodborne Pathogens.

SUMMARYResearch backgroundMicrobial contamination of food products is one of the significant causes of food spoilage and foodborne illnesses. The use of active packaging films incorporated with antimicrobial agents can be a measure to improve food quality and extend shelf life. Nevertheless, antimicrobial agents such as silver, copper, titanium and zinc in the packaging films have raised concerns among consumers due to toxicity issues.Experimental approachThe current study aims to develop biodegradable gelatine-based edible films incorporated with microcapsules of Clitoria ternatea-derived anthocyanins as a natural antimicrobial agent. The impact of incorporation of microcapsules with anthocyanins on the morphology, thermal, mechanical, water vapour barrier and physicochemical properties of the gelatine films was evaluated in this study. The effectiveness of the developed films against foodborne pathogens and their application for perishable food protection were also investigated.Results and conclusionsThe results show that incorporating anthocyanin microcapsules enhances the gelatine film physical and mechanical properties by increasing the thickness, tensile strength, Young's modulus and elongation at break of the films. Scanning electronic microscopy analysis revealed that the film surface morphology with anthocyanin microcapsules had a homogeneous and smooth surface texture compared to the control. The thermogravimetric analysis also showed a slight improvement in the thermal properties of the developed films. Agar well diffusion assay revealed that the developed films exhibit significant inhibition against a broad-spectrum of bacteria. Furthermore, the films composed of gelatine with anthocyanin microcapsules significantly reduced the total viable count of microorganisms in the bean curd during storage for 12 days compared with the control films.Novelty and scientific contributionIncreasing global awareness of healthy and safe food with minimal synthetic ingredients as preservatives has sparked the search for the use of antimicrobial agents of natural origins in active food packaging material. In this study, a safe and effective active packaging film was developed using an environmentally friendly biopolymer, gelatine film incorporated with microcapsules of Clitoria ternatea-derived anthocyanins as a natural antimicrobial agent. This study demonstrated that such a method is not only able to improve the film physical properties but can also significantly prolong the shelf life of food products by protecting them from microbial spoilage.

Thermal and Mechanical Behavior of Elastomers Incorporated with Thermoregulating Microcapsules

Polyurethane (PU) is one of the principal polymers in the global plastic market thanks to its versatility and continuous improvement. In this work, PU elastomeric materials having thermoregulating properties through the incorporation of microcapsules (mSD-(LDPE·EVA-RT27)) from low-density polyethylene and vinyl acetate containing paraffin®RT27 as PCM were produced. Elastomers were synthesized while varying the molar ratio [NCO]/[OH] between 1.05 and 1.1 and the microcapsule (MC) content from 0.0 to 20.0 wt.%. The successful synthesis of the PUs was confirmed by IR analyses. All the synthesized elastomers presented a structure formed by a net of spherical microparticles and with a minimum particle size for those with 10 wt.% MC. The density and tensile strength decreased with the MC content, probably due to worse distribution into the matrix. Elastomer E-1.05 exhibited better structural and stability properties for MC contents up to 15 wt.%, whereas E-1.1, containing 20 wt.% MC, revealed mechanical and thermal synergy effects, demonstrating good structural stability and the largest latent heat. Hence, elastomers having a large latent heat (8.7 J/g) can be produced by using a molar ratio [NCO]/[OH] of 1.1 and containing 20 wt.% mSD-(LDPE·EVA-RT27).

Self-healing epoxy coating based on tung oil-containing microcapsules for corrosion protection

In this work, urea-formaldehyde (UF) microcapsules loaded with tung oil were prepared by in-situ polymerization. The mean diameter of the obtained microcapsules was 8.5 μm. The self-healing coating was prepared by the addition of 5 wt.% microcapsules into an epoxy matrix and then painted on the AA2024 substrate. The effect on the coating properties after the incorporation of microcapsules was investigated by adhesion tests and electrochemical impedance spectroscopy (EIS). It is found that 5 wt.% microcapsules in coating formulations did not impart a significant negative effect on coating properties. SEM and EIS tests were used to evaluate the self-healing effect. According to the fitting results of the EIS data on the scratched samples, the new film that formed by the polymerization of tung oil at the scratched area in the self-healing coating displays a resistance value of more than 106 Ω·cm2, which is much higher than 103 Ω·cm2 of the oxide layer in the neat epoxy coating. The neutral salt spray tests also confirm the good anti-corrosion performance of the self-healing coating.

Ionic liquid-loaded microcapsules doped into dental resin infiltrants

Resin infiltrants have been effectively applied in dentistry to manage non-cavitated carious lesions in proximal dental surfaces. However, the common formulations are composed of inert methacrylate monomers. In this study, we developed a novel resin infiltrant with microcapsules loaded with an ionic liquid (MC-IL), and analyzed the physical properties and cytotoxicity of the dental resin. First, the ionic liquid 1-n-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI.NTf2) was synthesized. BMI.NTf2 has previously shown antibacterial activity in a dental resin. Then, MC-IL were synthesized by the deposition of a preformed polymer. The MC-IL were analyzed for particle size and de-agglomeration effect via laser diffraction analysis and shape via scanning electron microscopy (SEM). The infiltrants were formulated, and the MC-IL were incorporated at 2.5%, 5%, and 10 wt%. A group without MC-IL was used as a control. The infiltrants were evaluated for ultimate tensile strength (UTS), contact angle, surface free energy (SFE), and cytotoxicity. The MC-IL showed a mean particle size of 1.64 (±0.08) μm, shriveled aspect, and a de-agglomeration profile suggestive of nanoparticles' presence in the synthesized powder. There were no differences in UTS among groups (p > 0.05). The incorporation of 10 wt% of MC-IL increased the contact angle (p < 0.05), while the addition from 5 wt% reduced the SFE in comparison to the control group (p < 0.05). The human cell viability was above 90% for all groups (p > 0.05). The incorporation of microcapsules as a drug-delivery system for ionic liquids may be a promising strategy to improve dental restorative materials.

Influence of microcapsule parameters and initiator concentration on the self-healing capacity of resin-based dental composites

ObjectiveFracture is one of the main causes for failure of resin-based composite restorations. To overcome this drawback, self-healing resin-based composites have been designed by incorporation of microcapsules. However, the relationship between their self-healing capacity and microcapsule and resin parameters is still poorly understood. Therefore, the objective of this study was to systematically investigate the effect of initiator concentration (in the resin) and microcapsule size and concentration on the self-healing performance of commercially available flowable resin-based composites. MethodsPoly(urea-formaldehyde) (PUF) microcapsules containing acrylic healing liquid were synthesized in small (33±8μm), medium (68±21μm) and large sizes (198±43μm) and characterized. Subsequently, these microcapsules were incorporated into a conventional flowable resin-based composite (Majesty Flow ES2, Kuraray) at different contents (5–15wt%) and benzoyl peroxide (BPO) initiator concentrations (0.5–2.0wt%). Fracture toughness (KIC) of test specimens was tested using a single edge V-notched beam method. Immediately after complete fracture (KIC-initial), the two fractured parts were held together for 72h to allow for healing. Subsequently, fracture toughness of the healed resin-based composites (KIC-healed) was tested as well. ResultsThe fracture toughness of healed dental composites significantly increased with increasing microcapsule size and concentration (2wt% BPO, p<0.05). The highest self-healing efficiencies (up to 76%) were obtained with microcapsules sized 198±43 um. Significancecommercially available resin-based composites can be rendered self-healing most efficiently by incorporation of large microcapsules (198±43μm). However, long-term tests on fatigue and wear behavior are needed to confirm the clinical efficacy.

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.

Form-stable phase change composites with high thermal conductivity and adjustable thermal management capacity

In this work, form-stable phase change composites (PCCs) with high thermal conductivity and adjustable thermal management capacity are prepared based on phase change microcapsules (SiO2@SA) and surface-modified boron nitride (m-BN). The phase change properties are successfully infused into PCCs through the incorporation of microcapsules and the thermal conductivity can be elevated up to 0.506 Wm-1K-1. Furthermore, the phase change enthalpies of PCCs can be facilely tailored from 3.74 J/g to 18.52 J/g by changing the loading fraction of microcapsule, enabling adjustable thermal energy storage and thermal management ability. PCCs are proved to possess outstanding long-term stability even after 500 cycles of charging-discharging. Besides, practical application of PCCs as thermal regulating materials is explored through a self-designed temperature control system. Finally, the PCCs exhibit good leakage proof property at 100 °C due to the shielding effect of SiO2 shell. These results show that this work offers a promising strategy for the development of advanced form-stable PCCs with good comprehensive properties.

Preparation and tribological behaviour of poly(methyl methacrylate) (PMMA) microcapsules containing friction modifiers

Aims: Microcapsules comprising of a poly(methyl methacrylate) (PMMA) shell and friction modifier (FM) core were prepared to reduce the friction and extend the service life of engine lubricating oil.Methods: Microcapsules containing both organic FM and molybdenum FM were produced via solvent evaporation technique. The friction coefficient, thermal stability, and chemical composition of microcapsules were investigated.Results: The incorporation of microcapsules in lubricating oil dramatically reduced the friction coefficient to be lower than that of virgin FM. Organic FM and molybdenum FM are compatible during the encapsulation process. The release of the FM inside the microcapsules was controllable by thermal degradation of polymeric shell at 150 °C or mechanical rupture at room temperature.Conclusions: This study provided a novel approach to improve the tribological properties of lubricating oil with long service life, facile fabrication and low cost and will find potential applications in lubrication industry for internal combustion engines.