Size Of Microcapsules Research Articles

Numerical study on the thermal performance of space radiator using microencapsulated phase change material slurry as working medium

Microencapsulated phase change material slurry (MPCMS) has good prospects in the field of heat transfer because of its high latent heat and stability. In this research, MPCMS is applied to a space radiator to increase its heat load and temperature stability. The thermal performance of the space radiator is numerically studied by using the two-phase Eulerian (TPE) model and a multi-scale coupling model. The effects of velocity, volume fraction, microcapsule size, and microcapsule size distribution on the thermal performance of the space radiator are studied. Results show that the temperature flat area in the tube increases with the increase in the volume fraction or flow rate of the particle phase in the MPCMS, which means the heat dissipation capacity of the space radiator is also enhanced, and the maximum increase is 14 %. Compared with the use of pure water, the temperature difference between the highest and the lowest temperature of the radiator surface can be reduced by 40 %, and the heat dissipation power can be increased by 5 %. In addition, the large size of microcapsules limits the heat transfer between the two phases, especially when the size is greater than 50 μm. Compared with uniform microcapsule size distribution, the effect of lognormal distribution of variance σ = 0.7 on heat transfer is less than 1 %.

Microencapsulation of <i>Chromolaena odorata</i> Leaf Extract with Cellulose Esters for the Application as an Eco-Friendly Antibacterial Agent

The aim of this work is to develop an eco-friendly antibacterial agent in the form of microcapsules containing extract from Chromolaena odorata leaves using the solvent evaporation method. The wall materials for encapsulating were tested with various cellulose esters including cellulose acetate (CA), cellulose acetate butyrate (CAB), and cellulose acetate propionate (CAP). The evaluation of microcapsules containing C. odorata leaf extract was focused on their encapsulation efficiency, size, shape, thermal stability, and antimicrobial activities. The results showed that CAB was a suitable wall material for the encapsulation of C. odorata leaf extract. The CAB microcapsules exhibited the highest encapsulation efficiency, which was 65.82 ± 3.07. The size of CAB microcapsules was the smallest, at 1013.3 ± 66.5 nm. According to the thermogravimetric analysis, the prepared microcapsules were able to protect the extract of C. odorata leaves from the environment. Moreover, the CAB microcapsules containing C. odorata leaf extract showed the best antibacterial activities against Escherichia coli ATCC 25922 and Stapphylococcus aureus ATCC 25923. The minimum bactericidal concentration of the microcapsules was 25.6 mg/mL in both bacteria. This study proved the potential application of C. odorata leaf extract as a biomaterial in diverse industries in the future.

Microencapsulation of Azadirachta indica oil and Tinospora cordifolia extracts blend for single-use applications

The innovative utilization of the microencapsulation technique and the antimicrobial properties of Azadirachta Indica (A.I.) and Tinospora cordifolia (T.C.) present a novel approach to producing antiseptic wipes. In this study, microcapsules with A.I. oil and T.C. extracts were synthesized and integrated into non-woven cotton fabric aiming to create disposable antiseptic medical wipes. The T.C. extract and A.I. oil were used in a 1:1 ratio and microencapsulated utilizing sodium alginate as the encapsulation material through an ionic gelation process. The optical microscope analysis of microcapsules revealed diverse microcapsule sizes, ranging from 50 μm to 180 μm in diameter and scanning electron microscopy revealed that the treated fabric has uniform distribution of microcapsules across the entire fabric surface. The antimicrobial efficacy was evaluated through disk diffusion for the extract and oil and the fabric's antimicrobial activity was assessed by measuring bacterial reduction. The treated fabric displayed substantial reductions in both Gram-positive bacteria (Staphylococcus aureus (87 %) and Bacillus cereus (99 %)) and Gram-negative bacteria (Escherichia coli (81 %) and Pseudomonas aeruginosa (99 %)). Although the treated fabric exhibited a slight decrease in whiteness (48.5–39), this alteration did not adversely affect other fabric properties. These findings underscore the potential of microencapsulated natural extracts in producing effective antimicrobial medical wipes, thereby contributing to infection control.

High‐performance self‐healing epoxy by microencapsulated epoxy‐amine chemistry II: Performance of the system

AbstractThe self‐healing epoxy based on microencapsulated epoxy‐amine chemistry is a system with great potential for practical applications. Herein, microcapsules respectively containing epoxy and polyetheramine were fabricated using a microencapsulation technique via integrating electrospraying and interfacial polymerization (ES‐IP) and self‐healing epoxy based on the dual microcapsules were systematically investigated regarding the microcapsule dispersion, healing performance, failure mode, and mechanical properties. Microcapsules with different sizes were conveniently prepared by adjusting the injection rate. The microcapsules, regardless of the size, can be well dispersed in the epoxy matrix. The effects of the microcapsule size and concentration on the healing performance were studied. While full healing can be obtained for microcapsule >100 μm, high healing efficiency of about 90% and 70% can be achieved for microcapsules in 50 ~ 100 μm and ~ 50 μm, respectively. The healing performance decreases with the decreased microcapsule concentration. However, healing efficiency >70% can still be obtained when 5.0 wt% microcapsule of 50 ~ 100 μm were adopted. Mixed failure modes including adhesive failure, cohesive failure, and matrix failure, were observed, due to the good performance of the selected healant system. While the incorporated microcapsules, especially the small ones, evidently toughens the matrix, they deteriorate the tensile properties of the formulated self‐healing material.

Preparation, Characterization and Sustained-release Study of Encapsulated Cinnamon Essential Oil Microcapsules

Aims: The aim of this study is to study preparation, characterization and sustained release of Encapsulated Cinnamon Essential Oil Microcapsules. Background: In this work, encapsulated cinnamon essential oil (CEO) microcapsules were prepared, characterized, and analyzed for their sustained-release properties. CEO microcapsules were encapsulated from an alginate polymer using homogenization and extrusion, and the encapsulation mechanism used was ionic gelation. The potent antibacterial properties of natural cinnamon oil extracts and their shelf-life activity can be reduced or eliminated as a result of deterioration caused by light, heat, and oxygen exposure during production. High-speed homogenization was utilized for the encapsulation, which encloses and protects the volatile compounds from degradation. Objective: The objective of this study is to synthesize sustained-release encapsulated cinnamon essential oil (CEO) microcapsules. Method: The preparation of encapsulated cinnamon oil was achieved through homogenization. The extrusion method was employed to obtain microcapsules encapsulating liquid active ingredients (AI) with alginate polymer to induce ionic gelation. Results: SEM and Optical images reveal that all microcapsules maintain their spherical shape with clearly defined membranes. XPS analysis indicates the presence of oxygen (O), carbon (C), and sodium (Na) on the surface, suggesting the presence of an alginate-based ionic gelation. Chromatographic studies demonstrate a high encapsulation efficiency of 99%. The average microcapsule size is 261.5 nm for the fresh sample and 278 nm after 3.5 months. The zeta potential is -29.8 mV for the fresh sample and -28.2 mV after 3.5 months. Notably, there is no evidence of microcapsule agglomeration during the 3.5-month storage period as observed in the study. TGA data reveals that only 7.5% of the adsorbed water and essential oil mixture is lost at 40°C over 4 hours, in contrast to 11.7% for the adsorbed water material, indicating a sustained release of the encapsulated CEO from the microcapsules. Conclusion: The microcapsules exhibited an impressive encapsulation efficiency of 99%, demonstrating stability over the 3.5-month investigation period and showcasing sustained-release properties.

A simplified predictive model for the compression behavior of self-healing microcapsules using an empirical coefficient

Abstract This study is dedicated to predicting the compression behavior of microcapsules, a key aspect in self-healing applications. Understanding the compression behavior of microcapsules, mainly due to their liquid cores, is a complex task. Equally challenging is the evaluation of the shell properties. We aimed to streamline this prediction process by introducing the empirical coefficient C core, which accounts for core influence. We conducted experiments on microcapsules with MUF (Melamine–Urea–Formaldehyde) shells, compressing them between two plates and recording their responses to load and displacement. The empirical coefficient, influenced by capsule size, shell properties, and core volume fraction, was then analyzed in terms of microcapsule size and Young’s modulus. The research results showed that as the diameter of microcapsule and Young’s modulus of the shell increased, the Ccore also increased. This relationship could be represented in a three-dimensional surface. These findings could significantly contribute to estimating shell properties and modeling matrices with dispersed microcapsules.

Morphological Assessment of Thymol Essential Oil using Different Solvents and Stirring Time

Essential oils (EOs) have been used in numerous industries for ages including pharmaceutical, textile and food. Microencapsulation formulation and techniques are important to enhance the EOs characteristics and stability which could directly influence the yield and quality of EOs. This research paper evaluated the effect of using different solvents and stirring time on thymol EO microcapsules. Ethanol and methanol were used as solvents to encapsulate the core and wall material using a simple coacervation method. The microcapsules were collected at various time intervals which were 15, 30, 45, 60, 90, 120, 150, and 180 minutes. It has been noted that the stirring time influenced the size of microcapsules. Using Thymol oil, ethyl cellulose, methanol and polyvinyl alcohol (TM) produces the most microcapsules at 120 minutes of stirring time. The biggest microcapsule diameter was recorded at 90 min stirring time using formulation of thymol oil, ethyl cellulose, ethanol, and polyvinyl alcohol (TE). The encapsulation efficiency (EE) of both samples are 64.55% and 72.16%, respectively.

Recycling of waste edible oil derivatives as phase change materials for building energy conservation

A novel phase change microcapsule with waste edible oil derivatives core shelled by silica was prepared for building energy conservation. The substance composition, phase change parameters, and functional group of the derivatives were characterized. The phase change temperature, phase change enthalpy, and particle size of phase change microcapsules were determined. The effect of microcapsules on foamed concrete was evaluated, including mechanical and thermal properties. The results indicate that the waste edible oil derivatives with a phase change temperature of around 18 °C and a phase change enthalpy of about 140J/g are mainly composed of 73.8% methyl palmitate and 16.2% methyl oleate. The phase change temperature and enthalpy of the microcapsules with a 1:1 shell-to-core ratio are 20 °C and 73J/g, respectively. Additionally, the Dv (50) and Dv (90) of the microcapsules are 139 μm and 380 μm, respectively. Furthermore, the recommended dosage of microcapsules in foamed concrete should not exceed 6.0 wt% considering the mechanical properties of foamed concrete. During the heating process, the temperature of foamed concrete containing 6.0 wt% microcapsules is up to 4.3 °C lower than that of conventional concrete. On the other hand, the cooling rate of foamed concrete containing 6.0 wt% microcapsules is 51.5% lower than that of conventional concrete. This work realizes both building energy conservation and resource utilization of waste edible oil.

Novel eco-friendly nanodiamonds@chitosan hybrid microcapsules via facile electrospraying for self-healing and anticorrosion coating

Nanodiamonds were immobilized into chitosan biopolymer to fabricate hybrid microcapsules via electrospraying technique. Previously optimized electrospraying parameters for the formulation of chitosan microcapsules were adjusted to accommodate the immobilized nanodiamonds and maintain a suitable capsule size for the novel hybrid. The yield and entrapment efficiency of the composite microcapsules, including capsule strength were analyzed. The chemical structure, elemental composition, crystalline phases, size distribution, surface morphology, and thermal stability of microcapsules were assessed by Fourier transform infrared (FTIR) spectroscopy, energy dispersive x-ray spectroscopy (EDX), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), respectively. The results demonstrated a 39 % reduction in the size of composite microcapsules and sphericity improvement after the adjustment. There was a general observation of good yield and immobilization efficiency with the maximum at 96.2 % and 93.8 % for yield and entrapment efficiency, respectively. Characterized composite microcapsules showed desirable morphology, good thermal stability and enhanced mechanical strength, and overall successful fabrication of the hybrid microcapsules. The hybrid microcapsules were subsequently loaded in epoxy resin and coated on a steel substrate to assess their self-healing and anticorrosion abilities. Cross-scratched coating samples were monitored visually for healing efficiency and further analyzed with EIS and potentiodynamic polarization. The self-healing coating showed efficient self-healing and anticorrosion capabilities with a healing efficiency of 97.3 % and a protection efficiency of 99.4 %, confirming the unique feature of the hybrid chitosan-nanodiamonds microparticles for self-healing and anticorrosion purposes.

Study on the mechanical behavior of microcapsules during the mixing process of asphalt mixture

To enhance the survival rate of microcapsules during the mixing process of asphalt mixture, the mechanical behavior of microcapsules during this process was investigated through simulation. Initially, the asphalt mixture containing microcapsules was divided into mesoscopic and microscopic scales. Utilizing composite material models, the stepwise inclusion method and high-temperature tensile tests, the equivalent mechanical parameters for the microcapsules, asphalt mastic and asphalt mortar at mixing temperature were estimated. Following this, the mixing process of the asphalt mixture incorporating microcapsules was simulated employing the discrete element method (DEM) coupled with multi-body dynamics (MBD). This simulation was instrumental in identifying optimal mixing parameters and enabled the analysis of force chain transmission across the multi-scale model. Furthermore, the finite element method (FEM) was employed to develop a monomer model of the microcapsules, facilitating the assessment of their mechanical behavior under optimal mixing conditions. Finally, a detailed sensitivity analysis was performed to investigate the influence of various parameters on the mechanical behavior of microcapsules. The results indicated that, at the mixing temperature, the equivalent Young’s modulus and Poisson's ratio for urea-formaldehyde (UF) resin microcapsules, asphalt mastic, and asphalt mortar were determined to be 0.22 GPa and 0.478, 19.87 GPa and 0.4986, and 88.77 GPa and 0.468, respectively. The optimal mixing parameters for AC-16 asphalt mixture including mixing speed, filling rate and mixing duration were identified as 49 rpm, 50 % and 53 s, under which the most adverse load on the microcapsule is 80 mN. Under the most adverse load, microcapsules might rupture from the inside out, and their survival rate was not less than 68.9 %. Increasing the particle size of microcapsules and reducing the relative radius of the microcapsule core could potentially enhance the crack resistance of microcapsules during mixing.

Temperature-sensitive fragrance-releasing polymeric microcapsules

This research aimed to control release of fragrance using thermally-actuated microcapsules so that the release rate shows a considerable change at a certain temperature. Accordingly, four different polymers, namely, two grades of poly(methyl methacrylate) having different molecular weight as well as two poly[(methyl methacrylate)–co-(2-ethylhexyl acrylate)] copolymers, which were synthesized in this work, were designated as capsules’ shell. Number-average molecular weight of the copolymers and one of the two used PMMA grades was in the range of 47 to 56 kDa while that of the other PMMA grade was 344 kDa. Furthermore, Tg of the lower molecular weight grade PMMA and the two copolymers was determined as 119.3, 72.2 and 66.3 °C, respectively, using DSC experiments. Subsequently, R-Limonene as a model fragrance, was encapsulated by either of the polymers using solvent evaporation method. Effect of various parameters, including molecular weight and Tg of the shell polymer and concentration of emulsifier, on morphological characteristics of the microcapsules were investigated. Using two microscopic techniques, it was observed that increment of molecular weight of shell polymer enhances microcapsules’ size, shell thickness and porosity. Moreover, elevation of emulsifier concentration to a certain value of 1.5 wt% was shown to lessen size and porosity of microcapsules. The fragrance release profiles were determined and fitted to several mathematical models, proving that at least one more mechanism, in addition to diffusion, is involved in the release, which was attributed to capillary effects in the shell pores. Moreover, a pronounced increase in release rate upon elevation of temperature from 5 to 15 °C was observed for either of the copolymer shells. The effect was ascribed to remarkable strengthening of segmental mobility of the copolymers due to elevation of temperature and can be regarded as a promising way for the fabrication of smart microcapsules capable of thermal controlling fragrance release.

Self-healing anti-corrosive coating using graphene/organic cross-linked shell isophorone diisocyanate microcapsules

To enhance the anticorrosive performance of coatings in harsh corrosive environments, a graphene/isophorone diisocyanate (IPDI) microcapsule is prepared by in-situ polymerization. The self-healing and anticorrosive performance of coatings based on these microcapsules are studied. The microcapsule with cross-linked shells prepared in this study solves the problems of excessive size and insufficient strength of traditional microcapsules. The addition of microcapsules improves the anticorrosive performance of coatings. The shape of the microcapsules is in the form of round balls, and the average particle size and thickness of the microcapsules are in the range of 17–23 μm and 0.5–3.4 μm, which are conducive to the preparation of the coatings. The average strength of microcapsules is 20.64 MPa and the wrap-around rate reaches 68%. The microcapsules have an initial evaporation temperature of 231.3 °C， the graphene organic cross-linking shell enhances the strength and improves the thermal stability of microcapsules. The electrochemical impedance spectroscopy (EIS) indicates that the |Z|f=0.01 Hz value of the coating with 10 wt% of microcapsule after 168 h of immersion is about 9.4 × 109 Ω cm2, nearly three orders of magnitude higher than that of the coating without microcapsule (6.9 × 106 Ω cm2). Monitoring the artificial scratches of coating using a scanning electron microscope (SEM) for 24 h reveals that the microcapsule repairs the cracks well. It is demonstrated that the incorporation of graphene/IPDI microcapsules improves the anti-corrosive performance of the coating.

Simulation of Microcapsule Transport in Fractured Media Using Coupled CFD‐DEM

AbstractGeothermal energy is sustainable and gaining momentum as a solution to energy crises and environmental issues. However, challenges like production temperature and thermal breakthrough can impact geothermal project efficiency. One innovative solution to alleviate the thermal breakthrough is to inject polymer‐based materials that are encapsulated in microcapsules into fractures to modify fracture permeability and prevent preferential flow. In our study, we utilized a coupled computational fluid dynamics and discrete element method to simulate the transport of microcapsules under various scenarios controlled by microcapsule size, microcapsule concentration, and fracture roughness. For a smooth fracture, the results indicate that small microcapsules can travel through a smooth fracture regardless of their concentrations. Large microcapsules can transport through a smooth fracture when present in lower concentrations. However, medium and mixed‐size microcapsules tend to cause the sealing of a smooth fracture, irrespective of their concentrations. For a rough fracture, the transport of microcapsules is complicated by their interactions with the rough fracture walls. The presence of two sealing positions in a rough fracture adds further complexity to this transport phenomenon. The size and concentration of microcapsules control one sealing location, while the rough fracture walls determine the other sealing location. The rough walls substantially affect microcapsule transport, rendering the role of microcapsule size and concentration less significant. The simulation results suggest that complex fracture surfaces significantly elevate the occurrence of sealing behavior. To mitigate sealing behavior within more complex fractures, it would be beneficial to use smaller and lower concentrations of microcapsules.

Characterization of Polyallylamine/Polystyrene Sulfonate Polyelectrolyte Microcapsules Formed on Solid Cores: Morphology.

Polyelectrolyte microcapsules (PMC) based on polyallylamine and polystyrene sulfonate are utilized in various fields of human activity, including medicine, textiles, and the food industry, among others. However, characteristics such as microcapsule size, shell thickness, and pore size are not sufficiently studied and systematized, even though they determine the possibility of using microcapsules in applied tasks. The aim of this review is to identify general patterns and gaps in the study of the morphology of polyelectrolyte microcapsules obtained by the alternate adsorption of polystyrene sulfonate and polyallylamine on different solid cores. First and foremost, it was found that the morphological change in polyelectrolyte microcapsules formed on different cores exhibits a significant difference in response to varying stimuli. Factors such as ionic strength, the acidity of the medium, and temperature have different effects on the size of the microcapsules, the thickness of their shells, and the number and size of their pores. At present, the morphology of the microcapsules formed on the melamine formaldehyde core has been most studied, while the morphology of microcapsules formed on other types of cores is scarcely studied. In addition, modern methods of nanoscale system analysis will allow for an objective assessment of PMC characteristics and provide a fresh perspective on the subject of research.

Carbomer Hydrogels with Microencapsulated α-Tocopherol: Focus on the Biocompatibility of the Microcapsules, Topical Application Attributes, and In Vitro Release Study.

The microencapsulation of α-tocopherol based on the complex coacervation of low-molecular-weight chitosan (LMWC) and sodium lauryl ether sulphate (SLES) without harmful crosslinkers can provide biocompatible carriers that protect it from photodegradation and air oxidation. In this study, the influence of the microcapsule wall composition on carrier performance, compatibility with a high-water-content vehicle for topical application, and release of α-tocopherol were investigated. Although the absence of aldehyde crosslinkers decreased the encapsulation efficiency of α-tocopherol (~70%), the variation in the LMWC/SLES mass ratio (2:1 or 1:1) had no significant effect on the moisture content and microcapsule size. The prepared microcapsule-loaded carbomer hydrogels were soft semisolids with pseudoplastic flow behavior. The integrity of microcapsules embedded in the hydrogel was confirmed by light microscopy. The microcapsules reduced the pH, apparent viscosity, and hysteresis area of the hydrogels, while increasing their spreading ability on a flat inert surface and dispersion rate in artificial sweat. The in vitro release of α-tocopherol from crosslinker-free microcapsule-loaded hydrogels was diffusion-controlled. The release profile was influenced by the LMWC/SLES mass ratio, apparent viscosity, type of synthetic membrane, and acceptor medium composition. Better data quality for the model-independent analysis was achieved when a cellulose nitrate membrane and ethyl alcohol 60% w/w as acceptor medium were used.

Developing a self‐healing anticorrosion coating for steel protection in marine tidal zone

AbstractA self‐healing anticorrosion protective was developed for steel st‐37 exposed to the marine tidal zone, which is composed of a multi‐layer polymer coating. The coating includes zinc‐rich epoxy primer, self‐healing microencapsulated embedded epoxy, and a top coat consisting of polyurethane incorporated with silica nanoparticles. The size of microcapsules decreased with increasing agitation during encapsulation, which varies from 4 to 43 µm. Good performance was observed for producing the encapsulated particles with a size of up to 5 µm and more than 90% loading of the embedded healing agent, in which a 1680 rpm agitation along with a pH of 3 for the synthesis environment and a 130 min for the synthesis duration is set. The optimal amount of microcapsules and silica nanoparticles was 10 and 1.5 wt%, respectively. Also, the promised self‐healing anticorrosion coating leads the damaged areas to be fully healed in almost 12 h in the face of harsh conditions. In contrast to the non‐self‐healing one, the healing ability of the developed self‐healing coating shows good barrier properties and leads to a lesser loss of interface adhesion.

Mix design optimisation of self-sealing concrete containing microcapsules with polyurethane shell and water repellent cargo

Despite the robust ability of microcapsules (MIC) to break and release agent for healing/sealing efficacy, the reduction of concrete strength has been a major issue when using MIC. In this study, the optimisation of concrete mix design was initiated with employing three main parameters: MIC size (56, 93 μm), MIC dosage (0, 3, 6% by weight of cement) and water-cement (w/c) ratio (0.40, 0.50, 0.60). The used microcapsules consisted of water repellent agent core acting as a sealing agent and polyurethane as the shell material. Results confirmed the MIC dosage as the most significant factor affecting the mechanical properties, while no significant effect on the MIC size. Further, the MIC effect can be reduced by changing the concrete mix design from low to high w/c. The sealing efficiency of concrete was remarkably improved with the inclusion of MIC and a good bond between the capsules and concrete matrix was attained.

Unveiling antioxidant capacity of standardized chitosan-tripolyphosphate microcapsules containing polyphenol-rich extract of Portulaca oleraceae

The medicinal plant Portulaca oleraceae has a long history of usage in traditional medicine. Plant extracts have several interesting pharmacological effects but have some drawbacks that can be addressed via capsulation with chitosan. This work set out to do just that tally up the antioxidant effects of a polyphenol-rich P. olerace extract and see how capsulation affected them. The reflux extraction and response surface methodology (RSM) were carried out to optimize the phenolic and flavonoid content of P. oleraceae extract. Additionally, high-resolution mass spectrometry was employed to determine the secondary metabolite present in the extract. The microcapsules of extract-loaded chitosan were prepared using the ionic gelation method and characterized in terms of size, encapsulation efficiency (EE), and morphology of microcapsules. Fourier transform infrared (FTIR) was used to observe the successful production of microcapsules with a principal component analysis (PCA) approach. The antioxidant activity of microcapsules was established using the radical scavenging method. According to RSM, the highest amounts of TPC and TFC were obtained at 72.894 % ethanol, 2.031 h, and 57.384 °C. The compounds were employed from the optimized extract of P. oleraceae including phenolics and flavonoids. The microcapsules were secured with a %EE of 43.56 ± 2.31 %. The characteristics of microcapsules were approved for the obtained product's successful synthesis according to the PCA. The microcapsules have antioxidant activity in a concentration-dependent manner (p < 0.0001). The findings of this study underscored the benefits of employing chitosan as a nanocarrier for extract, offering a promising approach to enhance plant-derived therapies.

Chitosan-TPP microcapsules for controlled drug release

Production of chitosan/sodium tripolyphosphate (CS/TPP) microcapsules via spray drying involves atomizing an emulsion containing CS, TPP, acetic acid (AcOH), and folic acid (FA) into fine droplets exposed to high-temperature, low-pressure gas flow. Solvent evaporation within the drying chamber leads to solid particle formation. Spray drying is valuable for creating solid CS/TPP microcapsules. Precise equipment parameter adjustments, like inlet temperature and gas flow rate, enable the study of microcapsule morphology, size, and properties. This adaptability allows for customization to specific pH dissolution ranges. The production method's impact on CS/TPP microcapsules was studied by modifying spray drier parameters, including inlet temperature and aspirator pressure, to enhance understanding of their behavior in solution under varied production conditions.&#x0D; In chitosan delivery systems, various approaches can encapsulate drug agents like folic acid, an analog to the cancer treatment drug methotrexate. Agents can be added to the chitosan solution pre-crosslinking, incorporated into gelation-inducing agents pre-mixing with chitosan, or included in the crosslinking mixture. Experiments were conducted to assess CS/TPP microcapsules' behavior when encapsulating agents like folic acid. Release profiles were analyzed to understand their drug delivery capabilities and potential as controlled release carriers.

Controlling the Synthesis of Polyurea Microcapsules and the Encapsulation of Active Diisocyanate Compounds.

The encapsulation of active components is currently used as common methodology for the insertion of additional functions like self-healing properties on a polymeric matrix. Among the different approaches, polyurea microcapsules are used in different applications. The design of polyurea microcapsules (MCs) containing active diisocyanate compounds, namely isophorone diisocyanate (IPDI) or hexamethylene diisocyanate (HDI), is explored in the present work. The polyurea shell of MCs is formed through the interfacial polymerization of oil-in-water emulsions between the highly active methylene diphenyl diisocyanate (MDI) and diethylenetriamine (DETA), while the cores of MCs contain, apart from IPDI or HDI, a liquid Novolac resin. The hydroxyl functionalities of the resin were either unprotected (Novolac resin), partially protected (Benzyl Novolac resin) or fully protected (Acetyl Novolac resin). It has been found that the formation of MCs is controlled by the MDI/DETA ratio, while the shape and size of MCs depends on the homogenization rate applied for emulsification. The encapsulated active compound, as determined through the titration of isocyanate (NCO) groups, was found to decrease with the hydroxyl functionality content of the Novolac resin used, indicating a reaction between NCO and the hydroxyl groups. Through the thorough investigation of the organic phase, the rapid reaction (within a few minutes) of MDI with the unprotected Novolac resin was revealed, while a gradual decrease in the NCO groups (within two months) has been observed through the evolution of the Attenuated Total Reflectance-Fourier-Transform Infrared (ATR-FTIR) spectroscopy and titration, due to the reaction of these groups with the hydroxyl functionalities of unprotected and partially protected Novolac resin. Over longer times (above two months), the reaction of the remaining NCO groups with humidity was evidenced, especially when the fully protected Acetyl Novolac resin was used. HDI was found to be more susceptible to reactions, as compared with IPDI.