Synthesis Of Microcapsules Research Articles

Cerium nitrate microcapsules for coating application: characterization and corrosion study

Microcapsules show great potential in metal anticorrosive coating in recent years. In the following paper, first, urea-formaldehyde (UF) microcapsules containing cerium nitrate were synthesized under different parameter conditions. Three different quantities of the microcapsules were introduced to the epoxy coatings and applied on the AZ31B substrate to meet the increasing demands for anticorrosive coatings. An analysis of the scanning electron microscopy surface morphology of UF microcapsules synthesized by nine different parameter conditions shows that the ratio of formaldehyde to urea is 1.5:1, and 2 wt.% of emulsifier, 25 wt.% of cerium nitrate, and 150 r/min of rotation speed are the best choice for the synthesis of microcapsules, resulting in spherical particles with an average particle size of about 25 μm. The characteristics of microcapsules were studied by optical microscope, Fourier transform infrared, and thermogravimetric analysis. The result of electrochemical impedance spectroscopy indicated that the 2 wt.% microcapsule content in the defective coating shows better corrosion protection performance than neat epoxy coating and cerium nitrate inhibitor coating.

Synthesis, fabrication and tribo-mechanical studies of microcapsules filled and Al2O3/glass fibre reinforced UHMWPE based self-lubricating and self-healing composites

Development of composites containing both self-lubricating and self-healing (SLSH) characteristics is a nascent area of research for applications where direct lubrication is discouraged such as marine, textile, and food processing industries. For instance, SLSH composites may enhance the longevity of propeller shafts, bearings, and other dynamic components in such applications. The present work focuses on the synthesis of microcapsules with molybdenum disulfide (MoS2) as a core and polysulfone as a shell material, using the solvent evaporation method. The composites were fabricated by blending synthesized microcapsules in ultra-high molecular weight polyethylene (UHMWPE) matrix via injection moulding technique. Aluminum oxide (Al2O3) nanoparticles (3–12 wt.%) and glass fibres (10 wt.%) were also used as reinforcements. Flexural and tensile tests of the fabricated composites were conducted to evaluate their mechanical properties. Tribological behaviour was also investigated using a pin-on-disc tribometer. The polymer composites with a constant dose of 10 wt.% glass fibre and 5 wt.% microcapsules along with 6 wt.% Al2O3 exhibit the best performance. The maximum reductions in wear rate and coefficient of friction (COF) are 45.28% and 54.47%, respectively, as compared to the base matrix. Moreover, flexural and tensile strength increased by 43.55% and 39.77%, respectively. The worn surfaces exhibited fractured microcapsules which acted as SLSH agents, due to the high thermal stability of the polysulfone shell and release of the solid core. Various analytical tools, including optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), are employed in this study.

Synthesis of agro-industrial wastes/sodium alginate/bovine gelatin-based polysaccharide hydrogel beads: Characterization and application as controlled-release microencapsulated fertilizers

Synthesis of novel agro-industrial wastes/sodium alginate/bovine gelatin-based polysaccharide hydrogel beads, micromeritic/morphometric characteristics of the prepared formulations, greenhouse trials using controlled-release microencapsulated fertilizers, and acute fish toxicity testing were conducted simultaneously for the first time within the scope of an integrated research. In the present analysis, for the first time, 16 different morphometric features, and 32 disinct plant growth traits of the prepared composite beads were explored in detail within the framework of a comprehensive digital image analysis. The hydrogel beads composed of 19 different agro-industrial wastes/materials were successfully synthesized using the ionotropic external gelation technique and CaCl2 as cross-linker. According to micromeritic characteristics, the ionotropically cross-linked beads exhibited 77.86 ± 3.55 % yield percentage and 2.679 ± 0.397 mm average particle size. The dried microbeads showed a good swelling ratio (270.02 ± 80.53 %) and had acceptable flow properties according to Hausner's ratio (1.136 ± 0.028), Carr's index (11.94 ± 2.17 %), and angle of repose (25.03° ± 5.33°) values. The settling process of the prepared microbeads was observed in the intermediate flow regime, as indicated by the average particle Reynolds numbers (169.17 ± 82.81). Experimental findings and non-parametric statistical tests reveal that dried fertilizer matrices demonstrated noteworthy performance on the cultivation of red hot chili pepper plant (Capsicum annuum var. fasciculatum) according to the results of greenhouse trials. Surface morphologies of the best-performing fertilizer matrices were also characterized by Scanning Electron Microscopy. Moreover, the static fish bioassay experiment confirmed that no abnormalities and acute toxic reactions occurred in shortfin molly fish (Poecilia sphenops) fed with dried leaves of red hot chili pepper plants grown with formulated fertilizers. This study showcased a pioneering investigation into the synthesis of microcapsules using synthesized hydrogel beads along with digital image processing for bio-waste management and sustainable agro-application.

Modelling and optimization of epoxy-PMMA microcapsule synthesis parameter: A response surface methodology approach

The efficiency of self-healing microcapsule in restoring damages incurred by polymeric or composite materials is heavily dependent on modelling of encapsulation conditions to achieve optimized microcapsule with desired characteristics. This study modelled the effects of encapsulation conditions (core–shell ratio, agitation rate, and temperature) on the morphological, chemical, and thermal characteristics of epoxy-polymethylmethacrylate (epoxy-PMMA) microcapsules using response surface methodology (RSM). Epoxy-PMMA microcapsules were synthesized by encapsulating epoxy resin in polymethylmethacrylate (PMMA) at varied encapsulation conditions using solvent evaporation method. The morphology of the synthesized microcapsule using optical microscope (OP) revealed that the microcapsules are either mononuclear or irregular capsule types. The modelled effect showed that microcapsule percentage yield varied between 74.96 to 96.56%, was highly influenced by core–shell ratio and the effect of studied encapsulation conditions on percentage yield was best described by quadratic model. The core content of the microcapsules varied between 54.8 to 67.2%, observed to be highly influenced by both core–shell ratio and agitation rate which fit into linear model. The microcapsule average diameter was between 26 to 74 μm, highly influenced by agitation rate and fit linear model. Fourier transform infrared (FTIR) spectra of synthesized microcapsules revealed epoxy characteristic peak of C–O–C at 913 cm−1 and C–O-ph stretching at 1032 cm−1. C–O doublet of PMMA was observed at 1386 cm−1 and 1189 cm−1. Thermogravimetric analysis (TGA) of epoxy-PMMA microcapsule showed three stages of decomposition attributed to water evaporation, epoxy degradation, and PMMA shell degradation. Lastly, optimization process to achieve maximum yield, maximum core content and minimum capsule diameter was obtained with core–shell ratio of 1.5:3 and agitation rate of 1000 rpm at 40 °C. The synthesized epoxy-PMMA microcapsules exhibited chemical, thermal, morphological stability and the models can be optimized to achieve microcapsule with desired characteristics.

Tailoring Microemulsification Techniques for the Encapsulation of Diverse Cargo: A Systematic Analysis of Poly (Urea-Formaldehyde) Microcapsules.

Cargo encapsulation through emulsion-based methods has been pondered over the years. Although several microemulsification techniques have been employed for the microcapsule's synthesis, there are still no clear guidelines regarding the suitability of one technique over the others or the impacts on the morphological and physicochemical stability of the final particles. Therefore, in this systematic study, we investigated the influence of synthesis parameters on the fabrication of emulsion-based microcapsules concerning morphological and physicochemical properties. Using poly(urea-formaldehyde) (PUF) microcapsules as a model system, and after determining the optimal core/shell ratio, we tested three different microemulsification techniques (magnetic stirring, ultrasonication, and mechanical stirring) and two different cargo types (100% TEGDMA (Triethylene glycol dimethacrylate) and 80% TEGDMA + 20% DMAM (N,N-Dimethylacrylamide)). The resulting microcapsules were characterized via optical and scanning electron microscopies, followed by size distribution analysis. The encapsulation efficiency was obtained through the extraction method, and the percentage reaction yield was calculated. Physicochemical properties were assessed by incubating the microcapsules under different osmotic pressures for 1 day and 1, 2, or 4 weeks. The data were analyzed statistically with one-way ANOVA and Tukey's tests (α = 0.05). Overall, the mechanical stirring resulted in the most homogeneous and stable microcapsules, with an increased reaction yield from 100% to 50% in comparison with ultrasonication and magnetic methods, respectively. The average microcapsule diameter ranged from 5 to 450 µm, with the smallest ones in the ultrasonication and the largest ones in the magnetic stirring groups. The water affinities of the encapsulated cargo influenced the microcapsule formation and stability, with the incorporation of DMAM leading to more homogeneous and stable microcapsules. Environmental osmotic pressure led to cargo loss or the selective swelling of the shells. In summary, this systematic investigation provides insights and highlights commonly overlooked factors that can influence microcapsule fabrication and guide the choice based on a diligent analysis of therapeutic niche requirements.

Self-healing epoxy coatings via microencapsulation of aromatic diisocyanate in lignin stabilized Pickering emulsions

Isocyanate-filled microcapsules are gaining increased attention for their role in developing self-healing materials, thereby reducing maintenance costs and increasing polymer durability. Nevertheless, microencapsulating highly reactive -NCO groups remains a challenging task in the literature. Likewise, considerable efforts have been directed towards developing polymers from renewable and biobased sources, which could also be applied to microcapsule synthesis. In this work, lignin, an abundant biopolymer, was used as a solid stabilizer for oil-in-water (O/W) interfaces, enabling the encapsulation of highly reactive isocyanate. Hybrid polyurethane/polyurea microcapsules containing reactive methylenediphenyl diisocyanate (MDI) were obtained via optimized O/W Pickering emulsions using lignin for system stabilization. This optimized process facilitated shell formation via the reaction of diisocyanate with lignin and water, eliminating the need for additional chain extenders. Scanning electron microscopy revealed the formation of spherical and rough microcapsules, while infrared spectroscopy confirmed the presence of residual free -NCO groups, indicating effective encapsulation of MDI. Additionally, a core -NCO concentration of 11 wt% was confirmed by titration. The microcapsules were further assessed as components in self-healing epoxy coatings. Their incorporation resulted in the retardation of corrosion on a low carbon steel panel after 72 h of submersion in a saline solution. Electrochemical impedance spectroscopy (EIS) confirmed a significant increase of approximated 620% in impedance modulus after 83 days of immersion in a 3.5 wt% NaCl solution, compared to the neat epoxy coating. These findings suggest a promising technological application of this material for the advancement of self-healing epoxy-based coatings and composites.

Optimization of synthesis parameters of PUF/ENB microcapsules for self‐healing applications using factorial design methodology

AbstractThis study introduces a systematic experimental approach aimed at enhancing the production process of poly(urea‐formaldehyde) (PUF) microcapsules filled with 5‐ethylidene‐2‐norbonene (ENB) using in situ emulsion polymerization. Essential parameters were identified through a prior Plackett Burman (PB) design, leading to the implementation of a 24‐1 fractional factorial design. The key parameters selected encompassed stirring speed, poly(ethylene‐alt‐maleic anhydride) (EMA) emulsifier content, pH of the reaction, and the quantity of 1‐octanol. Optimal conditions for polymeric microcapsule synthesis were determined using a statistical analysis of the complete factorial design, facilitating the development of representative mathematical models for the process. A comprehensive evaluation of response variables including microcapsule diameter, yield, encapsulated content, stability, and thermal degradation was conducted. Utilizing response surface analysis (RSM), it was determined that the PUF/ENB(2C) condition (stirring at 700 rpm, a reaction pH of 3.0, and EMA content of 0.425 g) resides within the optimized synthesis region, producing microcapsules exhibiting favorable morphological characteristics, yield of 52% and encapsulated content of 80%.

Модификация свойств волокнистых материалов с использованием нанотехнологий

Nanotechnologies play an important role in the modern world economy. As they deal, as a rule, together with other convergent (nano-, bio-, info-, cognitive) technologies. This connection causes a synergy effect, i.e. non linear development of innovations. The growth dynamics of the world's nanotechnology products is impressive. The world market of nanotechnologies in 2021 was 85 billion dollars, in 2024 (plan) will be 140 billion dollars. The forecast for 2030 is $288 billion. The production of nanoparticles of different nature and their use in different industries, fields of science, and technology takes a special place in nanotechnology. Both nanotechnology itself and the production and application of nanoparticles are interdisciplinary and cross-sectoral ones. Their users and customers are developed industries, including the textile industry. Metal nanoparticles are used both in the form of colloidal solutions and as part of microcapsules containing functional substances of different nature in the core. The article considers some methods of obtaining metal nanoparticles and microcapsule synthesis. The authors list the technologies of microcapsules application for textile functionalization.

Modification of fibre materials properties with the use of nanotechnologies

Nanotechnologies play an important role in the modern world economy. As they deal, as a rule, together with other convergent (nano-, bio-, info-, cognitive) technologies. This connection causes a synergy effect, i.e. non linear development of innovations. The growth dynamics of the world's nanotechnology products is impressive. The world market of nanotechnologies in 2021 was 85 billion dollars, in 2024 (plan) will be 140 billion dollars. The forecast for 2030 is $288 billion. The production of nanoparticles of different nature and their use in different industries, fields of science, and technology takes a special place in nanotechnology. Both nanotechnology itself and the production and application of nanoparticles are interdisciplinary and cross-sectoral ones. Their users and customers are developed industries, including the textile industry. Metal nanoparticles are used both in the form of colloidal solutions and as part of microcapsules containing functional substances of different nature in the core. The article considers some methods of obtaining metal nanoparticles and microcapsule synthesis. The authors list the technologies of microcapsules application for textile functionalization.

Mucoadhesive chitosan microcapsules for controlled gastrointestinal delivery and oral bioavailability enhancement of low molecular weight peptides

A bioactive compound, collagen peptide (CP), is widely used for biological activities such as anti-photoaging and antioxidant effects, with increased oral bioavailability because of its low molecular weight and high hydrophilicity. However, controlling release time and increasing retention time in the digestive tract for a more convenient oral administration is still a challenge. We developed CP-loaded chitosan (CS) microcapsules via strong and rapid ionic gelation using a highly negative phytic acid (PA) crosslinker. The platform enhanced the oral bioavailability of CP with controlled gastrointestinal delivery by utilizing the mucoadhesiveness and tight junction-opening properties of CS. CS and CP concentrations varied from 1.5 to 3.5% and 0–30%, respectively, for optimal and stable microcapsule synthesis. The physicochemical properties, in vitro release profile with intestinal permeability, in vivo oral bioavailability, in vivo biodistribution, anti-photoaging effect, and antioxidant effect of optimized CS microcapsules were analyzed to investigate the impact of controlling parameters. The structure of CS microcapsules was tuned by PA diffused gradient ionic cross-linking degree, resulting in a controlled CP release region in the gastrointestinal tract. The optimized microcapsules increased Cmax, AUC, and tmax by 1.5-, 3.4-, and 8.0-fold, respectively. Furthermore, CP in microcapsules showed anti-photoaging effects by downregulating matrix metalloproteinases-1 via antioxidant effects. According to our knowledge, this is the first study to microencapsulate CP for oral bioavailability enhancement. The peptide delivery method employed is simple, economical, and can be applied to customize bioactive compound administration.

Development and properties of bio-based rice oil microcapsule and its dispersibility in emulsified asphalt

To develop a new bio-based rice oil microcapsule for the self-healing of emulsified asphalt, rice oil and melamine formaldehyde (MF) resin were utilized as core and wall materials, respectively, preparing rice oil-melamine formaldehyde resin (ROMF) microcapsule. Then its morphology, particle size distribution, encapsulating status, thermal stability, micromechanical properties and dispersity in emulsified asphalt was studied. The results show that the prepared microcapsules show regular 2–10 μm spherical shapes, following a normal distribution. The microcapsule surface has a large roughness, promoting a close combination with emulsified asphalt. Also, during the synthesis of microcapsules, the methylene is generated and the condensation reaction occurs on rice oil droplet surface, proving that core material of rice oil is successfully encapsulated by MF resin. The microcapsules exhibit excellent thermal stability. Further, the distribution regularities of adhesion force and Young's modulus on microcapsule surface are closely correlated with the particle sizes and thickness of MF resin. The Young's modulus of microcapsule surface is improved with the thickness increase of wall material. Finally, the microcapsule at the dosage of 5 % exhibits the best dispersibility in emulsified asphalt and a clear core–shell structure is observed. The proposed dosage of ROMF microcapsules used in emulsified asphalt is 5 %.

Aerogel-Like Material Based on PEGylated Hyperbranched Polymethylethoxysiloxane.

Aerogels are a class of materials that have gained increasing attention over the past several decades due to their exceptional physical and chemical properties. These materials are highly porous, with a low density and high surface area, allowing for applications such as insulation, catalysis, and energy storage. However, traditional aerogels, such as pure silica aerogels, suffer from brittleness and fragility, which limit their usefulness in many applications. Herein, we have addressed this problem by using organosilicon compounds, namely polymethylsilsesquioxane derivatives, for the synthesis of aerogel-like materials. Specifically, we have developed a novel approach involving surfactant-free synthesis of microcapsules from partially PEGylated hyperbranched polymethylethoxysiloxane. Due to the highly diphilic nature of these compounds, they readily concentrate at the oil/water interface in aqueous emulsions encapsulating oil droplets. During the subsequent condensation, the organosilicon precursor is consumed for hexane encapsulation (yielding hollow microcapsules) followed by the formation of a continuous condensed phase. Concurrently, methyl groups ensure the hydrophobicity of the resulting materials, which eliminates the need of using additional reagents for their hydrophobization.

High linoleic waste sunflower oil: A distinctive recycled source of self-healing agent for smart metal coatings

High Linoleic Waste Sunflower Oil (HLWSO) is a new self-healing agent viable to be encapsulated. Meanwhile, the unique mechanism behind the synthesis of microcapsules is deeply illustrated; the emulsification process of HLWSO by anionic surfactant and microencapsulation of HLWSO. In addition, the application of microencapsulated HLWSO in the coating matrix by the layering method is presented followed by a detailed explanation of the self-healing mechanism of a smart coating incorporating the polymerization mechanism of HLWSO developed by the diene structure. Microencapsulation of high linoleic waste sunflower oil (HLWSO) is a wall formation process in which urea-formaldehyde (UF) is attached with emulsified HLWSO to form a microcapsule. In this study, the HLWSO from recycled cooking oil is uniquely bonded with a diene structure, thus possessing the ability to dry fast and be encapsulated via the in-situ polymerization method. The microencapsulated HLWSO was characterized using Field Emission Scanning Electron Microscopy (FESEM) and Fourier Transformation Infra-Red Spectroscopy (FTIR). The optimum microcapsules synthesized from HLWSO resulted in a smooth shell structure with 2.88 μm diameter microcapsules at 0.31 μm shell thickness and 66% core content. It was demonstrated that increased stirring speed decreases the size, shell thickness, and core content of the microcapsules. The FTIR results indicated that HLWSO as a core, while urea-formaldehyde acted as a shell of microcapsules. The scratch on the coating matrix embedded with HLWSO was healed after five days. The corrosion rate of optimum sample was 0.0574 mm/year, with an optimum reduction of 58% from the reference sample. This study revealed that the HLWSO from recycled sources is a viable self-healing agent to be microencapsulated. The smart coating embedded with HLWSO also displayed self-healing performance, reduced corrosion rate and beneficial for the advancement of corrosion control technology.

Synthesis of magnetic targeted delivery microcapsules and its anti-corrosion self-healing behavior in epoxy resin coatings

This study proposed a tung-oil based magnetic targeted delivery microcapsules (MDTMs) to enhance the efficiency of self-healing coatings (SHC). Magnetic particles were used as function particles and emulsifier in synthesis of microcapsules (MC). DSC, OM, SEM, TEM, VSM, NSS, EIS and SKP were used to characterize the compounds, structure, healing behavior and anti-corrosion performance. Results indicate that magnetically driven SHC (MD-SHC) reduces 50% migration path of the released tung oil, and increases the release rate of tung oil after the coating is mechanically damaged. SKP and EIS results suggest that the healing part has impressive anti-corrosion performance, scratches were filled with a large amount of tung oil in a short time, and the released tung oil had formed a complete oil film on scratches at 24 h with higher polarization resistance (Rp). Rp of MD-SHC (2.5 × 105–3.6 × 105 Ω cm2) is 2.0–2.8 times of that the SHC (1.1 × 105–1.8 × 105 Ω cm2). The enrichment in MD-SHC at the interface decreases bonding strength from 7 to 4.5 MPa as the mass additive of microcapsules reaches 15 wt.%. The current work proves the effectiveness of MD-SHC in improving self-healing ability.

Synthesis of microcapsules containing a formaldehyde scavenger for the sustainable control of hazardous chemical release from particleboard.

Formaldehyde scavenger microcapsules were introduced into particleboard to prepare an ecofriendly particleboard with a low pollution release in response to the problem of long-term unstable free formaldehyde release from particleboards. By analyzing key parameters of formaldehyde emission from particleboard, the effects of microcapsules on the diffusion, migration and inhibition of free formaldehyde in particleboard pore structures was discussed. The results showed that microencapsulated formaldehyde scavenger prepared by an emulsification cross-linking method with chitosan as the wall material and urea as the core material resulted in a good long-term controlled release effect on formaldehyde emission. Compared with that of the control panel, the formaldehyde emission of the particleboard with microcapsules decreased by 51.4 % and 25.8 % at 28 d and 180 d, respectively. The addition of formaldehyde scavenger microcapsules increased the particleboard macroscopic pore volume, which facilitated the conversion of adsorbed formaldehyde into free formaldehyde in the pore structure, thereby promoting its migration and diffusion in the particleboard pores. Moreover, the synergistic effect of the addition-condensation and nucleophilic cross-linking of the core and wall materials quickly captured the free formaldehyde in the panels and reduced the releasable concentration of formaldehyde in the material, thus achieving the long-term effective control of formaldehyde emission.

Fabrication of highly durable functional textile through microencapsulation of organic citronella oil

The use of organic and eco-friendly plant-based materials has shown an increasing interest for researchers over recent years. This study describes the preparation of microcapsules from a natural citronella oil and its treatment on polyester-cotton blended (PC) fabric. The citronella oil is an essential oil obtained from the leaves and stems of various species of Cymbopogon. Microcapsules containing citronella oil as core material were produced by a complex coacervation technology and applied to fabric using the pad-dry-cure method. The morphology of the solution of microcapsules was investigated by optical microscope and the dried microcapsules were examined by scanning electron microscope (SEM). Furthermore, the microcapsules were also characterized for particle size distribution and zeta potential. SEM was also used to investigate the surface morphology of fabric surfaces after the treatment of microcapsules. A conventional test technique (cage test) was used to evaluate the medicated fabric's ability to keep mosquitoes away and comfort properties of fabric like air permeability and water absorbency were also studied. The fabric sample finished with 15% (solid in water) citronella oil microcapsules at zero wash exhibited 90% mosquito repellency, and after 30 washes the fabric possessed 80% mosquito repellency committing the durability of as prepared finished fabric. The medicated PC fabric revealed good air permeabilities and water absorbencies. Hence, this report presented an eco-friendly approach for the development of highly durable functional mosquito repellent textiles. • The successful synthesis of microcapsules using organic oils as core material. • Application of microcapsules on a polyester cotton blended fabric using the pad-dry-cure method. • Characterization of the prepared microcapsules by optical microscope, SEM, DLS, and zeta potential. • Establishing the mosquito repellent property of the prepared textile fabric in cage test. • Investigation of the durability under rigorous washing cycles.

Development of functional textile via microencapsulation of peppermint oils: a novel approach in textile finishing

PurposeThe efforts of researchers in the 21st century have been devoted to developing novel approaches to leave planet earth green for future generations. This study aims to report the synthesis of microcapsules from natural essential peppermint oil and their application to a bleached polyester and cotton (PC) blended fabric.Design/methodology/approachMicrocapsules were prepared by a complex coacervation process and applied through the conventional pad-dry-cure method. The liquid suspension of the microcapsules was examined by optical microscopy to investigate the surface morphology of the microcapsules. Scanning electron microscopy was used to examine the surface morphology of the fabric after the application of the microcapsules. The finished fabric was checked for its mosquito repellent activity at the lab scale using a standard test protocol (cage test) by inserting a human arm and hand enfolded with microcapsules treated fabric.FindingsPC fabric treated with 6% microencapsulated peppermint oil at zero wash showed 95.3% repellency against mosquitoes, and after 30 washes, the repellency was 85.8% which confirmed the durability of the developed finished fabric. The finished samples exhibited excellent air permeabilities and absorbencies.Originality/valueThis study successfully developed peppermint oil microencapsulated fabric with excellent efficacy against three mosquito species.

Study of the Effect of Hydrolysis Time on the Mechanical Properties of Polysiloxane Microcapsules

It is known that the microstructure and thereby the mechanical properties of membranes constituting microcapsules are sensitive to parameters such as precursor concentration and pH. In the case of polysiloxane microcapsules, the oligomers, which are already formed in the continuous oil phase, because of the inherent moisture content in the oil phase, deposit on the membrane surface, resulting in the formation of a microstructure with a hairy layer. An electrodeformation investigation shows that the deposition of these oligomers is predominant in the smaller microcapsules compared to the larger ones and results in strain hardening and plasticity in the microcapsule membrane at high deformation. However, if the hydrolysis time during the synthesis of microcapsules is controlled, a smooth morphology (with a diminished hairy layer) can be realized for smaller capsules, as well. This work, using the electrodeformation method, demonstrates significant viscoelasticity and plasticity in the response of the capsules to applied electric stress and establishes an equivalence between simple spring and dashpot element-based phenomenological models with respect to the membrane properties using a linearized viscoelastic elasto-electrohydrodynamic model. The model can capture plasticity and strain hardening that are otherwise missed in simplified elasticity-based models.

Study of Melamine-Formaldehyde/Phase Change Material Microcapsules for the Preparation of Polymer Films by Extrusion.

n-Eicosane-melamine formaldehyde microcapsules of an average size of 1.1 μm and latent heat of fusion of 146.2 ± 5.3 J/g have been prepared. They have been characterized by scanning electron microscopy, FTIR spectroscopy, calorimetric techniques, and thermogravimetric analyses. Under processing conditions, the microcapsules apparently preserved their properties, also maintaining their n-eicosane loading and heat storage capacity under washing conditions (water with detergent at 60 °C). The microcapsules synthesis has been scaled up for the fabrication of functional films by extrusion. For that, polymer films containing 10 wt.% of microcapsules were prepared at a pilot plant level. In those films, even though a fraction of the n-eicosane loading was lost during the extrusion process, the microcapsules showed good compatibility within the polyamide. The percentage of PCM in the polyamide 6 films was estimated by TGA, verifying also the heat storage capacity predicted by DSC (2.6 ± 0.7 J/g).

Biodegradable Polymers for Microencapsulation Systems

Environmentally friendly alternatives have become sought after upon the development of scientific research and industrial processes. Recent trends suggest biodegradable polymers as the most promising solution for synthetic microcapsule systems. Safety, efficiency, biocompatibility, and biodegradability are some of the properties that biodegradable systems in microencapsulation can provide for a broad spectrum of applications. The controlled release of encapsulated active agents is a research field that, over the years, has been constantly innovating due to the promising applications in the areas of pharmaceutical, cosmetic, textile industry, among others. This article presents an overview of different polymers with potential for microcapsule synthesis, namely, biodegradable polymers. First, natural polymers are discussed, which are divided into two categories: polysaccharide-based polymers (cellulose, starch, chitosan, and alginate) and protein polymers (gelatin). Second, synthetic polymers are described, where biodegradable polymers such as polyesters, polyamides, among others appear as examples. For each polymer, this review presents its origin, relevant properties, applications, and examples found in the literature regarding its use in biodegradable microencapsulation systems.