Kinds Of Microcapsules Research Articles

Polylactic acid-based microcapsules for moisture-triggered release of chlorine dioxide and its application in cherry tomatoes preservation

Polylactic acid (PLA)-based microcapsules, capable of releasing chlorine dioxide (ClO2) upon exposure to moisture, have been developed for fruits and vegetables preservation. The microcapsules were prepared by emulsion solvent evaporation, utilizing PLA as the wall material, and NaClO2 as the core material. After optimization, NaClO2 microcapsules exhibited an encapsulation efficiency of 55.75% and an average particle size of 498.08 μm. Citric acid microcapsules were prepared using the same process, but with citric acid as the core material. When the two kinds of microcapsules were mixed, gaseous ClO2 was released in a highly humid environment. The release rate could be adjusted by temperature and the ratio between the two microcapsules, and the release period could be as long as 17 days at 20 °C. With a certain amount of microcapsules placed in the package of cherry tomatoes, the decay rate and weight loss rate of the fruits were reduced by 63 % and 34 %, respectively, compared to the control group. The microcapsules also helped to maintain the good appearance, hardness, and the content of total soluble solid content and titratable acid content of cherry tomatoes. Therefore, the PLA-based microcapsules have satisfied convenience and effectiveness for application in fruit and vegetables preservation.

Development and characterization of symbiotic microcapsules to enhance the viability of probiotic under stressed conditions

ABSTRACT In the present research, the survival and sustainability of a Lactobacillus rhamnosus probiotic has been investigated with regard to the prebiotic impact of introducing two different kinds of onion (Allium cepa L.) peel extract to probiotic microcapsules. Effective inclusion of red and white onion peel extract featuring good prebiotic action into the microcapsules enhanced probiotic survival. The structure, distribution of size, zeta potential, and encapsulation efficacy of probiotics and substances in the extract were evaluated along with the probiotics capability to persist under simulated gastrointestinal circumstances. Fourier Transform Infrared Spectroscopy (FTIR) was employed to investigate the molecular structure and internal framework. The wall and core components possess adhesive relationships, as demonstrated by FTIR spectra. Probiotics that were free and those that were in capsules were evaluated as well in vitro in undesirable persistence performance (>90%). Probiotics with encapsulation exhibited substantially (p > .05) greater vitality compared free cells, in accordance with an in-vitro experiment. Under simulated gastrointestinal situations, free cells continued diminishing their vitality, but encapsulated cells maintained their viability count beyond the suggested level (107 cfu/g). SEM photographs indicated that probiotics have been effectively encapsulated inblends. The microcapsules were around 191 ± 2 and 176 ± 2 μm in size. These outcomes reveal that these kinds of microcapsules may encourage the probiotic L. rhamnosus prolonged viability and consistency under multiple conditions.

Preparation of Melamine-Formaldehyde Resin/Rice Husk Powder Coated Epoxy Resin Microcapsules and Effects of Different Microcapsule Contents on the Properties of Waterborne Coatings on Tilia europaea Surface

With the development of economy and science and technology, people put forward higher standards for the performance of the surface coating of wood products, which requires us to carry out innovative research on the coating. In this work, a kind of microcapsule was prepared with melamine-formaldehyde resin/rice husk powder as wall material and epoxy resin as core material. The microcapsules were added to the waterborne acrylic resin coating according to the contents of 0%, 1.0%, 4.0%, 7.0%, 10.0%, 13.0%, 16.0% and 20.0% respectively, and were coated on the surface of the Tilia europaea boards in the form of topcoat. The effects of different contents of microcapsules on the optical properties, mechanical properties and aging resistance of the coating were explored, and the optimal content that can effectively improve the properties of the coating was analyzed. Test results indicated that when the microcapsule content is 7.0%, the comprehensive properties of the coating is optimal. At this time, the color difference of the coating is 6.96, the gloss at 60° is 13.4%, the hardness is 2H, the adhesion grade is 1, and the impact resistance is 12.0 kg·cm. After the aging test, the gloss loss rate decreases, the color difference is 5.69, and the gloss at 60° is 11.6%. The results of aging test show that the coating with epoxy microcapsules has a certain self-healing function. In this study, the microcapsules which can optimize the mechanical properties waterborne coating and prolong the service life of wood were prepared. This can meet the diverse needs of consumers, supply a theoretical reference for the preparation of functional microcapsules, and provide reference value for the functional research of the coating on wood furniture surface.

The structural characterization, physicochemical properties, and stability of gardenia yellow pigment microcapsules

Gardenia yellow pigment (GYP) is a natural food coloring agent with a variety of pharmacological activities. However, the applications of GYP are limited due to its poor stability. The aim of this study was to prepare GYP microcapsules using different combinations of maltodextrin (MD), gum arabic (GA), soy protein isolate (SPI), and whey protein (WP) as wall materials to improve the stability of GYP, and evaluated its structural, physicochemical properties, and stability. Scanning electron microscopy (SEM), fourier transformed infrared spectrometer (FTIR), and X-ray diffraction (XRD) results confirmed inclusion of GYP within microcapsules. Thermogravimetric (TG) experiment indicated that GYP microcapsules had good thermal stability below 220 °C. Furthermore, the encapsulation efficiency (EE) and loading amount (LA) of GYP microcapsules were between 58.73 and 83.16% and 1.63–3.32 g/100 g, respectively. WP-MD microcapsule showed significantly higher EE and LA than other microcapsules. A significant lower hygroscopicity was observed in spray-dried double emulsion microcapsules (WP–O and WP-MD-O). The results of the stability studies revealed that the five kinds of microcapsules could significantly improve the thermal stability, light stability, and pH stability of GYP, and there was no significant difference. Overall, these results may guide the potential application of GYP microcapsules in nutraceutical and functional foods.

Preparation of Tung Oil Microcapsule and Its Effect on Wood Surface Coating.

Through the optimized preparation of tung oil microcapsules, five kinds of microcapsules containing different core material content were obtained to explore the influence of microcapsules on water-based paint film and the self-healing ability of microcapsules. The results showed that the microcapsules had good appearance, and the microcapsules were successfully prepared. The color difference in the paint film increased with the increase in microcapsule content, and the gloss decreased gradually. The mechanical test showed that adding microcapsules increased the toughness of the paint film to a certain extent, and the performance of the paint film was unchanged or better. The results showed that paint film with the core–wall ratio of 0.78:1 had the best performance and self-healing function when microcapsules were added.

Preparation and Characterization of Double-Layered Microcapsules Containing Nano-SiO2

The double-layered microencapsulation technology has been used in many fields. In this study, the double-layered microencapsulated anthocyanin of Passiflora edulis shells (APESs) was prepared via complex coacervation using gelatin and gum Arabic as the first wall materials (single-layered microcapsules (SMs)) and using gum Arabic containing nano-SiO2 as the second wall material (double-layered microcapsules (DMs)/nano-SiO2) to enhance the stability of the core material. Properties of microcapsules were analyzed on the basis of EE, morphology, scanning electron microscopy (SEM), droplet size, moisture content, and differential scanning calorimetry (DSC). The results showed that the EE values of SMs, DMs, and DMs/nano-SiO2 were 96.12%, 97.24%, and 97.85%, respectively. DMs/nano-SiO2 had the lowest moisture content (2.17%). The average droplet size of DMs/nano-SiO2 (34.93 μm) was higher than those of SMs and DMs. DSC indicated that the melting temperature of DMs/nano-SiO2 was 73.61°C and 45.33°C higher than those of SMs and DMs, respectively. SEM demonstrated that DMs/nano-SiO2 had the smoothest surface compared with the other two kinds of microcapsules. The storage stability of APESs and their microcapsules indicated that the stability of the microcapsules was improved by adding DMs/nano-SiO2 into the wall material of microcapsules. These results indicated double-layered microcapsules containing silica nanoparticles contribute to the stability of the core material.

Preparation and characterization of self-healing microcapsules of asphalt

Cracking is one of the main forms of damage to asphalt pavement. The self-healing process of asphalt pavement is the inverse process of crack formation and development. Strengthening the self-healing ability of asphalt materials could restrain cracking and prolong the service life of asphalt pavement. Microcapsule self-healing technology has achieved good results in the field of microcrack repair and has promising research prospects. In this study, two kinds of microcapsules, CA-mic and E-mic, were prepared by in situ polymerization with a self-developed rejuvenator CA and modified epoxy resin as core materials. The micromorphology, thermal stability and chemical structure of the microcapsules were characterized by fluorescence microscopy (FM), scanning electron microscopy (SEM), laser particle size analyzer (LPSA), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The freeze-heating cycle test was adopted to evaluate the durability of the microcapsules. The results showed that the two prepared microcapsules were spherical in shape and uniform in particle size distribution, with compact encapsulation and good durability. Additionally, they could survive under high temperature during asphalt construction. The rheological test of bending beams showed that the low temperature crack resistance of asphalt was improved after adding two kinds of microcapsules. The “Fracture - Healing- Fracture” tests showed that the two microcapsules could enhance the self-healing ability of the asphalt, and the maximum self-healing rate of the CA-mic could reach 52% and that of the E-mic could reach 47%.

A Novel Shell Material-Highland Barley Starch for Microencapsulation of Cinnamon Essential Oil with Different Preparation Methods.

Highland barley starch (HBS), as a carbohydrate shell material with excellent performance in microcapsule applications, has rarely been reported. In the present study, three different microcapsules (CEO-SWSM, CEO-PM, and CEO-UM) were synthesized successfully via saturated aqueous solution method, molecular inclusion method and ultrasonic method, respectively, using HBS as shell material coupled with cinnamon essential oil (CEO) as the core material. The potential of HBS as a new shell material and the influence of synthetic methods on the performance of microcapsules, encapsulation efficiency (EE), yield, and release rate of CEO-SWSM, CEO-PM, and CEO-UM were determined, respectively. The results confirmed that CEO-PM had the most excellent EE (88.2%), yield (79.1%), as well as lowest release rate (11.5%, after 25 days of storage). Moreover, different kinetic models were applied to fit the release process of these three kinds of microcapsules: CEO-SWSM, CEO-PM, and CEO-UM had the uppermost R-squared value in the Higuchi model, the zero-order model, and the first-level model, respectively. Over all, this work put forward a novel perspective for the improved encapsulation effect of perishable core materials (e.g., essential oil) for the food industry.

Effect of temperatures on self-healing capabilities of concrete with different shell composition microcapsules containing toluene-di-isocyanate

The ambient temperatures have significant effect on self-healing capabilities of concretes with microcapsules. Self-healing capabilities of mortars with different shell composition (paraffin, paraffin/PE wax and nano-SiO2/paraffin/PE wax) microcapsules containing toluene-di-isocyanate under the temperature of 10 °C, 30 °C, 50 °C and 60 °C were investigated in this paper. The compressive strength, chloride diffusion coefficient and pore size distribution of mortars containing microcapsules before and after self-healing were characterized by mechanical property test, rapid chloride migration test and nuclear magnetic resonance, respectively. The crack healing ratio of mortars during self-healing period were measured. The self-healing capabilities of mortars containing different microcapsules raised with the increase from 10 °C to 50 °C. Nevertheless, when the temperature reached 60 °C, the self-healing capability of the mortar containing paraffin microcapsules (AM1) decreased obviously, while the self-healing capabilities of the mortars containing paraffin/PE wax microcapsules (AM2) and nano-SiO2/paraffin/PE wax microcapsules (AM3) were almost unchanged. The self-healing capability of AM3 was superior to that of AM1 and AM2 at the same temperature. The compressive strength recovery rate, chloride diffusion coefficient recovery rate and harmful pores ratios of AM3 after pre-damaged at 50 °C for 7 d self-healing were 94.1%, 81.2% and 47.3%, respectively. When the ambient temperature reached 50 °C, the surface cracks of the mortar with three kinds of microcapsules could be completely self-healed in 5 h. However, when the temperature raised to 60 °C, the healing ratio of the crack in AM1 with a width of 0.4–0.5 mm decreased to 49.52% after 6 h self-healing. Meanwhile, the surface cracks of AM3 could be completely self-healed less than 3 h.

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

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

New β-Cyclodextrin-Based Microcapsules for Textiles Uses

In this paper, a novel kind of microcapsules containing 2-ethoxynaphtalene (neroline) was successfully synthesized into polyurethane shells through the interfacial polycondensation of β-cyclodextrin with 4,4’-methylene (bisphenyl isocyanate) (MDI) in direct emulsion. The IR spectroscopy was used, on the one hand to confirm the success of polymerization reaction leading to the polyurethane shell formation, but on the other hand to check the encapsulation efficiency of fragrance that accounts for 40%. Microcapsules’ spherical shape and particle size distributions were revealed by means of optical microscopy, scanning electron microscopy (SEM) observation, and small-angle light scattering measurement. The impregnation of neroline-loaded microcapsules on polyamide knitted fabric was tested as an application method at a yield of around 74%. Adhesion of synthesized microcapsules to textile materials was evaluated through microscopic observations. The durability of the impregnation effect was tested by SEM and UV-visible spectroscopy. Washing fastness test of the impregnated polyamide knitting proved that the loaded microparticles retained their efficiency after more than 35 washing cycles.

Preparation of microcapsule and its influence on self-healing property of asphalt

A kind of microcapsule was prepared, and a new type of self-healing asphalt was manufactured by mixing asphalt, microcapsule and curing agent with proper ratio. The ductility(15 °C and 10 °C), softening point and penetration of asphalt were tested both before and after adding microcapsule and curing agent into the asphalt. The results showed that the three indexes were kept in normal ranges after adding microcapsule and curing agent. However, the ductility(10 °C) was lower than the technical standard when the additive amount of microcapsule was 5.0wt%. Whereafter, the influence of additive amount, self-healing temperature and time on the asphalt self-healing property were all investigated by ductility self-healing tests (10 °C). The outcome indicated that the addition of microcapsule into the asphalt promote its self-healing properties obviously. The self-healing rate of blank asphalt in 20 °C and for 3 h was 20%, and when the microcapsule additive amount was 3.0wt%, the rate was improved to 40.0%. The highest self-healing rate was 52.0%. The elevation of temperature and extension of time were both beneficial for the promotion of the self-healing properties of asphalt. However, when healing temperature and healing time were improved to 30 °C and 7 h, the improvement of self-healing rate was not obvious.

Novel dual-functional coating with underwater self-healing and anti-protein-fouling properties by combining two kinds of microcapsules and a zwitterionic copolymer

Antibiofouling and repairing of the micro-cracked coating on the surface of the facilities in underwater environment are two great challenges in marine industries. This paper prepared a dual-functional coating with underwater self-healing and anti-protein-fouling properties by combining two kinds of microcapsules and a zwitterionic copolymer. First, epoxy resin microcapsules and underwater epoxy hardener microcapsules were prepared. Epoxy resin microcapsules with a poly(urea-formaldehyde) shell and the entrapped mixture of epoxy resin and n-butyl glycidyl ether showed homogeneous spherical morphology with encapsulation ratio of 90.42%. Underwater epoxy hardener microcapsules with a polymethyl methacrylate shell and the entrapped underwater epoxy hardener showed cellular spherical morphology with encapsulation ratio of 78.67%. Both of the microcapsules exhibited pretty thermal stability and acid, alkali and salt resistance. Then, two types of microcapsules were mixed with amine cured epoxy coating system to cast film on steel piece, and subsequently a zwitterionic polymer, ploy(sulfobetaine methacrylate-co-glycidyl methacrylate)(PSG) solution was casted on the surface of the un-cured epoxy coating. Therefore, a dual-functional coating with underwater self-healing and antibiofouling functions was obtained. The self-healing anticorrosion function attributed to the dual microcapsules and the anti-protein-fouling performance provided by PSG layer had been certificated. The facile combination of underwater self-healing and anti-protein-fouling functions may provide a new protection strategy for marine and other underwater facilities.

Synthesizing Sodium Tungstate and Sodium Molybdate Microcapsules via Bacterial Mineral Excretion

We present a method, the bacterial mineral excretion (BME), for synthesizing two kinds of microcapsules, sodium tungstate and sodium molybdate, and the two metal oxides' corresponding nanoparticles—the former being as small as 22 nm and the latter 15 nm. We fed two strains of bacteria, Shewanella algae and Pandoraea sp., with various concentrations of tungstate or molybdate ions. The concentrations of tungstate and molybdate were adjusted to make microcapsules of different length-to-diameter ratios. We found that the higher the concentration the smaller the nanoparticles were. The nanoparticles came in with three length-to-diameter ratios: 10:1, 3:1 and 1:1, which were achieved by feeding the bacteria respectively with a low concentration, a medium concentration, and a high concentration. The images of the hollow microcapsules were taken via the scanning electron microsphere (SEM). Their crystal structures were verified by X-ray diffraction (XRD)—the crystal structure of molybdate microcapsules is Na2MoO4 and that of tungstate microcapsules is Na2WO4 with Na2W2O7. These syntheses all were accomplished under a near ambient condition.

Synthesizing Sodium Tungstate and Sodium Molybdate Microcapsules via Bacterial Mineral Excretion.

We present a method, the bacterial mineral excretion (BME), for synthesizing two kinds of microcapsules, sodium tungstate and sodium molybdate, and the two metal oxides' corresponding nanoparticles—the former being as small as 22 nm and the latter 15 nm. We fed two strains of bacteria, Shewanella algae and Pandoraea sp., with various concentrations of tungstate or molybdate ions. The concentrations of tungstate and molybdate were adjusted to make microcapsules of different length-to-diameter ratios. We found that the higher the concentration the smaller the nanoparticles were. The nanoparticles came in with three length-to-diameter ratios: 10:1, 3:1 and 1:1, which were achieved by feeding the bacteria respectively with a low concentration, a medium concentration, and a high concentration. The images of the hollow microcapsules were taken via the scanning electron microsphere (SEM). Their crystal structures were verified by X-ray diffraction (XRD)—the crystal structure of molybdate microcapsules is Na2MoO4 and that of tungstate microcapsules is Na2WO4 with Na2W2O7. These syntheses all were accomplished under a near ambient condition.

Preparation methods and release kinetics of Litsea cubeba essential oil microcapsules.

In this paper, using β-cyclodextrin (β-CD) as the shell material, LCEO (Litsea cubeba essential oil) microcapsules were prepared by various preparation methods, such as grinding, saturated solution, freeze-drying and spray-drying. The encapsulation yield, encapsulation efficiency, retention rate of the microcapsules and the citral content of the microcapsules were investigated. The surface morphologies of the microcapsules were observed using SEM (Scanning Electronic Microscopy); the entrapment efficiencies of the microcapsules were detected using IR (Infrared Spectrum) analysis; the citral contents of microcapsules were detected by GC (Gas Chromatography) analysis. The highest encapsulation efficiency for the microcapsules was obtained using spray-drying, followed by freeze-drying, saturated aqueous solution and grinding, while the encapsulation yield followed the opposite sequence to the encapsulation efficiency. At a specific storage temperature (15 °C) and humidity (60%), spray-drying had the most satisfactory protective effect on citral in LCEO, followed by freeze-drying and saturated aqueous solution, while the grinding method appeared to provide the worst protective effect. Avrami's model was used to simulate the release rates of the four kinds of microcapsules. The release mechanism parameters of microcapsules prepared by grinding, saturated aqueous solution, freeze-drying and spray-drying were 0.961, 1.096, 1.156 and 0.945, respectively. The release rate constants of microcapsules prepared by grinding, saturated aqueous solution, freeze-drying and spray-drying were 2.53 × 10−2, 2.22 × 10−2, 1.84 × 10−2, and 7.27 × 10−3 d−1, respectively. It was concluded that the release reactions of the microcapsules prepared by grinding or spray-drying lay between the diffusion limiting kinetics and the first-order release kinetics, and the release reactions of the microcapsules prepared by saturated aqueous solution or freeze-drying were larger than the first-order release kinetics.

Cellular uptake of poly(allylamine hydrochloride) microcapsules with different deformability and its influence on cell functions

It is important to understand the safety issue and cell interaction pattern of polyelectrolyte microcapsules with different deformability before their use in biomedical applications. In this study, SiO2, poly(sodium-p-styrenesulfonate) (PSS) doped CaCO3 and porous CaCO3 spheres, all about 4μm in diameter, were used as templates to prepare microcapsules with different inner structure and subsequent deformability. As a result, three kinds of covalently assembled poly(allylaminehydrochloride)/glutaraldehyde (PAH/GA) microcapsules with similar size but different deformability under external osmotic pressure were prepared. The impact of different microcapsules on cell viability and functions are studied using smooth muscle cells (SMCs), endothelial cells (ECs) and HepG2 cells. The results demonstrated that viabilities of SMCs, ECs and HepG2 cells were not significantly influenced by either of the three kinds of microcapsules. However, the adhesion ability of SMCs and ECs as well as the mobility of SMCs, ECs and HepG2 cells were significantly impaired after treatment with microcapsules in a deformability dependent manner, especially the microcapsules with lower deformability caused higher impairment on cell functions. The cellular uptake kinetics, uptake pathways, intracellular distribution of microcapsules are further investigated in SMCs to reveal the potential mechanism. The SMCs showed faster uptake rate and exocytosis rate of microcapsules with lower deformability (Cap@CaCO3/PSS and Cap@CaCO3), leading to higher intracellular accumulation of microcapsules with lower deformability and possibly larger retardation of cell functions. The results pointed out that the deformability of microcapsules is an important factor governing the biological performance of microcapsules, which requires careful adjustment for further biomedical applications.

Preparation and characterization of macrocapsules containing microencapsulated PCMs (phase change materials) for thermal energy storage

This paper was aimed to prepare, characterize and determine the comprehensive evaluation of promising composite macrocapsules containing microencapsulated PCMs (phase change materials) with calcium alginate gels as the matrix material. Macrocapsules containing microcapsules were fabricated by piercing-solidifying incuber method. Two kinds of microcapsules with n-tetradecane as core material, UF (urea-formaldehyde) and PMMA (poly(methyl methacrylate)) respectively as shell materials were prepared initially. For application concerns, thermal durability and mechanical property of macrocapsules were investigated by TGA (thermal gravimetric analysis) and Texture Analyser for the first time, respectively. The results showed excellent thermal stability and the compressive resistance of macrocapsules was sufficient for common application. The morphology and chemical structure of the prepared microcapsules and macrocapsules were characterized by SEM (scanning electron microscopy) and FT-IR (fourier transform infrared) spectroscopy method. Phase change behaviors and thermal durability of microcapsules and macrocapsules were investigated by DSC (differential scanning calorimetry). In order to improve latent heat of composite microcapsules, the core-shell weight ratio of tetradecane/UF shell microcapsules was chosen as 5.5:1 which obtained the phase change enthalpy of 194.1 J g−1 determined by DSC. In conclusion, these properties make it a feasible composite in applications of textile, building and cold-chain transportation.

Scent properties by natural fragrance microencapsulation for footwear applications

AbstractThe aim of this study was to develop footwear materials and footwear packaging with scent properties using microencapsulated fragrances from essential oils. For that purpose, gelatine–carboxymethylcellulose (CMC) and melamine–formaldehyde (MF) resin‐based microcapsules containing limonene were synthesised using complex coacervation and in situ polymerisation processes, respectively. The microcapsules were characterised using various experimental techniques and applied to footwear materials (leather and textile) as well as to paperboard as packaging material to evaluate their performance. The microcapsule durability under various conditions, such as rubbing and ironing, was analysed in order to simulate shoe manufacturing and shoe wearing conditions. The characterisation of the synthesised microcapsules showed two different delivery behaviours. On the one hand, MF microcapsules are more resistant so they may be incorporated into footwear materials that have to be exposed to high mechanical and thermal stresses, such as linings. On the other hand, gelatine–CMC microcapsules should be incorporated into footwear components, such as insoles, which are exposed to lower stresses because they are less resistant and might not resist the process conditions. The combination of both kinds of microcapsules could ensure a rapid as well as a long‐lasting fragrance release. © 2015 Society of Chemical Industry

Controlled release in hard to access places by poly(methyl methacrylate) microcapsules triggered by gamma irradiation

Gamma irradiation was investigated as a triggering stimulus for the activation of poly(methyl methacrylate) (PMMA) microcapsules. PMMA was exposed to varying doses of irradiation and analyzed by differential scanning calorimetry, size‐exclusion chromatography, and nuclear magnetic resonance. It was found that the glass transition temperature (Tg) of the polymer decreases at low irradiation doses. Additionally, Tg can be physically adjusted by adding a plasticizer, and both kinds of microcapsules were successfully prepared with non‐plasticized and plasticized PMMA shell. Finally, impermeable microcapsules were shown to become permeable after irradiation and release an encapsulated cross‐linker, which enables the remotely controlled formation of polydimethylsiloxanes in traditionally unavailable places. Therefore, the activation method has significant implications for industrial application. Copyright © 2015 John Wiley & Sons, Ltd.