Production of multilayer capsules containing phase change material and their use in textile materials

Abstract

This invention comprises the production of multilayer microcapsules produced by using two different active agents (n-eicosane (1) and tea tree oil (3)) and two different capsule walls (melamine-formaldehyde (2) and ethyl cellulose (4)), and their integration into textile products. The invention aims to develop textile products that have thermal storage capacity and offer antibacterial properties by means of multilayer capsule design. As a first step, the core material n-eicosane (1) is encapsulated with melamine-formaldehyde prepolymer (2) and single-layer microcapsules are obtained. As a second step, single-layer microcapsules and tea tree oil (3) are used as active agents and encapsulated with ethyl cellulose (4). Thus, multilayer microcapsules are obtained. As a third step, the obtained multilayer microcapsules are transferred to 100% cotton woven fabric. As a result, thermal regulation and antibacterial effect are imparted to the fabric in a single step.

Description

[0001] PRODUCTION OF MULTILAYER CAPSULES CONTAINING PHASE CHANGE MATERIAL AND THEIR USE IN TEXTILE MATERIALS

[0002] This invention comprises the production method of multilayer microcapsules containing phase change material (PCM), which impart thermal balancing and antibacterial properties to textile materials, and the application of these capsules to textile surfaces. The invention aims to produce textile products with dual-function capsule structures by means of an innovative microencapsulation method.

[0003] The Aim of the Invention

[0004] The aim of the invention is to provide innovative energy storage solutions with multilayer capsule design and production, and to develop textile products that can balance body temperature. By means of the use of phase change materials, thermal balancing is achieved, and thus more comfortable garments are produced. Furthermore, antibacterial properties are imparted to textile products with biologically active components such as tea tree oil. These properties are of high importance particularly for sports garments, healthcare textiles and outdoor equipment.

[0005] Technical Field

[0006] This invention addresses the following technical fields:

[0007] Textile Engineering: imparting advanced thermal and antibacterial properties to textile products.

[0008] Energy Storage Systems: providing energy efficiency by means of innovative phase change materials (PCM).

[0009] Microencapsulation Technologies: developing functional textile products with duallayer microcapsules.

[0010] Healthcare and Medical Textiles: developing garments providing antibacterial and thermal balance. Innovative materials used in textile products offer new opportunities in terms of thermal management and energy storage.

[0011] Prior Art and Problems

[0012] Prior Art

[0013] The use of phase change materials in the textile industry is an important research subject, particularly in the field of heat balancing and energy storage. However, existing studies generally focus on single-layer and single-core material encapsulations. This leads to problems such as limited functionality and low thermal stability. In addition, recent studies have shifted towards the production of multilayer capsules, thereby attempting to impart multiple properties to the capsules produced. The studies have shown that it is on a single-core material and capsule shell that is functionalised once, twice, or more. As a result of the literature review, it has been observed that there is not much research regarding multilayer phase change materials, and in addition, in the literature there has been no encounter with both multilayer and dual-core material capsule production and their application to textile goods. This situation creates a significant gap for dual-core material and multilayer capsules. Antibacterial properties are generally provided by means of surface coating techniques, however these methods lose their effectiveness over time and do not provide as long-lasting an effect as microencapsulation.

[0014] Zhou and Duan (2024) mixed tetradecanol with crystal violet lactone having thermochromic property and performed microencapsulation by means of suspension polymerisation with a silica (SiO2) capsule shell modified with a silane binding agent. While the structure and composition of these thermochromic microcapsules were analysed by means of FTIR and SEM, their heat storage capacities were evaluated by means of DSC. SEM images revealed that these microcapsules exhibited a spherical shape with a core-shell structure. Both DSC and thermogravimetric (TG) analyses showed that the microcapsules exhibited a high phase transition enthalpy (98.57 J / g). In addition, they determined that the contact angle of the microcapsules increased significantly, and that the leakage rate decreased from 6.2% to 1 .2%. They observed that with the addition of a SiO2shell layer, the thermal conductivity of the microcapsules increased by 300%. In particular, the modified microcapsules not only exhibited high latent heat storage and release capacity, but also provided excellent shape stability, thermal stability, phase transition reliability and durability. Moreover, these microcapsules exhibited thermochromic properties during phase transition and were successfully transfered to textile applications. Therefore, they found that the dualfunctional microencapsulated phase change materials examined in this study have significant potential for various thermal management applications such as energyefficient buildings, smart material coatings and thermal sensors.

[0015] Madhu and Patel (2024) microencapsulated n-eicosane with pH-sensitive poly(methacrylic acid-co-acrylamide-co-acrylonitrile) [poly(MAA-co-ACR-co-ACN)] according to the in-situ method. The presence of the -COOH functional group within poly( MAA-co-AC R-co-ACN) allows its ionisation, thereby changing its structure under different pH conditions. These microcapsules were used to coat female hygiene pads in order to exhibit pH stimulus-sensitive controlled release performance. SEM, FTIR and TGA analyses were used to confirm the chemical structure and composition. In order to evaluate the absorbency of the microcapsule-transferred hygienic pads, free swelling capacity and absorption under load were measured in tap water and saline solution. In addition, the pH level and liquid impermeability of each coated sample were examined. It was observed that the microcapsule-coated pads had an acidic pH value, and since the pH of blood is alkaline during menstruation, it was considered that they would be more suitable for maintaining the acidic pH of the vagina. Therefore, the present study proposes pH-sensitive microcapsules for coating the top layer of hygienic pads, and the comparative results relating to SEM, FTIR, TGA, absorption capacity, liquid impermeability and pH clearly support the process. As a result, it was observed that the pH-sensitive polymer poly(MAA-co-ACR-co-ACN) helps to maintain acidic pH during the menstruation period, while n-eicosane contributes to optimum temperature control.

[0016] Kazemi, Mortazavi and Shahmoradi Ghaheh (2023) for the first time used a eutectic mixture of Na2HPO4- 12H2O and Na2CO3-10H2O as an inorganic phase change material and transferred it onto cotton fabric by means of a coating technique with silicone rubber for thermoregulation. The thermo-physical effects and thermal stability of the transferred fabric were examined by means of DSC and TGA. FT-IR, FE-SEM and EDX mapping were used to analyse the microstructure of the samples, and the mechanical and physical properties of the fabric were also evaluated. The results showed that the inorganic eutectic phase change material used in the coated fabric structure increased the time to reach a certain temperature by 150%. In addition, DSC analysis showed that the coated fabric had a melting temperature of 28.9 °C and a latent heat value of 14.9 J / g. This study demonstrates that it is possible to effectively retain phase change materials in textile structures using silicone rubber, and that such transferred textiles can be used as effective smart thermal insulators without microencapsulation.

[0017] Alkan et al. (2023) in this study produced microcapsules with a poly(methyl methacrylate) (PMMA) shell and 1 -tetradecanol core by means of the Pickering emulsion technique. Characterisation tests of the microcapsules produced were carried out by means of FT-IR, particle size distribution analysis, DSC, SEM and TGA techniques. The latent heat, melting temperature and encapsulation ratio of the microcapsules were determined as 108.4 J / g, 33 °C and 46.7%, respectively. In the study, the effect of the 1 -tetradecanol@PMMA microcapsule on the physical, mechanical and thermal performance properties of cement mortars was also investigated. For this purpose, 1 -tetradecanol@PMMA microcapsules were incorporated into mortar mixtures at the rates of 5%, 7.5% and 10% of the weight of cement. As the microcapsule ratio increased, water absorption and porosity increased, while workability, unit weight of mortar, ultrasonic pulse velocity, flexural strength and compressive strength parameters decreased. The compressive strength of the mortar containing 10% microcapsules was measured as 34.74 MPa on the 28th day. The highest thermal storage capacity was found in mortars containing 10% microcapsules. When the thermal performance of the reference and the mortars containing 10% microcapsules were compared, the indoor temperature differences at the end of the heating and cooling periods were measured as 4.7 °C and 3.9 °C, respectively. The results showed that the microcapsules produced by means of the Pickering emulsion technique have the potential to increase thermal comfort in buildings, reduce fuel consumption used for heating and thus reduce carbon emissions.

[0018] Sezer Higyilmaz et al. (2022) encapsulated n-octadecane with a melamine formaldehyde shell modified with graphene as a thermal conductivity enhancer and then coated the synthesised microcapsules onto polyester fabrics. The chemical, morphological, thermal properties and phase change behaviour of the microcapsules and coated fabrics were analysed. They found that the thermal conductivity of the microcapsule-coated polyester fabrics increased by 31 % with the addition of a very small amount of graphene (0.1 %).

[0019] Du et al. (2022) aimed to produce phase change microcapsules with photothermal transformation properties. For this purpose, they mixed copper(ll)sulphide (CuS) with dodecanol tetradecyl ester according to the Pickering emulsion and encapsulated it with melamine formaldehyde. Firstly, spherical CuS particles with a diameter of approximately 10 nm were synthesised by means of a simple hydrothermal reaction. The CuS nanoparticles obtained were used not only as a stabiliser but also as a photothermal transformation material in the preparation of the microcapsules. Then, PCM microcapsules were prepared by means of a one-step interfacial polymerisation method and exhibited a core-shell structure with an average size of 7 pm. The synthesised microcapsules have a latent heat of up to 180.3 J / g and an encapsulation efficiency of 81.36%. Since the hybrid shell was filled with CuS nanoparticles, the thermal conductivity of the microcapsules increased by 115-254% compared to the core material. The photothermal transformation capacity of the synthesised microcapsules was measured and calculated up to 85.6%, which provided light- induced phase change and thus passive thermal cycling. This study constitutes potential for the application of light-induced energy storage microcapsules in fabric insulation, solar water heating systems and solar thermal power systems.

[0020] Ozkayalar and Alay (2021 ) produced fatty alcohols n-dodecanol and 1 -tetradecanol with a poly(methyl methacrylate-co-methacrylic acid) (p(MM-co-MA)) shell by means of the emulsion polymerisation method. The nanocapsules prepared were incorporated into polyacrylonitrile nanofibres by means of the coaxial electrospinning method. In this study, a two-stage (TS) emulsion polymerisation process was described and compared with the known emulsion polymerisation method defined as one-stage (OS). The nanocapsules were characterised by means of FT-IR, TEM, DSC and TGA. According to the results, particles with a typical core-shell structure, spherical shape, uniform nanoscale size, high thermal stability and energy storage capacity were successfully produced. The enthalpy values of the nanocapsules prepared by means of the TS process were higher, reaching up to 171 J / g. It was concluded that the thermal degradation stability of the nanocapsules can be improved by using the TS emulsion polymerisation method. In addition, nanocapsules were incorporated into polyacrylonitrile nanofibres by means of the coaxial electrospinning method, and composite nanofibres with an energy storage capacity of 19 J / g were produced. Although the surfaces of the prepared nanofibres with a core-shell structure were rough and coarse, the diameter distribution was observed as unimodal.

[0021] De Castro et al. (2021 ) produced polyurethane microcapsules containing n-docosane (phase change transition temperature 36-45 °C) and transferred them onto cotton fabric. Fabrics impregnated with 8% by weight of microcapsules provided a temperature buffering effect of 11 °C during heating. During the cooling stage, the impregnated fabrics exhibited a temperature increase of 6 °C for more than 100 cycles with the switching on and off of the heat source. A similar heat regulation performance was also observed for impregnated fabrics stored at room temperature for 4 years (1500 days). In the aged fabric composites, the temperature buffering effect during the heating cycle reached 14 °C and the temperature increase effect during the cooling cycle reached 9 °C. Both effects remained stable for more than 100 heating / cooling cycles in the aged fabrics. The study demonstrates the high potential use of n- docosane microcapsules for thermal management applications such as high- performance technical textiles, footwear materials and building heat-regulating coatings and paints with high commercial application potential.

[0022] Itani et al. (2017) combined phase change materials with a hygroscopic substance used as a drying agent in order to determine the design parameters affecting heat and mass transfer occurring in cooling vests, and designed a jacket that cools and dries moist and hot skin from these materials. In order to validate the developed fabric model, an experimental setup containing a vertical wet cylinder with a heated garment was used. Experiments were conducted to confirm the accuracy and applicability of the developed model. They developed a fabric model to predict the temperature and moisture content of the microclimate air layer in the presence of (i) a PCM package and (ii) a PCM-desiccant package. The developed model was validated through experiments carried out on a wet and heated cylinder for two cases using (i) a PCM package and (ii) a PCM-desiccant package. The microclimate air temperatures and moisture content as well as the PCM and desiccant temperatures were experimentally measured and compared with the predicted values. A maximum relative error of 7% in the measured temperatures yielded a good result, a reduction in the moisture content of the microclimate air was detected in the presence of the solid desiccant (dry air decreased from 21 .23 g / kg to 19.74 g / kg), and at the end of the experiment an increase in the melted fraction of the PCM was observed from 0.24 to 0.5.

[0023] Carreira et al. (2017) prepared acrylic-based microcapsules containing octadecane by means of suspension polymerisation using different initiator types and polymerisation temperatures. As thermal initiators at temperatures between 40 °C and 80 °C, benzoyl peroxide, azobisisobutyronitrile and Trigonox 23 were used. The characterisation of the microcapsules was carried out as follows: their chemical composition by infrared spectroscopy, their morphology by scanning electron microscopy (SEM), their particle size distribution by laser diffraction, and their thermal properties by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The experimental results show that the reaction parameters studied affected the monomer transformation profiles, whereas their effect on the microcapsule properties was not entirely relevant. The particle sizes of the microcapsules were found to be around 12 pm, their melting enthalpy about 175 J / g, and they were thermally stable up to 170 °C. This study confirmed that octadecane can be successfully encapsulated by means of a suspension polymerisation technique exhibiting a well-defined core / shell structure. In addition, the use of TRIG as an initiator made it possible to use a reaction temperature as low as 40 °C. It was found that acrylic shell microcapsules containing encapsulated octadecane have good potential for the production of thermo-regulating textiles.

[0024] Huang et al. (2017) in their study investigated the thermal properties of an organic cetyl alcohol phase change material (PCM) combined with high-density polyethylene. The mass ratios of the PCMs ranged from 70% to 90% by weight. Cetyl alcohol (CtA) was selected as the solid-liquid PCM and HDPE was studied as the supporting material. Composite phase change materials (CPCMs) were produced by means of the impregnation method of CtA into HDPE. The thermal conductivity of the CPCMs was increased with carbon fibre (CF). The microstructure, crystal phase and chemical structure were characterised by means of scanning electron microscopy, x-ray diffractometer and Fourier transform infrared spectroscopy (FT-IR). The results showed that CtA was well absorbed into HDPE. Differential scanning calorimetry was used to analyse the thermal properties of the CPCMs, and as a result it was shown that they melted at about 50 °C with a latent heat of about 149.02-212.42 kJ / kg. Thermogravimetric analysis showed that CPCMs had better thermal reliability and that the addition of CF contributed to a significant reduction in CtA leakage. The thermal conductivity meter determined that the thermal conductivity of CPCMs with 5% by weight CF was 0.33 W / (mK) and 0.47 W / (mK) in liquid and solid state, respectively, and it was found that these values were 1.25 and 1.22 times higher than that of the original CPCMs without CF. The experimental results demonstrate that the prepared CPCMs can be used in the field of thermal energy storage.

[0025] Itani et al. (2017) aimed to optimise the arrangement of PCM packages in cooling vests by targeting the body segments that can trigger comfort when cooled. In order to maintain body temperature and determine thermal comfort, they used a fabric integrated with PCM and a bio-heat simulation model under hot environmental conditions and during activity. The variables of the optimisation were the number of PCM packages in the upper and lower front and back body segments. A core temperature not exceeding 38 °C, a comfort level not lower than -1.4, and a melted mass fraction of the PCM of 0.85-1 were taken as constraints. For the optimisation, three environmental conditions at 28 °C, 35 °C and 45 °C were considered, and according to the results it was observed that 8, 18 and 20 PCM packages were needed to provide cooling at an acceptable comfort level for an outdoor worker. At the very high ambient temperature of 45 °C, when the number of PCM packages was increased to 32, the working time could be extended from 45 minutes to 2 hours, similar to the permissible durations at 28 °C and 35 °C.

[0026] Shaid et al. (2016) prepared aerogel / eicosane microparticles by dispersing nanoporous silica aerogel powder in eicosane. The prepared microparticles were transferred to 100% meta-aramid woven fabric by coating. For particle dispersion, melt-infiltration (M), solvent-dissolution (D) and melt-dissolution combination (MD) were investigated. Differential scanning calorimetry analysis showed that the M microparticle had a maximum heat capacity of 198 J / g, whereas the heat capacity of microparticle D and MD was found to be 139 J / g and 144 J / g, respectively. FT-IR and SEM analyses of the microparticles revealed that the eicosane leaked and coated the fine aerogel particles, but the microparticles still remained in powder form. While the nanoporous aerogel structure retained the infiltrated eicosane, the ultra-high surface area of the silica aerogel held the surrounding eicosane by surface tension. Infrared thermal imaging showed that even at 120 °C the eicosane dripped from the microparticles, whereas pure PCM completely changed its phase to liquid when heated. The developed microparticles provided ease of coating application at room temperature for thermal protective textiles. The coated fabric exhibited significantly improved thermal resistance during the phase transition period. This opens up the possibility of using the developed microparticles as a thermal protective coating additive over a wide temperature range without melting or dripping from the applied substrates.

[0027] Chia et al. (2015) designed the encapsulation of n-eicosane with a crystalline titanium dioxide (TiO2) shell as a dual-functional microencapsulated phase change material (PCM), and successfully synthesised the microcapsules by in-situ polymerisation in a sol-gel process using tetrabutyl titanate. The characterisation of the resulting microcapsule samples was carried out by Fourier transform infrared spectroscopy, energy-dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy to determine their chemical compositions and structures. Scanning and transmission electron microscopy examinations showed that all of the resulting microcapsules presented an excellent spherical shape with a particle size of 1.5-2 pm, and also exhibited a well-defined core-shell structure as well as a smooth and compact shell. The crystalline TiO2shell of the obtained microcapsules produced a photocatalytic effect. By means of its photocatalytic effect, TiO2exhibited chemical decomposition and antimicrobial activity for gram-negative bacteria. In addition, all of the n-eicosane microcapsules showed good phase change performance and high thermal reliability for latent heat storage and release, and a high thermal storage capacity was obtained. The dual-functional microcapsules synthesised in this study became potential candidates for application in waste heat recovery and processing for underwear and medical protective clothing, smart textiles or fabrics, preservation and sterilisation of food, and storage and enhancement of solar energy.

[0028] Han et al. (2015) aimed to produce, characterise and determine composite macrocapsules containing microencapsulated PCMs, with calcium alginate gels as the matrix material. The macrocapsules containing microcapsules were manufactured by means of the coagulation-solidification incubator method. Two microcapsules were prepared, containing n-tetradecane as the core material, and urea-formaldehyde (UF) and poly(methyl methacrylate) (PMMA) as shell materials, respectively. The thermal resistance and mechanical properties of the macrocapsules were investigated by means of thermogravimetric analysis (TGA) and a texture analyser (FTC TMS-Pro), respectively. The results showed excellent thermal stability, and the compressive strength of the macrocapsules was sufficient for joint application. The morphology and chemical structure of the prepared microcapsules and macrocapsules were characterised by scanning electron microscopy and Fourier transform infrared spectroscopy. The phase change behaviours and thermal resistance of the microcapsules and macrocapsules were investigated by differential scanning calorimetry (DSC). To improve the latent heat degree of the composite microcapsules, the core-shell weight ratio of tetradecane / UF shell microcapsules was chosen as 5.5:1 , and a phase change enthalpy of 194.1 J / g was obtained as determined by DSC. As a result, these properties make them an applicable composition for use in textiles, buildings and cold-chain transportation.

[0029] Hassabo et al. (2015) prepared pure inorganic silica capsules and capsules containing inorganic hydrated salts using polyalkoxysiloxane (PAOS) as a cross-linker. During this study, six different aqueous inorganic salts used as inorganic PCMs (calcium nitrate tetrahydrate (Ca(NO3)24H2O), calcium chloride hexahydrate (CaCI26H2O), sodium sulphate decahydrate (Na2SO410H2O), disodium hydrogen phosphate dodecahydrate (Na2HPO412H2O), iron nitrate nonahydrate (Fe(NO3)39H2O) and manganese (II) nitrate hexahydrate (Mn(NO3)26H2O)) were used in silica-based microcapsules. Inorganic PCMs were investigated for textile applications. The best results were obtained for sodium sulphate decahydrate and disodium hydrogen phosphate dodecahydrate. Microcapsules exhibiting good phase change property were embedded into a polypropylene film during the extrusion stage. DSC data show that the effect of the phase change material (melting of the salt) was measurable in the film as well. The capsules were also used to coat wool or cotton textiles, and DSC results showed that the effect was maintained even after the textile was washed. The produced inorganic PCMs were found to be usable for inner textile composition in the textile industry. Jiang et al. (2014) designed magnetic microcapsules based on n-eicosane as the core material and an Fe3O4 / SiO2hybrid shell as dual-functional phase change materials. Fe3O4nanoparticles were first self-assembled at the interface of n-eicosane droplets in a Pickering emulsion system, and then produced in two stages by interfacial polycondensation of tetraethyl orthosilicate (TEOS) in a silica matrix sol-gel process. Based on scanning and transmission electron microscopy examinations, the resulting magnetic microcapsules were found to present an excellent spherical morphology with a particle size of 4-6 pm, and also exhibited a well-formed and well-defined core-shell structure. The chemical structures of the magnetic microcapsules were confirmed by Fourier transform infrared spectroscopy, while their chemical compositions from surface to inner layer were determined by x-ray photoelectron spectroscopy, energy- dispersive x-ray spectroscopy and Raman scattering spectroscopy. According to the phase change performance in the DSC analysis of the magnetic microcapsules produced, good thermal storage capacity and high thermal reliability were obtained. The magnetic microcapsules exhibited superparamagnetic effect with very low magnetic remanence (strength of the magnetic field) and coercivity. Thanks to such functional properties, the magnetic microcapsules developed in this study may provide a new way to meet both thermal energy storage and magnetic activity for certain high- technology fields.

[0030] Kazemi and Mortazavi (2014) for the first time used Glauber’s salt as an inorganic PCM in a thin film on the fabric surface and developed a simple method to retain inorganic PCMs on a fabric structure without dehydration. With this method, it was not necessary to microencapsulate the PCMs. The thermophysical properties and thermal stability effects of the treated fabric were examined by means of DSC and TGA. FT-IR and XRD analysis were used to examine the chemical structure of the PCM fabric. The air permeability, water permeability and some physical properties of the treated fabric were also investigated. The results showed that the silicone rubber polymer can be applied to the textile structure to retain the PCM without microencapsulation and that the treated textile can be used as a suitable smart thermal insulator.

[0031] Tdzum and Alay (2014) in this study aimed to investigate the properties of microcapsule-applied fabrics containing PCMs with regard to heat storage and comfort. For this purpose, the heat storage property of microcapsule-applied fabrics was measured by means of a DSC device. The presence of microcapsules in the fabric structure and the distribution of the microcapsules in the fabric structure were investigated by SEM analysis. The mechanical, physical and surface properties of the fabrics related to comfort were tested with standard test methods. According to the DSC results, it was determined that the microcapsule-applied fabrics had a heat storage capacity of 6.1749 J / g. According to the strength and friction test results, there was no significant difference between the properties of the reference fabric and the microcapsule-applied fabric. The bending stiffness test results showed that the microcapsule-applied fabrics had higher bending stiffness compared to the reference fabric. When the drapability test results were examined, it was found that the drapability of the microcapsule-applied fabrics was lower than that of the reference fabrics, in relation to the increased bending stiffness.

[0032] Vigneswaran and Arulmurugan (2014) in this study aimed to reduce thermal discomfort caused by sunlight by applying phase change material (PCM) to the inner surface of helmets, whose surface temperatures can reach 50-60 °C in hot weather without airflow. For this purpose, an experiment and various components were used to simulate air radiation conditions without sunlight. These were: an industrial safety helmet for temperature measurement, a head form, a K-type thermocouple, a closed container, a bulb and a DAQ card for temperature measurement. The experimental investigations were carried out on the left side of the helmet. In a closed box, the helmet was placed in a fixed position on the head form, and three light bulbs were focused on the upper left part of the helmet to simulate sunlight. Six thermocouples were placed on the left side of the helmet, and one on the front and one on the back. The thermocouples were connected to the data acquisition card and then the output was connected to the computer. Paraffin, with a melting temperature in the range of 46-68 °C, was preferred as the PCM. The PCMs were added into the helmet in packages. Since aluminium has high thermal conductivity, thin foil was used in the package design to provide effective heat transfer. Four bags were placed under the outer layer of the helmet. The package size was designed as 9x5x0.5 cm. Each pouch was filled with only three-quarters paraffin wax and the rest was left as a gap for the expansion of the PCM. The PCM pouch could be removed separately from the assembly by immersing the pouch in water, thereby allowing the release of the stored heat. With the aid of software, the thermal properties of the helmet containing PCM and the helmet without PCM were compared. As a result of the analysis, it was clearly observed that in the helmet containing PCM the average temperature decreased to 35 °C, while in the normal helmet the average temperature inside rose above 45 °C. As a result of the integration of PCM with the helmet, it was observed that the temperature inside the helmet did not exceed the thermal comfort zone for a long time compared to a normal helmet.

[0033] Borreguero et al. (2013) aimed to increase the thermal comfort of fabrics for the footwear sector. For this purpose, in their study they mixed microcapsules containing phase change material (PCM) and carbon nanofibres into a nonwoven fabric, three foams and leather used for shoe production in order to enhance thermal comfort. The carbon nanofibres provided thermal conductivity by compensating for the insulation effect of the phase change material. Polystyrene microcapsules containing paraffin Rubitherm_RT31 were used as the phase change material. In the study, five different fabrics were used: nonwoven fabric with adhesive, polyurethane foam with adhesive, foamed nonwoven fabric with adhesive, foamed nonwoven fabric without adhesive, and pigskin. The effect of the maximum microcapsule content added to the fabrics on their weight, thickness, thermal properties and behaviour was evaluated. The foamed nonwoven fabric without adhesive and pigskin enabled the highest microcapsule content to be obtained, with values of 254 g / m2and 256 g / m2, respectively, and due to the microPCMs in their structures, their thermal energy storage capacities were found to be 20.100 J / m2and 20.200 J / m2, respectively. The maximum thickness increase was 0.6 mm, and for shoes with lengths of 25 and 27 cm the weight increase was about 9 g and 11 g, respectively, which are acceptable variations for the footwear sector. Finally, it was proven that when the foot was exposed to a heat flux of 33.3 W / m2, the phase change material kept the foot at 35 °C for 33.5 minutes.

[0034] Yoo et al. (2013) designed a four-layer garment, and applied a nanosilver coating containing nanodecane to the layers of this garment. They investigated the thermal properties of the designed garment fabric. The heating and cooling effects of this PCM were evaluated by measuring the temperature changes in the air layers of the microclimate inside the garment using a human-clothing-environment simulator (HCE). By measuring the temperature differences in the air layers in the test garments, it was found that garments made using fabrics treated with PCM exhibited higher heat control effects than garments made using fabrics without PCM. This result was attributed to the exothermic phase change of PCM upon temperature rise and the corresponding endothermic phase change upon temperature increase. In addition, it was found that as the number of PCM-treated fabrics in a garment increased, the heating and cooling effects inside the garment also increased. The PCMs underwent phase changes depending on their position in the test garment, with the innermost layer generally not exhibiting a phase change. In four-layer garments where not all layers were made using PCM-treated fabrics, the selection of the location of the PCM-treated fabric was found to be important. In particular, if only one layer of PCM-treated fabric is added to the garment, it should be positioned on the outermost layer in order to maximise the heat control properties of the garment.

[0035] Oliveira et al. (2012) in their study examined the effect of plasma treatment on the adhesion of microPCMs to wool fabrics. Prethermo C-25 microcapsules were applied by impregnation to wool fabrics with and without plasma treatment. Plasma treatment excellently increased the hydrophilicity, surface energy and adhesion of wool fabrics, which enabled more microcapsules to be absorbed onto the fabric and more microcapsules to remain on the fabric surface after washing. XPS analyses showed that the dielectric barrier discharge (DBD) treatment increased the amount of oxygen on the surface of the substrate, created more polar groups and increased the hydrophi licity / wettabi lity ratio of the wool fibres. In the untreated wool fabric, after one wash the enthalpy decreased by 25.7%, while in the plasma-treated wool the enthalpy decreased by 11.7%. After ten washes, the enthalpy of the plasma-treated fabric (- 2.92 J / g) was found to be almost the same as the enthalpy of the untreated fabric before washing (-3.08 J / g).

[0036] Salaun et al. (2010) produced melamine formaldehyde microcapsules containing an n- hexadecane / n-eicosane mixture by means of the in-situ polymerisation method and applied them to cotton fabrics in order to produce thermoregulating textile fabrics. They applied the microcapsules to fabrics by means of the impregnation method using different crosslinker / microcapsule ratios. In the study where polyurethane was used as the crosslinker, it was stated that the air permeability of the fabrics decreased due to the binding of the crosslinker and the microcapsules into the fibre pores. It was determined that the thermal resistance of the microcapsule-applied fabrics was higher than that of untreated fabrics. In the study, it was determined that the thermoregulation properties of the fabrics depended on the resin / microcapsule ratio by weight and the deposited surface weight. The deposited surface weight on the fabric consisted of the crosslinker and the microPCMs deposited on the fabric. The use of resin / microcapsule ratios of 1 :2 and 1 :4 was found to be suitable for producing thermoregulating textiles. According to the findings obtained in the study, when microPCMs were applied to cotton fabrics, this textile structure exhibited a temporary cooling effect in the transition from a cold environment to a warm environment.

[0037] Gao et al. (2008) investigated the heating effects under sub-zero environmental conditions (-4 °C) of three vests applied with PCMs (melting temperatures 32 °C, 28 °C and 24 °C) using a thermal manikin (constant temperature of 30 °C). The vests were fitted with 21 PCM-containing packages, with a salt mixture used as the PCM. Before starting the thermal manikin test, the vests were heated to 40 °C to melt the PCMs. The results showed that the heating effects lasted for about 3-4 hours. The highest heating effect occurred on the torso during the first two hours with a heat loss of 20-30 W / m2. The results showed that the vest with the highest melting / solidification temperature exhibited a greater and longer heating effect. In the three clothing scenarios, the PCM vest worn directly and closely over the stretch suit without a winter jacket exhibited the highest heating effect on the torso. It was found that a PCM with a higher phase change temperature and greater crystallisation showed better heating effect.

[0038] Choi et al. (2005) in this study aimed to investigate objectively and subjectively the feeling that phase change materials (PCMs) give in clothing. Microcapsules containing octadecane were applied to a fabric with moisture vapour permeability and water repellency together with polyurethane by means of the coating method. Afterwards, the area of the garments treated with PCMs was calculated, and the heat of fusion and the crystallisation heat of the PCM were multiplied by the calculated area to determine the total calories of the garment. Wearing tests were applied to the fabrics under both hot (30 °C) and cold (5 °C) environmental conditions. Rectal, skin and clothing microclimate temperatures, saliva and subjective evaluation measurements were made during the wearing test. It was observed that there was no difference in rectal and average skin temperatures between fabrics with and without PCM, but that in hot environments the clothing microclimate temperature of the PCM fabric was slightly lower than that of the untreated one. In cold environments, PCM-applied fabrics showed higher temperature compared to untreated fabrics. In the saliva test there was no difference between the clothes, although a change was observed between the two environments. Although there was no significant difference in subjective sensation between fabrics with and without capsules, PCM-applied fabrics were rated cooler than untreated fabrics in hot environments and warmer than untreated fabrics in cold environments. The results of this study showed that microcapsules containing octadecane in water-repellent fabric provided a cooling effect.

[0039] Shin et al. (2005) in this study applied microcapsules containing eicosane to 100% polyester fabric by means of the impregnation method. Afterwards, these fabrics were evaluated in terms of thermal properties, air permeability, moisture vapour permeability, moisture regain, low-load mechanical properties and fabric handle in relation to the addition of microcapsules. The surface morphology of the treated fabrics was investigated by scanning electron microscopy. The low-stress mechanical properties of the treated fabrics, such as tensile, shear, bending, surface and compression properties, were measured by means of the Kawabata evaluation system for fabrics (KES-FB). As a result of the analyses, it was observed that as the microcapsule content increased, the heat storage capacity of the fabrics increased. It was found that the fabric with 22.9% microcapsule absorbed 4.44 J / g of heat. While air permeability and moisture vapour permeability decreased, the moisture regain increased. With the increase of microcapsules, tensile linearity and roughness increased, while elasticity, bending and shear properties decreased. As the capsule content increased, Koshi increased, whereas Numeri and Fukurami decreased, meaning that the total handle value of the fabric decreased.

[0040] Chung et al. (2004) in this study aimed to obtain a thermally adaptable moisture vapour permeable water-repellent fabric. For this reason, microcapsules containing octadecane were applied to the fabric by means of the coating method, and after obtaining polyurethane-coated fabrics with microcapsules and polyurethane-coated fabrics without microcapsules, these samples were compared with each other. The physical properties of the fabrics were measured by water vapour transmission according to ASTM E96-80 and water resistance according to AATCC 127. Air resistance was examined using an automatic air permeability tester (KES-F8-API, Kato Tech Co., Ltd., Japan). Water repellency was measured according to ASTM D 2721 (Spray Method). In addition, wearing tests were conducted to examine the wearing comfort of the fabrics. As a result of the tests, it was seen that the thermal property relatively remained after thirty washings. It was observed that the fabric applied with PCM exhibited a lower water vapour transmission value and lower air permeability compared to the fabric without PCM. The water resistance of both fabrics was 100%, but the water resistance of the PCM was significantly reduced. In the wearing tests, it was observed that the average skin temperature and microclimate temperature of individuals using the fabric with PCM were lower than those using the fabric without PCM. However, the microclimate humidity with PCM was observed to be higher than the other. When the fabrics were evaluated subjectively, although there was no significant difference between the fabrics, the PCM fabric was found to be cooler and more comfortable. The results of this study showed that microcapsules containing octadecane in water-repellent fabrics provided a cooling effect but sacrificed water resistance.

[0041] Zhao et al. (2024) synthesised a double-shell phase change microcapsule by means of a two-step method to enhance the conversion and storage of solar energy. The double shell was formed by using polyurethane (Pll) and polydopamine / silver (PDA / Ag), while n-octadecane and paraffin were used as core materials. For the inner shell of the microcapsules interfacial polymerisation was used, and for the outer shell self-polymerisation was applied. The produced microcapsules were transferred onto cotton fabric by means of the dip-coating method, and the antibacterial properties of the fabrics were examined. The synthesised microcapsules exhibited a unique doubleshell structure, a consistent spherical shape and a latent heat storage capacity exceeding 150 J / g. The coating exhibited high photothermal conversion performance due to the synergistic photothermal conversion effect of PDA and Ag in the first shell. The stepwise energy transfer inside the microcapsules was achieved by integrating polyethylene glycol into the polyurethane layer and using two different phase change materials as the core material. The antimicrobial activity of the microcapsule-coated fabrics against S. aureus and E. coli was determined as 99.99% and 99.56%, respectively. Han et al. (2024) produced single-layer microcapsules with a polyurea shell containing n-hexane as the core material by means of interfacial polymerisation. Then, in order to improve the expansion performance of the microcapsules, they prepared a second layer with styrene-maleic anhydride copolymer (SMA) by means of the co-precipitation method. They confirmed by thermal analysis device (TG-IR) that n-hexane was successfully encapsulated with polyurea. The properties of the thermally expandable microcapsules (TEMs) were investigated by means of thermogravimetric analysis (TGA), laser particle size analysis, optical microscope and thermomechanical analysis (TMA). The results revealed that polyurea exhibited a good encapsulation effect on n- hexane. When the amount of n-hexane was 60%, the encapsulation efficiency of the polyurea shell microcapsules was found to be 96.7%. However, they observed that the thermal expansion performance of the microcapsules was low. With the use of the SMA copolymer as a second layer, it was observed that although the amount of n- hexane in the microcapsules decreased, the thermal expansion performance improved significantly. The microcapsules were found to have a particle size of about 2.5 pm and an encapsulation efficiency of 41.1 % for n-hexane. The microcapsules were determined to have initial and peak expansion temperatures of 195 °C and 216 °C and to exhibit an expansion ratio of 2.4 times.

[0042] Zhao et al. (2023) encapsulated Perilla frutescens L. essential oil (PLEO) as singlelayer by means of the spray-drying method using octenyl succinic anhydride starch (OSAs) as the wall material, and then formed a second layer by means of the polyelectrolyte complex coacervation method with sodium alginate and chitosan. They observed that the best results were given by double-layer microcapsules created by using 2% sodium alginate and 1.5% chitosan on 4% OSAs-PLEO single-layer microcapsules. They found that these microcapsules had an encapsulation efficiency of 61 .29% and a loading degree of 41 .11 %. As a result of morphological analyses, it was determined that the double-layer microcapsules containing PLEO were millimetrescale spherical particles. FTIR analysis confirmed the physical settlement of octenyl succinic anhydride starch on PLEO and the formation of complex coacervates between sodium alginate and chitosan. TG and DSC analyses showed that chitosan / alginate / octenyl succinic anhydride starch complex coacervates as wall materials significantly improved the thermal stability of PLEO. In addition, it was determined that PLEO microcapsules had better stability in aqueous and acidic food formulations and were effective in complete and long-term release of PLEO. They stated that the best approach for the PLEO release profile was the Peppas-Sahlin model, and that the release phenomenon was mainly governed by Fickian diffusion.

[0043] Yu et al. (2023) formed a double-shell ammonium polyphosphate microcapsule (MAPP) by using ethyl cellulose and nano-SiO2as wall material and ammonium polyphosphate (APP) as core material by means of the in-situ precipitation method. The produced microcapsules were transferred onto kraft paper. They determined that the microcapsules exhibited improved flame retardancy and fire safety compared to ammonium polyphosphate alone, showing significant reductions in peak heat release rate and total heat release determined by thermogravimetric analysis (TGA), microcalorimetry (MCC) and vertical burning tests (VBT). Physical and hygroscopicity tests revealed that the microcapsules showed superior compatibility with substrates, and that microencapsulation of ammonium polyphosphate effectively solved the problems of compatibility and hygroscopicity while increasing flame retardant efficiency, thereby significantly advancing their applications in flame retardant materials. In addition, real-time Fourier transform infrared (RT-FTIR), scanning electron microscopy (SEM) and Raman spectrum analyses revealed that the modified kraft paper exhibited a crosslinked network structure formed by silica-based substrate and cellulose during combustion, and that this structure facilitated the formation of a carbon layer and ensured continuous flame retardancy. Compared to uncoated paper, the limiting oxygen index (LOI) value of kraft paper containing 25% MAPP increased from 19% to 33%, and the char yield at 700 °C of kraft paper containing MAPP increased from 26.23% to 29.97%. In addition, it was found that the peak heat release rate (pHRR) of kraft paper containing MAPP decreased from 328.2 W / g to 69.6 W / g, and the total heat release (THR) decreased from 19.4 kJ / g to 8.4 kJ / g, which effectively reduced the fire risk in kraft paper.

[0044] Zhao et al. (2023) designed a double-shell lignin microcapsule. The antibacterial and ultraviolet protective coating was prepared by mixing with water-based resin. The outermost layer of the microcapsules was a lignin-based polyurea shell used for UV protection. The inner layer was formed by copolymerisation of styrene and the temperature-responsive monomer N-isopropylacrylamide, which controlled the release of lemon oil by means of temperature response. The obtained microcapsules exhibited good temperature-controlled active substance release and UV resistance due to the double-shell structure. The produced microcapsules were transferred onto cotton fabric by means of the coating method. The UPF value of the coatings reached up to 154. When the antibacterial properties of the fabric coated with double-shell microcapsules were examined, the antibacterial rates against S. aureus and E. coli were found to be 98.07% and 87.26%, respectively. In addition, at the end of 7 days it was determined that more than 30% of the lemon oil remained on the surface of the microcapsule-transferred fabric, which revealed the long-term slow-release property and antibacterial effect of the double-shell microcapsules.

[0045] Chen et al. (2023) presented an innovative and effective approach for the encapsulation of shear thickening fluid (STF, non-Newtonian fluid) in polyurethanepolyurea double-layer microcapsules. Firstly, under Span80 emulsification, STF was well dispersed in liquid paraffin and droplets of about 100 pm diameter were formed. Since liquid paraffin regulated the density and polarity of the solution during the emulsification process, ensuring that the STF was well dispersed and suspended, it played an important role in the solution. Afterwards, the suspended droplets were coated with polyurethane / polyurea (Pll / PUA) shell by means of interfacial polymerisation. The polyurethane shell layer primarily served as a mould on the STF droplets, while the polyurea shell layer provided a more robust protection. With dibutyltin dilaurate used as catalyst, carbodiimide-modified 4,4'-diphenylmethane diisocyanate (CD-MDI) reacted with polyethylene glycol to form the polyurethane inner shell, and reacted with diethylenetriamine to form the polyurea outer shell. It was observed that the microcapsule walls provided an excellent coating effect and mechanical support to maximise the preservation of the rheological properties of the STF and effectively enhance the high-speed impact resistance of polymer materials. The hardness and impact resistance of the composites were analysed by a universal testing machine and drop hammer impact test. With the drop hammer test, the impact resistance of the polyurea composite was further improved by the addition of microcapsules. The double-layer shell material provided a good coating effect on the STF, supported force and stress transmission and improved the compatibility between the STF and the polyurea matrix. As the amount of microcapsule addition increased, the impact resistance and elongation at break of the composites increased, while the tensile strength decreased. STF-loaded microcapsules improved the impact resistance of the composite materials. Soft microcapsules increased the movement of chain segments in the composite at low content, while large amounts of microcapsules formed aggregates, thus affecting the movement of the segments. As a result, compared to pure polyurea material, at an addition amount of 2% the elongation at break increased by 22.70%, and at an addition amount of 1 % the impact resistance was the highest, 76.81 N higher than the pure sample. The encapsulation technique used for the production of STF microcapsules with high impact resistance and energy absorption capacity offers a new approach to design and produce multifunctional impact-resistant materials.

[0046] Liu et al. (2022) designed and developed a type of photoluminescent phase change microcapsule system. In this study, they encapsulated n-eicosane with a CaCO3 / Fe3O4composite shell doped with europium nitrate hexahydrate [Eu(NO3)36H2O, 99.9%] (Eu3+) by means of the Pickering emulsion method. For the encapsulation process, first they encapsulated n-eicosane with a CaCO3 / Fe3O4composite shell by in-situ precipitation, and then produced it by doping Eu3+onto the surface of the CaCO3 / Fe3O4composite shell. They observed that the microcapsules had a well-defined core-shell microstructure and a regular spherical morphology with rough surface due to the presence of Eu3+. The addition of Fe3O4nanoparticles as a light absorber to the CaCO3shell increased the solar photothermal energy utilisation efficiency of the microcapsules. The produced microcapsules not only exhibited satisfactory thermal regulation ability with a latent heat capacity above 125 J / g, but also achieved a high photothermal conversion efficiency of 67.6%. Eu3+doping imparted photoluminescent function to the microcapsules with fluorescence emission at an excitation wavelength of 394 nm.

[0047] Watanabe, Yasuhara and Ono (2022) prepared multilayer poly(ionic liquid) (PIL) microcapsules by means of sequential liquid-liquid phase separation within triple emulsion droplets and subsequent photopolymerisation of ionic liquid (IL) phases using a simple microfluidic process. They formed multilayer emulsion droplets consisting of IL-rich and water-rich phases. The number of droplet layers was controlled from one to five by changing the initial composition of the dispersed phase. The IL-rich phases in the multilayer emulsion droplets were easily solidified by photopolymerisation, and PIL microcapsules with multilayer structures were obtained. Anion exchange of the obtained PIL microcapsules transformed them from a hydrophobic structure into a hydrophilic structure, and by means of this hydrophilic structure the swelling properties and layer permeability of the microcapsules in various solvents were obtained.

[0048] Hu et al. (2022) investigated the performance properties of W1 / O / W2 emulsions containing gel polymers in W1 and their effect on microcapsules. In this study, they produced W1 / O / W2 emulsions loaded with vitamin C (VitC) with cationic polymer chitosan and nonionic polymer hydroxypropyl methylcellulose (HPMC) as gelling agents in W1, and their spray-dried microcapsules. The sample containing low- viscosity chitosan was observed to have the highest encapsulation efficiency (91 .9%) and high encapsulation stability (80.8%). In contrast, the two formulations containing HPMC were found to have a negative effect on these critical parameters. As a result of the studies, it was shown that VitC was effectively retained in W1 by electrostatic conjugation with chitosan and increased viscosity. It was found that the gel polymer was the dominant mechanism preventing the leakage of VitC from W1 to W2, while the increased viscosity of W1 positively influenced this process. In addition, it was observed that the addition of chitosan effectively strengthened the structure of multilayer emulsions during spray-drying and rehydration processes, while the addition of HPMC adversely affected these properties. This study demonstrated that selecting suitable gel polymers for W1 is an effective strategy to improve the encapsulation performance of W1 / O / W2 emulsions and the commercial production of the related dried microcapsules.

[0049] Copado et al. (2021 ) studied multilayer microencapsulation to protect chia oil, which offers high nutritional value but is highly susceptible to lipid oxidation. The first emulsion was prepared by means of high-pressure homogenisation using hydrolysed sunflower lecithins (pH 5). The secondary and tertiary layers were formed by means of the layer- by-layer technique by adding chitosan and chia mucilage, respectively. These emulsions were subjected to spray drying, and the effects of lecithin types and microcapsule types (single or multilayer) on the obtained microcapsules were examined. The accumulation of layers was determined by zeta potential analysis. The microcapsules were characterised by high microencapsulation efficiency (84-99%), low moisture content and water activity levels. Most microparticles were whitish and light-coloured, spherical in shape, and had continuous, slightly rough walls. In particular, three-layer microcapsules exhibited low oxidation levels after storage. The results suggest that multilayer systems can provide high stability against oxidative degradation of functional lipid components in chia oil.

[0050] Shilova et al. (2021 ) formed multilayer microcapsules of acetylsalicylic acid by means of layer-by-layer adsorption of the natural polysaccharides chitosan and sodium carboxymethyl cellulose onto calcium carbonate microparticles. Three different encapsulation methods were evaluated: physical adsorption of acetylsalicylic acid into the pores of calcium carbonate microparticles, co-precipitation of an acid with an inorganic material during preparation, and incorporation of an acid into hollow capsules together with changing the permeability of their shells. Shell permeability was realised by changing the polarity of the solvent by adding ethanol at a volume ratio of 50% to an aqueous solution. This method provided the highest efficiency in encapsulating the acid and prevented the release of acetylsalicylic acid from the capsules in acidic environments. The encapsulation efficiency of acetylsalicylic acid was found to be 6% by means of the physical adsorption method into the pores of calcium carbonate particles, 21 % by means of the co-precipitation method with an inorganic material during preparation, and the highest encapsulation efficiency of 85% was obtained by incorporating the acid into hollow capsules and changing the permeability of the polyelectrolyte shells. The optimal time for encapsulation of acetylsalicylic acid into hollow capsules was determined as 30-60 minutes. Although the drug release character depended on the pH of the solution, it was observed that 7% of the acid was released within 120 minutes in acidic environments, whereas 84% or more of the acid was released in alkaline environments.

[0051] Li et al. (2021 ) produced microcapsules with multiple functions such as thermal energy storage, photothermal tranformation, ultraviolet (UV) protection and superhydrophobicity for use in smart textiles. In the microcapsules they produced, n- eicosane was used as the core material and CuO-doped polyurea as the wall material. As a result of thermal analysis, it was revealed that these microcapsules had a high latent heat of 162.3 J / g and exhibited excellent thermal reliability. The microcapsules showed effective photothermal tranformation capabilities and reduced UV radiation by about 30%. In addition, these microcapsules exhibited superhydrophobic properties with a water contact angle exceeding 148°. When applied to cotton fabric, the coated microcapsules exhibited a high phase change enthalpy of 36.8 J / g, effective heat regulation ability and a significant contact angle of 141.6°. This showed that the microcapsule-coated fabric can maintain thermal comfort and effectively repel water while providing protection against UV radiation.

[0052] Skurkyte-Papieviene et al. (2021 ) attempted to improve the thermal performance of paraffin microcapsules for textile applications by modifying the outer shell. For this purpose, paraffin microcapsules (MPCM32D) with a transition temperature of 32.02 °C were encapsulated by the Layer by Layer technique to form multilayer thin coatings between the cationic melamine formaldehyde resin shell and the anionic thermally conductive additives [multi-walled carbon nanotubes (MWCNT’s) or poly (3,4- ethylenedioxythiophene) poly (styrene sulfonate) (PEDOT:PSS)] applied through electrostatic interaction. As additives, MWCNT’s and PEDOT:PSS at different weight ratios (1 %, 5%, and 10%) were used. The main aim of this modification was to improve the thermal performance of microencapsulated phase change materials designed for textile applications. The morphological analysis of the new coating of MWCNT’s or PEDOT:PSS on the microcapsule shell was observed using SEM. The heat storage and release capacity of the microcapsules after shell modification was evaluated, and the thermal conductivity coefficient (A) was measured by the comparative method. Based on the optimal parameters of thermal performance determined for the tested microcapsules, 5% MWCNT’s or 5% PEDOT:PSS shell-modified microcapsules together with an acrylic resin binder were applied to a 3D spacer fabric produced from polyester. An infrared heating source and an infrared camera were used to evaluate the dynamic thermal behaviour of the fabric samples with transferred microcapsules. The fabric containing 5% MWCNT’s or 5% PEDOT:PSS showed much faster heating and significantly slower cooling compared to the fabric with unmodified microcapsules transferred. The thermal conductivity of the fabric samples containing modified microcapsules gave better results compared to the fabric samples with unmodified microcapsules transferred.

[0053] Zhao et al. (2020) studied the design of a stimulus-responsive fabric containing polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) sodium salt (PSS) formed by the layer by layer (LBL) method with the aim of using the produced hollow microcapsules as carriers for loading and releasing chemicals under different pH conditions. The use of PAH and PSS ensured that the microcapsule structure was robust and pH-sensitive. SEM and TEM studies showed that the composite microcapsule (PAHZPSS)nPAH had a spherical morphology and a hollow structure, and FTIR demonstrated the presence of PAH and PSS, confirming the composition of the microcapsule shell. As a result of DSC, it was seen that the microcapsules were thermally stable. The microcapsules were found to be 4-6 pm in size. As a result of release studies carried out with Rhodamine-B, it was seen that the release rate from (PAHZPSS)nPAH microcapsules at pH 5.8 was higher than at pH 7.4. This result confirmed the pH sensitivity of the microcapsules. In addition, during the coating process, a compound with positively charged ethylene oxide groups was used to bind the microcapsules more efficiently to cotton fabric. Because of the easy combination of LBL microcapsules with fabrics, this study presents an applicable approach for the preparation of functional stimulus-responsive textiles.

[0054] Hou et al. (2020) studied a new microcapsule with a single-core double-shell structure that regulates temperature and humidity bidirectionally. In this study, they created a single-core and double-shell microcapsule through electrostatic assembly followed by chemical deposition and achieved both temperature-humidity regulation and low leakage. They produced multifunctional microcapsules with paraffin as the core for temperature regulation, chitosan-graphene oxide (GO)-chitosan as the inner shell as a barrier for low leakage, and hydrophilic porous SiO2 as the outer shell for humidity regulation. FT-IR and XRD measurements confirmed that the shell materials were successfully formed on the paraffin core by electrostatic assembly followed by chemical deposition. SEM, TEM, and optical microscope photographs showed that the microcapsules were spherical with layered shells, approximately 2-5 pm in diameter. The SiO2 shell consisted of nanosized particles and formed a loose and porous microstructure supported by the results of N2 adsorption-desorption isotherms. In addition, the synergistic effect of hydrophilic and porous loose (chitosanZGOZchitosan)- SiO2 double shells gave the microcapsules humidity regulation ability. The produced microcapsules exhibited temperature regulation behaviour due to the phase change performance of paraffin and showed good thermal durability after 10 thermal cycles. Furthermore, they showed stable humidity regulation performance after repeated adsorptionZdesorption. Temperature and humidity regulation simulation experiments showed that the microcapsules could keep temperature and humidity in a stable range. According to the obtained results, it was seen that the microcapsules had extraordinary temperature and humidity regulation properties and had potential applications in the field of energy saving.

[0055] Zhang et al. (2020) produced double-layer microcapsules containing (3-cyclodextrin in the inner layer and chitosan and sodium alginate in the outer layer in order to enhance the long-term effectiveness of lavender essential oil. The morphology, particle size, encapsulation efficiency, thermal stability, and controlled release effect of the doublelayer microcapsules were characterised. The microcapsules were spherical between 2-6 pm and showed thermal stability up to 250 °C. It was seen that the encapsulation efficiency was 80% and that the essential oil could continuously release the active components for a long time under normal temperature and high temperature conditions. In order to further examine the application effect of the double-layer microcapsule, it was transferred to cotton fabric by the impregnation method, and the cotton fabric showed excellent washing durability and friction resistance.

[0056] Ruiz-Calleja et al. (2020) transferred microcapsules containing phase change material and graphene onto cellulosic fabric containing 50% cotton and 50% flax fibre by coating. As a result of their analyses, they examined the synergy produced by using both materials in the same coating paste and proved that using graphene and PCM simultaneously provided more heat energy release than when used separately.

[0057] Alam, Seo and Lapitsky (2020) investigated the sustained antibacterial effect of pastelike complex coacervates formed by the combination of poly(allylamine hydrochloride) (PAH) and pentavalent tripolyphosphate (TPP) ions through the slow release of bactericides. They used triclosan (TC) as a bactericide and demonstrated that hydrophobic biocides could be dispersed in the main PAH solution together with anionic surfactants and encapsulated within PAH / TPP coacervates. They stated that the encapsulated bactericide could release for several months and that the release rate could be adjusted by changing the bactericide and surfactant compositions used during encapsulation. They determined that this release mechanism provided continuous bactericidal activity against both Gram-positive and Gram-negative bacteria, especially Staphylococcus aureus and Escherichia coli, for at least two weeks under nutrient-rich conditions. After this period, they saw that the activity continued, albeit at a reduced level, for up to one month, but the release rate slowed down and the capsules gradually lost their effectiveness.

[0058] Zhang et al. (2016) synthesized multifunctional microcapsules containing a silver / silica double-layered shell and n-eicosane as the active substance by interfacial polymerization. The obtained microcapsules exhibited a spherical shape with a uniform core-shell structure and a silver outer layer. With the characterization of chemical composition and crystal structure, it was observed that the microcapsules had an excellent silver outer layer when the reaction time for the reduction and deposition of silver ions was set to 20 hours. As a result of differential scanning calorimetry analysis, it was found that the microcapsules contained approximately 67% by weight n- eicosane under the encapsulation of 33% by weight shell materials. The microcapsules also provided high latent heat storage and showed good thermal regulation capability. It was found that the microcapsules had a high electrical conductivity of 130 Q. These microcapsules were found to have high antibacterial activity, especially against Staphylococcus aureus and Bacillus subtilis, and to exhibit good antimicrobial activity with a sterilization rate of over 95% within 4 hours of contact. This study shows that the microcapsules designed with multifunctional properties have potential in the fields of microelectronics and biomedicine.

[0059] Sun et al. (2015) synthesized double-layered polyurea microcapsules containing hexamethylene diisocyanate (HDI) by interfacial polymerization in an oil-in-water emulsion. The characterization of the obtained capsules was performed with SEM, TGA, and FT-IR spectroscopy. Reaction parameters including reaction temperature (40 °C, 50 °C, 60 °C), reaction time (1 , 1 .5, 2, and 2.5 hours), the amounts of Suprasec 2644 (2.4, 3, and 3.6 g), and emulsification time (15, 45, and 75 minutes) were examined and the core fraction was evaluated. The core part of the microcapsules decreased with the increase of reaction temperature, reaction time, Suprasec 2644 mass, and emulsification time, while irregularities occurred in the quality of the microcapsules. Their thermal and organic solvent resistance was evaluated using TGA and titration. The results showed that the microcapsules had a 1.6% weight loss compared to pure HDI with a 90% weight loss after isothermal treatment at 100 °C for 60 minutes. After immersion in various solvents for 24 days, it was observed that the release from the microcapsules was as low as 3% of the core in weak polar solvents (hexane and xylene), about 5-60% in polar aprotic solvents (ethyl acetate, acetone, DMF, and DMSO), and 60-90% in water and polar protic solvents (isopropanol and ethylene glycol). Both HDI capsules treated with hexane and those untreated exhibited excellent anticorrosion performance with a self-healing function in scratch coatings, indicating promising practical applications in industrial coating and paint systems.

[0060] Su et al. (2005) used melamine formaldehyde (MF) resin as the shell material and produced double-layered microcapsules for heat energy storage and investigated the properties of these microcapsules. As the active substance, a phase change material with a melting point of 24 °C and a phase transition heat of 225.5 J / g was used. The mass ratio of core to shell was used as 3:1 to ensure that the microcapsules had a good heat storage function. The surface morphological structure was examined by scanning electron microscopy, and the strength of the shell was evaluated by observing the surface change after pressure using scanning electron microscopy. It was found that the average diameter of the microcapsules was 5 pm to 10 pm, but diameters of 1 pm to 5 pm could also be obtained by using different stirring speeds. The capsule thickness was determined to be in the range of 0.5 pm to 1 pm. In addition, it was found that the melting point of the microcapsules was equal to that of the pure phase change material (24.7 °C). According to DSC results, it was clearly observed that the polymer shell of the microcapsules did not affect the properties of the phase change material. Furthermore, it was determined that the penetration resistance properties of double-layered microcapsules were better than those of single-layered microcapsules, and that the microcapsules with a diameter of 5 pm were better than those with a diameter of 1 pm. With the increase of the ratio of core material, the compressibility decreased and the shell thickness decreased. Analyses showed that the microcapsules did not crack under a pressure of 1 .96x105Pa.

[0061] Li et al. (2008) in this study developed a new method to prepare double-layered microcapsules. Polyurea (Pll) microcapsules were first produced by interfacial polymerization as the inner layer, and then the outer layer was produced by in-situ polymerization with urea-formaldehyde (UF) resin. SEM, optical image analyzer, FT- IR, and TGA were used to investigate morphology, particle size, material structures, and thermal properties. As a result of the studies, it was seen that the prepared microcapsules had (i) easy usability as powder-like materials; (ii) an ultra-thick capsule wall providing good protection for the core substances; (iii) double-layered structural properties with higher thermal stability than single-layered microcapsules.

[0062] Caruso et al. (2010) prepared double-layered polyurethane / poly(urea-formaldehyde) microcapsules (PU / UF) for use in self-healing materials. For the encapsulation process, they combined the in-situ polymerization method with the interfacial polymerization method, thus aiming to form a stronger capsule shell in a single process with this modified encapsulation procedure. The morphology of the obtained microcapsules was examined with SEM and atomic force microscopy (AFM), and TGA analysis was carried out for their thermal properties. As a result of the analyses, it was observed that the shell wall thickness of the capsules produced with the modified procedure increased from 200 nm to 675 nm as a function of the amount of Pll added to the core substance compared to a standard UF microcapsule. The thermal stability of PU / UF microcapsules prepared with variable amounts of PU was compared with UF microcapsules, and it was seen that PU / UF microcapsules had better stability.

[0063] Chong et al. (2018) successfully synthesized clove oil-containing double-layered polyurethane / poly(urea-formaldehyde) (PU / PUF) shell microcapsules with antibacterial properties through in-situ and interfacial polymerization reactions. The morphology, core-shell structure, and composition of the obtained microcapsules were examined. In addition, the release behaviors of the microcapsules synthesized under different reaction parameters were examined. As a result of the studies, it was found that the release rate of clove oil could be controlled by adjusting the amount of PU reactants and the length of PUF deposition time. In addition, it was seen that the release profile fully conformed to the Baker-Lonsdale model, which indicates diffusion as the primary release mechanism. Experimental results based on ASTM E2315 showed that the produced microcapsules had great antibacterial activities against marine bacteria Vibrio coralliilyticus, Escherichia coli, Exiguobacterium aestuarii, and biofilm-forming bacteria isolated from field-contaminated samples.

[0064] Arslan and Erba§ (2017) encapsulated the probiotics Saccharomyces boulardii, Lactobacillus acidophilus, and Bifidobacterium bifidum in this study with spray drying and spray cooling techniques as single and double-layered. For this purpose, in the spray drying experiment, 10% gum arabic and [3-cyclodextrin (9:1 ) were used as the wall material, and in the spray cooling experiment, hydrogenated palm oil was used. According to the results obtained, the numbers of S. boulardii, L acidophilus, and B. bifidum were found to be high in the single-layered microcapsules produced by spray cooling (P), as 8.21 , 8.10, and 8.25 log cfu / g, respectively. Double-layered microencapsulation increased the heat and gastric resistance of L acidophilus, while the spray-dried microcapsules showed a more protective effect in the simulated intestinal system and heat tolerance test. The microencapsulation of t. acidophilus and B. bifidum increased the survival ability of these probiotics under simulated stomach and intestinal conditions. In addition, while microencapsulated probiotic microorganisms could survive even at 80 °C, it was determined that free probiotic microorganisms could withstand only 50 °C for 30 minutes.

[0065] Tian et al. (2012), in this study, used diaminodiphenyl sulfone (DDS) as a curing agent adsorbed from the surrounding of single-layer microcapsules with melamine formaldehyde (MF) walls containing Ag-80 as a healing agent. Double-layer microcapsules were prepared according to in-situ polymerization of the MF capsule wall of single-layer microcapsules modified with DDS. With these double-layer microcapsules, it was aimed to release the healing agent and the curing agent simultaneously upon the rupture of the matrix surrounding the capsule, to increase the contact rate between the two agents, and thereby to increase the healing efficiency. The morphologies of the microcapsules were investigated by SEM, the presence and stability of the healing and curing agents before the rupture of the capsule were investigated by FTIR, and the mechanical properties of the double-layer microcapsules were investigated by nanoindentation. As a result of the studies carried out, it was observed that DDS adsorption played an important role in the formation and final morphology of the double-layer microcapsules. When a dispersant consisting of 30% Tween 80 and 70% Span 80 was used, the dispersed DDS particles were found to be homogeneous. When the pH value was between 3.5 and 4.5, since the dispersed DDS and MF / Ag-80 microcapsules had opposite surface charges, they tended to aggregate due to electrostatic interactions. The results showed that the microcapsules broke earlier than the matrix to repair a crack and that the mechanical properties of the cured microcapsules were the same as those of the resin matrix.

[0066] Butstraen et al. (2016), used microencapsulated flame retardant to produce flameretardant nonwoven fabric. Melamine-formaldehyde microcapsules containing Afflamit® PLF 280 (resorcinol bis (diphenyl phosphate)) as core material were coated with an external thermoplastic wall (polystyrene (PS) or polymethylmethacrylate). The prepared microcapsules were transferred according to the impregnation method to a core-shell type double-component PET / co-PET spunbond nonwoven fabric. The microcapsules were heated to the softening temperature of the thermoplastic outer shell to adhere to textile fibers. The thermal stability of the microcapsules was examined using thermogravimetric analysis. Textile samples were observed with a scanning electron microscope and the flame-retardant performance was evaluated using the NF P92-504 standard. The experimental results show that the composition of the external polymeric shell affected the thermal stability of the microcapsules, with PS-shelled particles being more stable. In addition, it was observed that the microcapsules settled more in the nonwoven fabric without affecting the thickness of the samples. According to the results of the NF P92-504 test, only the formulation with low PS content was classified as M2, while the others were classified as M3, and it was found that the flame spread rate was low for all the tested samples.

[0067] Chatterjee et al. (2014) combined the emulsification and phase coacervation method based on ionic interactions and studied the development of multilayer microcapsules with 11 alternating additions of chitosan (Chi) and sodium dodecyl sulfate (SDS). After alkaline treatment, they applied the microcapsules onto polyester (PET) fabric to investigate the washing durability on the fabric. Atmospheric air plasma treatment was performed on PET fabric to change the surface properties of the textile material. To characterize and determine the washing durability of the microcapsules on PET, zeta potential, X-ray photoelectron spectroscopy (XPS), wettability measurements, SEM, and AFM analyses were conducted. According to the results obtained from various characterization techniques, it is shown that the microcapsules can be directly bound to PET fabric through ionic interactions and that chitosan-based microcapsules are resistant to washing on PET fabric activated with atmospheric air plasma.

[0068] Salaun et al. (2009) developed uncoloured microparticles containing red acid dye to obtain bright red colour after heat transfer. Polyethylene (PE) and polystyrene (PS) were used as the outer wall material. The process was divided into two successive steps. Firstly, emulsification of the dye solution in carnauba wax solutions, and secondly, encapsulation of these particles according to a combined hot-melt dispersion-coacervation method was planned. The results obtained from this study clearly show that the use of a gelatin solution as a protective colloid in combination with cyclohexane as solvent gave good results and provided a reduction of dye diffusion during the first stage of the microencapsulation process. The obtained microparticles were in the size of 1 -5 pm. The morphology of these particles was strongly influenced by the polymers used to coat the particles in the second stage. Thus, while the use of PE led to a spherical, smooth surface, the use of PS was found to cause a rough surface with raspberry-like morphology. Although the amount of acid dye encapsulated in carnauba microspheres varied depending on the applied process, for the PE shell, the result decreased from 37% to 15%, while for the PS shell, it was found to be in the range of 32.9% to 38.5%. However, after the release of heat, the perception of colour provided a lighter difference. Therefore, it was determined that encapsulation with a PE outer shell ensured better encapsulation of dye microspheres instead of using PS. The results showed that the acid dye content and morphologies depend on the composition, the protective colloid, and also the outer polymeric shell and the way the solvent dissolves.

[0069] Chirila et al. (2024) focused on the development of various polymeric systems based on collagen-polyvinyl alcohol-active components in order to obtain biomaterials with potential use in the treatment of burn wounds. Hydrogels were prepared under proper homogenisation with polymeric matrix formers (collagen and polyvinyl alcohol), water and glycerol, accompanied by the nonionic surfactant polysorbate 80 (Tween 80®). In order to develop multifunctional textile materials designed for topical application, ciprofloxacin, chlorhexidine, tea tree essential oil and curcumin were used as active components. The obtained hydrogels were immobilised on 100% plain woven cotton by the padding method. Functional textile materials were characterised in terms of physicomechanical and comfort properties, hydrophilicity and antibacterial activity. The mass of functional textile materials increased compared to untreated fabric due to the remaining polymeric systems after the functionalisation process. The water vapour permeability and air permeability of the functional materials were lower than those of untreated samples. Antibacterial activity was observed in all analysed samples, and inhibition zones ranging from 14 mm for S. aureus to 27 mm for E. coli were obtained for textile materials treated with hydrogels. Textile materials treated with hydrogels containing ciprofloxacin showed the most significant antibacterial effect compared to similar samples containing chlorhexidine. The experimental data obtained showed that these hydrogels are suitable candidates for application in bum wound management.

[0070] Yang et al. (2024) used gelatin, gum arabic, and n-butyl cyanoacrylate as wall materials in this study and produced microcapsules containing tea tree essential oil (TTO) by combining composite coagulation and in-situ polymerisation methods. They found the encapsulation efficiency to be 73.61 % when the ratio of gelatin to gum arabic was 1 : 1 , the ratio of TTO to n-butyl cyanoacrylate was 4: 1 , and the curing time was 10 hours. The microcapsules were observed to have an average size of 10.51 pm and a spherical structure. Fourier transform infrared spectroscopy (FT-IR) confirmed a complex coagulation reaction between gelatin and gum arabic, and the disappearance of the n-butyl cyanoacrylate peak indicated that the film was formed in the condensation layer. Thermogravimetric analysis results showed that the thermal stability of tea tree oil was greatly increased by the presence of the capsule wall. Rheological tests showed that the composite capsule wall improved viscosity and viscoelasticity. In addition, the composite capsule showed good stability in an osmotic environment and was found to have average sustained release performance and antioxidant capacity.

[0071] Manzanelli et al. (2023) produced microcapsules containing tea tree oil to evaluate its effectiveness against bacterial strains isolated from eye infections and particularly to inhibit biofilm formation. Using the spray-drying technique, they prepared two formulations for microencapsulation with high encapsulation efficiency (80-85%), microencapsulation efficiency (90-95%), and tea tree oil loading rates (approximately 40%). With these formulations, they obtained microcapsules with diameters of 6-12 pm, which exhibited regular, spherical morphologies. Post-encapsulation UV-Vis analysis confirmed the presence of tea tree oil within the capsules and the preservation of its antioxidant and antimicrobial activities. By agar diffusion assay, they tested the antibacterial activity of tea tree oil against Corynebacterium spp., coagulase-negative Staphylococcus spp., and Staphylococcus aureus. For all tested microorganisms, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were found to be 0.2% and 0.4%, respectively, while Corynebacterium spp. was observed to be resistant to tea tree oil. Furthermore, it was determined that tea tree oil significantly reduced biofilm biomass by 30-70% through colourimetric evaluation with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide staining (MTT method). Analyses showed that microencapsulated tea tree oil has significant therapeutic potential in the treatment of eye infections.

[0072] Shelar and Madankar (2023), in their study, encapsulated tea tree oil using the complex coacervation technique with a chitosan-gum arabic system, since it is natural and safe for humans and the environment, and used tannic acid as a crosslinking agent. The analyses showed that the ratio of (chitosan:gum arabic):tea tree oil as (2:5):2 and pH 3.6 provided maximum encapsulation yield and better encapsulation efficiency. Morphological studies showed that the resulting microcapsules had a spherical shape and sizes within the desired range. The microcapsules were found to be stable at room temperature. These encapsulated tea tree oil microcapsules can be used in cosmetic, food, and pharmaceutical fields. The method they used achieved 84.50% efficiency.

[0073] Kwon, Yang, and Lee (2023) encapsulated tea tree oil in a polymer matrix by emulsion electrospinning with the aim of preparing and investigating composite nanofibrous membranes as potential carriers of the antimicrobial agent. Polyvinyl alcohol (PVA), a biodegradable polymer used as a medical material, was combined with tea tree oil for pharmaceutical and medical applications. Composite PVA nanofibres containing tea tree oil with a well-aligned core-shell structure were obtained by electrospinning from an emulsion consisting of oil and aqueous PVA solution. To stabilise the PVA-based nanofibrous membranes in moist environments, thermal treatment was applied. The effects of drying and thermal treatment on the release behaviour of tea tree oil from composite membranes were investigated in detail. The antimicrobial effects of tea tree oil embedded in nanofibrous membranes were evaluated against Propionibacterium acnes and Staphylococcus aureus. Although the thermal treatment of tea tree oil- loaded PVA nanofibres reduced the release of volatile organic compounds, terpinen-

[0074] 4-ol, the active antibacterial component of the oil, was continuously released for 14 days. Composite membranes containing tea tree oil showed strong antibacterial effects against Propionibacterium acnes and Staphylococcus aureus. Therefore, they considered these bioactive nanofibrous membranes carrying tea tree oil, which suppress microbial growth, as promising potential carrier systems for the treatment of topical skin infections. Flincec Grgac et al. (2022) aimed to enhance the antimicrobial activity of chitosan using tea tree essential oil and to create a long-lasting antimicrobial effect on cotton fabrics for use in hospital settings. The effect of crosslinkers and catalysts on the possibility of obtaining stable bonds between cellulosic material and chitosan with and without tea tree essential oil using hydrothermal in-situ synthesis was investigated in detail. Field emission scanning electron microscopy (FE-SEM) was used to examine the surface morphology of samples before and after treatment, and the textile care cycle (durability of the treatment) was assessed, showing the presence of chitosan and a thin film in all treated samples, confirming the durability of the treatment. With FTIR-ATR spectra, they observed structural physicochemical changes in all tested samples. As a result of measurements made with a goniometer to detect film formation on the surface of treated samples, it was found that the samples were hydrophilic. After textile care cycles, the mass per unit area of the samples was measured, confirming the presence of significant amounts of chitosan bound with tea tree oil. Antimicrobial activity results showed that materials treated with chitosan were resistant to bacteria and fungi in most cases, but only one of the samples (Bathroom I) showed an inhibition zone against Candida albicans.

[0075] Zhu, Hu, and Zhong (2022), in their study, encapsulated tea tree oil (TTO) with polylactic acid (PLA) modified with octenyl succinic anhydride chitosan (OSA-CS) as the shell material to form long-lasting antibacterial and pH-sensitive microcapsules. PLA / OSA-CS@TTO microcapsules were characterised by high-performance liquid chromatography (HPLC), scanning electron microscopy (SEM), and antibacterial performance tests. The results showed that the average particle size of the microcapsules was 10 pm, and the encapsulation efficiency and loading efficiency of TTO were 81.5% and 60.3%, respectively. After 4800 minutes of release in environments with different pH values (5 and 7), the microcapsules still retained 55.32% and 56.74% of tea tree oil, confirming that the shell of the microcapsules responded to different pH values. The microcapsules remained stable for 80 days after the drying process and retained 39.7% of the core material. The morphology of PLA / OSA-CS@TTO microcapsules revealed that the microcapsules had a uniform and robust structure. Antibacterial tests against Staphylococcus aureus showed that after 72 hours, the bacteriostatic rate reached 100%. Mani et al. (2022) aimed to develop a composite electrospun scaffold that mimics the structural and functional requirements of the extracellular matrix. For this purpose, they investigated the use of a novel bone tissue regeneration formulation consisting of tea tree oil (TT) and zinc nitrate [(ZnNOs)2] incorporated into polyurethane (PU). They found that the diameters of these nanocomposite fibres [(495±184 nm for Pll / TT and 409±155 nm for PU / TT / (ZnNO3)2 were smaller compared to polyurethane fibres (1099±118 nm). FT-IR spectra demonstrated that PU and additives interacted through hydrogen bond formation. When the wettability of PU / TT was measured, a hydrophobic structure (115°±2) was observed, but this property was reversed (69°±2) with the addition of (ZnNOs)2 to PU / TT. The addition of TT and (ZnNOs)2 was found to increase tensile strength. AFM results showed that PU / TT (633±297 nm) and PU / TT / (ZnNOs)2 (345±147 nm) fibres were smoother than PU (854±32 nm). The developed nanocomposites were found to exhibit delayed blood clotting activation and reduced toxicity as determined by anticoagulant studies. In addition, bone formation capabilities measured by in vitro calcium deposition studies showed increased calcium accumulation (5.6% for PU / TT and 10.8% for PU / TT / (ZnNOs)2 compared to PU (2.4%). It was concluded that the properties of these nanocomposites could be successfully utilised for bone reconstruction.

[0076] Mounesan, Akbari, and Brycki (2022) encapsulated 15% tea tree essential oil (TEO) and incorporated it into electrospun nanofibres of 13% polyacrylonitrile (PAN) using 10% polyamidoamine dendrimer (PAMAM) to combat hazardous bioaerosols. The results showed that electrospun samples containing both TEO and PAMAM had thinner nanofibres, with an average diameter reduction of 440 nm, and therefore exhibited higher filtration efficiencies of over 98% and 99% against NaCI and paraffin oil mist particles, respectively. These findings demonstrated that an active layer consisting of dendritic materials and essential oils could be an innovative candidate for further applications in face masks.

[0077] Revuelta et al. (2021 ) aimed to develop an eco-friendly water-based paint formulated with microcapsules containing essential oils as biocidal agents. The microcapsules were synthesised by the in-situ polymerisation method. Lavender and tea tree oils were used as active substances, and melamine-formaldehyde (MF) resin was used as the shell material. The synthesised microcapsules were characterised by scanning electron microscopy, Fourier transform infrared spectroscopy, and particle size analysis. Acrylic water-based paint and the microcapsules were applied to commercial gypsum boards. Antifungal tests were conducted on paints with and without microcapsules. The effectiveness of the microcapsules against Aspergillus fumigatus spore suspension on paint films was evaluated by fungal growth on the painted surface. Fungal growth was assessed according to the ASTM D5590 standard specification. On the painted surface containing lavender oil microcapsules, only trace growth (<10%) was detected, whereas growth was observed at 70% on paints without microcapsules and on those containing tea tree oil microcapsules.

[0078] Huang et al. (2020) studied the microencapsulation of tea tree oil by in-situ polymerisation with urea-formaldehyde resin. They investigated the effects of curing time and drying conditions on the particle size of the microcapsules and the loading of tea tree oil. The results showed that microcapsules with a curing time of 80 minutes exhibited a narrow size distribution and good wall coating. Ambient drying was found to be better than oven drying in preserving tea tree oil content. With an 80-m inute curing time, tea tree oil loading could reach up to 45% of the weight ratio of the prepared microcapsules, and more than 90% of the loaded tea tree oil was able to be sustainably released within approximately 5 days. Furthermore, the release kinetics of the microcapsules were well described by the Ritger-Peppas model, revealing non- Fickian diffusion. Promisingly, tea tree oil-loaded microcapsules with good stability could be used as a slow-release agent for antibacterial applications.

[0079] Be§en (2020), in this study, encapsulated tea tree oil with ethyl cellulose using the simple coacervation method and transferred it to cotton fabrics to examine its antimicrobial properties. FT-IR and ATR analyses were performed on the obtained capsules, and optical microscopy and SEM images were examined. Their antimicrobial properties against gram-negative and gram-positive bacteria were investigated. Analyses confirmed that the capsules were successfully formed. Antibacterial tests on capsule-transferred cotton fabrics showed that the fabrics exhibited protective properties against bacteria.

[0080] Be§en (2019), in this study, encapsulated tea tree oil with various wall materials and applied it to nonwoven surfaces. Beta cyclodextrin, PVA, and gum arabic were used as wall materials. The components of tea tree oil were identified by gas chromatography-mass spectrometry (GC-MS). The FT-IR spectra and SEM images of the obtained capsules were also examined. GC-MS identified 24 components of tea tree oil. SEM and FT-IR analysis results of the capsules showed that encapsulation was successful. The capsules were transferred to 100% viscose nonwoven fabric by impregnation, and the resistance of the fabrics against gram-positive and gramnegative bacteria was tested. Antimicrobial tests showed that the fabrics exhibited antibacterial properties.

[0081] Perez-Liminana et al. (2013) encapsulated tea tree oil by the complex coacervation method using gelatin-carboxymethylcellulose as the wall material and applied it to shoe fabric and leather. SEM images, particle size, thermal properties by differential thermal analysis (DTA), DSC, and TGA, as well as FT-IR spectra of the obtained capsules, were examined. Analyses showed that microencapsulation was successful, and the obtained microcapsules were in the range of 3-50 pm. The capsules were applied to shoe fabric and leather by impregnation, and SEM images of the fabric and leather surfaces confirmed the presence of capsules. Furthermore, ironing and rubbing fastness of the fabric and leather were tested, and the fastness results were found to be satisfactory.

[0082] Chen et al. (2016) developed antibacterial microcapsules loaded with tea tree oil (TTO) based on the complex coacervation of sodium alginate (SA) and the quaternary ammonium salt of chitosan (HACC). They found that microcapsules obtained with a core-to-shell ratio of 1 :1 , pH 6.0, and 0.6% CaCl2 solution had the highest actual encapsulation efficiency (EE) of 66.06 ± 2.53%. The resulting microcapsules were then characterised in terms of morphology, size, components, and thermal stability using scanning electron microscopy (SEM), laser particle size analyser (LPDA), Fourier transform infrared spectroscopy (FTIR), thermal gravimetry-differential thermal analysis (TG-DTA), and differential scanning calorimetry (DSC). In addition, both in vitro drug release and antimicrobial properties of the microcapsules were evaluated. The results showed that TTO-loaded microcapsules had a spherical shape with particle sizes ranging from 1 .91 to 13.18 pm. The microcapsules were found to be effective in terms of thermal stability, sustained release activity, antimicrobial effect, and long-term inhibitory activity. The release profiles of TTO from the microcapsules were well fitted to the Ritger-Peppas model. Sanchez-Navarro et al. (2011 ), in their study, investigated the biocidal properties of tea tree oil after microencapsulation and application to shoe fabric and leather. Antibacterial analysis of tea tree oil was conducted against E. coli, B. subtilis, K. pneumoniae, and S. aureus, and it was found to exhibit antibacterial properties. In the study, tea tree oil was encapsulated using melamine-formaldehyde prepolymer by the in-situ method. The optical images, particle size, and FT-IR analyses of the obtained capsules were examined, and after application to fabric and leather by impregnation, SEM images were taken. The studies confirmed that tea tree oil was successfully encapsulated with melamine-formaldehyde prepolymer, with particle sizes ranging from 0.073 to 1.20 pm. As a result, microencapsulated tea tree oil was determined to be applicable for biocidal effects in shoe materials.

[0083] Problems

[0084] Limited Thermal Capacity: Single layer capsules have limited thermal storage capacity, and this is insufficient in effectively balancing body temperature.

[0085] Functional Limitations: With a single active agent, only thermal balancing or only antibacterial property can be provided.

[0086] Solution

[0087] This invention proposes the production of double-layered and double-active-agent microcapsules. The first layer contains a phase-changing substance such as n- eicosane, while the second layer contains a substance with antibacterial properties such as tea tree oil. These capsules are surrounded by melamine formaldehyde and ethyl cellulose shells. These microcapsules aim to enhance the performance of textile products by providing both thermal balancing and antibacterial properties. Thus, both thermal and antibacterial properties have been imparted to textile goods.

[0088] First Layer:

[0089] Material: n-eicosane

[0090] Encapsulation Method: It has been encapsulated by the in-situ polymerization method using melamine formaldehyde prepolymer. This layer provides energy storage capacity and chemical stability. Properties: It has a melting temperature of around 36 °C, which provides effective thermal balancing at body temperature. Its latent heat of fusion is around 243 J / g, which provides high energy storage capacity.

[0091] Second Layer:

[0092] Material: Tea tree oil and the first layer

[0093] Encapsulation Method: It has been encapsulated with ethyl cellulose by using the coacervation method. This layer enables the microcapsules to gain antibacterial properties.

[0094] Properties: Tea tree oil has natural antibacterial properties and provides long-term antibacterial protection to textile products.

[0095] Transfer of Capsules to Fabric:

[0096] The produced microcapsules have been transferred to 100% cotton woven fabrics. During the transfer process, it has been ensured that the microcapsules are homogeneously distributed on the fabric, and it has been aimed that the capsules are resistant to mechanical processes such as washing and rubbing.

[0097] Descriptions of Drawings Explaining the Invention

[0098] The figures and related descriptions required for a better understanding of the invention are as follows.

[0099] Figure 1 : The design of the capsules that are the subject of the invention is schematically shown.

[0100] Reference Numbers

[0101] 1- n-eicosane (First Active Agent)

[0102] 2- Melamine formaldehyde prepolymer (First Shell Wall)

[0103] 3- Tea tree oil (Second Active Agent)

[0104] 4- Ethyl cellulose (Second Shell Wall) Detailed Description of the Invention

[0105] In this detailed description, the multilayer capsule production method and the transfer of the capsules to the textile material are explained for a better understanding and in a manner that will not create any limiting effect.

[0106] Capsule Production Process

[0107] Production Process of Single-Layer Capsules: In this description, the production method of the single-layer capsules to be used in the invention will be explained. This process has been optimized to provide energy storage capacity.

[0108] The production of single-layer capsules by means of the in-situ method comprises the process steps of:

[0109] - mixing 10 grams of n-eicosane (1 ), 2% Tween 20, and 150 millilitres of distilled water in a high-speed mixer at 70 °C and 7000 rpm,

[0110] - mixing 1 mol of melamine and 8 mol of formaldehyde (37%) in 50 millilitres of distilled water at 70 °C and 1500 rpm until transparent, in order to form melamineformaldehyde prepolymer (2),

[0111] - adjusting the pH to 8.5-9 with 0.1 M sodium hydroxide (NaOH) once transparency is achieved,

[0112] - gradually adding the melamine-formaldehyde prepolymer (2), which has become transparent and adjusted to pH 8.5-9, into the mixture of n-eicosane (1 ), Tween 20, and distilled water being stirred in the high-speed mixer,

[0113] - after addition, adjusting the pH to 4-4.5 with 2% acetic acid, and adding 0.02 grams of polyvinyl alcohol (PVA),

[0114] - stirring the obtained solution at 70 °C and 7000 rpm for 150 minutes,

[0115] - centrifuging the solution at the end of 150 minutes and collecting the obtained solid part,

[0116] - washing the solid capsules collected from the centrifuge once with 100% ethanol and twice with distilled water, and

[0117] - using the single-layer capsules in wet form for multilayer capsule production. The production process of multilayer capsules: In this description, the production method of the capsules that are the subject of the invention will be explained. This process forms the outer layer of the microcapsules and provides an antibacterial effect.

[0118] The production of multilayer capsules by means of the coacervation method comprises the process steps of: a) Formation of the organic phase, which comprises the steps of:

[0119] - dissolving 1 gram of ethyl cellulose (4) in 9 millilitres of ethyl acetate,

[0120] - once the ethyl cellulose (4) is dissolved, adding 2 grams of tea tree oil (3) and 1 gram / litre dispersant, and mixing until homogeneous, and

[0121] - adding 5 grams of wet single-layer capsules and mixing until homogeneous, and b) Formation of the continuous phase, which comprises the steps of:

[0122] - mixing 300 millilitres of distilled water, 30 millilitres of ethyl acetate, 4% Tween 20, and 1 gram / litre dispersant at 7000 rpm until homogeneous,

[0123] - adding the organic phase into the continuous phase and mixing at 7000 rpm for 60 minutes,

[0124] - after 60 minutes, adding 400 millilitres of cold distilled water at 2 °C into the solution and mixing for 30 minutes,

[0125] - filtering and centrifuging the prepared solution,

[0126] - washing the collected solid twice with distilled water, and

[0127] - drying at 30 °C in a vacuum oven.

[0128] The production of multilayer capsules by means of the coacervation method comprises the process steps of: a) Formation of the organic phase, which comprises the steps of:

[0129] - dissolving 1 gram of ethyl cellulose (4) in 9 millilitres of ethyl acetate,

[0130] - after the ethyl cellulose (4) is dissolved, adding 2 grams of tea tree oil (3) and 1 gram / litre dispersant, and mixing until homogeneous, and

[0131] - adding 5 grams of wet single-layer capsules and mixing until homogeneous, and b) Formation of the continuous phase, which comprises the steps of: - mixing 300 millilitres of distilled water, 30 millilitres of ethyl acetate, 4% Tween 20, and 1 gram / litre dispersant at 7000 rpm until homogeneous,

[0132] - adding the organic phase into the continuous phase and mixing at 7000 rpm for 60 minutes,

[0133] - after 60 minutes, adding 400 millilitres of cold distilled water at 2 °C into the solution and mixing for 30 minutes,

[0134] - filtering and centrifuging the prepared solution,

[0135] - washing the collected solid matter twice with distilled water, and

[0136] - drying at 30 °C in a vacuum oven.

[0137] The production of multilayer capsules by means of the coacervation method comprises the process steps of: a) Formation of the organic phase;

[0138] - dissolving 1 gram of ethyl cellulose (4) in 9 millilitres of ethyl acetate,

[0139] - after the ethyl cellulose (4) has dissolved, adding 2 grams of tea tree oil (3) and 1 gram / litre of dispersant, and mixing until homogeneous, and

[0140] - adding 5 grams of wet single-layer capsules and mixing until homogeneous, and b) Formation of the continuous phase;

[0141] - mixing 300 millilitres of distilled water, 30 millilitres of ethyl acetate, 4% Tween 20, and 1 gram / litre of dispersant at 7000 rpm until homogeneous,

[0142] - adding the organic phase into the continuous phase and mixing at 7000 rpm for 60 minutes,

[0143] - after 60 minutes, adding 400 millilitres of cold distilled water at 2 °C into the solution and mixing for 30 minutes,

[0144] - filtering and centrifuging the prepared solution,

[0145] - washing the collected solid material twice with distilled water, and

[0146] - drying in a vacuum oven at 30 °C.

[0147] Transfer of Multilayer Capsules onto Fabric: In this description, the transfer of the multilayer capsules that are the subject of the invention onto the fabric for the purpose of forming the textile surface that is the subject of the invention will be explained. The transfer of multilayer capsules onto 100% cotton fabric by means of the impregnation method comprises the process steps of:

[0148] - adding 10 grams / litre of crosslinker into distilled water and adjusting the pH of the solution to 5.5 with 2% acetic acid,

[0149] - adding 60 grams / litre of multilayer capsules into the solution at pH 5.5 and mixing until homogeneous,

[0150] - placing the 100% cotton fabric into the homogeneous impregnation solution,

[0151] - passing the fabric that has absorbed the solution through the padding machine so that the liquor pick-up ratio is 100%, and

[0152] - drying the fabric at 150 °C for 5 minutes.

[0153] Fields of Application of the Invention

[0154] Sportswear: Provides thermal regulation, enhancing athletes’ performance and comfort. It can be used especially in sports requiring high physical activity (running, football, basketball).

[0155] Outdoor Equipment: Provides thermal insulation in cold weather conditions and reduces the risk of freezing. It is suitable for mountaineering, camping, and other outdoor sports.

[0156] Healthcare Textiles: Offers antibacterial properties, reducing the risk of infection and providing a hygienic environment. These properties provide a great advantage in medical textiles such as hospital garments, bandages, and surgical drapes.

[0157] Smart Textile Applications: Can be integrated with wearable technologies for regulating body temperature and with health monitoring systems. It can especially be used together with wearable sensors and smart garments.

[0158] Construction and Automotive Sector: Offers thermal management solutions that can increase energy efficiency and reduce the carbon footprint. These capsules can be used in wall panels providing energy savings in buildings, insulation materials, and interior thermal management systems in the automotive sector.

Claims

1. CLAIMS1. A multilayer capsule comprising a phase change material (n-eicosane) (1 ) and an antibacterial agent (tea tree oil) (3), characterised in that; a) in the first layer of said multilayer capsule, there is a single-layer capsule with the active ingredient n-eicosane (1 ) and a melamine-formaldehyde (2) shell wall, b) in the second layer of said multilayer capsule, there is a capsule comprising tea tree oil (3) and the single-layer capsule of step a as active ingredients, with an ethyl cellulose (4) shell wall, and in that in the multilayer capsule design, step a is followed by step b from the inside out.

2. A production method according to claim 1 , comprising the process steps of:- producing the single-layer capsule, and- producing the multilayer capsules by forming the second layer with the singlelayer capsule and tea tree oil (3) using an ethyl cellulose (4) shell wall.

3. A multilayer capsule production method according to claim 2, characterised in that; the production of single-layer capsules by means of the in-situ method comprises the process steps of:- mixing 10 grams of n-eicosane (1 ), 2% Tween 20, and 150 millilitres of distilled water in a high-speed mixer at 70 °C and 7000 rpm,- mixing 1 mol of melamine and 8 mol of formaldehyde (37%) in 50 millilitres of distilled water at 70 °C and 1500 rpm until transparent, in order to form melamineformaldehyde prepolymer (2),- adjusting the pH to 8.5-9 with 0.1 M sodium hydroxide (NaOH) once transparency is achieved,- gradually adding the melamine-formaldehyde prepolymer (2), which has become transparent and adjusted to pH 8.5-9, into the mixture of n-eicosane (1 ), Tween 20, and distilled water being stirred in the high-speed mixer,- after addition, adjusting the pH to 4-4.5 with 2% acetic acid, and adding 0.02 grams of polyvinyl alcohol (PVA),- stirring the obtained solution at 70 °C and 7000 rpm for 150 minutes,- centrifuging the solution at the end of 150 minutes and collecting the obtained solid part,- washing the solid capsules collected from the centrifuge once with 100% ethanol and twice with distilled water, and- using the single-layer capsules in wet form for multilayer capsule production, and the production of multilayer capsules by means of the coacervation method comprises the process steps of: a) Formation of the organic phase, which comprises the steps of:- dissolving 1 gram of ethyl cellulose (4) in 9 millilitres of ethyl acetate,- once the ethyl cellulose (4) is dissolved, adding 2 grams of tea tree oil (3) and 1 gram / litre dispersant, and mixing until homogeneous, and- adding 5 grams of wet single-layer capsules and mixing until homogeneous, and b) Formation of the continuous phase, which comprises the steps of:- mixing 300 millilitres of distilled water, 30 millilitres of ethyl acetate, 4% Tween 20, and 1 gram / litre dispersant at 7000 rpm until homogeneous,- adding the organic phase into the continuous phase and mixing at 7000 rpm for 60 minutes,- after 60 minutes, adding 400 millilitres of cold distilled water at 2 °C into the solution and mixing for 30 minutes,- filtering and centrifuging the prepared solution,- washing the collected solid twice with distilled water, and- drying at 30 °C in a vacuum oven.

4. A method of transferring the multilayer capsules produced according to claim 3 onto textile surfaces so as to provide thermal and antibacterial properties, characterised in that:the transfer of multilayer capsules onto 100% cotton fabric by means of the impregnation method comprises the process steps of:- adding 10 grams / litre of crosslinker into distilled water and adjusting the pH of the solution to 5.5 with 2% acetic acid, - adding 60 grams / litre of multilayer capsules into the solution at pH 5.5 and mixing until homogeneous,- placing the 100% cotton fabric into the homogeneous impregnation solution,- passing the fabric that has absorbed the solution through the padding machine so that the liquor pick-up ratio is 100%, and - drying the fabric at 150 °C for 5 minutes.

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