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The purpose of this paper is to synthesise and characterise novel thermally expandable microcapsules having poly (acrylonitrile (AN)‐methyl methacrylate (MMA)‐butyl acrylate (BA)) copolymer shells and p‐toluenesulphonylhydrazide (TSH) cores.

The novel thermally expandable microcapsules are synthesised by suspension polymerisation. The effects of various parameters including monomers and surfactant compositions on thermal expandability and stability, and particle size and size distributions of the microcapsules obtained are studied. Fourier transform infrared (FTIR) and scanning electronic microscopy (SEM) analyses are employed to characterise the chemical structure and morphology of the microcapsules obtained.

Suspension polymerisation with the monomers composition of 70 per cent AN/20 per cent MMA/10 per cent BA can yield microcapsules having a good expansion property and heat stability at 150°C. The paper also finds that when the amount of the incorporated PA reaches 20 per cent, the shells of microcapsules obtained will adhere together and some shells rupture resulting in the collapse of many of the expanded microcapsules. During the course of polymerisation, high‐molecular surfactant styrene – maleic acid copolymer sodium salt can help to achieve microcapsules with more uniform size distribution. FTIR and SEM characterisation show that the chemical structure of microcapsules contain core material and copolymeric shell and the morphology of microcapsules is very well defined, core‐shell type, respectively.

The shell copolymer in the present context is synthesised from acrylonitrile‐methyl methacrylate‐ and butyl acrylate. Besides, it can be synthesised from other monomers also. In addition, the expansion efficiency of microcapsules can be studied.

The learning gained through this paper can be applied to the synthesis and application of other microcapsule or even nano‐capsule systems.

The method for preparation of TSH microcapsules by suspension polymerisation is novel and the microcapsules could find applications in water‐based intumescent and flame retardant wood coatings.

Microcapsule-embedded autonomic healing materials have the ability to repair microcracks when they come into contact with the crack by releasing the healing agent. The microcapsules with specific shape and thickness effect in releasing healing agent to the cracked surfaces. Thus, the purpose of this paper is to know the load bearing capacity of the self-healing microcapsules and the stresses developed in the material.

In the present study, self-healing microcapsule is modelled and integrated with the polymer matrix composite. The aim of the present study is to investigate failure criteria of Poly (methyl methacrylate) microcapsules by varying the shell thickness, capsule diameter and loading conditions. The strength of the capsule is evaluated by keeping the shell thickness as constant and varying the capsule diameter. Uniformly distributed pressure loads were applied on the capsule-reinforced polymer matrix composite to assess the failure strength of capsules and composite.

It is observed from the results that the load required to break the capsules is increasing with the increase in capsule diameter. The failure strength of microcapsule with 100 µm diameter and 5 µm thickness is observed as 255 MPa. For an applied load range of 40–160 N/mm² on the capsules embedded composite, the maximum stress developed in the capsules is observed as 308 MPa.

Failure strengths of microcapsules and stresses developed in the microcapsule-reinforced polymer composites were evaluated.

The purpose of this work was to prepare a catalyst-free microcapsules as self-healing agent in an automotive clearcoat to improve the scratch resistance of coatings.

In this research, microcapsule with isophorone diisocyanate (IDPI) core and polyurethane shell were prepared and used in self-healing coatings. Microcapsules synthesised were characterised by thermal gravimeter and infrared spectra. The microcapsules were dispersed in an acrylic-melamine clearcoat, and the scratch resistance was evaluated.

The triplex product and the formed polyurethane bonds were confirmed by thermal gravimeter and infrared spectra. In addition, smooth spherical particles with a diameter of 1.5 to 1.7 micronmeters were observed by a scanning electron microscope. The microcapsules dispersed in an acrylic-melamine clearcoat increased the scratch resistance of coatings. Also, the self-healing feature of those coatings was proved.

The size of microcapsules can affect its dispersion in the clearcoat and consequently affect the properties of the cured films.

The self-healing coatings are interested for many industries such as building and automotive industries. The reported data can be used by the formulators working in the R & D departments.

Self-healing systems are considered as one of the smart coatings. Therefore, the developing of its knowledge can help to extend its usage to different applications.

The application of microcapsules in the coating as healing agents is a great challenge, which has been hardly investigated so far. In the current research, the effect of polyurethane-IDPI microcapsules in an automotive clearcoat as a self-healing coating was investigated.

As an efficient self-healing intelligent material, the encapsulation-based self-healing resin mineral composite (SHC) has a broad application prospect.

Aiming at the cracking performance of SHC, the dynamic load condition is employed to replace the traditional static load condition, the initial damage of the material is considered and the triggered cracking process and influencing factors of SHC are analyzed based on the extended finite element method (XFEM). In addition, the mechanism of matrix cracking and microcapsule triggered cracking process is explained from the microscopic point of view, and the cracking performance conditions of SHC are studied. On this basis, the response surface regression analysis method is used to obtain a second-order polynomial model of the microcapsule crack initiation stress, the interface bonding strength and the matching relationship between elastic modulus. Therefore, the model could be used to predict the cracking performance parameters of the microcapsule.

The interfacial bonding strength has an essential effect on the triggered cracking of the microcapsule. In order to ensure that the microcapsule can be triggered cracking normally, the design strength should meet the following relationship, that is crack initiation stress of microcapsule wall < crack initiation stress of matrix < interface bonding strength. Moreover, the matching relationship between elastic modulus has a significant influence on the triggered cracking of the microcapsule.

The results provide a theoretical basis for further oriented designing of the cracking performance of microcapsules.

The purpose of this study is the investigation of self-healing materials containing encapsulated healing agents embedded in a polymer matrix with dispersed catalysts. In recent years, the high performance and design flexibility of composite materials have led to their widespread use in the aeronautics, space, automotive and marine fields. Simultaneously, as the need for advanced material properties has increased, many studies have been conducted on multifunctional materials, focusing on different fields of their desired capabilities.

A multiscale model was developed to simulate the effect of microcapsules on the mechanical behavior of the polymer matrix. Furthermore, the effects of microcapsule diameter and microcapsule concentration on the mechanical behavior of the composite were studied. Digimat and Ansys software were used to simulate the self-healing composites.

There is a trade-off between the efficiency of the microcapsules and the degradation of the properties of the composite material.

The generated model simulated an encapsulated healing agent in a polymeric matrix.

The purpose of this work was to express a facile method to fabricate microcapsules containing linseed oil with melamine-urea-formaldehyde (MUF) shell in the presence of polyvinylpyrrolidone (PVP) as an emulsifier. These microcapsules may be used in self-healing coating formulations.

In this work, different types of PVP (i.e., PVP with different molecular weights or K values) were used as emulsifiers and colloid protectors to encapsulate linseed oil in an MUF shell. Moreover, the effect of agitation rate on the morphology of the microcapsules was investigated. Microcapsule morphology and particle size distribution were evaluated using optical microscopy and scanning electron microscopy. Thermal studies were performed using a thermo-gravimetric analysis technique and chemical structure of materials was characterized by using Fourier transform infrared analysis.

In this work, microcapsules with a regular spherical shape and a shell thickness of about 330 nm were fabricated. The results revealed that the use of PVP in the fabrication of MUF could facilitate the synthesis process by eliminating the necessity of pH control during the reaction. In fact, the pH of the reaction media must be precisely controlled in conventional processes. The yield of microencapsulation was found to be 86.5 per cent when a high molecular weight of PVP (PVP K-90) was used. It was also found that the surface morphology of microcapsules became smoother when PVP K-90 was used. The results showed that the surface roughness and the average particle size decreased with an increase in stirring intensity. Mean diameter of the prepared microcapsules ranged from 34 to 346 μmin for various synthesis conditions.

This work is limited to the encapsulation of a hydrophobic liquid (such as linseed oil) by an in situ polymerisation of amino resins.

The presented results can be used by researchers (in academia and industry) who are working in the field of fabrication microcapsules, in various applications such as pharmaceuticals, electrophoretic displays, textiles, carbonless copy papers, cosmetics, printing and self-healing materials.

PVP is considered as an environmentally friendly emulsifier. Therefore, this process is less harmful to the environment. In addition, the prepared microcapsules may be used in self-healing coatings, which helps in reducing maintenance costs for buildings and steel structures.

Ethylene maleic anhydride and styrene maleic anhydride are usually used as emulsifiers in conventional methods for the preparation of amino resin microcapsules. These methods require an intensive and precise pH control to obtain favourable microcapsules, while in the present research, a facile method was used to fabricate MUF microcapsules containing linseed oil without needing any pH control during the reaction.

The aim of this work is to investigate the self-healing performance of epoxy coatings containing microcapsules. The microcapsule-based coatings were applied on AA6061 Al alloy and immersed in 3.5 per cent NaCl solution.

Microcapsules with urea–formaldehyde as the shell and linseed oil as the healing agent were prepared by in situ polymerization in an oil-in-water emulsion. For the sake of an optimum self-healing system, some coating samples were prepared by using different microcapsule concentrations: 0, 5, 10 and 20 Wt.%. The scratch-filling efficiency as the theoretical estimate of the self-healing performance was calculated for the coating samples with different microcapsule concentrations. The scratch-sealing efficiency (SSE) as a particularly crucial parameter in the self-healing evaluation of coatings was measured by both electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) techniques.

According to EIS and EN results, the coating samples containing 5 and 10 per cent microcapsules provided the insignificant self-healing performance, while the coating sample containing 20 per cent microcapsules exhibited the acceptable self-healing performance to AA6061 alloy in the NaCl solution. The measured SSE values confirmed the good agreement of EN data with electrochemical parameters obtained from the EIS technique.

This work is an attempt to evaluate the self-healing performance of microcapsule-based epoxy coatings applied on AA6061 Al alloy in sea water.

This study aims to elaborate on the microencapsulation of the plant extract (PE, from Camellia sinensis leaf, clover flower and cocoa flower) and the preparation of a slow-release lining fabric loading the PE microcapsule.

PE was microencapsulated into polyvinyl alcohol (PVA) shells through interfacial polymerization. The morphology, thermal stability, slow-release property and drug loading ratio of the PVA/PE microcapsules were characterized to ensure the availability in coating finishing. To find the optimum parameters, the composite fabrics were prepared from non-woven fabrics coated by calcium alginate hydrogel, which glued mass fractions of microcapsules and dried in different ways. To evaluate the effectiveness, a lipase enzyme activity test was conducted.

Under optimal conditions, the PVA/PE microcapsules with smooth surface have an average particle size of 14.5 um, and they are expected to reach a loading ratio of 38.5 per cent while remaining stable under 220°C. Given a microcapsule of 4 per cent (of the mass), the composite fabric has a good hand feeling, being prepared through calcium chloride coating. It is shown that the inhibition ratios of the microcapsules and composite fabrics on lipase are 31.3 and 21.0 per cent, respectively.

The composite fabric could be prepared through the other finishing methods such as padding and printing. In addition, the release mechanism of the composite could be studied.

This study provided a simple and effective way to prolong the duration of PE. This way was conductive to protect environmental sensitive PEs from being destroyed in compositing processes.

Preparing composite fabrics for transdermal delivery system was novel and other kind of plant extracts could be used in this way.

The purpose of this paper is to study the tribology behavior of steel–steel contact under the lubrication of water-based drilling mud with different oleic acid-filled microcapsules as lubricant additives.

A ball-on-disc tribometer was used to evaluate the lubrication properties of the steel–steel contact. The wear tracks of the worn surfaces were observed by a scanning electron microscope.

Results show that the dependence of both friction and wear on the category of additives shares a consistent pattern. In contrast to oleic acid and empty microcapsules, oleic acid-filled microcapsules achieve the best tribological performance which is related to the lubricant effect of oleic acid and the isolation and rolling abilities of microcapsules.

This study provides a helpful method of encapsulated lubricant additives to prolong lubrication performance for steel–steel contact.

This study has applied microcapsules to improve the tribological properties of drilling mud.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0320/

The purpose of this paper is to prepare microencapsulated phase change materials (PCMs) and apply them to cotton and wool fabrics for developing thermo-regulating fabrics.

Microencapsulated n-hexadecane and n-octadecane with poly(methylmethacrylate-co-2-hydroxy ethyl methacrylate) shell was prepared. Microcapsules were fabricated using oil-in-water emulsion polymerization method. Their chemical structure, microstructure, thermal energy storage properties and thermal stability were analyzed by Fourier-transform infrared spectroscopy, polarized light microscope, differential scanning calorimeter and thermogravimetric analyzer, respectively. The mean particle size was tested by a particle sized instrument. The microcapsules were applied to the wool and cotton fabrics using pad-dry-cure method. The thermo-regulating property of the fabrics was evaluated using the T-History test. The distribution and durability of the microcapsules on the fabrics was investigated with scanning electron microscopy.

Spherical microcapsules with p(MMA-co-HEMA) shell and n-alkane core have been produced successfully. n-hexadecane in microcapsule solidifies at 14.8−15.6°C with the latent heat of 65.6−129.8 J/g and melts at 16.7−16.9°C with the latent heat of 67.6−136.9 J/g. Microencapsulated n-octadecane solidifies at 25.8−26.3°C with the latent heat of 74.1−106.2 J/g and melts at 26.8−27.4°C with the latent heat of 80.3−113.4 J/g. The microcapsules have enough thermal stability to the temperature of 150°C that was applied during the fixation of microcapsules on the fabric. The thermo-regulating effect of the microcapsule-incorporated fabrics has been proved by the T-history test.

PCM microcapsules with p(MMA-co-HEMA) shell and n-hexadecane and n-octadecane core have been produced and their usage to produce thermo-regulating textiles have been proved. To determine the thermo-regulating property of the fabrics treated with these new PCM microcapsules, a T-History system has been designed.