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Article
Publication date: 3 July 2017

Amir Khalaj Asadi, Morteza Ebrahimi and Mohsen Mohseni

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…

392

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Research limitations/implications

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

Practical implications

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.

Social implications

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.

Originality/value

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.

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Article
Publication date: 6 March 2017

Arezoo Mamani, Morteza Ebrahimi and Maryam Ataeefard

The purpose of this paper is to investigate the effect of expandable graphite (EG) plates’ incorporation on the mechanical, thermal and fire-retardant properties of an…

246

Abstract

Purpose

The purpose of this paper is to investigate the effect of expandable graphite (EG) plates’ incorporation on the mechanical, thermal and fire-retardant properties of an epoxy–aliphatic amine system. In addition, the optimum amount of EG in epoxy/EG composites is determined to achieve the best thermal and mechanical properties at the same time.

Design/methodology/approach

The epoxy/EG composites were prepared by using (1-4) phr of EG. The morphological structure of epoxy/EG composites was studied by using scanning electron microscopy. The thermal, flame-retardant and mechanical properties of epoxy/EG composites were evaluated by using thermogravimetric analysis (TGA), oxygen index test and dynamic mechanical analysis and tensile and impact test, respectively.

Findings

TGA results showed that the incorporation of EG to the epoxy resin increased the initial decomposition temperature and residue weight of the composites. It was found that, with increasing EG concentration up to 4 phr, the oxygen index, glass transition temperature and Young’s modulus of epoxy/EG composites increased up to 60 per cent, 4.1°C and 50 per cent, respectively. On the other hand, the sample with 2 phr EG provided the maximum values of tensile strength, storage modulus, cross-linking density, ultimate tensile strain and impact strength.

Practical implications

Prepared epoxy/EG composites can be used as halogen-free flame-retardant composites. The proposed process for the preparation of the composites is simple and can easily be implicated in the industry.

Originality/value

To the best of the authors’ knowledge, there is no other publication that considers mechanical, thermal and fire-retardant properties of epoxy/EG composites in one paper. In this work, the optimum concentration of EG in epoxy/EG composites was determined, considering all these properties.

Details

Pigment & Resin Technology, vol. 46 no. 2
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 8 May 2018

Amir Khalaj Asadi, Morteza Ebrahimi and Mohsen Mohseni

The purpose of this investigation is to develop a facile method to encapsulate a sunlight-curable silicone-based resin into a melamine–urea–formaldehyde (MUF) shell in the…

207

Abstract

Purpose

The purpose of this investigation is to develop a facile method to encapsulate a sunlight-curable silicone-based resin into a melamine–urea–formaldehyde (MUF) shell in the presence of polyvinylpyrrolidone (PVP) as an emulsifier. These microcapsules can be used in self-healing coating formulations.

Design/methodology/approach

MUF microcapsules containing a sunlight-curable core (methacryloxypropyl-terminated polydimethylsiloxane, MAT-PDMS) have been fabricated by means of in situ polymerisation of an oil-in-water emulsion using PVP as an efficient and environmentally advantageous stabiliser. The effects of agitation rate and PVP concentration on the microencapsulation process have been investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The chemical structure and thermal stability of the microcapsules have been studied using Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The solvent resistance of the microcapsules has been determined as well.

Findings

It has been revealed that the pH of the reaction mixture remained almost constant during the reaction, which simplified the process. It has also been observed that the microencapsulation yield improved and the microcapsules’ surface morphology became smoother when a high PVP content was used. With an increase in stirring rate from 600 to 1,200 rpm, the surface roughness and the average particle size decreased. The mean diameter of the prepared microcapsules ranged from 32.1 to 327.1 µm depending on the synthesis conditions. It was demonstrated that the microcapsules had a high capacity for MAT-PDMS encapsulation (more than 88 Wt.%). The solvent stability of the microcapsules against different polar, semi-polar and non-polar solvents was also evaluated.

Research limitations/implications

This research is limited to the encapsulation of a hydrophobic and sunlight curable liquid (such as MAT-PDMS) by means of in situ polymerisation of amino resins.

Practical implications

The results can be used by researchers working on the fabrication of microcapsules for applications such as drugs, electrophoretic inks, electrophoretic displays, intumescent fire-retardant coatings and self-healing materials.

Social implications

In self-healing coatings, healing agents which can be cured by UV irradiation or sunlight are envisaged attractive because they are catalyst-free, environmentally friendly and relatively inexpensive. PVP is an environmentally friendly emulsifier. The prepared microcapsules can be used in self-healing coatings to help in reducing maintenance costs for buildings and steel structures.

Originality/value

The novel aspect of this work is the development of a sunlight-curable silicone-based resin that was encapsulated in a MUF shell in the presence of PVP. A simple method was used to fabricate MUF microcapsules containing MAT-PDMS without the need to control pH during the reaction. Conventional methods for the preparation of amino resin microcapsules require an intensive and precise pH control to obtain favourable microcapsules. MAT-PDMS can be cured by sunlight and is catalyst-free, environmentally friendly and relatively inexpensive.

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Article
Publication date: 16 October 2009

Rahman Farnoosh and Ebrahimi Morteza

The purpose of this paper is to provide a Monte Carlo variance reduction method based on Control variates to solve Fredholm integral equations of the second kind.

508

Abstract

Purpose

The purpose of this paper is to provide a Monte Carlo variance reduction method based on Control variates to solve Fredholm integral equations of the second kind.

Design/methodology/approach

A numerical algorithm consisted of the combined use of the successive substitution method and Monte Carlo simulation is established for the solution of Fredholm integral equations of the second kind.

Findings

Owing to the application of the present method, the variance of the solution is reduced. Therefore, this method achieves several orders of magnitude improvement in accuracy over the conventional Monte Carlo method.

Practical implications

Numerical tests are performed in order to show the efficiency and accuracy of the present paper. Numerical experiments show that an excellent estimation on the solution can be obtained within a couple of minutes CPU time at Pentium IV‐2.4 GHz PC.

Originality/value

This paper provides a new efficient method to solve Fredholm integral equations of the second kind and discusses basic advantages of the present method.

Details

Kybernetes, vol. 38 no. 9
Type: Research Article
ISSN: 0368-492X

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Article
Publication date: 8 March 2011

Rahman Farnoosh, Parisa Nabati, Ramazan Rezaeyan and Morteza Ebrahimi

The purpose of this paper is to analyze the effect of the white, colored and mixture noise perturbations as Gaussian process on the parameters of the RL electrical circuit…

528

Abstract

Purpose

The purpose of this paper is to analyze the effect of the white, colored and mixture noise perturbations as Gaussian process on the parameters of the RL electrical circuit including potential source and resistance.

Design/methodology/approach

By adding different noise terms in the voltage and resistance parameters of an RL electrical circuit, the deterministic model is replaced by a stochastic differential equation (SDE).

Findings

Owing to the application of multiple Ito's formula the analytical solutions of resulted SDEs have been obtained. Furthermore, based on a numerical method involving Euler‐Maruyama scheme, the solution of the problem at the point of interest as a continuous time stochastic process has been obtained. Also shown is that the confidence interval for mean of solutions with colored and mixture noises is better than white noise.

Practical implications

Numerical tests via Matlab programming are performed in order to show the efficiency and accuracy of the present work. Numerical experiments show that an excellent estimation on the solution can be obtained within a couple of minutes time at Pentium IV‐2.4 GHz PC.

Originality/value

It is believed that the stochastic model of an RL circuit with colored and mixture noises in potential source has not been studied before. Furthermore, according to latest information from the research works, two stochastic parameters in voltage and resistance of RL circuit including colored and mixture noise processes have been investigated for the first time in this paper.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 30 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 25 February 2014

Ghodsieh Mashouf, Morteza Ebrahimi and Saeed Bastani

The purpose of this work was to perform a systematic study on the effect of formulation on the physical and mechanical properties of ultaviolet (UV) curable urethane acrylate…

795

Abstract

Purpose

The purpose of this work was to perform a systematic study on the effect of formulation on the physical and mechanical properties of ultaviolet (UV) curable urethane acrylate resins. In addition, the authors wanted to derive mathematical formula for the prediction of physical and mechanical properties for the aforementioned system.

Design/methodology/approach

The experiments were carried out based on mixture experimental design to determine the effect of different multifunctional acrylates (i.e. 1,6-hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), trimethyolpropane triactylate (TMPTA)) concentration on the physical and mechanical properties of a UV curable polyurethane acrylate system. The urethane oligomer was synthesized and characterized by the research team. Microhardness, adhesion strength and scratch resistance of the cured films were evaluated as the physical and mechanical properties.

Findings

The results revealed that the resin and TMPTA concentrations had the most significant effects on the microhardness property. Adhesion strength of the films showed a linear trend with respect to all variables. Moreover, all components also had a significant and complex influence on the scratch resistance of the cured systems. In addition, mathematical equations proposed by mixture experimental design were derived for all the mentioned properties.

Research limitations/implications

Other multifunctional acrylate monomers (i.e. more than three functional) can be used in the formulations. The kinetics of the curing can affect on the network formation and consequently on the properties of the cured films.

Practical implications

The obtained results can be used by the researchers who are active in the field of structure-property relationship of polymers and surface coatings. The reported data and the mathematical equations can also be used for the formulating of an appropriate formulation based on a specific application.

Originality/value

A systematic and statistical-based approach, i.e. mixture experimental design, was used to evaluate the effect of formulation on some of the properties of a UV curable polyurethane acrylate system. A urethane oligomer and three different multifunctional acrylate monomers as reactive diluents were used in the formulations. Noteworthy to mention that several mathematical models were derived by using analysis of variance for the prediction of the properties studied in this system.

Details

Pigment & Resin Technology, vol. 43 no. 2
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 1 July 2014

Pooneh Kardar, Morteza Ebrahimi and Saeed Bastani

The purpose of this work was to study the effect of chemical structure of reactive diluents on the curing behaviour and physical–mechanical properties of a titanium dioxide…

473

Abstract

Purpose

The purpose of this work was to study the effect of chemical structure of reactive diluents on the curing behaviour and physical–mechanical properties of a titanium dioxide pigmented UV-curable epoxy acrylate system.

Design/methodology/approach

Two different tri-functional and two different tetra-functional acrylate monomers were used as reactive diluents in the formulations. The curing behaviour of the formulations was studied by using photo-differential scanning calorimetry analysis. The rate of curing, conversion at the maximum rate and ultimate conversion for different formulations were calculated. In addition, the physical and mechanical characteristics of the cured films, including glass transition temperature and modulus, were measured by using a dynamic mechanical analysis technique.

Findings

The results showed that the ultimate conversion for non-pigmented pentaerythritol triacrylate (PETA) and trimethylol propane triacrylate (TMPTA) formulations were almost similar, but the interference effect of titanium dioxide particles on the curing of the PETA formulations was found to be more considerable in comparison to the TMPTA formulations. The extent of reaction for tetra-functional acrylate monomers was considerably less than those for tri-functional acrylate monomers. The Tg and storage modulus of non-pigmented PETA, TMPTA and pentaerythritol tetraacrylate (PE4TA) formulations were almost the same and higher than that for ditrimethylol propane tetraacrylate (DiTMP4TA) formulations. However, Tg and storage modulus of pigmented tetra-functional acrylate monomer formulations were higher than those for tri-acrylate monomer formulations.

Research limitations/implications

The curing conditions (temperature and UV intensity) can affect the network formation and consequently will affect on the properties of the cured films.

Practical implications

The pigmented UV-curable coatings are interested for many industries such as wood and automotive industries. The reported data can be used by the formulators working in the R&D departments. In addition, the results obtained can be used by the researchers who are active in the field of structure–property relationship for UV-curable coatings.

Social implications

UV-curing systems are considered as one of the most environment-friendly coatings system. Therefore, the developing of its knowledge can help to extend its usage to different applications.

Originality/value

The photopolymerisation of pigmented coatings is a great challenge and is hardly investigated in the literature. Therefore, in this research, the effect of chemical structure and functionality of different multifunctional acrylate monomers on the curing behaviour of pigmented formulations was investigated.

Details

Pigment & Resin Technology, vol. 43 no. 4
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 2 November 2015

Bahram Tarvirdizadeh, Esmaeel Khanmirza, Morteza Ebrahimi, Ahmad Kalhor and Shidvash Vakilipour

The purpose of this paper is to propose an efficient and straightforward approach for system identification of a rotating single link flexible manipulator (RSLFM). Also, the…

227

Abstract

Purpose

The purpose of this paper is to propose an efficient and straightforward approach for system identification of a rotating single link flexible manipulator (RSLFM). Also, the achieved results are experimentally validated through identification procedure.

Design/methodology/approach

The proposed system identification approach is applied to a RSLFM with a tip mass. At first, the dynamic model of the system is derived using Lagrange method. Then, an efficient method is developed for identification of such a system. This method facilitates the nonlinear complicated identification problem of the RSLFM to a simplified root finding problem.

Findings

The main advantage of the developed method is to convert a complicated system identification process to a simple nonlinear equation solution. This approach uses small-size input/output data set and requires a short-time interval of data acquisition, which gives important advantages in lower computational load and lower execution time. The investigated approach is studied on experimental system identification of a single link flexible manipulator. To demonstrate this fact, the developed method is successfully applied in identification of two other mechanical systems; the inverted pendulum on a cart and the ball and beam apparatus.

Originality/value

In this work, the proposed identification approach has been originally applied to a RSLFM and two other mechanical examples. All obtained identification results show the performance and applicability of the developed method clearly. This approach is not restricted in using state space or transfer function. It has significant superiority in comparison with other known approaches including autoregressive with exogenous input (ARX) and Box-Jenkins (BJ).

Details

Engineering Computations, vol. 32 no. 8
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 30 October 2019

Morteza Behzadnasab, Ali Akbar Yousefi, Dariush Ebrahimibagha and Farahnaz Nasiri

With recent advances in additive manufacturing (AM), polymer-based three-dimensional (3D) printers are available for relatively low cost and have found their way even in domestic…

752

Abstract

Purpose

With recent advances in additive manufacturing (AM), polymer-based three-dimensional (3D) printers are available for relatively low cost and have found their way even in domestic and educational uses. However, the optimum conditions for processing and post-processing of different materials are yet to be determined. The purpose of this paper is to examine the effects of printing temperature, pattern and annealing conditions on tensile strength and modulus of samples printed with polylactic acid (PLA).

Design/methodology/approach

This study focuses on fused deposition modelling according to ISO/ASTM 52900 material extrusion AM. To print parts with maximum mechanical properties, the printing variables must be optimised. To determine the printing and annealing condition on physical and mechanical properties of PLA-based parts, dogbone-shaped tensile samples were printed at four different nozzle temperatures and five different filling patterns embedded in a 3D printing software. The samples were further annealed at three different temperatures for three different time intervals. The mechanical properties were evaluated and the changes in mechanical properties were analysed with the help of rheometrical measurements.

Findings

The results showed that printing condition has a significant influence on final properties, for example, the strain at break value increases with increasing nozzle temperature from 34 to 56 MPa, which is close to the value of the injected sample, namely, 65 MPa. While tensile strength increases with printing temperature, the annealing process has negative effects on the mechanical properties of samples.

Originality/value

The authors observed that traditional findings in polymer science, for example, the relationship between processing and annealing temperature, must be re-evaluated when applied in 3D printing because of major differences in processing conditions resulting from the layer-by-layer manufacturing.

Details

Rapid Prototyping Journal, vol. 26 no. 2
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 14 May 2019

Morteza Ezzati

This paper aims to explain and present a theoretical framework for providing people with savings to finance two sectors: profitable investment and Gharz-al-Hassane. To do this…

595

Abstract

Purpose

This paper aims to explain and present a theoretical framework for providing people with savings to finance two sectors: profitable investment and Gharz-al-Hassane. To do this first, assumptions and presumptions of the theory and framework are expressed, and then the effect of belief on this behavior is explained. Subsequently, this theoretical framework is evaluated in an empirical research.

Design/methodology/approach

The theoretical framework is explained by mathematical and logical methods. The experimental study is carried out using real data of 500 households from Zahedan (Center of Sistan and Baluchestan Province of Iran). Data were collected using questionnaire and were analyzed using statistical and econometric methods.

Findings

The result indicates that demands of Iranian people are not met within the framework of official markets. This disparity in supply and demand has led to the actions of people outside the formal framework, and so, banks and financial institutions cannot exploit the supply of people’s savings. On this basis, key factors determining people supply in a variety of markets are religious belief, age, income, education level, religious experience and so on, which should be considered in designing the Islamic banking and financial tools.

Originality/value

Today, economics and marketing have shown that an enterprise needs to meet customer demand to succeed. In the field of Islamic banking and finance, financial firms and banks should know this too. However, there are not many research studies in this area.

Details

Journal of Islamic Marketing, vol. 10 no. 4
Type: Research Article
ISSN: 1759-0833

Keywords

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