Mehdi Entezam - Academia.edu (original) (raw)

Papers by Mehdi Entezam

Research paper thumbnail of Molecular and thermo-mechanical assessment of long-chain branched polypropylene: Effect of irradiation dose, multifunctional monomer content and molecular weight

Radiation Physics and Chemistry

Research paper thumbnail of A Model of Mechanotransduction in Polyvinyl Alcohol‐Based Composite Hydrogels for Regulating Musculoskeletal Differentiation

Macromolecular Materials and Engineering

In regenerative medicine, extracellular matrix (ECM)‐inspired materials are currently being explo... more In regenerative medicine, extracellular matrix (ECM)‐inspired materials are currently being explored to imitate mechanotransduction pathways and control cell fate. In musculoskeletal tissue regeneration, enhancing mechano‐biological signals require biomaterials that are both biocompatible and viscoelastic and can retain water content. Herein, based on these requirements, various polyvinyl alcohol (PVA)‐based composite hydrogels, reinforced by polyhydroxy butyrate (PHB) nanofibers, are proposed to differentiate equine adipose‐derived stem cells for musculoskeletal regeneration. To study the role of fiber embedding in improving scaffold properties, different nanofiber assemblies, including chopped short ones with random orientation (PVAS), single‐layer (PVAL1), and double‐layer membranes (PVAL2) are positioned into the PVA matrix. PHB reinforcements negatively affect swelling and positively enhanced phase transition temperatures and crystallinity of PVA hydrogel. According to mechanic...

Research paper thumbnail of Physical and drug release characteristics of nanoliposomes modified poly(vinyl alcohol) (PVA)/poly(ethylene glycol) (PEG) hydrogels

The main objective of this research is to investigate how curcumin liposomal nanocarriers influen... more The main objective of this research is to investigate how curcumin liposomal nanocarriers influence the drug release behaviour of PVA/PEG hydrogels in relation to physico-mechanical properties. For this purpose, optimal nanoliposomes from drug loading and release viewpoints, prepared by the thin-film hydration method, were incorporated into the hydrogel composition. Hydrogel samples were physically crosslinked using the freeze-thaw procedure. According to the atomic force microscopy and field-emission scanning electron microscopy observations, nanoliposomes showed a spherical morphology with an average particle size of 100 nm and narrow size distribution. The X-ray diffraction results revealed that adding nanoliposomes to the hydrogel increases the degree of PVA chains crystallinity, enhances tensile modulus and tensile strength of the hydrogel, while decreasing swelling and dehydration rates. SEM micrographs observation displayed that the porosity in the hydrogel structure in the p...

Research paper thumbnail of Irradiation processing of immiscible PP/EOC blend: Morphology control and processability modification

Journal of Applied Polymer Science, 2020

In this study, applying electron beam irradiation method at a relatively low‐irradiation dose (20... more In this study, applying electron beam irradiation method at a relatively low‐irradiation dose (20 kGy) under the air atmosphere to prepare injectable polypropylene (PP)/ethylene‐octene copolymer (EOC) blends with fine morphology and appropriate performance was investigated. For this purpose, an extrusion PP grade with an EOC grade suitable to improve its impact resistance was melting blended. Gel content and rheological measurements revealed long‐chain branching is predominant phenomenon occurring during the irradiation process of EOC. Blend irradiation resulted in changing its melt flow index proper for injection molding. A fine morphology obtained for the unirradiated blend was preserved for the irradiated blend. Moreover, irradiation thermally stabilized the blend morphology. Blends linear viscoelastic behavior discussed by proper rheological models revealed the existence of interfacial interactions and a reduction of the interfacial tension between irradiated blend phases. No si...

Research paper thumbnail of Mechanical properties and drug release rate of poly(vinyl alcohol)/poly(ethylene glycol)/clay nanocomposite hydrogels: Correlation with structure and physical properties

Journal of Applied Polymer Science, 2019

ABSTRACTPoly(vinyl alcohol)/poly(ethylene glycol) hydrogels containing curcumin as a drug and the... more ABSTRACTPoly(vinyl alcohol)/poly(ethylene glycol) hydrogels containing curcumin as a drug and the various amounts of a montmorillonite nanoclay are prepared using the freezing–thawing method. Nanoclay quantity influence on the physicomechanical properties and the drug release rate of the hydrogel as well as relationship between them is investigated. X‐Ray diffraction and Atomic force microscopy analysis reveal the nanoclays have an intercalation structure in the hydrogel, and the hydrogel crystallization decreases with increasing the nanoclay inclusion. From the SEM micrographs observation, it was revealed that due to the presence of the nanoclay in the hydrogel, its porosity decreased. The naonoclay has an amount‐depended dual effect on the hydrogel swelling. The swelling mechanism is a normal Fickian diffusion for all the hydrogel samples. Strong physical interactions between the nanoclays and the polymer chains in the nanocomposite hydrogels are evidenced by the rheological studi...

Research paper thumbnail of Mechanical and water absorption properties of municipal solid waste and banana fiber-reinforced urea formaldehyde composites

Environmental Progress & Sustainable Energy, 2014

In this study, hybrid composites of municipal solid waste (MSW)/banana fiber reinforced urea form... more In this study, hybrid composites of municipal solid waste (MSW)/banana fiber reinforced urea formaldehyde were prepared in different filler ratio. Mechanical properties such as tensile, flexural, and impact strengths were investigated as a function of total volume fraction (Vf) of filler (MSW and banana fiber), relative volume fraction of MSW and banana fiber and its chemical modification. The mechanical properties were found to be high at 40% Vf of filler which indicates effective stress transfer between fiber and matrix. Then, composites with different volume ratios of MSW and banana fiber (100:0, 75:25, 50:50, 25:75, 0:100) are prepared by keeping total Vf of filler as 40%. It is observed that addition of banana fiber imparts better mechanical and thermal stability properties to composites. Also, banana fiber addition increased the water absorption properties of composites. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 211–221, 2015

Research paper thumbnail of Electron beam irradiation method to change polypropylene application: Rheology and thermomechanical properties

Irradiation of polymers is one of the most effective and economical methods for modifying their p... more Irradiation of polymers is one of the most effective and economical methods for modifying their properties and for changing their applications. In this study, an extrusion grade polypropylene (PP) was treated by electron beam irradiation to produce a PP suitable for injection molding. Irradiation was carried out at different doses (0-80 kGy) under atmosphere air and at ambient temperature. Melt flow index (MFI) measurements showed PP samples irradiated in the range of 10 to 40 kGy are suitable to use in injection molding. Electron beam irradiation decreased the viscosity and the shear thinning rheological behavior of PP. The differential scanning calorimetry (DSC) analysis revealed that electron beam irradiation increased the crystallinity percentage and temperature of PP, but decreased the melting temperature. Among all treated samples, the PP20, irradiated at the dose of 20 kGy, showed the highest impact resistance. It had higher Young’s modulus and tensile strength, but lower elo...

Research paper thumbnail of Liposomal Nanocarriers-Loaded Poly(vinyl alcohol) (PVA)/Poly(ethylene glycol) (PEG) Hydrogels: Physico-mechanical Properties and Drug Release

Journal of Polymers and the Environment

Research paper thumbnail of Electron beam irradiation induced compatibilization of immiscible polyethylene/ethylene vinyl acetate (PE/EVA) blends: Mechanical properties and morphology stability

Radiation Physics and Chemistry, 2017

Gel content, mechanical properties and morphology of immiscible PE/EVA blends irradiated by high ... more Gel content, mechanical properties and morphology of immiscible PE/EVA blends irradiated by high energy electron beam were studied. The results of gel content measurements showed that the capability of cross-linking of the blend samples increased with an increase of the EVA composition. Also, the gel content for most compositions of the blends displayed a positive deviation from the additive rule. The results of mechanical properties showed that the tensile strength and elongation at break of the samples increased and decreased, respectively, with irradiation dose. On the other hand, the mechanical properties of the irradiated blends also depicted a positive deviation from additive rule contrary to the un-irradiated blends. A synergistic effect observed for the mechanical properties improvement of the irradiated blends and it was attributed to the probable formation of the PE-graft-EVA copolymers at the interface of the blends during the irradiation process. A theoretical analysis revealed that irradiation induced synergistic effect was more significant for EVA-rich blends with weaker interfacial interaction as compared to PE-rich blends. The morphological analysis indicated that the blend morphology was not affected obviously, whereas it was stabilized by irradiation.

Research paper thumbnail of Physical modification approaches to enhance cell supporting potential of poly (vinyl alcohol)‐based hydrogels

Journal of Applied Polymer Science, 2021

Research paper thumbnail of Switchable phase transition behavior of thermoresponsive substrates for cell sheet engineering

Journal of Polymer Science Part B: Polymer Physics, 2018

Recently, there are significant interests in the development of biomaterials with nonlinear respo... more Recently, there are significant interests in the development of biomaterials with nonlinear response to an external stimulus. Thermoresponsive polymers as a well-known class of stimuliresponsive materials represent reversible hydrophilicity/hydrophobicity characteristics around a critical temperature. This switchable behavior applies for nondestructive cellular detachment from cultivation substrates. In this study, poly (N-isopropylacrylamide) (PNIPAAm)-grafted dishes were made up to harvest retinal pigmented epithelial (RPE) and periodontal ligament cell (PDLC) sheets. Wettability assessments verified that all functionalized surfaces were inverted from hydrophilic to hydrophobic state when the temperature rises from lower critical solution temperature (LCST) at 37 C. Other physicochemical characteristics such as chemical composition, grafting thickness, and surface topography were investigated through attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and atomic force microscopy (AFM). ATR-FTIR results showed typical peaks of amide group corresponding to successful PNIPAAm polymerization. AFM microscopy results also proved creating a rough PNI-PAAm layer with thickness of 29.2 nm after grafting process in the mixture of methanol and water. Cell culture experiments showed an irreversible cellular attachment/detachment from modified surfaces upon temperature changes. These results introduced thermoresponsive TCPS to noninvasively harvest RPE and PDLCs sheets especially for application in scaffold-free tissue engineering decorations.

Research paper thumbnail of Irradiation processing to modify HDPE molecular architecture: Correlation with irradiation conditions and polymer grade

Materials Today Communications

Research paper thumbnail of Morphology, Rheology and Impact Resistance of PS/EOC/SEBS Ternary Blends

Eco-friendly and Smart Polymer Systems, 2020

Immiscible polystyrene (PS)/ethylene-octene copolymer (EOC) blends with different amounts of styr... more Immiscible polystyrene (PS)/ethylene-octene copolymer (EOC) blends with different amounts of styrene-ethylene-butylene-styrene copolymer (SEBS) as compatibilizer were prepared by melt mixing method and the morphology, rheology and impact resistance of the blend samples were investigated. The scanning electron microscopy (SEM) micrographs revealed that incorporation of SEBS into PS/EOC blend leads to change the shape of EOC dispersed phase from droplet to fibrillar. From the melt linear viscoelastic rheological studies, the interaction between SEBS and each of PS matrix and EOC dispersed phases in the ternary blends was confirmed. Moreover, the micelle formation of the compatibilizer in PS matrix phase of the ternary blends with relatively high amounts of SEBS was founded by the rheological analysis. The impact resistance of PS/EOC blend enhanced with increasing the SEBS quantity.

Research paper thumbnail of Study of High Energy Electron Beam Irradiation Dose Effects on Physical and Thermal Properties of PVA-Based Hydrogels

Polyvinyl alcohol (PVA) with the desired bio-properties and relatively low cost has attracted spe... more Polyvinyl alcohol (PVA) with the desired bio-properties and relatively low cost has attracted special interest to make hydrogels, especially with the wound dressing application. On the one hand, irradiation is an appropriate method to prepare hydrogels based on PVA. In this method, the irradiation conditions, especially the irradiation dose, influence significantly the physical properties and therefore affect the performance of the hydrogel. The main objective of this research was to investigate the effect of electron beam irradiation dose on the physical and thermal (crystallinity) properties of PVA hydrogels. The hydrogels were prepared by irradiation of the aqueous solution of PVA (7 wt.%) at different doses. The gel content, equilibrium swelling degree and dehydration behavior of the hydrogels were evaluated. The chemical structure changes of the PVA due to irradiation and thermal behavior of the dried PVA gels were probed respectively by FTIR and DCS experiments. In the wake of...

Research paper thumbnail of Effect of accelerator solubility on the curing characteristics and physico-mechanical properties of SBR/NBR blends: correlation with feeding sequence and blend composition

Polymer Bulletin, 2021

The main objective of this study was to investigate how the effect of accelerator solubility in t... more The main objective of this study was to investigate how the effect of accelerator solubility in the blend components on the curing characteristics and mechanical properties of blend and its components could be affected by the accelerator feeding sequence to the blend and the blend composition. For this purpose, the properties of styrene-butadiene copolymer rubber (SBR)/acrylonitrile-butadiene copolymer rubber (NBR) (50/50 and 75/25 wt%/wt%) blends cured using the sulfur curing system with only one of accelerators, zinc dibutyldithiocarbamate (ZDBC) and zinc diethyldithiocarbamate (ZDEC), or with a combination of them as well as the properties of the vulcanized components (SBR and NBR) were examined. The EDX results revealed that ZDBC and sulfur are more localized in the SBR phase of SBR/NBR blends, while ZDEC is more located in the NBR phase. The accelerators feeding sequence to the blend in the way that each accelerator was loaded in an appropriate elastomer phase in terms of solubility could improve the curing characteristics and tensile mechanical properties of the blend, especially for 50/50 blend with a co-continuous morphology.

Research paper thumbnail of Melt rheology and interfacial properties of binary and ternary blends of PS, EOC, and SEBS

Journal of Applied Polymer Science, 2019

This works systematically investigates the interfacial properties of the binary and the ternary b... more This works systematically investigates the interfacial properties of the binary and the ternary blends based on polystyrene (PS), ethylene octene copolymer (EOC), and styrene-ethylene-butylene-styrene (SEBS) by analyzing the melt linear rheological behavior of the blends and neat components. Moreover, the relationship between rheology, phase morphology, and mechanical properties of PS/EOC ternary blends with various quantities of SEBS were studied. The surface shear modulus (β) and interfacial tension values obtained by Palierne model indicated that the EOC/SEBS blend has the best interfacial properties, while the lowest interaction was found for PS/EOC blend. Based on the Palierne model and Harkin's spreading coefficients a core-shell type morphology with EOC phase encapsulated by the SEBS shell dispersed in the PS matrix was determined for the ternary blends. Scanning electron microscopy results revealed that both fibrillar and droplet forms of dispersed phase could be developed during the blending of PS and EOC in presence of SEBS. The extent of fibrillar morphology and interfacial interactions in PS/EOC/SEBS ternary blends was dependent on the SEBS content. The improvement of the mechanical properties of PS/EOC blends in the presence of SEBS was evidenced by the tensile and impact resistance experiments. The tensile strength reinforcement was more pronounced for the ternary blends with more fibrillar dispersed phase.

Research paper thumbnail of Assessment of compatibilization role of nanoclay in immiscible polystyrene/ethylene–octene copolymer blends via wide‐angle X‐ray scattering, microstructure, rheological analyses, and mechanical properties

Journal of Applied Polymer Science, 2019

Polystyrene (PS)/ethylene-octene copolymer (EOC) blends with 80/20 wt % composition containing di... more Polystyrene (PS)/ethylene-octene copolymer (EOC) blends with 80/20 wt % composition containing different amounts (0, 1.0, 2.5, 5.0 and 7.5 wt %) of an organically modified nanoclay were prepared by one-step melt-mixing method. Also, the EOC-rich blends with 80 wt % EOC content loaded with 0 and 5.0 wt % of the nanoclay were prepared under the similar processing conditions. Presence of both PS and EOC chains in between clay layers localized at the interface of the blends could be deduced by X-ray diffraction analysis, which suggested formation possibility of PS-EOC physical structures at the blend interface. Transmission electron microscopy results confirmed that clay nanoparticles were mainly localized at the interface of the blends and also partly in the PS and EOC components of the systems. The localization of the nanoclay was also described by the linear viscoelastic melt rheological studies. It is also revealed that nanoclay had stronger interactions with PS than EOC. This is reflected in the higher tensile properties in the PS-rich system. The analysis of morphology of the developed systems by emulsification curve revealed that the optimum amount of nanoclay to modify PS-rich blend is 2.5 wt %. At this clay loading, the blend exhibited the highest impact resistance. According to the overall results, suitability of nanoclay was confirmed for compatibilization of the PS/EOC blends.

Research paper thumbnail of On physical and antibacterial properties and drug release behavior of poly(vinyl alcohol) hydrogels: effect of drug loaded chitosan nanoparticles

Polymer-Plastics Technology and Materials, 2018

This paper deals with influence of chitosan nanoparticles (CNPs) loaded by tetracycline, as a dru... more This paper deals with influence of chitosan nanoparticles (CNPs) loaded by tetracycline, as a drug, on the physico-mechanical and antibacterial properties as well as drug release behavior of poly (vinyl alcohol), PVA, hydrogels prepared by electron beam irradiation. The formation of spherical chitosan particles in nanoscale size prepared by an ionic gelation method was confirmed by FTIR and UV spectroscopy, and scanning electron microscopy analyses. The drug release kinetic studies from drug loaded chitosan nanoparticles (DLCNPs) at pH = 7.4 revealed a linear and steady release behavior over long period of time. The theoretical analysis of the swelling kinetic data, using Peppas's model showed that the swelling kinetic is governed by Fickian diffusion for all the prepared hydrogels, however, the water diffusion coefficient, and therefore, the swelling content were lower for the hydrogels loaded with DLCNPs as compared to the ones with the neat drug. In agreement with these results, the hydrogels containing DLCNPs exhibited a more controlled drug release behavior with significantly stronger antibacterial activity. The tensile mechanical properties of the hydrogels not affected by the DLCNPs were found to be suitable for wound dressing applications.

Research paper thumbnail of Physicomechanical and antimicrobial characteristics of hydrogel based on poly(vinyl alcohol): Performance improvement via inclusion of chitosan-modified nanoclay

Journal of Applied Polymer Science, 2019

The effect of a chitosan-modified nanoclay (CMNC) on the physical, mechanical, and antimicrobial ... more The effect of a chitosan-modified nanoclay (CMNC) on the physical, mechanical, and antimicrobial properties of poly(vinyl alcohol) (PVA) hydrogels prepared by the electron beam irradiation method is reported in comparison with pristine nanoclay (PNC). The X-ray diffraction (XRD) results confirm that the chitosan modification process of nanoclay led to an enhancement in the clay gallery spacing. The inclusion of nanoclays in the PVA matrix decreased the gel content while it increased the swelling degree of the hydrogels. Both PNC and CMNC played a role, depending on their amounts, in swelling of the hydrogel. The swelling kinetic studies revealed a diffusion-controlled swelling process. The diffusion coefficient of water molecules in hydrogels was decreased in the presence of PNC, while it increased with CMNC. Rheological investigations verified the influential role of nanoclays in decreasing the chemical crosslink density of the hydrogel. CMNC exhibited a higher reinforcing effect on hydrogel mechanical properties than PNC did, although the rheological analysis, in agreement with the XRD results, indicated a better dispersion of PNC in the PVA matrix. According to the antimicrobial tests, perfect inhibition of bacteria growth was obtained only for the hydrogels with CMNC.

Research paper thumbnail of Morphology, drug release behavior, thermal, and mechanical properties of poly(ethylene oxide) (PEO)/poly(vinyl pyrrolidone) (PVP) blends

Journal of Applied Polymer Science, 2018

Poly(ethylene oxide) (PEO)/poly(vinyl pyrrolidone) (PVP) blends containing different amounts of P... more Poly(ethylene oxide) (PEO)/poly(vinyl pyrrolidone) (PVP) blends containing different amounts of PVP (0, 10, 25, 50, and 100 wt %) prepared by a solution casting method were characterized in terms of microstructure, thermal, and mechanical properties along with their drug release behavior. Fourier-transform infrared spectroscopy results confirmed formation of hydrogen bonds between PEO and PVP. Although scanning electron microscopy micrographs showed no phase separation in the blends, the elemental analysis data obtained by energy dispersive X-ray technique revealed partial miscibility between the blend components. The miscibility of the blend and degree of crystallinity of PEO component of the blend were decreased with increasing PVP content of the blend. The nucleating role of PVP in crystallization of PEO was confirmed by differential scanning calorimetry analysis. A synergistic effect on mechanical properties was obtained as a result of blending PVP with PEO. The results of curcumin release studies from the films indicated that, the blends have lower diffusion coefficients and slower drug release rate as compared to the neat PEO. Theoretical analysis of the drug release data using Peppas's model revealed that the kinetic of drug release from all the films is governed by a non-Fickian diffusion mechanism.

Research paper thumbnail of Molecular and thermo-mechanical assessment of long-chain branched polypropylene: Effect of irradiation dose, multifunctional monomer content and molecular weight

Radiation Physics and Chemistry

Research paper thumbnail of A Model of Mechanotransduction in Polyvinyl Alcohol‐Based Composite Hydrogels for Regulating Musculoskeletal Differentiation

Macromolecular Materials and Engineering

In regenerative medicine, extracellular matrix (ECM)‐inspired materials are currently being explo... more In regenerative medicine, extracellular matrix (ECM)‐inspired materials are currently being explored to imitate mechanotransduction pathways and control cell fate. In musculoskeletal tissue regeneration, enhancing mechano‐biological signals require biomaterials that are both biocompatible and viscoelastic and can retain water content. Herein, based on these requirements, various polyvinyl alcohol (PVA)‐based composite hydrogels, reinforced by polyhydroxy butyrate (PHB) nanofibers, are proposed to differentiate equine adipose‐derived stem cells for musculoskeletal regeneration. To study the role of fiber embedding in improving scaffold properties, different nanofiber assemblies, including chopped short ones with random orientation (PVAS), single‐layer (PVAL1), and double‐layer membranes (PVAL2) are positioned into the PVA matrix. PHB reinforcements negatively affect swelling and positively enhanced phase transition temperatures and crystallinity of PVA hydrogel. According to mechanic...

Research paper thumbnail of Physical and drug release characteristics of nanoliposomes modified poly(vinyl alcohol) (PVA)/poly(ethylene glycol) (PEG) hydrogels

The main objective of this research is to investigate how curcumin liposomal nanocarriers influen... more The main objective of this research is to investigate how curcumin liposomal nanocarriers influence the drug release behaviour of PVA/PEG hydrogels in relation to physico-mechanical properties. For this purpose, optimal nanoliposomes from drug loading and release viewpoints, prepared by the thin-film hydration method, were incorporated into the hydrogel composition. Hydrogel samples were physically crosslinked using the freeze-thaw procedure. According to the atomic force microscopy and field-emission scanning electron microscopy observations, nanoliposomes showed a spherical morphology with an average particle size of 100 nm and narrow size distribution. The X-ray diffraction results revealed that adding nanoliposomes to the hydrogel increases the degree of PVA chains crystallinity, enhances tensile modulus and tensile strength of the hydrogel, while decreasing swelling and dehydration rates. SEM micrographs observation displayed that the porosity in the hydrogel structure in the p...

Research paper thumbnail of Irradiation processing of immiscible PP/EOC blend: Morphology control and processability modification

Journal of Applied Polymer Science, 2020

In this study, applying electron beam irradiation method at a relatively low‐irradiation dose (20... more In this study, applying electron beam irradiation method at a relatively low‐irradiation dose (20 kGy) under the air atmosphere to prepare injectable polypropylene (PP)/ethylene‐octene copolymer (EOC) blends with fine morphology and appropriate performance was investigated. For this purpose, an extrusion PP grade with an EOC grade suitable to improve its impact resistance was melting blended. Gel content and rheological measurements revealed long‐chain branching is predominant phenomenon occurring during the irradiation process of EOC. Blend irradiation resulted in changing its melt flow index proper for injection molding. A fine morphology obtained for the unirradiated blend was preserved for the irradiated blend. Moreover, irradiation thermally stabilized the blend morphology. Blends linear viscoelastic behavior discussed by proper rheological models revealed the existence of interfacial interactions and a reduction of the interfacial tension between irradiated blend phases. No si...

Research paper thumbnail of Mechanical properties and drug release rate of poly(vinyl alcohol)/poly(ethylene glycol)/clay nanocomposite hydrogels: Correlation with structure and physical properties

Journal of Applied Polymer Science, 2019

ABSTRACTPoly(vinyl alcohol)/poly(ethylene glycol) hydrogels containing curcumin as a drug and the... more ABSTRACTPoly(vinyl alcohol)/poly(ethylene glycol) hydrogels containing curcumin as a drug and the various amounts of a montmorillonite nanoclay are prepared using the freezing–thawing method. Nanoclay quantity influence on the physicomechanical properties and the drug release rate of the hydrogel as well as relationship between them is investigated. X‐Ray diffraction and Atomic force microscopy analysis reveal the nanoclays have an intercalation structure in the hydrogel, and the hydrogel crystallization decreases with increasing the nanoclay inclusion. From the SEM micrographs observation, it was revealed that due to the presence of the nanoclay in the hydrogel, its porosity decreased. The naonoclay has an amount‐depended dual effect on the hydrogel swelling. The swelling mechanism is a normal Fickian diffusion for all the hydrogel samples. Strong physical interactions between the nanoclays and the polymer chains in the nanocomposite hydrogels are evidenced by the rheological studi...

Research paper thumbnail of Mechanical and water absorption properties of municipal solid waste and banana fiber-reinforced urea formaldehyde composites

Environmental Progress & Sustainable Energy, 2014

In this study, hybrid composites of municipal solid waste (MSW)/banana fiber reinforced urea form... more In this study, hybrid composites of municipal solid waste (MSW)/banana fiber reinforced urea formaldehyde were prepared in different filler ratio. Mechanical properties such as tensile, flexural, and impact strengths were investigated as a function of total volume fraction (Vf) of filler (MSW and banana fiber), relative volume fraction of MSW and banana fiber and its chemical modification. The mechanical properties were found to be high at 40% Vf of filler which indicates effective stress transfer between fiber and matrix. Then, composites with different volume ratios of MSW and banana fiber (100:0, 75:25, 50:50, 25:75, 0:100) are prepared by keeping total Vf of filler as 40%. It is observed that addition of banana fiber imparts better mechanical and thermal stability properties to composites. Also, banana fiber addition increased the water absorption properties of composites. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 211–221, 2015

Research paper thumbnail of Electron beam irradiation method to change polypropylene application: Rheology and thermomechanical properties

Irradiation of polymers is one of the most effective and economical methods for modifying their p... more Irradiation of polymers is one of the most effective and economical methods for modifying their properties and for changing their applications. In this study, an extrusion grade polypropylene (PP) was treated by electron beam irradiation to produce a PP suitable for injection molding. Irradiation was carried out at different doses (0-80 kGy) under atmosphere air and at ambient temperature. Melt flow index (MFI) measurements showed PP samples irradiated in the range of 10 to 40 kGy are suitable to use in injection molding. Electron beam irradiation decreased the viscosity and the shear thinning rheological behavior of PP. The differential scanning calorimetry (DSC) analysis revealed that electron beam irradiation increased the crystallinity percentage and temperature of PP, but decreased the melting temperature. Among all treated samples, the PP20, irradiated at the dose of 20 kGy, showed the highest impact resistance. It had higher Young’s modulus and tensile strength, but lower elo...

Research paper thumbnail of Liposomal Nanocarriers-Loaded Poly(vinyl alcohol) (PVA)/Poly(ethylene glycol) (PEG) Hydrogels: Physico-mechanical Properties and Drug Release

Journal of Polymers and the Environment

Research paper thumbnail of Electron beam irradiation induced compatibilization of immiscible polyethylene/ethylene vinyl acetate (PE/EVA) blends: Mechanical properties and morphology stability

Radiation Physics and Chemistry, 2017

Gel content, mechanical properties and morphology of immiscible PE/EVA blends irradiated by high ... more Gel content, mechanical properties and morphology of immiscible PE/EVA blends irradiated by high energy electron beam were studied. The results of gel content measurements showed that the capability of cross-linking of the blend samples increased with an increase of the EVA composition. Also, the gel content for most compositions of the blends displayed a positive deviation from the additive rule. The results of mechanical properties showed that the tensile strength and elongation at break of the samples increased and decreased, respectively, with irradiation dose. On the other hand, the mechanical properties of the irradiated blends also depicted a positive deviation from additive rule contrary to the un-irradiated blends. A synergistic effect observed for the mechanical properties improvement of the irradiated blends and it was attributed to the probable formation of the PE-graft-EVA copolymers at the interface of the blends during the irradiation process. A theoretical analysis revealed that irradiation induced synergistic effect was more significant for EVA-rich blends with weaker interfacial interaction as compared to PE-rich blends. The morphological analysis indicated that the blend morphology was not affected obviously, whereas it was stabilized by irradiation.

Research paper thumbnail of Physical modification approaches to enhance cell supporting potential of poly (vinyl alcohol)‐based hydrogels

Journal of Applied Polymer Science, 2021

Research paper thumbnail of Switchable phase transition behavior of thermoresponsive substrates for cell sheet engineering

Journal of Polymer Science Part B: Polymer Physics, 2018

Recently, there are significant interests in the development of biomaterials with nonlinear respo... more Recently, there are significant interests in the development of biomaterials with nonlinear response to an external stimulus. Thermoresponsive polymers as a well-known class of stimuliresponsive materials represent reversible hydrophilicity/hydrophobicity characteristics around a critical temperature. This switchable behavior applies for nondestructive cellular detachment from cultivation substrates. In this study, poly (N-isopropylacrylamide) (PNIPAAm)-grafted dishes were made up to harvest retinal pigmented epithelial (RPE) and periodontal ligament cell (PDLC) sheets. Wettability assessments verified that all functionalized surfaces were inverted from hydrophilic to hydrophobic state when the temperature rises from lower critical solution temperature (LCST) at 37 C. Other physicochemical characteristics such as chemical composition, grafting thickness, and surface topography were investigated through attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and atomic force microscopy (AFM). ATR-FTIR results showed typical peaks of amide group corresponding to successful PNIPAAm polymerization. AFM microscopy results also proved creating a rough PNI-PAAm layer with thickness of 29.2 nm after grafting process in the mixture of methanol and water. Cell culture experiments showed an irreversible cellular attachment/detachment from modified surfaces upon temperature changes. These results introduced thermoresponsive TCPS to noninvasively harvest RPE and PDLCs sheets especially for application in scaffold-free tissue engineering decorations.

Research paper thumbnail of Irradiation processing to modify HDPE molecular architecture: Correlation with irradiation conditions and polymer grade

Materials Today Communications

Research paper thumbnail of Morphology, Rheology and Impact Resistance of PS/EOC/SEBS Ternary Blends

Eco-friendly and Smart Polymer Systems, 2020

Immiscible polystyrene (PS)/ethylene-octene copolymer (EOC) blends with different amounts of styr... more Immiscible polystyrene (PS)/ethylene-octene copolymer (EOC) blends with different amounts of styrene-ethylene-butylene-styrene copolymer (SEBS) as compatibilizer were prepared by melt mixing method and the morphology, rheology and impact resistance of the blend samples were investigated. The scanning electron microscopy (SEM) micrographs revealed that incorporation of SEBS into PS/EOC blend leads to change the shape of EOC dispersed phase from droplet to fibrillar. From the melt linear viscoelastic rheological studies, the interaction between SEBS and each of PS matrix and EOC dispersed phases in the ternary blends was confirmed. Moreover, the micelle formation of the compatibilizer in PS matrix phase of the ternary blends with relatively high amounts of SEBS was founded by the rheological analysis. The impact resistance of PS/EOC blend enhanced with increasing the SEBS quantity.

Research paper thumbnail of Study of High Energy Electron Beam Irradiation Dose Effects on Physical and Thermal Properties of PVA-Based Hydrogels

Polyvinyl alcohol (PVA) with the desired bio-properties and relatively low cost has attracted spe... more Polyvinyl alcohol (PVA) with the desired bio-properties and relatively low cost has attracted special interest to make hydrogels, especially with the wound dressing application. On the one hand, irradiation is an appropriate method to prepare hydrogels based on PVA. In this method, the irradiation conditions, especially the irradiation dose, influence significantly the physical properties and therefore affect the performance of the hydrogel. The main objective of this research was to investigate the effect of electron beam irradiation dose on the physical and thermal (crystallinity) properties of PVA hydrogels. The hydrogels were prepared by irradiation of the aqueous solution of PVA (7 wt.%) at different doses. The gel content, equilibrium swelling degree and dehydration behavior of the hydrogels were evaluated. The chemical structure changes of the PVA due to irradiation and thermal behavior of the dried PVA gels were probed respectively by FTIR and DCS experiments. In the wake of...

Research paper thumbnail of Effect of accelerator solubility on the curing characteristics and physico-mechanical properties of SBR/NBR blends: correlation with feeding sequence and blend composition

Polymer Bulletin, 2021

The main objective of this study was to investigate how the effect of accelerator solubility in t... more The main objective of this study was to investigate how the effect of accelerator solubility in the blend components on the curing characteristics and mechanical properties of blend and its components could be affected by the accelerator feeding sequence to the blend and the blend composition. For this purpose, the properties of styrene-butadiene copolymer rubber (SBR)/acrylonitrile-butadiene copolymer rubber (NBR) (50/50 and 75/25 wt%/wt%) blends cured using the sulfur curing system with only one of accelerators, zinc dibutyldithiocarbamate (ZDBC) and zinc diethyldithiocarbamate (ZDEC), or with a combination of them as well as the properties of the vulcanized components (SBR and NBR) were examined. The EDX results revealed that ZDBC and sulfur are more localized in the SBR phase of SBR/NBR blends, while ZDEC is more located in the NBR phase. The accelerators feeding sequence to the blend in the way that each accelerator was loaded in an appropriate elastomer phase in terms of solubility could improve the curing characteristics and tensile mechanical properties of the blend, especially for 50/50 blend with a co-continuous morphology.

Research paper thumbnail of Melt rheology and interfacial properties of binary and ternary blends of PS, EOC, and SEBS

Journal of Applied Polymer Science, 2019

This works systematically investigates the interfacial properties of the binary and the ternary b... more This works systematically investigates the interfacial properties of the binary and the ternary blends based on polystyrene (PS), ethylene octene copolymer (EOC), and styrene-ethylene-butylene-styrene (SEBS) by analyzing the melt linear rheological behavior of the blends and neat components. Moreover, the relationship between rheology, phase morphology, and mechanical properties of PS/EOC ternary blends with various quantities of SEBS were studied. The surface shear modulus (β) and interfacial tension values obtained by Palierne model indicated that the EOC/SEBS blend has the best interfacial properties, while the lowest interaction was found for PS/EOC blend. Based on the Palierne model and Harkin's spreading coefficients a core-shell type morphology with EOC phase encapsulated by the SEBS shell dispersed in the PS matrix was determined for the ternary blends. Scanning electron microscopy results revealed that both fibrillar and droplet forms of dispersed phase could be developed during the blending of PS and EOC in presence of SEBS. The extent of fibrillar morphology and interfacial interactions in PS/EOC/SEBS ternary blends was dependent on the SEBS content. The improvement of the mechanical properties of PS/EOC blends in the presence of SEBS was evidenced by the tensile and impact resistance experiments. The tensile strength reinforcement was more pronounced for the ternary blends with more fibrillar dispersed phase.

Research paper thumbnail of Assessment of compatibilization role of nanoclay in immiscible polystyrene/ethylene–octene copolymer blends via wide‐angle X‐ray scattering, microstructure, rheological analyses, and mechanical properties

Journal of Applied Polymer Science, 2019

Polystyrene (PS)/ethylene-octene copolymer (EOC) blends with 80/20 wt % composition containing di... more Polystyrene (PS)/ethylene-octene copolymer (EOC) blends with 80/20 wt % composition containing different amounts (0, 1.0, 2.5, 5.0 and 7.5 wt %) of an organically modified nanoclay were prepared by one-step melt-mixing method. Also, the EOC-rich blends with 80 wt % EOC content loaded with 0 and 5.0 wt % of the nanoclay were prepared under the similar processing conditions. Presence of both PS and EOC chains in between clay layers localized at the interface of the blends could be deduced by X-ray diffraction analysis, which suggested formation possibility of PS-EOC physical structures at the blend interface. Transmission electron microscopy results confirmed that clay nanoparticles were mainly localized at the interface of the blends and also partly in the PS and EOC components of the systems. The localization of the nanoclay was also described by the linear viscoelastic melt rheological studies. It is also revealed that nanoclay had stronger interactions with PS than EOC. This is reflected in the higher tensile properties in the PS-rich system. The analysis of morphology of the developed systems by emulsification curve revealed that the optimum amount of nanoclay to modify PS-rich blend is 2.5 wt %. At this clay loading, the blend exhibited the highest impact resistance. According to the overall results, suitability of nanoclay was confirmed for compatibilization of the PS/EOC blends.

Research paper thumbnail of On physical and antibacterial properties and drug release behavior of poly(vinyl alcohol) hydrogels: effect of drug loaded chitosan nanoparticles

Polymer-Plastics Technology and Materials, 2018

This paper deals with influence of chitosan nanoparticles (CNPs) loaded by tetracycline, as a dru... more This paper deals with influence of chitosan nanoparticles (CNPs) loaded by tetracycline, as a drug, on the physico-mechanical and antibacterial properties as well as drug release behavior of poly (vinyl alcohol), PVA, hydrogels prepared by electron beam irradiation. The formation of spherical chitosan particles in nanoscale size prepared by an ionic gelation method was confirmed by FTIR and UV spectroscopy, and scanning electron microscopy analyses. The drug release kinetic studies from drug loaded chitosan nanoparticles (DLCNPs) at pH = 7.4 revealed a linear and steady release behavior over long period of time. The theoretical analysis of the swelling kinetic data, using Peppas's model showed that the swelling kinetic is governed by Fickian diffusion for all the prepared hydrogels, however, the water diffusion coefficient, and therefore, the swelling content were lower for the hydrogels loaded with DLCNPs as compared to the ones with the neat drug. In agreement with these results, the hydrogels containing DLCNPs exhibited a more controlled drug release behavior with significantly stronger antibacterial activity. The tensile mechanical properties of the hydrogels not affected by the DLCNPs were found to be suitable for wound dressing applications.

Research paper thumbnail of Physicomechanical and antimicrobial characteristics of hydrogel based on poly(vinyl alcohol): Performance improvement via inclusion of chitosan-modified nanoclay

Journal of Applied Polymer Science, 2019

The effect of a chitosan-modified nanoclay (CMNC) on the physical, mechanical, and antimicrobial ... more The effect of a chitosan-modified nanoclay (CMNC) on the physical, mechanical, and antimicrobial properties of poly(vinyl alcohol) (PVA) hydrogels prepared by the electron beam irradiation method is reported in comparison with pristine nanoclay (PNC). The X-ray diffraction (XRD) results confirm that the chitosan modification process of nanoclay led to an enhancement in the clay gallery spacing. The inclusion of nanoclays in the PVA matrix decreased the gel content while it increased the swelling degree of the hydrogels. Both PNC and CMNC played a role, depending on their amounts, in swelling of the hydrogel. The swelling kinetic studies revealed a diffusion-controlled swelling process. The diffusion coefficient of water molecules in hydrogels was decreased in the presence of PNC, while it increased with CMNC. Rheological investigations verified the influential role of nanoclays in decreasing the chemical crosslink density of the hydrogel. CMNC exhibited a higher reinforcing effect on hydrogel mechanical properties than PNC did, although the rheological analysis, in agreement with the XRD results, indicated a better dispersion of PNC in the PVA matrix. According to the antimicrobial tests, perfect inhibition of bacteria growth was obtained only for the hydrogels with CMNC.

Research paper thumbnail of Morphology, drug release behavior, thermal, and mechanical properties of poly(ethylene oxide) (PEO)/poly(vinyl pyrrolidone) (PVP) blends

Journal of Applied Polymer Science, 2018

Poly(ethylene oxide) (PEO)/poly(vinyl pyrrolidone) (PVP) blends containing different amounts of P... more Poly(ethylene oxide) (PEO)/poly(vinyl pyrrolidone) (PVP) blends containing different amounts of PVP (0, 10, 25, 50, and 100 wt %) prepared by a solution casting method were characterized in terms of microstructure, thermal, and mechanical properties along with their drug release behavior. Fourier-transform infrared spectroscopy results confirmed formation of hydrogen bonds between PEO and PVP. Although scanning electron microscopy micrographs showed no phase separation in the blends, the elemental analysis data obtained by energy dispersive X-ray technique revealed partial miscibility between the blend components. The miscibility of the blend and degree of crystallinity of PEO component of the blend were decreased with increasing PVP content of the blend. The nucleating role of PVP in crystallization of PEO was confirmed by differential scanning calorimetry analysis. A synergistic effect on mechanical properties was obtained as a result of blending PVP with PEO. The results of curcumin release studies from the films indicated that, the blends have lower diffusion coefficients and slower drug release rate as compared to the neat PEO. Theoretical analysis of the drug release data using Peppas's model revealed that the kinetic of drug release from all the films is governed by a non-Fickian diffusion mechanism.