Miklos Zrinyi - Academia.edu (original) (raw)

Papers by Miklos Zrinyi

Springer eBooks, 1988

Elastic and swelling properties of chemically crosslinked poly (vinyl acetate) gel homologues swo... more Elastic and swelling properties of chemically crosslinked poly (vinyl acetate) gel homologues swollen by good and θ-diluents were studied. Deswelling was induced by unidirectional compression of the gels, on the one hand, and by lowering the chemical potential of the diluent in the surrounding liquid phase, on the other. An attempt was made to take into account the effect of unidirectional deformation on the equilibrium concentration of the gel. The results were compared with experimental findings. Satisfactory agreement was found both in good and θ-diluents. The equivalence of the response of the network to istropic shrinking and to unidirectional compression was confirmed experimentally.

Die makromolekulare Chemie, Nov 1, 1993

The ratio of t h e shear modulus over t h e longitudinal osmotic modulus has been determined by d... more The ratio of t h e shear modulus over t h e longitudinal osmotic modulus has been determined by different experimental methods. Osmotic deswelling, swelling kinetics as well a s deswelling induced by unidirectional compression were performed. For t h e experiments chemically cross-linked poly(viny1 acetate) gels swollen in toluene and acetone (good solvents) and iso-propyl alcohol(poor solvent) have been used. The results are in agreement with t h e theoretical predictions.

Springer proceedings in physics, 1989

Die makromolekulare Chemie, Oct 1, 1989

Many experiments show t h a t t h e second Mooney-Rivlin coefficient disappears f o r highly swol... more Many experiments show t h a t t h e second Mooney-Rivlin coefficient disappears f o r highly swollen chemically cross-linked gels. Hence we are led to a paradox: Highly swollen gels seem to behave phenomenologically like phantom networks. Due t o t h e finite extensibility of network chains, entanglements and excluded volume effects, one should-o n t h e contrary-expect non-Gaussian behaviour. O n t h e basis of t h e phenomenological van der Waals equation of s t a t e , we have concluded t h a t t h e virtual ideality of highly swollen gels is t h e consequence of a compensation between global interactions and excluded volume effects.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, Mar 1, 1996

The aggregation and spreading of silanized glass microspheres (diameter: 62–74 μm) were investiga... more The aggregation and spreading of silanized glass microspheres (diameter: 62–74 μm) were investigated at water (electrolyte)-fluid interfaces by evaporating hexane or chloroform from the water surface. Redispersion of aggregates was attributed to non-equilibrium interfacial tension at the water-fluid interface in the final stage of evaporation. The effect of particle wettability on this phenomenon was studied. Two different hydrophobic samples (Sample A: Θwater/air=77 ± 1°; Sample B: Θwater/air=44 ±1°) were prepared for experiments. Two-liquid wettability of particles was also characterized by contact angles (Sample A: Θwaterhexane = 100 ± 4°; Sample B: Θwaterhexane= 57 ± 3°) by means of which the colloid and capillary pair-potential energies have been calculated. In every case the aggregation yielded well-packed aggregates at the water-organic liquid interface, but spreading experiments showed that while the aggregate of the lower hydrophobic sample could disperse into little clusters or single particles, the higher hydrophobic particles remained together in the final stage of organic liquid evaporation. The speed and extent of redispersion of the lower hydrophobic sample were found to be dependent on the spreading liquids (hexane or chloroform), but the electrolyte (KCl) content of the subphase could not influence the process. The aggregates of higher hydrophobic particles could be redispersed in neither case investigated. It was proposed, on the basis of the calculated interparticle energies, that the higher hydrophobic particles could come into direct contact during the organic liquid evaporation due to the strong “immersion-type” capillary and hydrophobic attractive interactions. We characterized the dispersing ability of the spreading liquids used by a parameter (“dispersing energy”: 25.1 mN m−1 for hexane; 46.8 mN m−1 for chloroform) which could be calculated from a supposed interfacial tension difference at the water-air interface arising during the final stage of organic liquid evaporation. These values were compared with the “pull-off energy” (≈90 mN m−1) obtained earlier for silanized glass surfaces [J.L. Parker and P.M. Claesson, Langmuir, 10 (1994) 635]. The results confirmed the above suggestion that hydrophobic spheres (Sample A) can reach a situation in which the strong adhesion between them can hinder their redispersion and, furthermore, made it reasonable to assume that the aggregates of lower hydrophobic particles (Sample B) could be redispersed better if chloroform was used as spreading liquid.

Polymers for Advanced Technologies, 2003

Measurements are reported on the swelling behaviour at 20°C of poly (N‐isopropylacrylamide) (PNIP... more Measurements are reported on the swelling behaviour at 20°C of poly (N‐isopropylacrylamide) (PNIPA) gels in aqueous solutions of two weak aromatic acids, phenol and resorcinol. For solute concentrations below 45 mmol/l, the uptake of these solutions is similar. Phenol exhibits an excess equilibrium concentration inside the gel of 5% over that in the surrounding bath, while for resorcinol, the excess is found to be 12%. At 50 mmol/l solute concentration, both systems display a volume transition accompanied by expulsion of the solvent. The solubility limits in water of these aromatic compounds are significantly different (870 and 9080 mmol/l, respectively), and are far above this critical concentration. In the collapsed condition, the expelled liquid spreads on the surface of the phenol‐treated gel, while an ordered arrangement of separate droplets is generated in the case of resorcinol. In the latter case, an acute contact angle was observed. Copyright © 2003 John Wiley & Sons, Ltd.

Polymer, 1993

Measurements are made of the osmotic swelling pressure and small angle X-ray scattering from ligh... more Measurements are made of the osmotic swelling pressure and small angle X-ray scattering from lightly crosslinked poly(vinyl acetate) (PVAc) gels swollen in toluene and containing known amounts of free PVAc chains. Gels with different amounts of free chains, but with identical total ...

Polymer, 1991

An investigation is reported of the elastic and osmotic propemes of end-linked polydimethyl silox... more An investigation is reported of the elastic and osmotic propemes of end-linked polydimethyl siloxane networks swollen in toluene. These were prepared both in the presence and in the absence of silica filler particles. A comparison is made between the values of the elastic moduli of the unfilled gels, obtained by uniaxial compression experiments and from the concentration dependence of the swelling pressure respectively. For all the gels studied, the elastic modulus was found to vary with polymer volume fraction q) as ~o 1/3. The osmotic behaviour can be described by a power law relation in agreement with scaling theory, but cannot be interpreted in a consistent manner by using the osmotic pressure data relevant to the uncrosslinked polymer. For the filled gels, the neutral filler particles produce a reinforcement of the elastic modulus. The concentration dependence of the swelling pressure is affected mainly through the volume occupied by the filler in the network.

The Journal of Chemical Physics, 1997

Unidirectional elongation of magnetic field sensitive polymer gels, called ferrogels, have been s... more Unidirectional elongation of magnetic field sensitive polymer gels, called ferrogels, have been studied. In ferrogels, finely distributed colloidal particles having superparamagnetic behavior are incorporated into a swollen network. These particles couple the shape of the gel to the nonuniform magnetic field. Shape distortion occurs instantaneously and disappears when the external field is removed. A discontinuous elongation and contraction in response to infinite-small change in the external magnetic field has been observed and a theoretical interpretation based on coupled magnetic and rubber elastic properties is provided.

The Journal of Chemical Physics, 1997

Different structure-analyzing methods were applied to experimental and computer generated two-dim... more Different structure-analyzing methods were applied to experimental and computer generated two-dimensional clusters. The real structures formed at water–air interfaces from polydisperse, cylindrical-shape carbon (thickness: 35 μm; average length: 140 μm) and close to monodisperse, spherical-shape glass (75 μm diam) microparticles. The clusters were characterized by the fractal dimension (Df) and the surface coverage (q) values in the case of individual clusters. For a series of different sized aggregates, the fractal dimension (Df) was also evaluated from the ln q versus ln Rg functions where Rg is the radius of gyration. The fractal dimensions for individual clusters determined by box counting, sand box, and by correlation function methods, were compared with each other and with those obtained for the series of clusters. Using the above methods, the aggregation of cylindrical carbon and spherical glass particles was studied from a structural point of view. The surface of glass beads...

Fractals, 1993

Interfacial aggregation of surface modified glass beads (62–74 μm diameter) at water/air interfac... more Interfacial aggregation of surface modified glass beads (62–74 μm diameter) at water/air interface was carried out by using two differently hydrophobic samples, respectively. The effect of aggregation time on the self-similar structure of forming aggregates was studied comparing the actual results to those obtained previously.1 The time dependence of restructuring from the point of view of fractal geometry has been proved but the results call attention to another time dependent process— orientation of growing clusters during their collisions due to anisotropy of cluster-cluster interactions.

Colloids and Surfaces, 1991

Abstract Two-dimensional aggregation of surface-modified glass beads was carried out in the bound... more Abstract Two-dimensional aggregation of surface-modified glass beads was carried out in the boundary layer of water—air phases. The effect of the hydrophobicity of the beads on the structure of forming aggregates and on the growth process was investigated. The structure of the aggregates and their growth were characterized by a density function which expresses the change of mean density of the aggregates as a function of size. The growth yielded fractal or non-fractal structures in the systems studied. The fractal structure of the aggregates was dependent on restructuring processes controlled by the surface properties of the beads.

Beilstein Journal of Nanotechnology, 2019

Polymer hydrogels are ideal scaffolds for both tissue engineering and drug delivery. A great adva... more Polymer hydrogels are ideal scaffolds for both tissue engineering and drug delivery. A great advantage of poly(amino acid)-based hydrogels is their high similarity to natural proteins. However, their expensive and complicated synthesis often limits their application. The use of poly(aspartic acid) (PASP) seems an appropriate solution for this problem due to the relatively cheap and simple synthesis of PASP. Using amino acids not only as building blocks in the polymer backbone but also as cross-linkers can improve the biocompatibility and the biodegradability of the hydrogel. In this paper, PASP cross-linked with cystamine (CYS) and lysine-methylester (LYS) was introduced as fully amino acid-based polymer hydrogel. Gels were synthesized employing six different ratios of CYS and LYS. The pH dependent swelling degree and the concentration of the elastically active chain were determined. After reduction of the disulfide bonds of CYS, the presence of thiol side groups was also detected. ...

Journal of Nanomaterials, 2017

The size effect of magnetomechanical response of chemically cross-linked disk shaped magnetic ela... more The size effect of magnetomechanical response of chemically cross-linked disk shaped magnetic elastomers placed on a permanent magnet has been investigated by unidirectional compression tests. A cylindrical permanent magnet with a size of 35 mm in diameter and 15 mm in height was used to create the magnetic field. The magnetic field strength was approximately 420 mT at the center of the upper surface of the magnet. The diameter of the magnetoelastic polymer disks was varied from 14 mm to 35 mm, whereas the height was kept constant (5 mm) in the undeformed state. We have studied the influence of the disk diameter on the stress-strain behavior of the magnetoelastic in the presence and in the lack of magnetic field. It was found that the smallest magnetic elastomer with 14 mm diameter did not exhibit measurable magnetomechanical response due to magnetic field. On the opposite, the magnetic elastomers with diameters larger than 30 mm contracted in the direction parallel to the mechanica...

Periodica Polytechnica Chemical Engineering, 2000

Rheological properties of materials are related to their response to applied stress. The field in... more Rheological properties of materials are related to their response to applied stress. The field induced chain formation of a large number of organic and inorganic substances such as starch, aluminium oxide, ferric oxide, carbon black, ion-exchange resins, and polymer powders have been studied mainly in insulating oils. Much less is studied and understood the clectrorheological effect of pigments in polymer dispersions. Titanium dioxide is one of the most frequently used surface coatings due to its highquality and ecologically acceptable properties. In the present paper the authors first review the basic principle ofclectrorheology. then it is followed by experimental studies on structuring and rheological properties.

Scientific Reports, 2019

This paper presents the results of unidirectional strain-controlled experiments on fibrous electr... more This paper presents the results of unidirectional strain-controlled experiments on fibrous electrospun networks used to study damage formation during elongation. The experimental loading curve shows a symmetrical parabolic type dependence at large scale and saw tooth-like force−extension behaviour at small scale. The damage formation was quantified by determining the number and the magnitude of abrupt force drops. The experiments evidenced that damage evolution is a consequence of strain induced random events. The frequency distribution of the number of damages as well as the magnitude of rupture force were represented by histograms. The results of the present study provide a better insight into damage tolerance and complex nonlinear tensile properties of electrospun networks. In addition, it could suggest a possible probabilistic approach to the fiber bundle model which has mainly motivated this study.

Magyar Kémiai Folyóirat, 2018

Periodica Polytechnica Chemical Engineering, 2017

We have presented the first direct observation of electric field induced rotation of epoxy based ... more We have presented the first direct observation of electric field induced rotation of epoxy based polymer rotors. Polymer disks and gears were prepared in few micrometer dimensions as rotors. Electrorotation of these sub-millimeter sized tools was studied under uniform DC electric field. The rotational speed of micron-sized polymer rotors can be conveniently tuned in wide range (between 300 – 3000 rpm) by the DC electric field intensity, opening new perspectives for their use in micro electric motor applications.

Smart Materials and Structures, 2015

We have presented the first direct observation of electric field induced rotation of epoxy based ... more We have presented the first direct observation of electric field induced rotation of epoxy based polymer rotors. Polymer disks, hollow cylinders and gears were prepared in few micrometer dimensions as rotors. Electrorotation of these sub-millimeter sized tools was studied under uniform DC electric field. The effects of shape, size and thickness were investigated. The novel epoxy based micro devices show intensive spinning in uniform DC electric field. The rotational speed of micron-sized polymer rotors can be conveniently tuned in wide range (between 300-3000 rpm) by the electric field intensity, opening new perspectives for their use in several MEMS applications.

Springer eBooks, 1988

Elastic and swelling properties of chemically crosslinked poly (vinyl acetate) gel homologues swo... more Elastic and swelling properties of chemically crosslinked poly (vinyl acetate) gel homologues swollen by good and θ-diluents were studied. Deswelling was induced by unidirectional compression of the gels, on the one hand, and by lowering the chemical potential of the diluent in the surrounding liquid phase, on the other. An attempt was made to take into account the effect of unidirectional deformation on the equilibrium concentration of the gel. The results were compared with experimental findings. Satisfactory agreement was found both in good and θ-diluents. The equivalence of the response of the network to istropic shrinking and to unidirectional compression was confirmed experimentally.

Die makromolekulare Chemie, Nov 1, 1993

The ratio of t h e shear modulus over t h e longitudinal osmotic modulus has been determined by d... more The ratio of t h e shear modulus over t h e longitudinal osmotic modulus has been determined by different experimental methods. Osmotic deswelling, swelling kinetics as well a s deswelling induced by unidirectional compression were performed. For t h e experiments chemically cross-linked poly(viny1 acetate) gels swollen in toluene and acetone (good solvents) and iso-propyl alcohol(poor solvent) have been used. The results are in agreement with t h e theoretical predictions.

Springer proceedings in physics, 1989

Die makromolekulare Chemie, Oct 1, 1989

Many experiments show t h a t t h e second Mooney-Rivlin coefficient disappears f o r highly swol... more Many experiments show t h a t t h e second Mooney-Rivlin coefficient disappears f o r highly swollen chemically cross-linked gels. Hence we are led to a paradox: Highly swollen gels seem to behave phenomenologically like phantom networks. Due t o t h e finite extensibility of network chains, entanglements and excluded volume effects, one should-o n t h e contrary-expect non-Gaussian behaviour. O n t h e basis of t h e phenomenological van der Waals equation of s t a t e , we have concluded t h a t t h e virtual ideality of highly swollen gels is t h e consequence of a compensation between global interactions and excluded volume effects.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, Mar 1, 1996

The aggregation and spreading of silanized glass microspheres (diameter: 62–74 μm) were investiga... more The aggregation and spreading of silanized glass microspheres (diameter: 62–74 μm) were investigated at water (electrolyte)-fluid interfaces by evaporating hexane or chloroform from the water surface. Redispersion of aggregates was attributed to non-equilibrium interfacial tension at the water-fluid interface in the final stage of evaporation. The effect of particle wettability on this phenomenon was studied. Two different hydrophobic samples (Sample A: Θwater/air=77 ± 1°; Sample B: Θwater/air=44 ±1°) were prepared for experiments. Two-liquid wettability of particles was also characterized by contact angles (Sample A: Θwaterhexane = 100 ± 4°; Sample B: Θwaterhexane= 57 ± 3°) by means of which the colloid and capillary pair-potential energies have been calculated. In every case the aggregation yielded well-packed aggregates at the water-organic liquid interface, but spreading experiments showed that while the aggregate of the lower hydrophobic sample could disperse into little clusters or single particles, the higher hydrophobic particles remained together in the final stage of organic liquid evaporation. The speed and extent of redispersion of the lower hydrophobic sample were found to be dependent on the spreading liquids (hexane or chloroform), but the electrolyte (KCl) content of the subphase could not influence the process. The aggregates of higher hydrophobic particles could be redispersed in neither case investigated. It was proposed, on the basis of the calculated interparticle energies, that the higher hydrophobic particles could come into direct contact during the organic liquid evaporation due to the strong “immersion-type” capillary and hydrophobic attractive interactions. We characterized the dispersing ability of the spreading liquids used by a parameter (“dispersing energy”: 25.1 mN m−1 for hexane; 46.8 mN m−1 for chloroform) which could be calculated from a supposed interfacial tension difference at the water-air interface arising during the final stage of organic liquid evaporation. These values were compared with the “pull-off energy” (≈90 mN m−1) obtained earlier for silanized glass surfaces [J.L. Parker and P.M. Claesson, Langmuir, 10 (1994) 635]. The results confirmed the above suggestion that hydrophobic spheres (Sample A) can reach a situation in which the strong adhesion between them can hinder their redispersion and, furthermore, made it reasonable to assume that the aggregates of lower hydrophobic particles (Sample B) could be redispersed better if chloroform was used as spreading liquid.

Polymers for Advanced Technologies, 2003

Measurements are reported on the swelling behaviour at 20°C of poly (N‐isopropylacrylamide) (PNIP... more Measurements are reported on the swelling behaviour at 20°C of poly (N‐isopropylacrylamide) (PNIPA) gels in aqueous solutions of two weak aromatic acids, phenol and resorcinol. For solute concentrations below 45 mmol/l, the uptake of these solutions is similar. Phenol exhibits an excess equilibrium concentration inside the gel of 5% over that in the surrounding bath, while for resorcinol, the excess is found to be 12%. At 50 mmol/l solute concentration, both systems display a volume transition accompanied by expulsion of the solvent. The solubility limits in water of these aromatic compounds are significantly different (870 and 9080 mmol/l, respectively), and are far above this critical concentration. In the collapsed condition, the expelled liquid spreads on the surface of the phenol‐treated gel, while an ordered arrangement of separate droplets is generated in the case of resorcinol. In the latter case, an acute contact angle was observed. Copyright © 2003 John Wiley & Sons, Ltd.

Polymer, 1993

Measurements are made of the osmotic swelling pressure and small angle X-ray scattering from ligh... more Measurements are made of the osmotic swelling pressure and small angle X-ray scattering from lightly crosslinked poly(vinyl acetate) (PVAc) gels swollen in toluene and containing known amounts of free PVAc chains. Gels with different amounts of free chains, but with identical total ...

Polymer, 1991

An investigation is reported of the elastic and osmotic propemes of end-linked polydimethyl silox... more An investigation is reported of the elastic and osmotic propemes of end-linked polydimethyl siloxane networks swollen in toluene. These were prepared both in the presence and in the absence of silica filler particles. A comparison is made between the values of the elastic moduli of the unfilled gels, obtained by uniaxial compression experiments and from the concentration dependence of the swelling pressure respectively. For all the gels studied, the elastic modulus was found to vary with polymer volume fraction q) as ~o 1/3. The osmotic behaviour can be described by a power law relation in agreement with scaling theory, but cannot be interpreted in a consistent manner by using the osmotic pressure data relevant to the uncrosslinked polymer. For the filled gels, the neutral filler particles produce a reinforcement of the elastic modulus. The concentration dependence of the swelling pressure is affected mainly through the volume occupied by the filler in the network.

The Journal of Chemical Physics, 1997

Unidirectional elongation of magnetic field sensitive polymer gels, called ferrogels, have been s... more Unidirectional elongation of magnetic field sensitive polymer gels, called ferrogels, have been studied. In ferrogels, finely distributed colloidal particles having superparamagnetic behavior are incorporated into a swollen network. These particles couple the shape of the gel to the nonuniform magnetic field. Shape distortion occurs instantaneously and disappears when the external field is removed. A discontinuous elongation and contraction in response to infinite-small change in the external magnetic field has been observed and a theoretical interpretation based on coupled magnetic and rubber elastic properties is provided.

The Journal of Chemical Physics, 1997

Different structure-analyzing methods were applied to experimental and computer generated two-dim... more Different structure-analyzing methods were applied to experimental and computer generated two-dimensional clusters. The real structures formed at water–air interfaces from polydisperse, cylindrical-shape carbon (thickness: 35 μm; average length: 140 μm) and close to monodisperse, spherical-shape glass (75 μm diam) microparticles. The clusters were characterized by the fractal dimension (Df) and the surface coverage (q) values in the case of individual clusters. For a series of different sized aggregates, the fractal dimension (Df) was also evaluated from the ln q versus ln Rg functions where Rg is the radius of gyration. The fractal dimensions for individual clusters determined by box counting, sand box, and by correlation function methods, were compared with each other and with those obtained for the series of clusters. Using the above methods, the aggregation of cylindrical carbon and spherical glass particles was studied from a structural point of view. The surface of glass beads...

Fractals, 1993

Interfacial aggregation of surface modified glass beads (62–74 μm diameter) at water/air interfac... more Interfacial aggregation of surface modified glass beads (62–74 μm diameter) at water/air interface was carried out by using two differently hydrophobic samples, respectively. The effect of aggregation time on the self-similar structure of forming aggregates was studied comparing the actual results to those obtained previously.1 The time dependence of restructuring from the point of view of fractal geometry has been proved but the results call attention to another time dependent process— orientation of growing clusters during their collisions due to anisotropy of cluster-cluster interactions.

Colloids and Surfaces, 1991

Abstract Two-dimensional aggregation of surface-modified glass beads was carried out in the bound... more Abstract Two-dimensional aggregation of surface-modified glass beads was carried out in the boundary layer of water—air phases. The effect of the hydrophobicity of the beads on the structure of forming aggregates and on the growth process was investigated. The structure of the aggregates and their growth were characterized by a density function which expresses the change of mean density of the aggregates as a function of size. The growth yielded fractal or non-fractal structures in the systems studied. The fractal structure of the aggregates was dependent on restructuring processes controlled by the surface properties of the beads.

Beilstein Journal of Nanotechnology, 2019

Polymer hydrogels are ideal scaffolds for both tissue engineering and drug delivery. A great adva... more Polymer hydrogels are ideal scaffolds for both tissue engineering and drug delivery. A great advantage of poly(amino acid)-based hydrogels is their high similarity to natural proteins. However, their expensive and complicated synthesis often limits their application. The use of poly(aspartic acid) (PASP) seems an appropriate solution for this problem due to the relatively cheap and simple synthesis of PASP. Using amino acids not only as building blocks in the polymer backbone but also as cross-linkers can improve the biocompatibility and the biodegradability of the hydrogel. In this paper, PASP cross-linked with cystamine (CYS) and lysine-methylester (LYS) was introduced as fully amino acid-based polymer hydrogel. Gels were synthesized employing six different ratios of CYS and LYS. The pH dependent swelling degree and the concentration of the elastically active chain were determined. After reduction of the disulfide bonds of CYS, the presence of thiol side groups was also detected. ...

Journal of Nanomaterials, 2017

The size effect of magnetomechanical response of chemically cross-linked disk shaped magnetic ela... more The size effect of magnetomechanical response of chemically cross-linked disk shaped magnetic elastomers placed on a permanent magnet has been investigated by unidirectional compression tests. A cylindrical permanent magnet with a size of 35 mm in diameter and 15 mm in height was used to create the magnetic field. The magnetic field strength was approximately 420 mT at the center of the upper surface of the magnet. The diameter of the magnetoelastic polymer disks was varied from 14 mm to 35 mm, whereas the height was kept constant (5 mm) in the undeformed state. We have studied the influence of the disk diameter on the stress-strain behavior of the magnetoelastic in the presence and in the lack of magnetic field. It was found that the smallest magnetic elastomer with 14 mm diameter did not exhibit measurable magnetomechanical response due to magnetic field. On the opposite, the magnetic elastomers with diameters larger than 30 mm contracted in the direction parallel to the mechanica...

Periodica Polytechnica Chemical Engineering, 2000

Rheological properties of materials are related to their response to applied stress. The field in... more Rheological properties of materials are related to their response to applied stress. The field induced chain formation of a large number of organic and inorganic substances such as starch, aluminium oxide, ferric oxide, carbon black, ion-exchange resins, and polymer powders have been studied mainly in insulating oils. Much less is studied and understood the clectrorheological effect of pigments in polymer dispersions. Titanium dioxide is one of the most frequently used surface coatings due to its highquality and ecologically acceptable properties. In the present paper the authors first review the basic principle ofclectrorheology. then it is followed by experimental studies on structuring and rheological properties.

Scientific Reports, 2019

This paper presents the results of unidirectional strain-controlled experiments on fibrous electr... more This paper presents the results of unidirectional strain-controlled experiments on fibrous electrospun networks used to study damage formation during elongation. The experimental loading curve shows a symmetrical parabolic type dependence at large scale and saw tooth-like force−extension behaviour at small scale. The damage formation was quantified by determining the number and the magnitude of abrupt force drops. The experiments evidenced that damage evolution is a consequence of strain induced random events. The frequency distribution of the number of damages as well as the magnitude of rupture force were represented by histograms. The results of the present study provide a better insight into damage tolerance and complex nonlinear tensile properties of electrospun networks. In addition, it could suggest a possible probabilistic approach to the fiber bundle model which has mainly motivated this study.

Magyar Kémiai Folyóirat, 2018

Periodica Polytechnica Chemical Engineering, 2017

We have presented the first direct observation of electric field induced rotation of epoxy based ... more We have presented the first direct observation of electric field induced rotation of epoxy based polymer rotors. Polymer disks and gears were prepared in few micrometer dimensions as rotors. Electrorotation of these sub-millimeter sized tools was studied under uniform DC electric field. The rotational speed of micron-sized polymer rotors can be conveniently tuned in wide range (between 300 – 3000 rpm) by the DC electric field intensity, opening new perspectives for their use in micro electric motor applications.

Smart Materials and Structures, 2015

We have presented the first direct observation of electric field induced rotation of epoxy based ... more We have presented the first direct observation of electric field induced rotation of epoxy based polymer rotors. Polymer disks, hollow cylinders and gears were prepared in few micrometer dimensions as rotors. Electrorotation of these sub-millimeter sized tools was studied under uniform DC electric field. The effects of shape, size and thickness were investigated. The novel epoxy based micro devices show intensive spinning in uniform DC electric field. The rotational speed of micron-sized polymer rotors can be conveniently tuned in wide range (between 300-3000 rpm) by the electric field intensity, opening new perspectives for their use in several MEMS applications.