A. Apostolov - Academia.edu (original) (raw)

Papers by A. Apostolov

Journal of Materials Science, 2007

... p 311 3. Apostolov AA, Samokovliyski O, Fakirov S, Stribeck N, Denchev Z, Evstatiev M, Friedr... more ... p 311 3. Apostolov AA, Samokovliyski O, Fakirov S, Stribeck N, Denchev Z, Evstatiev M, Friedrich K, Funari SS (2005) Prog Colloid Polym Sci 130:159 4. Evstatiev M, Apostolov AA, Denchev Z, Fakirov ... Clark ES (1996) In: Mark JE (ed) Physical properties of polymers handbook. ...

Journal of Applied Polymer Science, Apr 5, 2004

Natural rubber (NR), polyurethane rubber (PUR), and NR/PUR-based nanocomposites were produced fro... more Natural rubber (NR), polyurethane rubber (PUR), and NR/PUR-based nanocomposites were produced from the related latices by adding a pristine synthetic layered silicate (LS; sodium fluorohectorite) in 10 parts per hundred parts rubber (phr). The dispersion of the LS latices in the composite was studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Further information on the rubber/LS interaction was received from Fourier transform infrared spectroscopy (FTIR) and dynamic mechanical thermal analysis (DMTA). Tensile and tear tests were used to characterize the performance of the rubber nanocomposites. It was found that LS is more compatible and thus better intercalated by PUR than by NR. Further, LS was preferably located in the PUR phase in the blends, which exhibited excellent mechanical properties despite the incompatibility between NR and PUR. Nano-reinforcement was best reflected in stiffness-and strength-related properties of the rubber composites.

European Polymer Journal, Apr 1, 2009

ABSTRACT

Journal of Macromolecular Science Part B

ABSTRACT

Synopsis. Poly(ether ester)s (PEE) are multiblock copolymers which exhibit phase separation on a ... more Synopsis. Poly(ether ester)s (PEE) are multiblock copolymers which exhibit phase separation on a nanoscale (hard and soft domains). Fibres from PEE material are made and studied during deformation utilising small-angle X-ray scattering (SAXS) at beamline A2. Data are evaluated using a quantitative method developed previously[1, 2]. The results show that beginning from medium elongation the process is not governed by homogeneous deformation. Macroscopic deformation first causes slack microfibrils to be transformed into a taut component. The latter vanishes when hard domains are destroyed during continuing elongation.

Materials Science Forum, 2005

The nanocomposite formation in ethylene/propylene/diene rubber (EPDM) mixed with montmorillonite ... more The nanocomposite formation in ethylene/propylene/diene rubber (EPDM) mixed with montmorillonite modified with octadecylamine (MMT-ODA) was investigated. The rubber formulation used proved to be critical for the final materials’ properties. The combined action of the curatives and glycidyl methacrylate (GMA), which was grafted on the EPDM, resulted in better intercalation and enhanced mechanical behavior of the rubber nanocomposites.

Die Makromolekulare …, 1992

Page 1. Makromol. Chem. 193,2391-2404 (1992) 2391 Multiblock poly(ether-ester-amide)s based on po... more Page 1. Makromol. Chem. 193,2391-2404 (1992) 2391 Multiblock poly(ether-ester-amide)s based on polyamide-6 and poly(ethy1ene glycol), 1 Effect of polyether segment length on the properties of poly(ether-ester-amide)s with various polyamide/polyether ratios ...

Polymer Engineering and Science, 1992

ABSTRACT

Polymer, 2003

Polyamide 6/polypropylene (PA6/PP ¼ 70/30 parts) blends containing 4 phr (parts per hundred resin... more Polyamide 6/polypropylene (PA6/PP ¼ 70/30 parts) blends containing 4 phr (parts per hundred resin) of organophilic modified montmorillonite (organoclay) were prepared using twin screw extruder followed by injection molding. Maleated polypropylene (MAH-g-PP) was used to compatibilize the blend system. The mechanical properties of PA6/PP nanocomposites were studied through tensile and flexural tests. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to assess the fracture surface morphology and the dispersion of the organoclay, respectively. X-ray diffraction (XRD) was used to characterize the formation of nanocomposites. The thermal properties were characterized by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The dynamic mechanical properties of PA6/PP nanocomposites were analyzed by using dynamic mechanical thermal analyzer (DMTA). The strength and stiffness of PA6/PP nanocomposites were improved significantly in the presence of MAH-g-PP. This has been attributed to the synergistic effect of organoclay and MAH-g-PP. The MAH-g-PP compatibilized PA6/PP nanocomposites showed a homogeneous morphology supporting the compatibility improvement between PA6, PP and organoclay. TEM and XRD results revealed the formation of nanocomposites as the organoclay was intercalated and exfoliated. A possible chemical interaction between PA6, PP, organophilic modified montmorillonite and MAH-g-PP was proposed based on the experimental work.

Polymer, 1994

Poly(butylene terephthalate) (PBT), poly(ether ester) (PEE) based on PBT and poly(ethylene glycol... more Poly(butylene terephthalate) (PBT), poly(ether ester) (PEE) based on PBT and poly(ethylene glycol) (PEG) (PBT/PEG=49/51 wt%) and their blend are extruded with quenching, drawn x 5 and annealed together with undrawn samples at 170, 180, 190 and 200°C for 6 h in vacuum. All samples are characterized by differential scanning calorimetry (d.s.c.), small-angle and wide-angle X-ray scattering, dynamic mechanical thermal analysis and static mechanical measurements. D.s.c. and X-ray results show the absence of complete cocrystallization of homo-PBT and PBT from PEE in the blend in accordance with other reports. The drawn blend annealed at 200°C reveals much higher (by 30°C) T m than the PEE component (49/51). Also the mechanical properties of the blend are in between those of the components (homo-PBT and PEE 49/51) but improved compared to those of PEE with the same chemical composition (PEE 75/25). Both observations are explained by partial cocrystallization, i.e. formation of crystallites consisting of two populations of crystallites differing in their size, perfection, origin and time of appearance. The lack of complete cocrystallization and miscibility in this particular blend as well as in other cases with PEE containing less than 75 wt% PBT is explained by the insufficient length of PBT hard segments in PEE necessary for the formation of lamellar thickness typical of the crystallites of homo-PBT.

Macromolecules, 2000

The stretching-induced alpha-beta polymorphic transition in the crystalline regions of poly-(buty... more The stretching-induced alpha-beta polymorphic transition in the crystalline regions of poly-(butylene terephthalate) (PBT) is studied by small-angle X-ray scattering (SAXS), instead of by the wideangle X-ray scattering (WAXS) usually used for this purpose. An expression for the increase of the long spacing upon the transition is derived from a simple model of oriented PBT as a set of microfibrils, each consisting of alternating crystalline and amorphous regions. This increase is calculated on the basis of the c unit cell parameter of both alpha and beta phases and the degree of crystallinity as obtained from differential scanning calorimetry. There is a fairly good agreement between this value and the experimentally measured one. The affine deformation model holds for both the alpha and beta phases in the whole interval of the strain, from zero up to the strain at break. Without external stress the microfibrils are in the fully relaxed state, as concluded from the values of the corresponding long spacing (from SAXS) comprising exclusively the alpha modification (from WAXS). Both the polymorphic transition and the change in the long spacing with strain are completely reversible in the deformation range investigated.

Macromolecules, 2001

The nanostructure deformation mechanism of a predrawn and annealed blend of poly-(ethylene tereph... more The nanostructure deformation mechanism of a predrawn and annealed blend of poly-(ethylene terephthalate) (PET) and polyethylene (PE) (PET/PE: 50/50 by wt %) was studied. For the first time six-point small-angle X-ray scattering (SAXS) patterns were observed as a function of elongation in the investigation of a drawn polymer blend fiber sample. It was found that the meridional two-point pattern arises from PET and the inclined four-point one from PE. Long spacings and the angle between inclined reflections and fiber axis were determined as a function of draw ratio. At lower external strain (elongation up to 13%) the macrodeformation is related to conformational changes located only in amorphous material outside the lamellar stacks, whereas at higher elongation destruction of layer crystallites is observed, possibly due to pull-out of chains.

Macromolecules, 1999

... HG Zachmann, † M. Stamm, § and S. Fakirov ‡. ... Fakirov, S.; Zachmann, HG Europhysics Confer... more ... HG Zachmann, † M. Stamm, § and S. Fakirov ‡. ... Fakirov, S.; Zachmann, HG Europhysics Conference on Macromolecular Science: Application of Synchrotron Radiation in Polymer Science, Hamburg, Germany, September 13−15, 1995. (13) Peterlin, A. Text. Res. J.1972, 42, 20. ...

Macromolecular Materials and Engineering, 2003

ABSTRACT

Macromolecular Materials and Engineering, 2004

Macromolecular Materials and Engineering, 2002

Journal of Materials Science, 2007

... p 311 3. Apostolov AA, Samokovliyski O, Fakirov S, Stribeck N, Denchev Z, Evstatiev M, Friedr... more ... p 311 3. Apostolov AA, Samokovliyski O, Fakirov S, Stribeck N, Denchev Z, Evstatiev M, Friedrich K, Funari SS (2005) Prog Colloid Polym Sci 130:159 4. Evstatiev M, Apostolov AA, Denchev Z, Fakirov ... Clark ES (1996) In: Mark JE (ed) Physical properties of polymers handbook. ...

Journal of Applied Polymer Science, Apr 5, 2004

Natural rubber (NR), polyurethane rubber (PUR), and NR/PUR-based nanocomposites were produced fro... more Natural rubber (NR), polyurethane rubber (PUR), and NR/PUR-based nanocomposites were produced from the related latices by adding a pristine synthetic layered silicate (LS; sodium fluorohectorite) in 10 parts per hundred parts rubber (phr). The dispersion of the LS latices in the composite was studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Further information on the rubber/LS interaction was received from Fourier transform infrared spectroscopy (FTIR) and dynamic mechanical thermal analysis (DMTA). Tensile and tear tests were used to characterize the performance of the rubber nanocomposites. It was found that LS is more compatible and thus better intercalated by PUR than by NR. Further, LS was preferably located in the PUR phase in the blends, which exhibited excellent mechanical properties despite the incompatibility between NR and PUR. Nano-reinforcement was best reflected in stiffness-and strength-related properties of the rubber composites.

European Polymer Journal, Apr 1, 2009

ABSTRACT

Journal of Macromolecular Science Part B

ABSTRACT

Synopsis. Poly(ether ester)s (PEE) are multiblock copolymers which exhibit phase separation on a ... more Synopsis. Poly(ether ester)s (PEE) are multiblock copolymers which exhibit phase separation on a nanoscale (hard and soft domains). Fibres from PEE material are made and studied during deformation utilising small-angle X-ray scattering (SAXS) at beamline A2. Data are evaluated using a quantitative method developed previously[1, 2]. The results show that beginning from medium elongation the process is not governed by homogeneous deformation. Macroscopic deformation first causes slack microfibrils to be transformed into a taut component. The latter vanishes when hard domains are destroyed during continuing elongation.

Materials Science Forum, 2005

The nanocomposite formation in ethylene/propylene/diene rubber (EPDM) mixed with montmorillonite ... more The nanocomposite formation in ethylene/propylene/diene rubber (EPDM) mixed with montmorillonite modified with octadecylamine (MMT-ODA) was investigated. The rubber formulation used proved to be critical for the final materials’ properties. The combined action of the curatives and glycidyl methacrylate (GMA), which was grafted on the EPDM, resulted in better intercalation and enhanced mechanical behavior of the rubber nanocomposites.

Die Makromolekulare …, 1992

Page 1. Makromol. Chem. 193,2391-2404 (1992) 2391 Multiblock poly(ether-ester-amide)s based on po... more Page 1. Makromol. Chem. 193,2391-2404 (1992) 2391 Multiblock poly(ether-ester-amide)s based on polyamide-6 and poly(ethy1ene glycol), 1 Effect of polyether segment length on the properties of poly(ether-ester-amide)s with various polyamide/polyether ratios ...

Polymer Engineering and Science, 1992

ABSTRACT

Polymer, 2003

Polyamide 6/polypropylene (PA6/PP ¼ 70/30 parts) blends containing 4 phr (parts per hundred resin... more Polyamide 6/polypropylene (PA6/PP ¼ 70/30 parts) blends containing 4 phr (parts per hundred resin) of organophilic modified montmorillonite (organoclay) were prepared using twin screw extruder followed by injection molding. Maleated polypropylene (MAH-g-PP) was used to compatibilize the blend system. The mechanical properties of PA6/PP nanocomposites were studied through tensile and flexural tests. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to assess the fracture surface morphology and the dispersion of the organoclay, respectively. X-ray diffraction (XRD) was used to characterize the formation of nanocomposites. The thermal properties were characterized by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The dynamic mechanical properties of PA6/PP nanocomposites were analyzed by using dynamic mechanical thermal analyzer (DMTA). The strength and stiffness of PA6/PP nanocomposites were improved significantly in the presence of MAH-g-PP. This has been attributed to the synergistic effect of organoclay and MAH-g-PP. The MAH-g-PP compatibilized PA6/PP nanocomposites showed a homogeneous morphology supporting the compatibility improvement between PA6, PP and organoclay. TEM and XRD results revealed the formation of nanocomposites as the organoclay was intercalated and exfoliated. A possible chemical interaction between PA6, PP, organophilic modified montmorillonite and MAH-g-PP was proposed based on the experimental work.

Polymer, 1994

Poly(butylene terephthalate) (PBT), poly(ether ester) (PEE) based on PBT and poly(ethylene glycol... more Poly(butylene terephthalate) (PBT), poly(ether ester) (PEE) based on PBT and poly(ethylene glycol) (PEG) (PBT/PEG=49/51 wt%) and their blend are extruded with quenching, drawn x 5 and annealed together with undrawn samples at 170, 180, 190 and 200°C for 6 h in vacuum. All samples are characterized by differential scanning calorimetry (d.s.c.), small-angle and wide-angle X-ray scattering, dynamic mechanical thermal analysis and static mechanical measurements. D.s.c. and X-ray results show the absence of complete cocrystallization of homo-PBT and PBT from PEE in the blend in accordance with other reports. The drawn blend annealed at 200°C reveals much higher (by 30°C) T m than the PEE component (49/51). Also the mechanical properties of the blend are in between those of the components (homo-PBT and PEE 49/51) but improved compared to those of PEE with the same chemical composition (PEE 75/25). Both observations are explained by partial cocrystallization, i.e. formation of crystallites consisting of two populations of crystallites differing in their size, perfection, origin and time of appearance. The lack of complete cocrystallization and miscibility in this particular blend as well as in other cases with PEE containing less than 75 wt% PBT is explained by the insufficient length of PBT hard segments in PEE necessary for the formation of lamellar thickness typical of the crystallites of homo-PBT.

Macromolecules, 2000

The stretching-induced alpha-beta polymorphic transition in the crystalline regions of poly-(buty... more The stretching-induced alpha-beta polymorphic transition in the crystalline regions of poly-(butylene terephthalate) (PBT) is studied by small-angle X-ray scattering (SAXS), instead of by the wideangle X-ray scattering (WAXS) usually used for this purpose. An expression for the increase of the long spacing upon the transition is derived from a simple model of oriented PBT as a set of microfibrils, each consisting of alternating crystalline and amorphous regions. This increase is calculated on the basis of the c unit cell parameter of both alpha and beta phases and the degree of crystallinity as obtained from differential scanning calorimetry. There is a fairly good agreement between this value and the experimentally measured one. The affine deformation model holds for both the alpha and beta phases in the whole interval of the strain, from zero up to the strain at break. Without external stress the microfibrils are in the fully relaxed state, as concluded from the values of the corresponding long spacing (from SAXS) comprising exclusively the alpha modification (from WAXS). Both the polymorphic transition and the change in the long spacing with strain are completely reversible in the deformation range investigated.

Macromolecules, 2001

The nanostructure deformation mechanism of a predrawn and annealed blend of poly-(ethylene tereph... more The nanostructure deformation mechanism of a predrawn and annealed blend of poly-(ethylene terephthalate) (PET) and polyethylene (PE) (PET/PE: 50/50 by wt %) was studied. For the first time six-point small-angle X-ray scattering (SAXS) patterns were observed as a function of elongation in the investigation of a drawn polymer blend fiber sample. It was found that the meridional two-point pattern arises from PET and the inclined four-point one from PE. Long spacings and the angle between inclined reflections and fiber axis were determined as a function of draw ratio. At lower external strain (elongation up to 13%) the macrodeformation is related to conformational changes located only in amorphous material outside the lamellar stacks, whereas at higher elongation destruction of layer crystallites is observed, possibly due to pull-out of chains.

Macromolecules, 1999

... HG Zachmann, † M. Stamm, § and S. Fakirov ‡. ... Fakirov, S.; Zachmann, HG Europhysics Confer... more ... HG Zachmann, † M. Stamm, § and S. Fakirov ‡. ... Fakirov, S.; Zachmann, HG Europhysics Conference on Macromolecular Science: Application of Synchrotron Radiation in Polymer Science, Hamburg, Germany, September 13−15, 1995. (13) Peterlin, A. Text. Res. J.1972, 42, 20. ...

Macromolecular Materials and Engineering, 2003

ABSTRACT

Macromolecular Materials and Engineering, 2004

Macromolecular Materials and Engineering, 2002