Showing papers on "Polymer blend published in 2004"
TL;DR: In this article, the electrical conductivity of polyamide-6 and carbon nanotubes (NT) composites was analyzed and compared to carbon black filled polyamide 6 composites.
695 citations
TL;DR: In this paper, a review of recent approaches for making intumescent systems is described and commented on, and synergistic aspects using zeolites and organoclays are also considered and discussed new strategies are examined on the basis of the intumescence.
Abstract: Summary: This paper reviews recent approaches for making intumescent systems The mechanisms of action involving intumescence are described and commented on Synergistic aspects using zeolites and organoclays are also considered and discussed New strategies are examined on the basis of the mechanism of intumescence The approach of using char forming polymers as additives (blend technology) is also fully discussed This consists of substituting classical polyols (char forming agents) with char forming polymers (polyamides and thermoplastic polyurethane) It will be shown that the advantages of this concept are to obtain flame-retarded (FR) polymer blends with improved mechanical properties in comparison with polymers loaded with classical formulations, and the avoidance of problems due to the water solubility of the polyols and their migration The “nanocomposite approach” enhances the performance of intumescent systems by using a nanostructured char forming polymer It will be shown that this combination of intumescence via the blending approach and nanocomposites enhances both flame retardancy and mechanical properties, and allows many specifications to be produced (for example, the design of EVA-based materials for flame retarded low voltage cables and wire) This appears to be one of the most promising ways for designing new efficient intumescent materials
Intumescent residue after LOI test of an intumescent poly(propylene)
635 citations
TL;DR: The hydrogen bond in polymer blends is an interesting and important subject of research as its presence usually enhances the miscibility of the blend as discussed by the authors, and methods to incorporate interassociated hydrogen bonds into immiscible blends are reviewed, based on work over the last twenty or so years.
438 citations
TL;DR: In this article, the role of organically modified layered silicate as a compatibilizer for immiscible polystyrene (PS) with polypropylene (PP) or polyethylene grafted with maleic anhydride (PP-g-MA) blends was investigated.
412 citations
TL;DR: In this paper, the effect of organoclay platelets on morphologies of three blend compositions (80/20, 20/80, and 99.5/0.5 w/w) of nylon-6 (N6) and poly(ethylene-ran-propylene) rubber (EPR) has been studied by scanning and transmission electron micrographs.
Abstract: The effect of organoclay platelets on morphologies of three blend compositions (80/20, 20/80, and 99.5/0.5 w/w) of nylon-6 (N6) and poly(ethylene-ran-propylene) rubber (EPR) has been studied by scanning and transmission electron micrographs. For the 80/20 (w/w) N6/ERP blend, the dispersed domain size (D) of EPR phase in the N6 matrix decreased significantly even if a small amount of the organoclay was added. The extent of the decrease in D in this blend was similar to N6/EPR blend with an in-situ reactive compatibilizer of EPR-g-maleic anhydride. The D of the blend with the clay did not change upon further annealing at high temperatures, which suggests that the clay seems to be an effective compatibilizer. But, for the 20/80 (w/w) N6/EPR blend, dispersed N6 domain did not decrease with increasing the amount of the clay up to 2 wt %. Moreover, the dispersed N6 domains were not stable against further annealing at high temperatures; thus, coalescence of N6 domains was observed. Furthermore, for 99.5/0.5 (w/w...
355 citations
TL;DR: In this article, a series of blend biodegradable nanofibrous mats comprising polyvinyl alcohol (PVA) and cellulose acetate (CA) were prepared via multi-jet electrospinning.
353 citations
TL;DR: In this paper, it was demonstrated that the nanofibers can be fabricated by co-electrospinning the solutions of conjugated polymers with a spinnable matrix polymer solution and the morphology and diameters of the resulting fibers can be controlled by adjusting the processing parameters.
Abstract: Nanofibers of conjugated polymers and their blends were described. It was demonstrated that the nanofibers can be fabricated by co-electrospinning the solutions of polymers with a spinnable matrix polymer solution. It was also found that the morphology and diameters of the resulting fibers can be controlled by adjusting the processing parameters. Compared with spin-cast films, the polymer chains in electrospun fibers were found to have a more extended conformation and better spatial orientation.
342 citations
TL;DR: In this article, solid polymer electrolyte films containing poly(vinyl alcohol) (PVA)/PMMA-LiBF4-X (X=EC, PC, DEC, GBL) were prepared by solvent casting technique.
326 citations
TL;DR: Genipin-cross-linking produced chitosan networks that were insoluble in acidic and alkaline solutions but were able to swell in these aqueous media, and were more hydrophobic than un-crosslinked ones.
325 citations
TL;DR: Several blends have been prepared of polyvinyl alcohol, starch and glycerol, and their modified forms have been characterised by atomic force microscopy, x-ray diffraction, Fourier transform infra-red spectroscopy, contact angle measurements, 13C-NMR spectrograms, and scanning electron microscopy.
307 citations
01 Mar 2004
TL;DR: In this article, the morphology of blends of PS/PMMA, PC/SAN24, and PMMA/EVA was compared with and without modified organoclay cloisite 20A or Cloisite 6A clays, and it was proposed that in-situ grafts were forming on the clay surfaces during blending and the grafts then had to be localized at the interfaces.
Abstract: We have studied the morphology of blends of PS/PMMA, PC/SAN24, and PMMA/EVA and compared the morphologies with and without modified organoclay Cloisite 20A or Cloisite 6A clays. In each case we found a large reduction in domains size and the localization of the clay platelets along the interfaces of the components. The increased miscibility was accompanied in some cases, with the reduction of the system from multiple values of the glass transition temperatures to one. In addition, the modulus of all the systems increased significantly. A model was proposed where it was proposed that in-situ grafts were forming on the clay surfaces during blending and the grafts then had to be localized at the interfaces. This blending mechanism reflects the composition of the blend and is fairly nonspecific. As a result, this may be a promising technology for use in processing recycled blends where the composition is often uncertain and price is of general concern.
TL;DR: In this paper, a negative polymer−polymer interaction energy density was calculated on the basis of the melting point depression of PEO and a negative deviation of Tg from the weighted average values observed.
Abstract: Blends of poly(ethylene oxide) with organosolv lignin (Alcell) were prepared by thermal blending. Excellent fiber spinning was achieved over the entire blend ratio. The good thermal properties of the Alcell lignin arise from its unique chemical structure. HMQC 2D NMR analysis revealed the presence of alkoxyl chains at the Cα and Cγ positions of the Alcell lignin side chain structure acting as internal plasticizers and enhancing the thermal mobility of the lignin. The addition of a small amount of Alcell lignin to PEO resulted in an increase of the PEO crystalline domain size. However, both PEO crystallinity and crystalline domain size decreased with lignin incorporation beyond 25 wt %. A negative polymer−polymer interaction energy density “B” was calculated on the basis of the melting point depression of PEO and a negative deviation of Tg from the weighted average values observed. Good prediction of the Tg-composition behavior was obtained indicating the presence of favorable interactions between blend co...
TL;DR: In this paper, a review of recent advances in the use of supercritical carbon dioxide (scCO2) in materials synthesis and materials processing is presented, focusing on the development of new polymer processing and polymer blend technologies in scCO2, which enable the synthesis of some very complex polymer composites and blends.
Abstract: Supercritical carbon dioxide (scCO2) is a unique solvent with a wide range of interesting properties. This review focuses upon recent advances in the use of scCO2 in materials synthesis and materials processing. In particular, we consider the advances made in three major areas. First the design and application of new surfactants for use in scCO2, which enable the production of metal nanoparticles, porous polymers and polymers of high molecular weight with excellent morphology. Second the development of new polymer processing and polymer blend technologies in scCO2, which enable the synthesis of some very complex polymer composites and blends. Finally, the application of scCO2 in the preparation of novel biomedical materials, for example biodegradable polymer particles and scaffolds. The examples described here highlight that scCO2 allows facile synthesis and processing of materials, leading to new products with properties that would otherwise be very difficult to achieve.
TL;DR: In this paper, the effects of hydrogen-bonding on lignin-based thermoplastics were studied in a series of Lignin/synthetic polymer blends prepared by melt extrusion.
Abstract: The development of lignin-based thermoplastics relies on altering the viscoelastic properties of lignin through chemical modification or polymer blending. In polymer blends, miscibility is dependent on the occurrence of exothermic reactions such as hydrogen-bonding, acid–base interactions and the like. The effects of polymer–polymer interactions, specifically hydrogen-bonding, on lignin-based thermoplastics was studied in a series of lignin/synthetic polymer blends prepared by melt extrusion. Thermal analysis revealed miscible blend behavior in the lignin blends containing PEO and PET, whereas the PVA and PP lignin blends appeared immiscible. The glass transition ( T g ) of the lignin/PEO and lignin/PET blends showed a negative deviation from a linear mixing rule, indicative of specific intermolecular interactions. DRFT-IR analysis revealed the formation of a strong intermolecular hydrogen bond between lignin and PEO, but not with PET.
TL;DR: In this article, the extensional viscosity of several polypropylene polymers and their blends was measured and the foam processing of these blends using carbon dioxide blowing agent was studied.
Abstract: Extensional viscosity of several polypropylene polymers and their blends was measured and the foam processing of these blends using carbon dioxide blowing agent was studied. Foaming was carried out on a co-rotating twin-screw extrusion line, with a gear pump to build pressure. A linear isotactic polypropylene and two branched polypropylenes were considered. The uniaxial extensional viscosity was quantified and the foam characterized based on bulk density, cell size, and cell concentration. The linear polymer exhibits no strain hardening, while both branched polymers show pronounced strain hardening. Blends of low concentrations of branched polymer in the linear polypropylene show significant strain hardening down to 10-wt% branched polypropylene. Strain hardening is expected to prevent cell coalescence and lead to higher cell concentrations. The branched polymers were found to have a lower cell concentration than the linear polymer. Yet blends of linear and branched polypropylenes attained a cell concentration higher than either of the neat polymers. This suggests that even small amounts of branched polypropylene blended in linear polypropylene can improve the foaming process. Polym. Eng. Sci. 44:2090–2100, 2004. © 2004 Society of Plastics Engineers.
TL;DR: In this article, phase separation in polyfluorene-based electroluminescent polymer blends consisting of poly(2,7-(9,9-di-n-octylfluorene)-alt-benzothiadiazole) (F8BT) and poly( 2,7(9, 9-di)-n-orthogonal poly(1,4)-phenylene-((4-sec-butylphenyl)imino)-1, 4-phenylene)) (TFB)) is studied.
Abstract: We have studied phase separation in polyfluorene-based electroluminescent polymer blends consisting of poly(2,7-(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) and poly(2,7-(9,9-di-n-octylfluorene)-alt-(1,4-phenylene-((4-sec-butylphenyl)imino)-1,4-phenylene)) (TFB). We present detailed studies on spin-cast thin-film morphology of the blends, using micro-Raman spectroscopy and X-ray photoelectron spectroscopy. Micron-scale lateral phase separation is observed in these blend thin films. However, these phase-separated domains are not pure at the submicron length scale, and a nanoscale vertical phase segregation occurs with enrichment of the lower surface energy component (TFB) at both air and substrate interfaces. Imaging of the spatial uniformity of electroluminescence emission on the microscopic scale indicates spatially localised charge-carrier recombination in light-emitting diodes (LEDs) fabricated with these blends. On the basis of these studies, we propose a model for the development of thin-film...
TL;DR: In this article, the authors have fabricated organic photovoltaic devices with blends of regioregular poly(3-hexylthiophene) (P3HT) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) as an electron donor and an electron acceptor, respectively.
Abstract: We have fabricated organic photovoltaic devices with blends of regioregular poly(3-hexylthiophene) (P3HT) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) as an electron donor and an electron acceptor, respectively Several fabrication parameters such as blend composition, film thickness, solvent, and presence of LiF layer were varied in order to find the maximum device performance The highest external quantum and power conversion efficiencies were achieved for the blend film with 60 wt % P3HT using p-xylene as a solvent Insertion of a LiF layer further improved the power conversion efficiency from 002% to 013% under AM15 condition (1 Sun) To understand the relatively poor efficiency even in the optimized device, this polymer blend system was analyzed in relation to the following factors: charge separation efficiency, as measured by photoluminescence quantum efficiency; charge carrier mobility, measured by time-of-flight; and charge recombination dynamics, measured by transient absorption s
TL;DR: In this paper, the morphology of PPO/PA6 nanocomposite with various amounts of clay has been investigated using scanning electron microscope (SEM), transmission electron microsc (TEM), and wide-angle X-ray diffraction (WAXD).
TL;DR: This study prepares porous PLLA from a blend of two biodegradable polymers based on a detailed and quantitative morphology control of the blends and indicates that this material also has potential as a substrate for controlled release applications.
TL;DR: In this paper, the effects of filler content and mixing time on the phase morphology, crystallization behavior, rheology, and mechanical properties of immiscible polypropylene(PP)/polystyrene(PS) blends compatibilized with nano-SiO 2 particles were investigated.
TL;DR: The synergy between the two materials, both produced from renewable resources, is attributed to the retardation of crystallization of PHA copolymers finely dispersed in a PLA matrix as discrete domains.
Abstract: Properties of polymer alloys comprising poly (lactic acid) and Nodax copolymers are investigated. Nodax is a family of bacterially produced polyhydroxyalkanoate (PHA) copolymers comprising 3-hydroxybutyrate (3HB) and other 3-hydroxyalkanoate (3HA) units with side groups greater than or equal to three carbon units. The incorporation of 3HA units with medium-chain-length (mcl) side groups effectively lowers the crystallinity and the melt temperature, T m , of this class of PHA copolymers, in a manner similar to that of alpha olefins controlling the properties of linear low density polyethylene. The lower T m makes the material easier to process, as the thermal decomposition temperature of PHAs is then relatively low. The reduced crystallinity provides the ductility and toughness required for many plastics applications. When a small amount of ductile PHA is blended with poly(lactic acid) (PLA), a new type of polymer alloy with much improved properties is created. The toughness of PLA is substantially increased without a reduction in the optical clarity of the blend. The synergy between the two materials, both produced from renewable resources, is attributed to the retardation of crystallization of PHA copolymers finely dispersed in a PLA matrix as discrete domains.
TL;DR: In this article, a mixture of an unreactive poly[styrene- b -(ethylene- co-butylene)- b -styrene] (SEBS) triblock copolymer and a reactive maleic anhydride-grafted SEBS- g -MA was produced via melt blending in a co-rotating twin-screw extruder.
TL;DR: In this article, the effects of layer thickness, interface morphology, top contact, and polymer-metal combination on the performance of photovoltaic devices consisting of a fluorene-bithiophene copolymer and nanocrystalline TiO2 were reported.
Abstract: We report the effects of layer thickness, interface morphology, top contact, and polymer–metal combination on the performance of photovoltaic devices consisting of a fluorene–bithiophene copolymer and nanocrystalline TiO2. Efficient photoinduced charge transfer is observed in this system, while charge recombination is relatively slow (∼100 μs–10 ms). External quantum efficiencies of 13% and monochromatic power conversion efficiencies of 1.4% at a wavelength of 440 nm are achieved in the best device reported here. The device produced an open-circuit voltage of 0.92 V, short-circuit current density of about 400 μA cm−2, and a fill factor of 0.44 under simulated air mass 1.5 illumination. We find that the short-circuit current density and the fill factor increase with decreasing polymer thickness. We propose that the performance of the indium tin oxide/TiO2/polymer/metal devices is limited by the energy step at the polymer/metal interface and we investigate this situation using an alternative fluorene-based ...
TL;DR: In this paper, a forecast approach has been developed to predict blend compatibility, based on the analysis of the compatibility of these blends which vary according to their formulation, in order to improve the properties of plasticized wheat starch and to conserve its final biodegradability.
Abstract: In order to improve the properties of plasticized wheat starch (PWS) and to conserve its final biodegradability, PWS can be blended with biodegradable polyesters [polyesteramide, poly(e-caprolactone), poly(lactic acid), poly(butylene succinate adipate) and poly(butylene adipate terephthalate)] which exhibit variable polar characteristics. This paper is focused on the analysis of the compatibility of these blends which vary according to their formulation. To understand the lack of affinity between the different phases, interface adhesion has been investigated by contact angle measurements to obtain the work of adhesion. From these determinations a forecast approach has been developed to predict blend compatibility. Blend structures were obtained by scanning electron microscopy observations. Blends show either a dispersed structure or a co-continuous morphology. Percolation thresholds (co-continuity) and full continuity regions were determined thanks to a method based on solvent extraction. Finally, rheological investigations have been carried out on the different biodegradable polymers to understand better the blend structure formation during the process. Copyright © 2004 Society of Chemical Industry
TL;DR: In this paper, a series of air-stable, solution-processed blends of an n-type polymer poly (benzobisimidazobenzophenanthroline) and a p-type small molecule, copper phthalocyanine (CuPc) are demonstrated, where all fabrication and measurements are performed under ambient conditions.
Abstract: Ambipolar thin-film transistors based on a series of air-stable, solution-processed blends of an n-type polymer poly(benzobisimidazobenzophenanthroline) (BBL) and a p-type small molecule, copper phthalocyanine (CuPc) are demonstrated, where all fabrication and measurements are performed under ambient conditions. The hole mobilities are in the range of 6.0 × 10–6 to 2.0 × 10–4 cm2 V–1 s–1 and electron mobilities are in the range of 2.0 × 10–6 to 3.0 × 10–5 cm2 V–1 s–1, depending on the blend composition. UV-vis spectroscopy and electron diffraction show crystallization of CuPc in the metastable α-crystal form within the semicrystalline BBL matrix. These CuPc domains develop into elongated ribbon-like crystalline nanostructures when the blend films are processed in methanol, but not when they are processed in water. On methylene chloride vapor annealing of the blend films, a phase transformation of CuPc from the α-form to the β-form is observed, as shown by optical absorption spectroscopy and electron diffraction. Ambipolar charge transport is only observed in the blend films where CuPc crystallized in the elongated ribbon-like nanostructures (α-form). Ambipolar behavior is not observed with CuPc in the β-polymorph. Unipolar hole mobilities as high as 2.0 × 10–3 cm2 V–1 s–1 are observed in these solution-processed blend field-effect transistors (FETs) on prolonged treatment in methanol, comparable to previously reported hole mobilities in thermally evaporated CuPc FETs. These results show that ambipolar charge transport and carrier mobilities in multicomponent organic semiconductors are intricately related to the phase-separated nanoscale and crystalline morphology.
TL;DR: In this paper, the effect of nanometer sized silica particles (R≈16mm) on the flow-induced morphology of immiscible polymer blends is studied, and it is shown that the particles alter the sensitivity of the dispersed phase/matrix microstructure to shear flow.
Abstract: The effect of nanometer sized silica particles (R≈16 nm) on the flow-induced morphology of immiscible polymer blends is studied. Polydimethylsiloxane (PDMS) and polyisobutylene (PIB) are chosen as model components. A stable droplet/matrix microstructure is obtained for blends of 30% PIB in 70% PDMS or vice versa. Rheological measurements are used to show that the silica particles alter the sensitivity of the of dispersed phase/matrix microstructure to shear flow. Coalescence is suppressed or at least slowed down on a practical time scale, especially when PDMS is the matrix phase. The effect of mixing conditions, pre-shear rate and particle concentration on the blend morphology are studied. Cryo-SEM is used to observe the accumulation of the particles at the interface. Blends stabilized by solid particles could provide an interesting alternative to blends compatibilized by block-copolymers.
TL;DR: In this paper, the authors investigated the mechanisms for improved mechanical and electrical properties of an injection molded, carbon nanotubes (CNTs) filled, polyethylene terephthalate (PET)/polyvinylidene fluoride (PVDF) blend, and found that the improved properties are due to the formation of a triple continuous structure in the CNT-filled polymer blend; CNT segregates in the continuous PET phase, forming a continuous conductive path to provide the composite an electrical short circuit.
TL;DR: In this paper, the authors reported photoconductivity at infrared wavelengths, 975-1300nm, from a conjugated polymer poly[2-methoxy-5-(2′-ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV) sensitized with PbS nanocrystals (∼5nm diameter).
Abstract: We report photoconductivity at infrared wavelengths, 975–1300nm, from a polymer∕nanocrystal quantum dot composite. Biased films of the conjugated polymer poly[2-methoxy-5-(2′-ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV) sensitized with PbS nanocrystals (∼5nm diameter) demonstrate photocurrent at wavelengths beyond the response of the polymer and corresponding to the absorption of the nanocrystals. The photocurrent is attributed to absorption in the nanocrystals with subsequent hole transfer to the polymer and had an internal quantum efficiency of ∼5×10−6to∼10−5charges∕photon at 5V bias.
TL;DR: In this paper, the properties of photovoltaic devices with a blend of single-component PFB and F8BT particles were compared with those of solar cells based on blend particles.
Abstract: Polymer solar cell devices with nanostructured blend layers have been fabricated using single- and dual-component polymer nanospheres. Starting from an electron-donating and an electron-accepting polyfluorene derivative, PFB and F8BT, dissolved in suitable organic solvents, dispersions of solid particles with mean diameters of ca. 50 nm, containing either the pure polymer components or a mixture of PFB and F8BT in each particle, were prepared with the miniemulsion process. Photovoltaic devices based on these particles have been studied with respect to the correlation between external quantum efficiency and layer composition. It is shown that the properties of devices containing a blend of single-component PFB and F8BT particles differ significantly from those of solar cells based on blend particles, even for the same layer composition. Various factors determining the quantum efficiency in both kinds of devices are identified and discussed, taking into account the spectroscopic properties of the particles....