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Showing papers on "Polymer blend published in 2009"


Journal ArticleDOI
06 Mar 2009-Polymer
TL;DR: In this paper, a review of the current knowledge on how solid nanoparticles organize in polymer blends is presented, focusing on the competition between thermodynamic wetting of the solid by the polymeric phases and kinetic control of the filler localization.

551 citations


Journal ArticleDOI
TL;DR: In this article, the authors examined the research in shape memory polymers (SMPs) composites and blends achieved by numerous research groups around the world, mainly for five aims: (1) to improve shape recovery stress and mechanical properties; (2) to decrease shape recovery induction time by increasing thermal conductivity; (3) to create new polymer/polymer blends with shape-memory effect (SME); (4) to tune switch temperature, mechanical properties, and biomedical properties of SMPs; (5) to fabricate shape memory materials sensitive to electricity,
Abstract: Shape memory polymers (SMPs) are a kind of very important smart polymers. In order to improve the properties or obtain new functions of SMPs, SMP composites and blends are prepared. We thoroughly examine the research in SMP composites and blends achieved by numerous research groups around the world. The preparation of SMPs composites and blends is mainly for five aims: (1) to improve shape recovery stress and mechanical properties; (2) to decrease shape recovery induction time by increasing thermal conductivity; (3) to create new polymer/polymer blends with shape-memory effect (SME); (4) to tune switch temperature, mechanical properties, and biomedical properties of SMPs; (5) to fabricate shape memory materials sensitive to electricity, magnetic, light and moisture. The trend of SMP composite development is discussed. SMP composites and blends exhibit novel properties that are different from the conventional SMPs and thus can be utilized in various applications.

525 citations


Journal ArticleDOI
TL;DR: In this paper, the development and characterization of novel polymer blends based on chitosan and polyvinyl alcohol and chemically crosslinked by glutaraldehyde for possible use in a variety of biomedical applications is reported.

432 citations


Journal ArticleDOI
TL;DR: Owing to that unique selective interface-localization and improved phase morphology, the ternary composites present far lower rheological and conductive percolation thresholds than those of the binary composites, and also present extraordinary mechanical properties even at very low loading levels of the MWCNTs.

336 citations


Journal ArticleDOI
TL;DR: In this paper, the microstructure of conjugated polymer blends has been studied in both LEDs and photovoltaic devices, and the authors demonstrate how the blend structure leads to performance advantages.
Abstract: Solution-processed polymer optoelectronic devices such as light-emitting diodes and solar cells have many advantages for large-area manufacture, and show increasing levels of performance. Here, we review recent progress in using blends of two conjugated polymers for optoelectronic devices. The blending of two or more polymers allows tuning of device performance, and for photovoltaics presents an attractive way to combine donor and acceptor materials with a morphology controlled by polymer phase separation. We discuss recent advances in imaging the microstructure of conjugated polymer blends, and we demonstrate how the blend structure leads to performance advantages in both LEDs and photovoltaic devices.

297 citations


Journal ArticleDOI
TL;DR: In this paper, the electrical breakdown of a polar fluoropolymer, poly(vinylidene fluoride-hexafluoropropylene) which exhibits an exceptionally high discharged electrical energy density (>25 J/cm3), was investigated.
Abstract: This paper investigates the electrical breakdown of a polar fluoropolymer, poly(vinylidene fluoride-hexafluoropropylene) which exhibits an exceptionally high discharged electrical energy density (>25 J/cm3). It is shown that above room temperature, the breakdown strength decreases with temperature. It is further shown that such a temperature dependence of breakdown strength is consistent with the electromechanical breakdown model by taking into consideration of the plastic deformation of semicrystalline polymers.

239 citations


Journal ArticleDOI
06 Mar 2009-Polymer
TL;DR: In this article, a novel styrene-butadiene-styrene tri-block copolymer (SBS) and poly(δ-caprolactone) (PCL) blend was introduced for its shape memory properties.

228 citations


Journal ArticleDOI
TL;DR: In this article, the compatibility, phase structure, and component interaction of poly(lactic acid) (PLA) and glycidyl methacrylate grafted poly(ethylene octane) (GMA-g-POE denoted as mPOE) blend by Fourier transform infrared (FTIR) spectra, dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and wide-angle X-ray diffraction (WAXD), respectively.

199 citations


Journal ArticleDOI
TL;DR: In this article, three low bandgap conjugated polymers, i.e., PDTPBT-C8 and C6, which consist of alternating N-alkyl dithieno[3,2-b:2′,3′-d]pyrrole and 2,1,3-benzothiadiazole units and carry 1-octylnonyl, 1-hexylheptyl and 1-pentylhexyl as side chains, respectively, were synthesized.
Abstract: Three low bandgap conjugated polymers, i.e., PDTPBT-C8, PDTPBT-C6 and PDTPBT-C5, which consist of alternating N-alkyl dithieno[3,2-b:2′,3′-d]pyrrole and 2,1,3-benzothiadiazole units and carry 1-octylnonyl, 1-hexylheptyl and 1-pentylhexyl as side chains, respectively, were synthesized. These polymers show strong absorption in the wavelength range of 600–900 nm with enhanced absorption coefficient as the length of alkyl chain decreases. The film morphology of the polymers and 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-C-61 (PCBM) blends is also dependent on the alkyl chain length. As the length decreases, the film becomes more uniform and the domian size decreases from 400–900 nm for PDTPBT-C8 to ∼50 nm for PDTPBT-C5. Bulk heterojunction photovoltaic solar cells (PSCs) were fabricated based on the blend of the polymers and PCBM with a weight ratio of 1:3. The device performance is dramatically improved as the length of the side chain decreases, due to enhanced film absorption coefficient and improved film morphology. With the polymer PDTPBT-C5, which carries the shortest alkyl chain, power conversion efficiency (PCE) up to 2.80% has been achieved. This result indicates that optimizing the structure of the solublizing alkyl chain is also crucial for the design and synthesis of high performance PSC polymeric materials.

195 citations


Journal ArticleDOI
TL;DR: In this article, the performance of binary blends of biodegradable aliphatic polyesters was investigated with scanning electron microscopy and differential scanning calorimetry, and the initial modulus, stress and strain at yield, strain at break, and impact toughness were investigated.
Abstract: The aim of this work was to better understand the performance of binary blends of biodegradable aliphatic polyesters to overcome some limitations of the pure polymers (e.g., brittleness, low stiffness, and low toughness). Binary blends of poly(e-caprolactone) (PCL) and poly(lactic acid) (PLA) were prepared by melt blending (in a twin-screw extruder) followed by injection molding. The compositions ranged from pure biodegradable polymers to 25 wt % increments. Morphological characterization was performed with scanning electron microscopy and differential scanning calorimetry. The initial modulus, stress and strain at yield, strain at break, and impact toughness of the biodegradable polymer blends were investigated. The properties were described by models assuming different interfacial behaviors (e.g., good adhesion and no adhesion between the dissimilar materials). The results indicated that PCL behaved as a polymeric plasticizer to PLA and improved the flexibility and ductility of the blends, giving the blends higher impact toughness. The strain at break was effectively improved by the addition of PCL to PLA, and this was followed by a decrease in the stress at break. The two biodegradable polymers were proved to be immiscible but nevertheless showed some degree of adhesion between the two phases. This was also quantified by the mechanical property prediction models, which, in conjunction with material property characterization, allowed unambiguous detection of the interfacial behavior of the polymer blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

183 citations


Journal ArticleDOI
TL;DR: In this paper, the thermal properties of Chitosan acetate with polyvinyl alcohol (PVA) were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA).

Journal ArticleDOI
TL;DR: The preparation of a supramolecular polymer network that exploits the principle of pi-pi stacking interactions to drive miscibility in two-component polymer blends is reported on.
Abstract: Utilising supramolecular π–π stacking interactions to drive miscibility in two-component polymer blends offers a novel approach to producing materials with unique properties. We report in this paper the preparation of a supramolecular polymer network that exploits this principle. A low molecular weight polydiimide which contains multiple π-electron-poor receptor sites along its backbone forms homogeneous films with a siloxane polymer that features π-electron-rich pyrenyl end-groups. Compatibility results from a complexation process that involves chain-folding of the polydiimide to create an optimum binding site for the π-electron-rich chain ends of the polysiloxane. These complementary π-electron-rich and -poor receptors exhibit rapid and reversible complexation behaviour in solution, and healable characteristics in the solid state in response to temperature. A mechanism is proposed for this thermoreversible healing behaviour that involves disruption of the intermolecular π–π stacking cross-links as the temperature of the supramolecular film is increased. The low Tgsiloxane component can then flow and as the temperature of the blend is decreased, π–π stacking interactions drive formation of a new network and so lead to good damage-recovery characteristics of the two-component blend.

Journal ArticleDOI
TL;DR: In this article, a melting-blended poly(L-lactide) with four rubber components (ethylene-propylene copolymer, ethylene-acrylic rubber, acrylonitrile-butadiene rubber (NBR), and isoprene rubber (IR) was used to toughen PLA.
Abstract: Poly(L-lactide) (PLA) was melt-blended with four rubber components—ethylene–propylene copolymer, ethylene–acrylic rubber, acrylonitrile–butadiene rubber (NBR), and isoprene rubber (IR)—in an effort to toughen PLA. All the blend samples exhibited distinct phase separation. Amorphous PLA constituted a topologically continuous matrix in which the rubber particles were dispersed. According to Izod impact testing, toughening was achieved only when PLA was blended with NBR, which showed the smallest particle size in its blend samples. In agreement with the morphological analysis, the value of the interfacial tension between the PLA phase and the NBR phase was the lowest, and this suggested that rubber with a high polarity was more suitable for toughening PLA. Under the tensile stress conditions for NBR and IR blend samples, these rubbers displayed no crosslinking and showed a high ability to induce plastic deformation before the break as well as high elongation properties; this suggested that the intrinsic mobility of the rubber was important for the dissipation of the breaking energy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Journal ArticleDOI
TL;DR: The upconverting properties of a dye cocktail composed of palladium(II) octaethylporphyrin and 9,10-diphenylanthracene and DPA were investigated and the phosphorescence intensity decay of PdOEP in the polymer host, Tecoflex EG-80A, adequately fits to a sum of two exponential functions as well as the Kohlrausch-Williams-Watts (KWW) stretched exponential model.
Abstract: The upconverting properties of a dye cocktail composed of palladium(II) octaethylporphyrin (PdOEP, triplet sensitizer) and 9,10-diphenylanthracene (DPA, triplet acceptor/annihilator) were investigated as a function of temperature in several low glass transition temperature (Tg) polymer hosts including an ethyleneoxide-epichlorohydrin copolymer (EO-EPI) and the polyurethanes Texin 270, Texin 285, and Tecoflex EG-80A. Selective excitation of PdOEP at 544 nm in the presence of DPA in these materials resulted in anti-Stokes blue emission from DPA, a consequence of sensitized triplet−triplet annihilation (TTA) photochemistry, confirmed by the quadratic dependence of the upconverted fluorescence intensity with respect to incident light power. The upconversion process was completely suppressed by cooling a PdOEP/DPA blend film to below the Tg of the respective polymer. However, the blue emission was clearly visible by the naked eye upon heating these films to room temperature (290 K). Subsequently, the upconvert...

Journal ArticleDOI
TL;DR: In this article, photoelectron spectroscopy was used to investigate poly(3-hexylthiophene) (P3HT), [6,6]-phenyl C61 butyric acid methyl ester (PCBM), and their blends on various conductive substrates.
Abstract: Photoelectron spectroscopy was used to investigate poly(3-hexylthiophene) (P3HT), [6,6]-phenyl C61 butyric acid methyl ester (PCBM), and their blends on various conductive substrates. The study shows a P3HT-rich layer at the top of the P3HT:PCBM blend films. The energy level alignment of the top P3HT changes with the work function of the substrate and the PCBM concentration at the bottom surface of the blend film. The results can be explained using the integer charge transfer model.

Journal ArticleDOI
TL;DR: In this article, the effects of untreated and pretreated carbon nanofibers (CNFs) on the crystallization behavior, friction behavior, and mechanical properties of ultra high molecular weight polyethylene (UHMWPE)/high density polyethylenes (HDPE) nanocomposites prepared by a twin-screw extrusion were studied.

Journal ArticleDOI
20 Mar 2009-Polymer
TL;DR: Rubber toughened polypropylene nanocomposites using two types of modified montmorillonite (organoclay) were explored with the objective of achieving an improved balance between stiffness and toughness as mentioned in this paper.

Journal ArticleDOI
TL;DR: Results suggest hydrophobic but not hydrophilic polymer surfaces support adhesion of activated monocytes to the polymer scaffold, which supports the hypothesis that polymer composition is a feature that dictates in vitro biocompatibility as measured by monocyte driven inflammation.
Abstract: Polymer coatings are essential for local delivery of drug from the stent platform. In designing a DES, it is critical to balance the hydrophilic and hydrophobic components of the polymer system to obtain optimal biocompatibility, while maintaining controlled drug elution. This study investigates the impact of polymer composition of the BioLinx polymer blend on in vitro biocompatibility, as measured by monocytic adhesion. Comparable evaluation was performed with polymers similar to those utilized in various DES that are currently being marketed. Relative hydrophilicities of polymer surfaces were determined through contact angle measurements and surface analyses. Polymer biocompatibility was evaluated in a novel in vitro assay system in which activated monocyte cells were exposed to polymer coated on 96-well plates. Enhanced monocyte adhesion was observed with polymers of a more hydrophobic nature, whereas those which were more hydrophilic did not induce activated monocyte adhesion. Our data supports the hypothesis that polymer composition is a feature that dictates in vitro biocompatibility as measured by monocyte driven inflammation. Monocyte adhesion has been shown to induce local inflammation as well as promote vascular cell proliferation factors contributing to in stent restenosis (Rogers et al., Arterioscler Thromb Vasc Biol 1996;16:1312-1318). Observed results suggest hydrophobic but not hydrophilic polymer surfaces support adhesion of activated monocytes to the polymer scaffold. The proprietary DES polymer blend BioLinx has a hydrophilic surface architecture and does not induce an inflammatory response as measured by these in vitro assays.

Journal ArticleDOI
TL;DR: In this paper, a ball milling process was used to improve the compatibilization between the PCL and the starch phases, while promoting the dispersion of clay minerals at nanometric level.

Journal ArticleDOI
TL;DR: In this article, the authors describe the structure-property relationships between poly octahedral oligomeric silsesquioxane (POSS) fillers and the thermomechanical properties of the polymer composites using polystyrene, poly(methyl methacrylate), and ethylene-(vinyl acetate) copolymer.
Abstract: In this article, we describe the structure–property relationships between the polyoctahedral oligomeric silsesquioxane (POSS) fillers and the thermomechanical properties of the polymer composites using polystyrene, poly(methyl methacrylate), and ethylene-(vinyl acetate) copolymer. We used eight kinds of octa-substituted aliphatic and aromatic POSS as a filler, and homogeneous polymer composites were prepared with various concentrations of these POSS fillers. From a series of measurements of thermal and mechanical properties of the polymer composites, it was summarized that the longer alkyl chains and unsaturated bonds at the side chains in POSS are favorable to improve the thermal stability and the elasticity of polymer matrices. It was found that phenyl-POSS can show superior ability to improve the thermomechanical properties of conventional polymers used in this study. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5690–5697, 2009

Journal ArticleDOI
TL;DR: In this article, cellulose and chitosan were mixed in N -methylmorpholine-N -oxide (NMMO) and heated to 100°C, and then were processed under a pressure of 70 kg/cm 2 exerted by a compression molding machine at 100°c for 8 min.

Journal ArticleDOI
TL;DR: A mean-field theory and complementary computer simulations are presented to shed light on the parametric underpinnings of the experimental observations of polymer grafted nanoparticles in solvents, suggesting that such self-assembled structures occur most readily when the nanoparticle size is comparable to the radius of gyration of the polymer brush chains.
Abstract: Recent experimental results demonstrated that polymer grafted nanoparticles in solvents display self-assembly behavior similar to the microphase separation of block copolymers and other amphiphiles. We present a mean-field theory and complementary computer simulations to shed light on the parametric underpinnings of the experimental observations. Our theory suggests that such self-assembled structures occur most readily when the nanoparticle size is comparable to the radius of gyration of the polymer brush chains. Much smaller particle sizes are predicted to yield uniform particle dispersions, while larger particles are expected to agglomerate due to phase separation from the solvent. Selected aspects of our theoretical predictions are corroborated by computer simulations.

Journal ArticleDOI
16 Nov 2009-Polymer
TL;DR: In this paper, the interface/morphology relationship in polyethylene/TPS blends prepared by a one-step extrusion process is examined in detail, and the level of glycerol content in the TPS is shown to lead to different emulsification behaviors.

Journal ArticleDOI
TL;DR: A series of blends of poly(lactic acid) (PLA) and poly(e-caprolactone) (PCL) with different mass ratio were prepared by means of the melt blending method to study their crystallization, miscibility, morphology, and thermal and mechanical properties as discussed by the authors.
Abstract: A series of blends of poly(lactic acid) (PLA) and poly(e-caprolactone) (PCL) with different mass ratio were prepared by means of the melt blending method to study their crystallization, miscibility, morphology, and thermal and mechanical properties. The result of DSC tests showed that the melting temperatures of PLA and PCL shifted toward each other, and that the largest shift appeared at the PLA70PCL30 blend. This result reveals that the PLA70PCL30 blend gives the strongest interaction intensity among the blends. Combined the result of dynamic mechanical analysis and SEM morphologies, it was found that PLA and PCL form a partial miscible blend, in which an amount of amorphous PCL (amorphous PLA) is dissolved in the PLA-rich phase (PCL-rich phase), leading to a depression of the Tg. value. The polarized optical micrographs showed that PCL can serve as a nucleating agent to promote PLA crystallization in the PLA/PCL blend. Moreover, the PLA70PCL30 blend gave the largest growth rate of PLA spherulite. Final...

Journal ArticleDOI
TL;DR: In this paper, the structural concept of shape-memory polymers (SMP) is based on two key components: covalent or physical crosslinks determining the permanent shape and switching domains fixing the temporary shape as well as determining the switching temperature Tsw.
Abstract: The structural concept of shape-memory polymers (SMP) is based on two key components: covalent or physical crosslinks (hard domains) determining the permanent shape and switching domains fixing the temporary shape as well as determining the switching temperature Tsw. In conventional thermoplastic SMP hard and switching domains determining segments are combined in one macromolecule. In this paper we report on binary polymer blends from two different multiblock copolymers, whereby the first one provides the segments forming hard domains and the second one the segments forming the switching domains. A poly(alkylene adipate) mediator segment is incorporated in both multiblock copolymers to promote their miscibility as the hard segment poly(p-dioxanone) (PPDO) and the switching segment poly(e-caprolactone) (PCL) are non-miscible. All polymer blends investigated showed excellent shape-memory properties. The melting point associated to the PCL switching domains Tm,PCL is almost independent of the weight ratio of the two blend components. At the same time the mechanical properties can be varied systematically. In this way complex synthesis of new materials can be avoided. Its biodegradability, the variability of mechanical properties and a Tsw around body temperature are making this binary blend system an economically efficient, suitable candidate for diverse biomedical applications.

Journal ArticleDOI
TL;DR: This article analyzes single blend-average and effec- tive Tgs of miscible polymer blends in full concentration ranges and tests a recently proposed equation for the blend Tg as a function of composition.
Abstract: Knowledge of the glass transition temperatures (Tgs) as function of com- position reflects miscibility (or lack of it) and is decisive for virtually all properties of polymer-based materials. In this article, we analyze single blend-average and effec- tive Tgs of miscible polymer blends in full concentration ranges. Shortcomings of the extant equations are discussed to support the need for an alternative. Focusing on the deviation from a linear relationship, defined as DTg ¼ Tgu1Tg,1 � u2Tg,2 (where ui and Tg,i are, respectively, the weight fraction and the Tg of the i-th compo- nent), a recently proposed equation for the blend Tg as a function of composition is tested extensively. This equation is simple; a quadratic polynomial centered around 2u1 � 1 ¼ 0 is defined to represent deviations from linearity, and up to three param- eters are used. The number of parameters needed to describe the experimental data, along with their magnitude and sign, provide a measure of the system complexity. For most binary polymer systems tested, the results obtained with the new equation are better than those attained from existing Tg equations. The key parameter of the equation a0 is related to parameters commonly used to represent intersegmental interactions and miscibility in binary polymer blends. V C 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 80-95, 2008

Journal ArticleDOI
31 Jul 2009-Polymer
TL;DR: In this paper, a ternary nanocomposites approach is adopted to prepare electrically conductive and super-tough hybrid polyamide 6/carbon nanotube/elastomer.

Journal ArticleDOI
TL;DR: In this paper, a novel nanocomposite polymer electrolyte membrane composed of PVA polymer matrix and nanosized Montmorillonite (MMT) filler, was prepared by a solution casting method.

Journal ArticleDOI
TL;DR: In this paper, the influence of surfactants on the production of electrospun nanofibers was investigated by adding nonionic polyoxyethylene glycol dodecyl ether (Brij 35), anionic sodium dodecayl sulfate, or cationic dodecylon trimethyl ammonium bromide below, at, and above their specific critical micellar concentration to the polymer blend solution.
Abstract: Electrospun blend nanofibers were fabricated from chitosan (1,000 kDa, 80% DDA) and poly(ethylene oxide) (PEO; 900 kDa) at a ratio of 3:1 dispersed in 50% and 90% acetic acid. The influence of surfactants on the production of electrospun nanofibers was investigated by adding nonionic polyoxyethylene glycol dodecyl ether (Brij 35), anionic sodium dodecyl sulfate, or cationic dodecyl trimethyl ammonium bromide below, at, and above their specific critical micellar concentration to the polymer blend solution. Viscosity, conductivity, and surface tension of polymer solutions, as well as morphology and composition, of nanofibers containing surfactants were determined. Pure chitosan did not form fibers and was instead deposited as beads. Addition of PEO and an increasing concentration of surfactants induced spinnability and yielded larger fibers with diameters ranging from 10 to 240 nm. Surfactants affected morphology yielding needle-like, smooth, or beaded fibers. Compositional analysis revealed that nanofibers consisted of both polymers and surfactants with concentration of the constituents in nanofibers differing from that in polymer solutions. Results suggest that surfactants may modulate polymer–polymer interactions thus influencing the morphology and composition of deposited nanostructures.

Journal ArticleDOI
TL;DR: In this paper, the effects of both MWNT reinforcement and phase affinity of MWNT on thermal and rheological properties of the PLA/PBAT blends were investigated by TGA and rotational rheometer.
Abstract: Biodegradable poly (lactic acid) (PLA)/poly (butyleneadipate-co-butyleneterephthalate) (PBAT)/multi-walled carbon nanotube (MWNT) polymer blend nanocomposites were prepared by using a laboratory-scale twin-screw extruder. Fractured surface morphology of the polymer blend/MWNT nanocomposites were examined via SEM. Furthermore, cross sectioned samples obtained using an ultramicrotome was observed via TEM. In addition, effects of both MWNT reinforcement and phase affinity of MWNT on thermal and rheological properties of the PLA/PBAT blends were investigated by TGA and rotational rheometer. Immiscible PLA/PBAT blend with MWNT nanocomposites showed two-step thermal degradation. The onset temperature of thermal degradation started in the PLA much earlier than in the PBAT. Nonetheless, based on TGA data, it was found that the MWNT enhanced thermal property of the PLA/PBAT blend/MWNT nanocomposites. Rheological properties revealed that both shear and complex viscosities showed unique shear thinning behavior due to selectively localized MWNT dispersion state.