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Blend Morphology (blend + morphology)
Selected AbstractsOnline Light Scattering Measurements as a Means to Assess Influence of Extrusion Parameters on Non-reactive Polymer Blend Morphology: Experimental Procedure and Preliminary ResultsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2002Christophe Serra Abstract The influence of extrusion parameters on the morphology of non-reactive blends has been investigated by means of online light-scattering measurements. A light-scattering device was especially designed to be mounted on a twin screw extruder at different locations along the barrel. The obtained light-scattering patterns were interpreted with respect to the variation of the processing parameters. Preliminary results show that there is little effect of the rotational speed, position along the screw and feed throughput on the morphology but a quite noticeable effect of the blend composition. These results were confirmed by SEM micrographs. On a étudié l'influence des paramètres d'extrusion sur la morphologie de mélanges non réactifs par des mesures de diffusion de la lumière en ligne. Un système de diffusion de la lumière a été spécialement conçu pour être monté sur une extrudeuse bi-vis à différents endroits le long du fourreau. Les modèles de diffusion de la lumière obtenus sont interprétés en tenant compte de la variation des paramètres de procédé. Les résultats préliminaires montrent le peu d'effet de la vitesse rotationnelle, de la position sur la vis et de la capacité d'alimentation sur la morphologie mais un effet assez appréciable de la composition du mélange. Ces résultats sont confirmés par des micrographes en microscopie électronique à balayage. [source] Reactive processing of syndiotactic polystyrene with an epoxy/amine solvent systemMACROMOLECULAR SYMPOSIA, Issue 1 2003Jaap Schut Abstract Syndiotactic polystyrene (sPS) is a new semi-crystalline thermoplastic which is believed to fill the price-performance gap between engineering and commodity plastics. In order to reduce the high processing temperature of sPS (>290°C), an epoxy-amine model system was used as a reactive solvent. Such a processing aid can be used to achieve a 50 to 500 fold lowering of the melt viscosity. When initially homogeneous solutions of sPS in a stoechiometric epoxy-amine mixture are thermally cured, Reaction Induced Phase Separation (RIPS) takes place, leading to phase separated thermoplastic-thermoset polymer blends. We focus our study on low (wt% sPS < 20%) and high concentration blends (wt% sPS > 60%) prepared by two processing techniques (mechanical stirring in a laboratory reactor or internal mixer/ reactive extrusion respectively). These blends have different potential interests. Low concentration blends (sPS domains in an epoxy-amine matrix) are prepared to create new, tunable blend morphologies by choosing the nature of the phase separation process, i.e. either crystallisation followed by polymerization or polymerization followed crystallisation. High concentration blends (sPS matrix containing dispersed epoxy-amine particles after RIPS) are prepared to facilitate the extrusion of sPS. In this case, the epoxy amine model system served as a reactive solvent. The time to the onset of RIPS is in the order of 7-9 min for low concentration blends, while it increases to 20-45 min for high concentration samples, as the reaction rates are substantially slowed down due to lower epoxy and amine concentrations. During the curing reaction the melting temperature of sPS in the reactive solvent mixture evolves back from a depressed value to the level of pure sPS. This indicates a change in the composition of the sPS phase, caused by (complete) phase separation upon reaction. We conclude that our epoxy amine system is suited for reactive processing of sPS, where final properties depend strongly on composition and processing conditions. [source] Ultrafast Hole-Transfer Dynamics in Polymer/PCBM Bulk HeterojunctionsADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Artem A. Bakulin Abstract Ultrafast dynamics of the hole-transfer process from methanofullerene to a polymer in a polymer/PCBM bulk heterojunction are directly resolved. Injection of holes into MDMO-PPV is markedly delayed with respect to [60]PCBM excitation. The fastest component of the delayed response is attributed to the PCBM,polymer hole-transfer process (30,±,10,fs), while the slower component (,150,fs) is provisionally assigned to energy transfer and/or relaxation inside PCBM nanoclusters. The charge generation through the hole transfer is therefore as fast and efficient as through the electron-transfer process. Exciton harvesting efficiency after PCBM excitation crucially depends on the concentration of the methanofullerene in the blend, which is related to changes in the blend morphology. Ultrafast charge generation is most efficient when the characteristic scale of phase separation in the blend does not exceed ,20,nm. At larger-scale phase separation, the exciton harvesting dramatically declines. The obtained results on the time scales of the ultrafast charge generation after PCBM excitation and their dependence on blend composition and morphology are instrumental for the future design of fullerene-derivative-based photovoltaic devices. [source] Modification of polypropylene by melt vibration blending with ultra high molecular weight polyethyleneADVANCES IN POLYMER TECHNOLOGY, Issue 3 2002Kejian Wang Abstract A novel vibration internal mixer was used to prepare polypropylene/ultra high molecular weight polyethylene PP/UHMWPE blends with two additional adjustable processing parameters (vibration frequency and vibration amplitude) as compared with those prepared in the steady mode. Microscopy, mechanical tests, and differential scanning calorimetry showed that vibration influenced the blend morphology and the product properties. The good phase homogeneity of the blends might be due to the variation of shear rate either spatially or temporally in blending. Additionally, the vibration internal mixer could be used to analyze the dependency of viscosity on the shear rate. Vibration enhanced the interpenetration of UHMWPE into PP and vice versa. Subsequently, the formed crystals of two components were connected, and there was epitaxy between PP and UHMWPE crystals. Moreover, the crystalline aggregates, with the amorphous UHMWPE, formed a complex network-like continuous structure, which improved the elongation ratio at the break and the yield strength. The higher the vibration frequency and/or the larger the vibration amplitude at a fixed average rotation speed of the mixer, the more significant these effects were. The larger amount of the connected crystals, especially of , form of PP in the bulk , form PP as well as with the continuous phase structure, led to a higher tensile properties of PP/UHMWPE vibration blended. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 164,176, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/adv.10020 [source] Effects of addition of acrylic compatibilizer on the morphology and mechanical behavior of amorphous polyamide/SAN blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010D. Becker Abstract Amorphous polyamide (aPA)/acrylonitrile-styrene copolymer (SAN) blends were prepared using methyl methacrylate-maleic anhydride copolymer MMA-MA as compatibilizer. The aPA/SAN blends can be considered as a less complex version of the aPA/ABS (acrylonitrilebutadiene-styrene) blends, due to the absence of the ABS rubber phase in the SAN material. It is known that acrylic copolymer might be miscible with SAN, whereas the maleic anhydride groups from MMA-MA can react in situ with the amine end groups of aPA during melt blending. As a result, it is possible the in situ formation of aPA-g-MMA-MA grafted copolymers at the aPA/SAN interface during the melt processing of the blends. In this study, the MA content in the MMA-MA copolymer and its molecular weight was varied independently and their effects on the blend morphology and stress,strain behavior were evaluated. The morphology of the blends aPA/SAN showed a minimum in the SAN particle size at low amounts of MA in the compatibilizer, however, as the MA content in the MMA-MA copolymer was increased larger SAN particle sizes were observed in the systems. In addition, higher MA content in the compatibilizer lead to less ductile aPA/SAN blends under tensile testing. The results shown the viscosity ratio also plays a very important role in the morphology formation and consequently on the properties of the aPA/SAN blends studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Shear-induced migration of nanoclay during morphology evolution of PBT/PS blendJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Joung Sook Hong Abstract In this study, we investigated clay migration and its localization in multiphase blend nanocomposite systems during the evolution of blend morphology to elucidate how a hydrodynamic stress and chemical affinity between the polymer and clay induce them. To observe the morphology evolution, a multilayered blend, alternatively superposed poly(butylenes terephthalate) (PBT) and polystyrene (PS)/clay films or PBT/clay and PS films, was subjected to homogeneous shear flow, 1 s,1. Furthermore, the morphology was observed at different shear rates 1 s,1. When the PBT/(PS/clay) multilayered blend is subjected to flow, the clay dispersed in the PS layer first migrates to the interface depending on the amount of applied strain. The clay at the interface causes the average drop size of blend morphology to become smaller and the blend morphology becomes more stable because of the coalescence suppression effect. As more shear is applied, the clay at the interface moves further into more compatible phase, PBT, although the viscosity of PBT is higher than PS. On the contrary, the clay in the PBT layer does not migrate to the PS phase at any shear rate, which means that its chemical affinity is strong enough to prevent shear-induced migration. The clay increases the viscosity of the PBT phase and results in a different morphology with a droplet, cocontinuous structure. As a result, when the clay is induced to migrate by hydrodynamic stress, it migrates into thermodynamically more stable positions at the interface or in the chemically more compatible phase, depending on the applied strain. Once it is located at a thermodynamically more stable position, it is difficult to push it out only by hydrodynamic stress. The location of clay is significantly affected by the morphology during evolution, which means that the blend morphology can control the droplet form and cocontinuous structure by control of the clay migration kinetics. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Nonuniformity of phase structure in immiscible polymer blendsPOLYMER ENGINEERING & SCIENCE, Issue 3 2008Ivan Fortelný This article is focused on the phase structure development in immiscible polymer blends during melt mixing. Nonuniformity of the phase structure, i.e., the coexistence of areas containing particles with markedly different size distribution, was detected in quenched and compression molded samples of a number of various blends prepared by long and intensive mixing in the chamber of a Plasticorder. The same effect was found also for polystyrene/polyamide blends prepared in a twin-screw extruder. It was shown that neglecting nonuniformity of the phase structure can lead to considerable error in evaluation of the effect of system parameters on the blend morphology. The reasons for the effect were discussed and it was found that inhomogeneous flow field in mixers is a plausible explanation of the nonuniform phase structure. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Effect of mixing protocol on compatibilized polymer blend morphologyPOLYMER ENGINEERING & SCIENCE, Issue 5 2006Bin Lin We investigated the effect of mixing protocol on the morphology of compatibilized polymer blends made with premade compatibilizer and reactively formed in-situ compatibilizer in a custom-built miniature mixer Alberta Polymer Asymmetric Minimixer (APAM). The compatibilized blends show a finer morphology than uncompatibilized blends if the polymers are mixed together in the dry state and then fed into the mixer. It is found that premelting one polymer, and premixing polymers and compatibilizer, both greatly affect the compatibilized blends' morphology. The effects are complex since the dispersed phase particle size and distribution of the compatibilized blends may be smaller or larger when compared with the uncompatibilized system, depending on the material's physical and chemical properties; for example, diblock molecular weight or the preference of copolymer to migrate to a particular phase can change the final morphology. Good mobility of the copolymer to reach the interface is crucial to obtain a finer morphology. Micelles are observed when a high molecular weight diblock copolymer P(S- b -MMA) is used for a PS/PMMA blend. Because of its enhanced mobility, no micelles are found for a low molecular weight diblock copolymer P(S- b -MMA) in a PS/PMMA blend. For PS/PE/P(S- b -E) blends, finer morphology is obtained when P(S- b -E) is first precompounded with PS. Because the block copolymer prefers the PE phase, if the P(S- b -E) block copolymer is compounded with PE first, some remains inside the PE phase and does not compatibilize the interface. In the case of reactive blend PSOX/PEMA, premelting and holding the polymers at high temperature for 5 min decreases final dispersed phase particle size; however, premelting and holding for 10 min coarsens the morphology. POLYM. ENG. SCI. 46:691,702, 2006. © 2006 Society of Plastics Engineers. [source] Morphological and fractal studies of polypropylene/poly(ethene-1-octene) blends during melt mixing using scanning electron microscopyPOLYMER INTERNATIONAL, Issue 3 2008Xinhua Xu Abstract BACKGROUND: Polymer blending creates new materials with enhanced mechanical, chemical or optical properties, with the exact properties being determined by the type of morphology and the phase dimension of the blend. In order to control blend properties, morphology development during processing needs to be understood. The formation and evolution of polypropylene/poly(ethylene-1-octene) (PP/POE) blend morphology during blending are qualitatively represented by a series of time-dependent scanning electron microscopy (SEM) patterns. The area diameter and its distribution of dispersed phase domains are discussed in detail. In order to characterize the formation and evolution of phase morphology quantitatively, two fractal dimensions, Ds and Dd, and their corresponding scaling functions are introduced to analyze the SEM patterns. RESULTS: The evolution of the area diameter indicates that the major reduction in phase domain size occurs during the initial stage of melt mixing, and the domain sizes show an increasing trend due to coalescence with increasing mixing times. The distribution in dispersed phase dimension obeys a log-normal distribution, and the two fractal dimensions are effective to describe the phase morphology: Ds for dispersed phase dimension and Dd for the distribution in it. CONCLUSIONS: The fractal dimensions Ds and Dd can be used quantitatively to characterize the evolutional self-similarity of phase morphology and the competition of breakup and coalescence of dispersed phase domains. It is shown that the fractal dimensions and scaling laws are useful to describe the phase morphology development at various mixing times to a certain extent. Copyright © 2007 Society of Chemical Industry [source] Morphology and properties of ternary polyamide 6/polyamide 66/elastomer blendsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2003D. Tomova Abstract The aim of the work presented is to evaluate the mechanisms and phase interactions in ternary blends based on different polyamides and functionalised elastomers, and to establish a correlation between the morphology controlled by the specific binary interactions, and physical and technological properties, respectively. The properties of the ternary system polyamide 6/polyamide 66/ elastomer depend on the specific blend morphology which is determined mainly by the differences of the surface tension of the components. A phase-in-phase structure was observed by microscopic study (AFM) in the ternary polyamide 6/polyamide 66/elastomer blends with maleic anhydride grafted ethene-octene copolymer, and a "quasi" phase-in-phase structure in blends with maleic anhydride grafted ethene-propene-diene copolymer as the elastomer phase. An incorporation of polyamide inside of the elastomer particles was observed in the first case due to the difunctionality of polyamide 66. This type of morphology causes an increased elongation at break and toughness of these blends. In comparison to the binary polyamide based blends the ternary blends show an increased elastic modulus, elongation at break and yield stress as well as a high impact strength at low temperatures up to ,20,°C. Copyright © 2003 John Wiley & Sons, Ltd. [source] Effect of mixing protocol on compatibilized polymer blend morphologyPOLYMER ENGINEERING & SCIENCE, Issue 5 2006Bin Lin We investigated the effect of mixing protocol on the morphology of compatibilized polymer blends made with premade compatibilizer and reactively formed in-situ compatibilizer in a custom-built miniature mixer Alberta Polymer Asymmetric Minimixer (APAM). The compatibilized blends show a finer morphology than uncompatibilized blends if the polymers are mixed together in the dry state and then fed into the mixer. It is found that premelting one polymer, and premixing polymers and compatibilizer, both greatly affect the compatibilized blends' morphology. The effects are complex since the dispersed phase particle size and distribution of the compatibilized blends may be smaller or larger when compared with the uncompatibilized system, depending on the material's physical and chemical properties; for example, diblock molecular weight or the preference of copolymer to migrate to a particular phase can change the final morphology. Good mobility of the copolymer to reach the interface is crucial to obtain a finer morphology. Micelles are observed when a high molecular weight diblock copolymer P(S- b -MMA) is used for a PS/PMMA blend. Because of its enhanced mobility, no micelles are found for a low molecular weight diblock copolymer P(S- b -MMA) in a PS/PMMA blend. For PS/PE/P(S- b -E) blends, finer morphology is obtained when P(S- b -E) is first precompounded with PS. Because the block copolymer prefers the PE phase, if the P(S- b -E) block copolymer is compounded with PE first, some remains inside the PE phase and does not compatibilize the interface. In the case of reactive blend PSOX/PEMA, premelting and holding the polymers at high temperature for 5 min decreases final dispersed phase particle size; however, premelting and holding for 10 min coarsens the morphology. POLYM. ENG. SCI. 46:691,702, 2006. © 2006 Society of Plastics Engineers. [source] | |||||||||||||