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Base Polymer (base + polymer)
Selected AbstractsA flammability performance comparison between synthetic and natural clays in polystyrene nanocompositesFIRE AND MATERIALS, Issue 4 2005Alexander B. Morgan Abstract Polymer-clay nanocomposites are a newer class of flame retardant materials of interest due to their balance of mechanical, thermal and flammability properties. Much more work has been done with natural clays than with synthetic clays for nanocomposite flammability applications. There are advantages and disadvantages to both natural and synthetic clay use in a nanocomposite, and some of these, both fundamental and practical, will be discussed in this paper. To compare natural and synthetic clays in regards to polymer flammability, two clays were used. The natural clay was a US mined and refined montmorillonite, while the synthetic clay was a fluorinated synthetic mica. These two clays were used as inorganic clays for control experiments in polystyrene, and then converted into an organoclay by ion exchange with an alkyl ammonium salt. The organoclays were used to synthesize polystyrene nanocomposites by melt compounding. Each of the formulations was analysed by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). Flammability performance was measured by cone calorimeter. The data from the experiments show that the synthetic clay does slightly better at reducing the heat release rate (HRR) than the natural clay. However, all the samples, including the inorganic clay polystyrene microcomposites, showed a decreased time to ignition, with the actual nanocomposites showing the most marked decrease. The reason for this is postulated to be related to the thermal instability of the organoclay (via the quaternary alkyl ammonium). An additional experiment using a more thermally stable organoclay showed a time to ignition identical to that of the base polymer. Finally, it was shown that while polymer-clay nanocomposites (either synthetic or natural clay based) greatly reduce the HRR of a material, making it more fire safe, they do not provide ignition resistance by themselves, at least, at practical loadings. Specifically, the cone calorimeter HRR curve data appear to support that these nanocomposites continue to burn once ignited, rather than self-extinguish. Copyright © 2004 John Wiley & Sons, Ltd. [source] Reduction in tactoid size as a means for reinforcing high-density polyethylene/montmorillonite nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2009Carla Marega Abstract Nanocomposites were prepared by adding montmorillonite clay to a high-density polyethylene matrix. Their structure, morphology, thermal behavior, and physical, mechanical properties were studied. The filler did not alter much the structure and morphology of the matrix, with the exception of a disruptive effect on the lamellar stacks. The crystallization behavior, equilibrium melting temperature, and work of chain folding of the nanocomposites were also unaltered with respect to that of the PE base polymer. However, significant improvements in physical,mechanical properties were observed. The reason for this increase in performance was ascribed to the interaction between the filler and the matrix, especially because of a reduction in size of the original tactoids to stacks of just a few layers, albeit not intercalated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Conducting nanocomposites of polyacrylamide with acetylene black and polyanilinePOLYMER COMPOSITES, Issue 4 2009Pramod Kumar Verma A conducting nanocomposite of polyacrylamide (PAA) with acetylene black was prepared via Na2AsO3 -K2CrO4 redox initiated polymerization of acrylamide in water containing a suspension of acetylene black. FTIR analyses confirmed the presence of PAA in the nanocomposites. The composite possessed lower thermal stability than AB and exhibited three stages of decomposition upto 430°C. DSC thermogram revealed three endotherms due to minor thermal degradation (at ,100°C), melting and decomposition (at ,230°C) and major decomposition (at ,430°C). TEM analyses indicated the formation of globular composite particles with sizes in 30,70 nm range. In contrast to the very low conductivity of the base polymer the composite showed a dramatic increase in conductivity (0.19,6.0 S/cm) depending upon AB loading. Log (conductivity) ,1/T plot showed a change in slope at ,127°C indicating the manifestation of an intrinsic conductivity region and an impurity conductivity region. The activation energy for conduction as estimated from the slope of region I was 0.008 eV/mol. The C,V plot was linear showing a metallic behavior. For comparison in conductivity PAA-polyaniline composite was also prepared which however displayed much lower conductivity values. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Tensile properties of carbon filled liquid crystal polymer composites,POLYMER COMPOSITES, Issue 1 2008Jason M. Keith Electrically and thermally conductive resins can be produced by adding carbon fillers. Mechanical properties such as tensile modulus, ultimate tensile strength, and strain at ultimate tensile strength are vital to the composite performance in fuel cell bipolar plate applications. This research focused on performing compounding runs followed by injection molding and tensile testing of carbon filled Vectra A950RX liquid crystal polymer composites. The four carbon fillers investigated included an electrically conductive carbon black, thermocarb synthetic graphite particles, and two carbon fibers (Fortafil 243 and Panex 30). For each different filler type, resins were produced and tested that contained varying amounts of these single carbon fillers. The carbon fiber samples exhibited superior tensile properties, with a large increase in tensile modulus over the base polymer, and very low drop in the ultimate tensile strength as the filler volume fraction was increased. The strain at the ultimate tensile strength was least affected by the addition of the Panex carbon fiber but was significantly affected by the Fortafil carbon fiber. In general, composites containing synthetic graphite did not perform as well as carbon fiber composites. Carbon black composites exhibited poor tensile properties. POLYM. COMPOS., 29:15,21, 2008. © 2007 Society of Plastics Engineers [source] Characteristics of polystyrene/polyethylene/clay nanocomposites prepared by ultrasound-assisted mixing processPOLYMER ENGINEERING & SCIENCE, Issue 7 2004J. G. Ryu In this study, polymer-clay nanocomposites of various concentrations were prepared by ultrasonically assisted polymerization and melt-mixing processes. A sonication process using power ultrasonic waves was employed to enhance nano-scale dispersion during melt-mixing of polymer blends and organically modified clay. We expected enhanced breakup of layered silicate bundles and further reduction in the size of the dispersed phase, with better homogeneity compared to the different immiscible blend pairs. X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to characterize the structures of the nanocomposites. The rheological behaviors of the obtained nanocomposites were measured with parallel plate rheometry. It was found that the ultrasound-assisted process successfully generated exfoliated nanocomposites and promoted in-situ compatibilization of the matrix comprising an immiscible pair of polymers in a blend. The resulting nanocomposite exhibited superior thermal stability and elastic modulus compared to the base polymer. Polym. Eng. Sci. 44:1198,1204, 2004. © 2004 Society of Plastics Engineers. [source] Schiff base substitute polyphenol and its metal complexes derived from o -vanillin with 2,3-diaminopyridine: synthesis, characterization, thermal, and conductivity propertiesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2008smet Kaya Abstract Poly-2,3 - bis[(2-hydroxy-3-methoxyphenyl)methylene]diamino pyridine (PHMPMDAP) that a new Schiff base polymer has been synthesized and characterized by spectroscopy, elemental, and thermal analyses techniques. This azomethine polymer was found to form complexes readily with Cu(II), Zn(II), Co(II), Pb(II), and Fe(II). From IR and UV-Vis studies, the phenolic oxygen and imine nitrogen of the ligand were found to be the coordination sites. Thermogravimetric analysis (TGA) data indicate the polymer to be more stable than the monomer. The structure of the polymer obtained was confirmed by FT-IR, UV-Vis, 13C-NMR, and 1H-NMR. Characterization was undertaken by TGA, size exclusion chromatography (SEC), and solubility tests. Also, electrical conductivities of PHMPMDAP and polymer,metal complexes are measured by four probe technique. Copyright © 2008 John Wiley & Sons, Ltd. [source] Blends of triazine-based hyperbranched polyether with LDPE and plasticized PVCJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Jyotishmoy Borah Abstract Triazine-based hyperbranched polyether was obtained by earlier reported method and blended with low density polyethylene (LDPE) and plasticized poly(vinyl chloride) (PVC) separately to improve some desirable properties of those linear polymers. The properties like processability, mechanical properties, flammability, etc. of those linear polymers were studied by blending with 1,7.5 phr of hyperbranched polyether. The mechanical properties were also measured after thermal aging and leaching in different chemical media. SEM study indicates that both polymers exhibit homogenous morphology at all dose levels. The mechanical properties like tensile strength, elongation at break, hardness, etc. of LDPE and PVC increase with the increase of dose level of hyperbranched polyether. The flame retardant behavior as measured by limiting oxygen index (LOI) for all blends indicates an enhanced LOI value compared to the polymer without hyperbranched polyether. The processing behavior of both types of blends as measured by solution viscosity and melt flow rate value indicates that hyperbranched polyether acts as a process aid for those base polymers. The effect of leaching and heat aging of these linear polymers on the mechanical properties showed that hyperbranched polyether is a superior antidegradant compared to the commercially used N -isopropyl- N -phenyl p -phenylene diamine. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 648,654, 2007 [source] | ||||||||||