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Bulk Polymer (bulk + polymer)
Selected AbstractsSynergistic Ordering of Side-Group Liquid Crystal Polymer and Small Molecule Liquid Crystal: Order and Phase Behavior of Nematic Polymer Solutions,MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 19-20 2007Neal R. Scruggs Abstract Addition of a small-molecule liquid crystal (5CB) to a cyanobiphenyl-based side-group liquid crystal polymer (SGLCP) stabilizes nematic order, increasing the isotropization temperature (TNI) more than 15,°C. Despite synergistic ordering at high concentration, small amounts of polymer destabilize nematic order. Even though TNI(SGLCP) is 27,°C greater than TNI(5CB), 2H NMR shows that the order parameter of the SGLCP is less than that of 5CB at concentrations for which monodomains were accessible (,10 wt.-%). The results imply that nematic order is frustrated in the bulk polymer and addition of small molecule LC relaxes this frustration by allowing greater configurational freedom. Conversely, adding small amounts of polymer to the bulk 5CB introduces frustration, resulting in the strong asymmetry of the phase diagram. [source] Orientation and strain cycle effects on the impact performance of polyethylenePOLYMER ENGINEERING & SCIENCE, Issue 4 2005Alexis Paizis The effects of orientation by plastic strain on the impact fracture resistance of a pipe-grade polyethylene have been investigated. Isotropic samples of bulk polymer were subjected, by plane-strain compression, to uniform Hencky strains of up to ±40%. In some samples this strain was reversed to restore the original dimensions. Impact bend specimens were prepared from samples oriented either normal to or within the fracture plane. Plane-strain fracture resistance and transition temperature were measured at 1 m/s by using the ISO 17281 method, and plane stress fracture resistance was measured by using the Reversed Charpy test. Orientation within the fracture plane by plastic compression across it compromises the relatively high plane-stress toughness of this material and increases the brittle-tough transition temperature, while the opposite is true of plastic extension. Reversion from a state of adverse orientation, by completing a strain cycle, only partially restores the fracture resistance of the isotropic polymer. POLYM. ENG. SCI., 45:596,605, 2005. © 2005 Society of Plastics Engineers [source] Properties of poly(ethylene terephthalate),poly(ethylene naphthalene 2,6-dicarboxylate) blends with montmorillonite clayPOLYMER INTERNATIONAL, Issue 12 2005Antonio Sanchez-Solis Abstract The production and properties of blends of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalene 2,6-dicarboxylate) (PEN) with three modified clays are reported. Octadecylammonium chloride and maleic anhydride (MAH) are used to modify the surface of the montmorillonite,Na+ clay particles (clay,Na+) to produce clay,C18 and clay,MAH, respectively, before they are mixed with the PET/PEN system. The transesterification degree, hydrophobicity and the effect of the clays on the mechanical, rheological and thermal properties are analysed. The PET,PEN/clay,C18 system does not show any improvements in the mechanical properties, which is attributed to poor exfoliation. On the other hand, in the PET,PEN/clay,MAH blends, the modified clay restricts crystallization of the matrix, as evidenced in the low value of the crystallization enthalpy. The process-induced PET,PEN transesterification reaction is affected by the clay particles. Clay,C18 induces the largest proportion of naphthalate,ethylene,terephthalate (NET) blocks, as opposed to clay,Na+ which renders the lowest proportion. The clay readily incorporates in the bulk polymer, but receding contact-angle measurements reveal a small influence of the particles on the surface properties of the sample. The clay,Na+ blend shows a predominant solid-like behaviour, as evidenced by the magnitude of the storage modulus in the low-frequency range, which reflects a high entanglement density and a substantial degree of polymer,particle interactions. Copyright © 2005 Society of Chemical Industry [source] Nanostructuring polymers with cyclodextrins,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2-3 2005Cristian C. Rusa Abstract Bulk solid polymer samples formed by the coalescence of guest polymer chains from their inclusion compounds (ICs) formed with host cyclodextrins (CDs) can result in significant reorganization of their phase structures, morphologies, and even chain conformations from those more commonly produced from randomly-coiled, entangled polymer solutions and melts. When the cyclic host CDs are threaded by polymer chains to form crystalline polymer-CD-ICs, the guest polymers become highly extended due to the narrow host CD diameters (,5, 7, and 9 Å for , -, , -, and , -CDs) and are segregated from neighboring guest polymer chains by the CD-IC channel walls. As a consequence, when polymer-CD-IC crystals are treated with CD solvents that do not dissolve the guest polymers or are treated with amylase enzymes, the resulting coalesced bulk polymer samples often display properties distinct from those of normally produced bulk samples of the same polymers. In this article the CD-IC processing of polymers to generate novel polymer microstructures and morphologies are described, to control the phase separation of immiscible blocks in block copolymers, and to form well-mixed intimate blends of two or more polymers that are normally incompatible. The thermal and temporal stabilities of polymer samples coalesced from their ICs formed with CDs will also be mentioned, and it is suggested that the range of polymer properties can be greatly expanded by their CD-IC processing. Copyright © 2005 John Wiley & Sons, Ltd. [source] The effect of temperature and ventilation condition on the toxic product yields from burning polymersFIRE AND MATERIALS, Issue 1 2008A. A. Stec Abstract A major cause of death or permanent injury in fires is inhalation of toxic gases. Moreover, every fire is unique, and the range of products, highly dependant on fire conditions, produces a wide variety of toxic and irritant species responsible for the most fire fatalities. Therefore, to fully understand each contribution to the toxicity it is necessary to quantify the decomposition products of the material under the test. Fires can be divided into a number of stages from smouldering combustion to early well-ventilated flaming through to fully developed under-ventilated flaming. These stages can be replicated by certain bench-scale physical fire models using different fuel-to-oxygen ratios, controlled by the primary air flow, and expressed in terms of the equivalence ratio (the actual fuel/air ratio divided by the stoichiometric fuel/air ratio). This work presents combustion product yields generated using a small-scale fire model. The Purser Furnace apparatus (BS7990 and ISO TS 19700) enables different fire stages to be created. Identification and quantification of combustion gases and particularly their toxic components from different fire scenarios were undertaken by continuous Fourier transform infrared spectroscopy. The relationship between type of the fire particularly the temperature and ventilation conditions and the toxic product yields for four bulk polymers, low-density polyethylene, polystyrene (PS), Nylon 6.6 and polyvinyl chloride (PVC) is reported. For all the polymers tested, except PVC, there is a dramatic increase in the yield of products of incomplete combustion (CO and hydrocarbons) with increase in equivalence ratio, as might be expected. For PVC there is a consistently high level of products of incomplete combustion arising both from flame inhibition by HCl and oxygen depletion. There is a low sensitivity to furnace temperature over the range 650,850°C, except that at 650°C PS shows an unexpectedly high yield of CO under well-ventilated conditions and PVC shows a slightly higher hydrocarbon yield. This demonstrates the dependence of toxic product yields on the equivalence ratio, and the lack of dependence on furnace temperature, within this range. Copyright © 2007 John Wiley & Sons, Ltd. [source] Response Characteristics of Thermoresponsive Polymers Using Nanomechanical Cantilever SensorsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2009Calvin Bradley Abstract We investigated coatings of thermally responsive thin polymer films prepared on nanomechanical cantilever sensor (NCS): (i) a PNIPAM brush, and (ii) an interlinked ppDEA polymer. Upon heating from 22 to 50,°C in water, a minimum in the differential deflection between 31.9,±,1.7,°C (PNIPAM) and 47.7,±,1.9,°C (ppDEA) was measured. The minimum in differential deflection can be associated with the lower critical solution temperature (LCST) of the films. Below the LCST the NCS deflection corresponds to a bending toward the thermally responsive polymer film side, associated to dehydration. At higher temperature, the deflection was reversed, i.e., away from the polymer coating. This response is mainly attributed to a bimaterial effect between the collapsed polymer and the NCS material. The LCST of the PNIPAM brush layer and the ppDEA film were close to that reported for the bulk polymers. [source] Synthesis of Polar and Non-Polar Nano-Corundum and Uses for Aluminium Carboxylate Hybrid Nanocomposites with Enhanced Surface Mechanical and Viscoelastic PropertiesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10-11 2007Hans-Jürgen Gläsel Abstract Amorphous aluminium carboxylate nanoparticles were checked for their potential as precursors for nano-corundum powders prepared by a high-temperature conversion process. Exemplifying x-ray photoelectron spectroscopy studies of the aluminium carboxylate nanoparticles with polar and non-polar ligands showed that, during the course of the high-temperature treatment, specific features of the ultrafine organo-aluminium powders such as polarity/non-polarity and concomitant hydrophilic/hydrophobic properties were preserved. The resulting nano-corundum powders were in turn identified as positive synergists for the enforcement of radiation-cured aluminium carboxylate/acrylate coatings. The simultaneous (optional) use of micro-corundum particles yielded polymer hybrid coatings. In comparison to acrylate-based organo-aluminium nanocomposites, polymeric hybrid coatings revealed significantly improved surface mechanical and viscoelastic properties. In addition to acrylate coatings, other polar and even non-polar bulk polymers were subject to nano/micro modification using polar and non-polar nano-corundum powders, respectively. [source] | ||||||||||