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Same Polymer (same + polymer)
Selected AbstractsPolymerization of itaconic acid initiated by a potassium persulfate/N,N -dimethylethanolamine systemJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008S. J. Veli Abstract The synthesis and characterization of poly(itaconic acid) (PIA) with a novel initiator/activator system is presented. The initiator in this system was potassium persulfate, whereas the activator was N,N -dimethylethanolamine (DMEA). PIA was synthesized in distilled water and in 0.1M HCl at 40°C with reaction times of 72 and 96 h. PIA was investigated with differential scanning calorimetry, gel permeation chromatography, and pulse gradient spin echo-NMR and compared to the same polymer synthesized in dioxane with 2,2,-azobisisobutyronitrile as the initiator. It was shown that, despite the fact that some residual DMEA remained in the system, the properties of the PIA polymerized in the aqueous phase were very similar to the dioxane-synthesized polymer, which will enable a faster, cheaper, and environmentally more acceptable polymerization of itaconic acid. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Morphology, Thermal and Mechanical Properties of Poly(propylene) Fibre-Matrix CompositesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 8 2003Shadi Houshyar Abstract Preparation and properties of poly(propylene)-poly(propylene) composites have been investigated. Poly(propylene) fibres of varying diameter have been incorporated in a random ethylene co -poly(propylene). The composites prepared from the same semi-crystalline polymer in the matrix and reinforcement have lead to inherently strong interfacial bonding between the two phases of the same polymer. The composites demonstrated enhanced stiffness, which increased with fibre diameter. The structure, thermal, static and mechanical properties of poly(propylene) long fibre reinforced random co -poly(propylene) composites have been studied with reference to the fibre diameter. The matrix and fibre components retained their separate melting temperatures. After melting, the two phases remained separate and showed their individual crystallization temperatures on cooling, and melting temperatures on a second heating. The melting temperature of the poly(propylene) fibres increased after formation of the composites. The compression molding of the composites at a temperature below the melting temperature of the fibres caused annealing of the fibre crystals. By incorporation of long poly(propylene) fibre into random co -poly(propylene), the glass transition, storage and static modulus have been found to be increasing and composite with the largest fibre diameter shows better properties. Transcrystallization of the matrix poly(propylene) was observed. Optical microscopy of composites with fibre diameter 68 ,m. [source] Effect of ,-irradiation on the physical properties and dyeability of poly(vinyl butyral) blends with polystyrene and poly(ethylene glycol)POLYMER COMPOSITES, Issue 6 2008Horia M. Nizam El-Din Cast films of polymer blends essentially based on poly(vinyl butyral) (PVB) and equal ratios of polystyrene (PS) and poly(ethylene glycol) (PEG) were prepared from benzene and butyl alcohol solutions of the individual polymers. The effect of ,-irradiation on the thermal decomposition and tensile mechanical properties was investigated. Moreover, the effect of ,-irradiation on the dye affinity of PVB/PS and PVB/PEG for basic and acid dyestuffs was studied. The thermogravimetric analysis (TGA) study showed that the unirradiated PVB polymer films prepared in benzene displayed higher thermal stability than the same polymer films prepared in butanol. However, in all cases the thermal stability was found to increase with increasing ,-irradiation dose. On the other hand, PVB/PS blend possesses higher thermal stability than PVB/PEG, as shown from the determination of the weight loss (%) at different heating temperatures, the temperatures of the maximum rate of reaction and the activation energy. While, pure PS films showed the stress-strain behavior of brittle polymers, PVB/PS films showed the behavior of tough polymers with yielding properties. The results of dyeing clearly showed that the solvent type, blend composition, and irradiation dose are determining factors for the dye affinity for basic or acid dyes. For example, unirradiated PVB films prepared from butanol displayed a higher affinity for the basic and acid dyes than the same polymer prepared from the same benzene. However, PVB prepared from butanol showed higher affinity to the dyes than PS prepared from the same solvent. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] HMGA1a Protein Unfolds or Refolds Synthetic DNA,Chromophore Hybrid Polymers: A Chaperone-Like BehaviorCHEMBIOCHEM, Issue 2 2008Wei Wan Abstract High group mobility protein, HMGA1a, was found to play a chaperone-like role in the folding or unfolding of hybrid polymers that contained well-defined synthetic chromophores and DNA sequences. The synthetic and biological hybrid polymers folded into hydrophobic chromophoric nanostructures in water, but existed as partially unfolded configurations in pH or salt buffers. The presence of HMGA1a induced unfolding of the hybrid DNA,chromophore polymer in pure water, whereas the protein promoted refolding of the same polymer in various pH or salt buffers. The origin of the chaperone-like properties probably comes from the ability of HMGA1a to reversibly bind both synthetic chromophores and single stranded DNA. The unfolding mechanisms and the binding stoichiometry of protein,hybrid polymers depended on the sequence of the synthetic polymers. [source] CO2 and SnII Adducts of N-Heterocyclic Carbenes as Delayed-Action Catalysts for Polyurethane SynthesisCHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2009Bhasker Bantu Abstract Catalytic rivals: Both CO2 -protected tetrahydropyrimidin-2-ylidene-based N-heterocyclic carbenes (NHCs) and SnII -1,3-dimesitylimidazol-2-ylidene, as well as SnII -1,3-dimesitylimidazolin-2-ylidene complexes (example displayed), have been identified as truly latent catalysts for polyurethane (PUR) synthesis rivaling all existing systems both in activity and latency. A series of CO2 -protected pyrimidin-2-ylidenes as well as 1,3-dimesitylimidazol-2-ylidene and dimesitylimidazolin-2-ylidene complexes of SnII have been prepared. Selected single-crystal X-ray structures are reported. The new compounds were investigated for their catalytic behavior in polyurethane (PUR) synthesis. All compounds investigated showed excellent catalytic activity, rivaling the industrially most relevant catalyst dibutyltin dilaurate. Even more important, all compounds displayed pronounced latent behavior, in selected cases rivaling and exceeding the industrially relevant latent catalyst phenylmercury neodecanoate both in terms of latency and catalytic activity. This allows for creating one-component PUR systems with improved pot lifetimes. Pseudo-second-order kinetics were found for both CO2 -protected tetrahyropyrimidin-2-ylidenes and for [SnCl2(1,3-dimesityldihydroimidazol-2-ylidene)], indicating a fast pre-catalyst decomposition prior to polyurethane formation. 1,3-Di(2-propyl)tetrahydropyrimidin-2-ylidene was additionally found to be active in the cyclotrimerization of various isocyanates, offering access to a broad variability in polymer structure, that is, creating both urethane and isocyanurate moieties within the same polymer. [source] The effect of water-soluble polymers on rheology of microfibrillar cellulose suspension and dynamic mechanical properties of paper sheetJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Arja-Helena Vesterinen Abstract Rheological properties of fiber/polymer suspensions and dynamic mechanical analysis (DMA) of paper sheets containing the same polymers were measured. Correlations between viscoelastic properties of suspensions and strength of paper sheet are presented. Rheological properties of suspensions of microfibrillar cellulose (MFC) and a set of water soluble polymers were measured. Rheological properties of these complex fluids vary considerably depending on the added polymer. A suspension of fiber and carboxymethyl cellulose (CMC) exhibits a viscosity higher than the sum of the viscosity of the individual components in the suspension. In contrast, when cationic starch (CS) is used together with the fiber, the yielding behavior rather than the viscosity is characteristic of the suspension. Dynamic mechanical properties of paper sheets containing CMC or CS as additives were studied at different humidity levels. Different yielding behavior observed in oscillatory rheology can be correlated with straining behavior in dynamic mechanical properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [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] | |||||||||||||