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Chain Extender (chain + extender)
Selected AbstractsA novel aromatic,aliphatic copolyester consisting of poly(1,4-dioxan-2-one) and poly(ethylene- co -1,6-hexene terephthalate): Preparation, thermal, and mechanical propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2010Jie Gong Abstract A novel multiblock aromatic,aliphatic copolyester poly(ethylene- co -1,6-hexene terephthalate)-copoly(1,4-dioxan-2-one) (PEHT-PPDO) was successfully synthesized via the chain-extension reaction of dihydroxyl teminated poly(ethylene- co -hexane terephthalate) (PEHT-OH) with dihydroxyl teminated poly(1,4-dioxan-2-one) (PPDO-OH) prepolymers, using toluene-2,4-diisocyanate as a chain extender. To produce PEHT-OH prepolymer with an appropriate melting point which can match the reaction temperature of PEHT-OH prepolymer with PPDO-OH prepolymer, 1,6-hexanediol was used to disturb the regularity of poly(ethylene terephthalate) segments. The chemical structures and molecular weights of PEHT-PPDO copolymers were characterized by 1H NMR, FTIR, and GPC. The DSC data showed that PPDO-OH segments were miscible well with PEHT-OH segments in amorphous state and that the crystallization of copolyester was predominantly contributed by PPDO segments. The TGA results indicated that the thermal stability of PEHT-PPDO was improved comparing with PPDO homopolymer. The novel aromatic,aliphatic copolyesters have good mechanical properties and could find applications in the field of biodegradable polymer materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2828,2837, 2010 [source] Synthesis and properties of segmented main-chain liquid-crystalline polyurethanes with a high aspect ratio mesogenic diol as a chain extenderJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2002T. Padmavathy Abstract Main-chain liquid-crystalline polyurethanes were synthesized based on a high aspect ratio mesogenic diol (4-{[4-(6-hydroxyhexyloxy)-phenylimino]-methyl}-benzoic acid 4-{[4-(6-hydroxyhexyloxy)-phenylimino]-methyl}-phenyl ester) as a chain extender; polycaprolactone (PCL) diol soft segments of different number-average molecular weights (530, 1250, or 2000); and different diisocyanates, including 1,4-hexamethylene diisocyanate (HMDI), 4,4,-methylene bis(cyclohexyl isocyanate) (H12MDI), and 4,4,-methylene bis(phenyl isocyanate) (MDI). The structure of the polymers was confirmed with Fourier transform infrared spectroscopy, and differential scanning calorimetry and polarizing microscopy measurements were carried out to examine the liquid-crystalline and thermal properties of the polyurethanes, respectively. The mesogenic diol was partially replaced with 20,50 mol % PCL. A 20 mol % mesogen content was sufficient to impart a liquid crystalline property to all the polymers. The partial replacement of the mesogenic diol with PCL of various molecular weights, as well as the various diisocyanates, influenced the phase transitions and the occurrence of mesophase textures. Characteristic liquid-crystalline textures were observed when a sufficient content of the mesogenic diol was present. Depending on the flexible spacer length and the mesogenic content, grained and threadlike textures were obtained for the HMDI and H12MDI series polymers, whereas the polyurethanes prepared from MDI showed only grained textures for all the compositions. The polymers formed brittle films and could not be subjected to tensile tests. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1527,1538, 2002 [source] Solid polymer electrolytes III: Preparation, characterization, and ionic conductivity of new gelled polymer electrolytes based on segmented, perfluoropolyether-modified polyurethaneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2002Chi-Chang Chen Abstract New segmented polyurethanes with perfluoropolyether (PFPE) and poly(ethylene oxide) blocks were synthesized from a fluorinated macrodiol mixed with poly(ethylene glycol) (PEG) in different ratios as a soft segment, 2,4-toluene diisocyanate as a hard segment, and ethylene glycol as a chain extender. Fourier transform infrared, NMR, and thermal analysis [differential scanning calorimetry and thermogravimetric analysis (TGA)] were used to characterize the structures of these copolymers. The copolymer films were immersed in a liquid electrolyte (1 M LiClO4/propylene carbonate) to form gel-type electrolytes. The ionic conductivities of these polymer electrolytes were investigated through changes in the copolymer composition and content of the liquid electrolyte. The relative molar ratio of PFPE and PEG in the copolymer played an important role in the conductivity and the capacity to retain the liquid electrolyte solution. The copolymer with a 50/50 PFPE/PEG ratio, having the lowest decomposition temperature shown by TGA, exhibited the highest ionic conductivity and lowest activation energy for ion transportation. The conductivities of these systems were about 10,3 S cm,1 at room temperature and 10,2 S cm,1 at 70 °C; the films immersed in the liquid electrolyte with an increase of 70 wt % were homogenous with good mechanical properties. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 486,495, 2002; DOI 10.1002/pola.10119 [source] Photocurable Shape-Memory Copolymers of , -Caprolactone and L -LactideMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2010Minoru Nagata Abstract Biodegradable and photocurable block copolymers of , -caprolactone and L -lactide were synthesized by polycondensation of PLLA diol (,=,10,000,g,·,mol,1), PCL diol (,=,10,000,g,·,mol,1), and a chain extender bearing a coumarin group. The effect of copolymer composition on the thermal and mechanical properties of the photocured copolymers was studied by means of DSC and cyclic tensile tests. An increase in Young's modulus and a decrease in the tensile strain with increasing PLLA content was observed for the block copolymers. Block copolymers with high PCL content showed good to excellent shape-memory properties. Random copolymers exhibited Rf and Rr values above 90% at 45,°C for an extremely large tensile strain of 1,000%. [source] Composites of carbon nanofibers and thermoplastic polyurethanes with shape-memory properties prepared by chaotic mixingPOLYMER ENGINEERING & SCIENCE, Issue 10 2009Guillermo A. Jimenez Composites of carbon nanofibers (CNFs), oxidized carbon nanofibers (ox-CNFs), and shape-memory thermoplastic polyurethane (TPU) were prepared in a chaotic mixer and their shape-memory properties evaluated. The polymer was synthesized from 4,4,-diphenylmethane diisocyanate, 1,4-butanediol chain extender, and semicrystalline poly(,-caprolactone) diol soft segments. The shape-memory action was triggered by both conductive and resistive heating. It was found that soft segment crystallinity and mechanical reinforcement by nanofibers produced competing effects on shape-memory properties. A large reduction in soft segment crystallinity in the presence of CNF and stronger mechanical reinforcement by well-dispersed ox-CNF determined the shape-memory properties of the respective composites. It was found that the maximum shape recovery force, respectively, 3 and 4 MPa, was obtained in the cases of 5 and 1 wt% CNF and ox-CNF, respectively, compared with ,1.8 MPa for unfilled TPU. The degree of soft segment and hard segment phase separation and thermal stability of the composites were analyzed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers. [source] Poly(ester-urethane)s synthesized using polyoxalate diolsPOLYMER ENGINEERING & SCIENCE, Issue 2 2005Hideho Tanaka Amorphous poly(ester-urethane)s (PEUs) were synthesized by reacting polyoxalate diols (PODs), which are oligoester diols prepared from condensation polymerization of dimethyl oxalate (DMO) and alkane diols, with 4, 4,-diphenylmethane diisocyanate (MDI) and propylene diamine (PDA), a chain extender. Their structure,property relationships were studied, mainly focused on effects of molecular weight and alkylene chain length of the POD. The synthesized PEUs were buried in compost soil at 30°C and incubated to conveniently evaluate their biodegradability. Their hydrolytic characteristics were also examined, and what made poly(oxalate-urethane) (POU) biodegradable was discussed. Poly(oxalate carbonate-urethane) (POCU), which can be produced adding a polycarbonate diol (PCD) into the POD and then copolymerizing them with DMO, provided biodegradable polyurethanes with mechanical properties appropriate for practical uses. In addition, the microstructure of these copolyurethanes was characterized. POLYM. ENG. SCI., 45:163,173, 2005. © 2005 Society of Plastics Engineers. [source] Synthesis and properties of room temperature curable trimethoxysilane-terminated polyurethane and their dispersionsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 8 2007Sankaraiah Subramani Abstract The purpose of this research is to study the synthesis and characterization of stable aqueous dispersions of externally chain extended polyurethane/urea compositions terminated by hydrolyzable or hydrolyzed trialkoxysilane groups incorporated through secondary amino groups. These dispersions with excellent storage stability are substantially free from organic solvents which cure to water and solvent resistant, tough, scratch resistant, preferably light stable (non-yellowing) silylated polyurethane (SPU) films. The films were characterized by FT-IR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile strength and water contact angle measurements, nanoindentation, gel content, water and xylene swellability tests. The properties of the films were discussed and correlated in detail by changing length of soft segment, diisocyanates, NCO/OH ratio and chain extender, ethylenediamine (EDA). From the results, it was found that the particle size and viscosity are lower whereas the gel content and thermal stability are higher for SPUs. Modulus, hardness and tensile properties of SPU films are superior compared to EDA-PU film. Higher water contact angle and residual weight percentage of SPU films confirm silylation of PU by [3-(phenylamino)propyl]trimethoxysilane (PAPTMS). Increase in NCO/OH ratios consumes more quantity of PAPTMS which makes PU with superior mechanical properties. Higher PAPTMS content in SPU results in effective crosslinking of the functional silanol groups formed by hydrolysis reaction of trimethoxysilane groups. Overall, SPUs synthesized at 1.4 NCO/OH ratio using Poly-(oxytetramethylene)glycol (PTMG)-2000 and isophorone diisocyanate (or) toluene-2,4-diisocyanate have excellent properties compared to SPUs prepared using PTMG-1000 and at 1.2 and 1.6 NCO/OH ratios. SPUs prepared at 1.6 NCO/OH ratio are brittle due to higher crosslinking density. In addition, the crosslinking density of the films can be modified through silane end-group modification to produce SPUs with a wide range of physical properties. Copyright © 2007 John Wiley & Sons, Ltd. [source] Conformational aspects of segmented poly(ester-urethanes)MACROMOLECULAR SYMPOSIA, Issue 1 2003S. Ioan Abstract Segmented poly(ester-urethanes) containing hard and soft segments, were obtained from aromatic diisocyanates with thiodiglycol or diethylene glycol as chain extenders, and poly(ethylene glycol)adipate usig a multistep polyaddition process. Transition temperatures by differential scanning calorimetry and thermo-optical analysis were employed to characterize polyurethane materials. Changes in the conformation of these polyurethanes were analyzed also, by viscometer measurements in N,N-dimethyl-formamide. The obtained data revealed that the thermal curves are influenced by the soft and hard segment structures in the temperature range studied. [source] Preparation and characterization of polyurethane,gold nanocomposites prepared using encapsulated gold nanoparticlesPOLYMER INTERNATIONAL, Issue 7 2010Chao-Ching Chang Abstract Gold nanoparticles (GNPs) have been widely studied due to their unique properties. Although many research groups have developed the synthesis of GNPs using various polymers as stabilizing or reducing agents, the effects of GNPs on the structures and properties of polymer matrices have been less reported. We propose a new design for the preparation of polyurethane,gold (PU,Au) nanocomposites. 11-Mercapto-1-undecanol-coated GNPs acted as the chain extenders and reacted with isocyanates to form covalent bonds between PU and GNPs. PU,Au nanocomposites were successfully synthesized, and the effects of multifunctional GNPs on the structures, morphology and properties of poly(ester urethane) were investigated. Scanning electron microscopy images suggested the GNPs can be dispersed uniformly in the PU matrix. Maltese-cross of spherical crystals was observed in the PU,Au nanocomposites, and the size of the crystals decreased with an increase in gold content. As the gold content increased, the thermal decomposition temperature and the temperature of the maximum decomposition rate increased. The glass transition temperature, crystal melting temperature and melting enthalpy of the soft segment also increased progressively. The results showed that multifunctional GNPs concentrated hard segments and resulted in an increase of heterogeneous nucleation, phase separation and elasticity. Copyright © 2010 Society of Chemical Industry [source] Fireproofing of polyurethane elastomers by reactive organophosphonatesPOLYMER INTERNATIONAL, Issue 1 2003Wassef El Khatib Abstract Polyurethane elastomers were prepared with hydroxytelechelic polybutadiene (HTPB) as polyol, modified 4,4,-diphenylmethane diisocyanate (modified MDI) as liquid polyisocyanate, and phosphonate diols as chain extenders and flame retardant compounds. These phosphonate diols were synthesized by radical thiol,ene addition of allyl or vinyl dialkyl phosphonate to 3-mercapto-1,2-propanediol. For various percentages of phosphorus (0 to 3%, w/w), polyurethane elastomers remain stable up to 250,°C. The percentage of residual char at 600,°C increases with increasing phosphorus content. For the soft segments, no variation in the glass transition temperature (Tg) is observed as the percentage of P increases, whereas the Tg of hard segments increases. Above 0.5% phosphorus content, the limiting oxygen index (LOI) becomes higher than the percentage of oxygen in the air. © 2003 Society of Chemical Industry [source] | ||||||||||