The Experts below are selected from a list of 14844 Experts worldwide ranked by ideXlab platform
Angels Serra - One of the best experts on this subject based on the ideXlab platform.
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New anhydride/epoxy thermosets based on diglycidyl ether of bisphenol A and 10-undecenoyl modified poly(ethyleneimine) with improved impact resistance
Progress in Organic Coatings, 2015Co-Authors: Cristina Acebo, Xavier Fernández-francos, Xavier Ramis, Silvia De La Flor, Angels SerraAbstract:Abstract New dendritic modifiers have been synthesized by amidation of hyperbranched poly(ethylenimine) (PEIs) with 10-undecenoic acid to obtain hyperbranched polymers (HBPs) with different degree of modification. These HBPs have been used as toughness modifiers in a proportion of 10 and 20% in reference to the epoxy resin in diglycidyl ether of bisphenol A (DGEBA)/methyltetrahydrophthalic anhydride (MTHPA) formulations. The curing process has been studied by Dynamic Scanning Calorimetry and by rheometry, which allow the kinetic constants and the gel and vitrification times to be evaluated. The materials obtained have been thermally characterized and their mechanical properties have been evaluated. An increase in impact resistance has been achieved and the T g of all thermosets prepared was higher than 100 °C in spite of the flexible structure of the PEI modifiers.
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New Epoxy-Anhydride Thermosets Modified with Multiarm Stars with Hyperbranched Polyester Cores and Poly(ϵ-caprolactone) Arms
Polymer-Plastics Technology and Engineering, 2014Co-Authors: Adrian M. Tomuta, Xavier Fernández-francos, Francesc Ferrando, Angels Serra, Xavier RamisAbstract:Multiarm star polymers with hyperbranched aromatic or aromatic-aliphatic cores and poly(ϵ-caprolactone) arms have been used as toughness modifiers in epoxy-anhydride formulations catalyzed by benzyldimethylamine. The curing process has been studied by Dynamic Scanning Calorimetry, demonstrating little influence of the mobility of the reactive species and the hydroxyl content on the kinetics of this process. The obtained materials were characterized by thermal and mechanical tests and the microstructure by electron microscopy. Homogeneous thermosets have been obtained with a remarkable increase in impact strength without compromising glass transition temperature, thermal stability or hardness.
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Effect of hydroxyl ended and end-capped multiarm star polymers on the curing process and mechanical characteristics of epoxy/anhydride thermosets
Progress in Organic Coatings, 2014Co-Authors: Cristina Acebo, Xavier Fernández-francos, Xavier Ramis, Annamaria Picardi, Silvia De La Flor, Angels SerraAbstract:Abstract Multiarm star polymers have been synthesized by cationic ring-opening polymerization of ɛ-caprolactone from a hyperbranched poly(ethyleneimine) core and end-capped with acetic anhydride. These star polymers have been used as modifiers in diglycidylether of bisphenol A/methyl tetrahydrophthalic anhydride/benzyl dimethylamine formulations. The curing process is studied by Dynamic Scanning Calorimetry and rheometry and the resulting thermosets are characterized by Dynamic mechanical thermal analysis and thermogravimetry. Internal stresses generated during curing are measured and interpreted in terms of the thermal-mechanical properties of the cured materials. The influence of the modifier in the toughness improvement of the cured thermosets is determined by standardized impact tests and the microstructure of the material observed by Scanning electron microscopy.
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Multiarm star with poly(ethyleneimine) core and poly(ε-caprolactone) arms as modifiers of diglycidylether of bisphenol A thermosets cured by 1-methylimidazole
Reactive and Functional Polymers, 2013Co-Authors: Cristina Acebo, Xavier Fernández-francos, Francesc Ferrando, Angels Serra, Josep Maria Salla, Xavier RamisAbstract:Abstract Well-defined multiarm star copolymers, with hyperbranched poly(ethyleneimine) (PEI) as the core and poly(e-caprolactone) (PCL) arms with different degree of polymerization were synthesized by cationic ring-opening polymerization of e-caprolactone from a hyperbranched poly(ethyleneimine) core and used to modify diglycidylether of bisphenol A formulations cured with 1-methylimidazole as anionic initiator. The curing process was studied by Dynamic Scanning Calorimetry (DSC) and FTIR. By rheometry the complex viscosity of the multiarm stars synthesized and the influence of their addition to the reactive mixture was analyzed in detail. The resulting materials were characterized by thermal and mechanical tests. The addition of the multiarm star to the formulation led to homogeneous materials with a slightly toughened fracture in comparison to neat DGEBA thermosets without compromising thermal characteristics.
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New epoxy thermosets modified with multiarm star poly(lactide) with poly(ethyleneimine) as core of different molecular weight
European Polymer Journal, 2013Co-Authors: Cristina Acebo, Xavier Fernández-francos, Francesc Ferrando, Angels Serra, Xavier RamisAbstract:Multiarm stars containing a hyperbranched poly(ethyleneimine) core of different molecular weight and poly(lactide) arms were synthesized by cationic ring-opening polymerization of lactide from a hyperbranched poly(ethyleneimine) core. After characterization by rheometry, Calorimetry, thermogravimetry and nuclear magnetic resonance, these polymers were used as chemically modifiers in the anionic curing of diglycidylether of bisphenol A epoxy resin. The curing process was studied by Dynamic Scanning Calorimetry, demonstrating the influence of the mobility of the reactive species and the hydroxyl content on the curing kinetics. The resulting materials were characterized by thermal and mechanical tests. The addition of the multiarm stars led to homogeneous materials with a slight improvement on the impact strength in comparison with the neat material, without compromising the glass transition temperature. The reworkable nature of the materials was demonstrated by monitoring the changes in their glass transition under thermal rework conditions.
Xavier Ramis - One of the best experts on this subject based on the ideXlab platform.
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New anhydride/epoxy thermosets based on diglycidyl ether of bisphenol A and 10-undecenoyl modified poly(ethyleneimine) with improved impact resistance
Progress in Organic Coatings, 2015Co-Authors: Cristina Acebo, Xavier Fernández-francos, Xavier Ramis, Silvia De La Flor, Angels SerraAbstract:Abstract New dendritic modifiers have been synthesized by amidation of hyperbranched poly(ethylenimine) (PEIs) with 10-undecenoic acid to obtain hyperbranched polymers (HBPs) with different degree of modification. These HBPs have been used as toughness modifiers in a proportion of 10 and 20% in reference to the epoxy resin in diglycidyl ether of bisphenol A (DGEBA)/methyltetrahydrophthalic anhydride (MTHPA) formulations. The curing process has been studied by Dynamic Scanning Calorimetry and by rheometry, which allow the kinetic constants and the gel and vitrification times to be evaluated. The materials obtained have been thermally characterized and their mechanical properties have been evaluated. An increase in impact resistance has been achieved and the T g of all thermosets prepared was higher than 100 °C in spite of the flexible structure of the PEI modifiers.
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New Epoxy-Anhydride Thermosets Modified with Multiarm Stars with Hyperbranched Polyester Cores and Poly(ϵ-caprolactone) Arms
Polymer-Plastics Technology and Engineering, 2014Co-Authors: Adrian M. Tomuta, Xavier Fernández-francos, Francesc Ferrando, Angels Serra, Xavier RamisAbstract:Multiarm star polymers with hyperbranched aromatic or aromatic-aliphatic cores and poly(ϵ-caprolactone) arms have been used as toughness modifiers in epoxy-anhydride formulations catalyzed by benzyldimethylamine. The curing process has been studied by Dynamic Scanning Calorimetry, demonstrating little influence of the mobility of the reactive species and the hydroxyl content on the kinetics of this process. The obtained materials were characterized by thermal and mechanical tests and the microstructure by electron microscopy. Homogeneous thermosets have been obtained with a remarkable increase in impact strength without compromising glass transition temperature, thermal stability or hardness.
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Effect of hydroxyl ended and end-capped multiarm star polymers on the curing process and mechanical characteristics of epoxy/anhydride thermosets
Progress in Organic Coatings, 2014Co-Authors: Cristina Acebo, Xavier Fernández-francos, Xavier Ramis, Annamaria Picardi, Silvia De La Flor, Angels SerraAbstract:Abstract Multiarm star polymers have been synthesized by cationic ring-opening polymerization of ɛ-caprolactone from a hyperbranched poly(ethyleneimine) core and end-capped with acetic anhydride. These star polymers have been used as modifiers in diglycidylether of bisphenol A/methyl tetrahydrophthalic anhydride/benzyl dimethylamine formulations. The curing process is studied by Dynamic Scanning Calorimetry and rheometry and the resulting thermosets are characterized by Dynamic mechanical thermal analysis and thermogravimetry. Internal stresses generated during curing are measured and interpreted in terms of the thermal-mechanical properties of the cured materials. The influence of the modifier in the toughness improvement of the cured thermosets is determined by standardized impact tests and the microstructure of the material observed by Scanning electron microscopy.
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Multiarm star with poly(ethyleneimine) core and poly(ε-caprolactone) arms as modifiers of diglycidylether of bisphenol A thermosets cured by 1-methylimidazole
Reactive and Functional Polymers, 2013Co-Authors: Cristina Acebo, Xavier Fernández-francos, Francesc Ferrando, Angels Serra, Josep Maria Salla, Xavier RamisAbstract:Abstract Well-defined multiarm star copolymers, with hyperbranched poly(ethyleneimine) (PEI) as the core and poly(e-caprolactone) (PCL) arms with different degree of polymerization were synthesized by cationic ring-opening polymerization of e-caprolactone from a hyperbranched poly(ethyleneimine) core and used to modify diglycidylether of bisphenol A formulations cured with 1-methylimidazole as anionic initiator. The curing process was studied by Dynamic Scanning Calorimetry (DSC) and FTIR. By rheometry the complex viscosity of the multiarm stars synthesized and the influence of their addition to the reactive mixture was analyzed in detail. The resulting materials were characterized by thermal and mechanical tests. The addition of the multiarm star to the formulation led to homogeneous materials with a slightly toughened fracture in comparison to neat DGEBA thermosets without compromising thermal characteristics.
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New epoxy thermosets modified with multiarm star poly(lactide) with poly(ethyleneimine) as core of different molecular weight
European Polymer Journal, 2013Co-Authors: Cristina Acebo, Xavier Fernández-francos, Francesc Ferrando, Angels Serra, Xavier RamisAbstract:Multiarm stars containing a hyperbranched poly(ethyleneimine) core of different molecular weight and poly(lactide) arms were synthesized by cationic ring-opening polymerization of lactide from a hyperbranched poly(ethyleneimine) core. After characterization by rheometry, Calorimetry, thermogravimetry and nuclear magnetic resonance, these polymers were used as chemically modifiers in the anionic curing of diglycidylether of bisphenol A epoxy resin. The curing process was studied by Dynamic Scanning Calorimetry, demonstrating the influence of the mobility of the reactive species and the hydroxyl content on the curing kinetics. The resulting materials were characterized by thermal and mechanical tests. The addition of the multiarm stars led to homogeneous materials with a slight improvement on the impact strength in comparison with the neat material, without compromising the glass transition temperature. The reworkable nature of the materials was demonstrated by monitoring the changes in their glass transition under thermal rework conditions.
Henri Cramail - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of Polyaniline Nano-Objects Using Poly(vinyl alcohol)-, Poly(ethylene oxide)-, and Poly[(N-vinyl pyrrolidone)-co-(vinyl alcohol)]-Based Reactive Stabilizers
Langmuir, 2009Co-Authors: Muhammad Mumtaz, Christine Labrugere, Eric Cloutet, Henri CramailAbstract:Well-defined polyaniline (PANI) nano-objects (e.g., spheres, peanuts, rice grains, corals, and fibers) were prepared by aniline dispersion polymerization in aqueous media in the presence of various reactive polymer stabilizers (i.e., poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA), and poly[(N-vinyl pyrrolidone)-co-(vinyl alcohol)] (PNVP-co-PVA)). It was found that the shape, size, and conductivity of resulting PANI nanostructures depended on the acidic conditions along with the nature, molecular weight, and functionality of the reactive stabilizer. PANI samples were analyzed by X-ray photoelectron spectroscopy (XPS), Dynamic Scanning Calorimetry (DSC), thermogravimetric analysis (TGA), UV-visible and FTIR spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and conductivity measurements. PANI samples show conductivities between 5 x 10(-3) to 5 x 10(-1) S/cm depending upon the experimental conditions. The best conductivities were obtained when aniline was polymerized in a mixture of DMSO and water (2:3) in the presence of PEO- or PNVP-co-PVA-based reactive stabilizers.
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synthesis of polyaniline nano objects using poly vinyl alcohol poly ethylene oxide and poly n vinyl pyrrolidone co vinyl alcohol based reactive stabilizers
Langmuir, 2009Co-Authors: Muhammad Mumtaz, Christine Labrugere, Eric Cloutet, Henri CramailAbstract:Well-defined polyaniline (PANI) nano-objects (e.g., spheres, peanuts, rice grains, corals, and fibers) were prepared by aniline dispersion polymerization in aqueous media in the presence of various reactive polymer stabilizers (i.e., poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA), and poly[(N-vinyl pyrrolidone)-co-(vinyl alcohol)] (PNVP-co-PVA)). It was found that the shape, size, and conductivity of resulting PANI nanostructures depended on the acidic conditions along with the nature, molecular weight, and functionality of the reactive stabilizer. PANI samples were analyzed by X-ray photoelectron spectroscopy (XPS), Dynamic Scanning Calorimetry (DSC), thermogravimetric analysis (TGA), UV−visible and FTIR spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and conductivity measurements. PANI samples show conductivities between 5 × 10−3 to 5 × 10−1 S/cm depending upon the experimental conditions. The best conductivities were obtained when aniline was polymerized in a...
Tong Zhao - One of the best experts on this subject based on the ideXlab platform.
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a novel condensation addition type phenolic resin mpn synthesis characterization and evaluation as matrix of composites
Polymer, 2005Co-Authors: Mingcun Wang, Tong ZhaoAbstract:This paper reports a novel methylol and propargyl-containing dual-cure-mechanism novolac-based phenolic resin (MPN). MPN resins with varying contents of reactive groups were synthesized by a two-step one-pot method facilly and characterized by Flourier transfer infrared spectra (FT-IR), hydrogen magnetic resonance spectra (1H NMR), gel permeation chromatography (GPC), Dynamic Scanning Calorimetry (DSC) and Dynamic mechanical analysis (DMA) techniques. The resins could be thermally cured by two gradual but fused stages: Condensation of methylol groups and addition polymerization of propargyl groups. This novel resin has advantages over conventional condensation-cure and addition-cure phenolic resins in processing capability. The results of DMA and thermogravimetry analysis (TGA) showed the cured resins possessed high thermal properties. Evaluation of MPN as matrices for advanced composites indicated the enhanced crosslink network derived from dense reactive groups in one single molecule was beneficial to the admirable thermal stability, but was detrimental to the mechanical properties of the resultant composites. MPN resin was amongst ideal candidates for matrices of high temperature materials.
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a novel condensation addition type phenolic resin mpn synthesis characterization and evaluation as matrix of composites
Polymer, 2005Co-Authors: Mingcun Wang, Liuhe Wei, Tong ZhaoAbstract:This paper reports a novel methylol and propargyl-containing dual-cure-mechanism novolac-based phenolic resin (MPN). MPN resins with varying contents of reactive groups were synthesized by a two-step one-pot method facilly and characterized by Flourier transfer infrared spectra (FT-IR), hydrogen magnetic resonance spectra (1H NMR), gel permeation chromatography (GPC), Dynamic Scanning Calorimetry (DSC) and Dynamic mechanical analysis (DMA) techniques. The resins could be thermally cured by two gradual but fused stages: Condensation of methylol groups and addition polymerization of propargyl groups. This novel resin has advantages over conventional condensation-cure and addition-cure phenolic resins in processing capability. The results of DMA and thermogravimetry analysis (TGA) showed the cured resins possessed high thermal properties. Evaluation of MPN as matrices for advanced composites indicated the enhanced crosslink network derived from dense reactive groups in one single molecule was beneficial to the admirable thermal stability, but was detrimental to the mechanical properties of the resultant composites. MPN resin was amongst ideal candidates for matrices of high temperature materials.
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A novel condensation–addition-type phenolic resin (MPN): Synthesis, characterization and evaluation as matrix of composites
Polymer, 2005Co-Authors: Mingcun Wang, Liuhe Wei, Tong ZhaoAbstract:Abstract This paper reports a novel methylol and propargyl-containing dual-cure-mechanism novolac-based phenolic resin (MPN). MPN resins with varying contents of reactive groups were synthesized by a two-step one-pot method facilly and characterized by Flourier transfer infrared spectra (FT-IR), hydrogen magnetic resonance spectra (1H NMR), gel permeation chromatography (GPC), Dynamic Scanning Calorimetry (DSC) and Dynamic mechanical analysis (DMA) techniques. The resins could be thermally cured by two gradual but fused stages: Condensation of methylol groups and addition polymerization of propargyl groups. This novel resin has advantages over conventional condensation-cure and addition-cure phenolic resins in processing capability. The results of DMA and thermogravimetry analysis (TGA) showed the cured resins possessed high thermal properties. Evaluation of MPN as matrices for advanced composites indicated the enhanced crosslink network derived from dense reactive groups in one single molecule was beneficial to the admirable thermal stability, but was detrimental to the mechanical properties of the resultant composites. MPN resin was amongst ideal candidates for matrices of high temperature materials.
Elisabete Moreira Assaf - One of the best experts on this subject based on the ideXlab platform.
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alternative route for the synthesis of high surface area η al2o3 nb2o5 catalyst from aluminum waste
Materials Chemistry and Physics, 2016Co-Authors: Francisco G E Nogueira, Yvan J O Asencios, Cristiane B Rodella, Andre L M Porto, Elisabete Moreira AssafAbstract:Abstract This paper describes an alternative route for the production of a high-surface-area ɳ-Al2O3/Nb2O5 catalyst synthesized from aluminum waste and niobium ammonium oxalate (NH4H2[NbO (C2O4)3]·3H2O). The effects of thermal treatment on the morphology and crystal structure were examined by X-ray powder diffraction (XPD), surface area measurements (BET), Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence, Dynamic Scanning Calorimetry (DSC) and thermogravimetry (TG) measurement. The catalysts were evaluated in the glycerol dehydration reaction. Catalytic tests were carried out with reactants in gas-phase with a fixed-bed reactor at 300° and 400 °C.
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Alternative route for the synthesis of high surface-area η-Al2O3/Nb2O5 catalyst from aluminum waste
Materials Chemistry and Physics, 2016Co-Authors: Francisco G E Nogueira, Yvan J O Asencios, Cristiane B Rodella, Andre L M Porto, Elisabete Moreira AssafAbstract:Abstract This paper describes an alternative route for the production of a high-surface-area ɳ-Al2O3/Nb2O5 catalyst synthesized from aluminum waste and niobium ammonium oxalate (NH4H2[NbO (C2O4)3]·3H2O). The effects of thermal treatment on the morphology and crystal structure were examined by X-ray powder diffraction (XPD), surface area measurements (BET), Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence, Dynamic Scanning Calorimetry (DSC) and thermogravimetry (TG) measurement. The catalysts were evaluated in the glycerol dehydration reaction. Catalytic tests were carried out with reactants in gas-phase with a fixed-bed reactor at 300° and 400 °C.
