Degradation Temperature (degradation + temperature)

Distribution by Scientific Domains

Kinds of Degradation Temperature

  • thermal degradation temperature

  • Selected Abstracts

    Preparation and properties of the single-walled carbon nanotube/cellulose nanocomposites using N -methylmorpholine- N -oxide monohydrate

    Dong-Hun Kim
    Abstract Single-walled carbon nanotube (SWNT)/cellulose nanocomposite films were prepared using N -methylmorpholine- N -oxide (NMMO) monohydrate as a dispersing agent for the acid-treated SWNTs (A-SWNTs) as well as a cellulose solvent. The A-SWNTs were dispersed in both NMMO monohydrate and the nanocomposite film (as confirmed by scanning electron microscopy) because of the strong hydrogen bonds of the A-SWNTs with NMMO and cellulose. The mechanical properties, thermal properties, and electric conductivity of the nanocomposite films were improved by adding a small amount of the A-SWNTs to the cellulose. For example, by adding 1 wt % of the A-SWNTs to the cellulose, tensile strain at break point, Young's modulus, and toughness increased , 5.4, , 2.2, and , 6 times, respectively, the degradation temperature increased to 9C as compared with those of the pure cellulose film, and the electric conductivities at , (the wt % of A-SWNTs in the composite) = 1 and 9 were 4.97 10,4 and 3.74 10,2 S/cm, respectively. Thus, the A-SWNT/cellulose nanocomposites are a promising material and can be used for many applications, such as toughened Lyocell fibers, transparent electrodes, and soforth. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Synthesis and characterization of a silicone resin with silphenylene units in Si-O-Si backbones

    Mengqiu Jia
    Abstract A silicone resin with silphenylene units in Si-O-Si backbones was synthesized by hydrolysis-polycondensation of 1,4-bis(hydroxydimethylsilyl)benzene (BHB) with chlorosilanes. The structure and property of this novel silicone resin were characterized by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), thermogarvimetric analysis (TG), scanning electron microscope (SEM), and electrochemical impedance spectrum (EIS). This silicone resin could be applied as the film forming material of coating when it is prepared under the condition of R/Si, Ph/R, and the content of silphenylene units being 1.3, 0.5, and 10 mol %, respectively. GPC, IR, and NMR results show that the silphenylene units have been incorporated into the polymer of silicone resin. The TG analysis indicates that this novel silicone resin has good heat resistance with the onset degradation temperature of 500.3C and residual weight of 85.6% at 900C. SEM results demonstrate that the silicone resin with silphenylene units can form full and uniform films, and its surface morphology of clear paints were not damaged by heat below 350C. EIS analysis reveals that clear paints of the silicone resin with silphenylene units have good resistance to corrosion. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

    Thermomechanical characteristics of benzoxazine,urethane copolymers and their carbon fiber-reinforced composites

    Sarawut Rimdusit
    Abstract Copolymers of polybenzoxazine (BA-a) and urethane elastomer (PU) with three different structures of isocyanates [i.e., toluene diisocyanate (TDI), diphenylmethane diisocyanate, and isophorone diisocyanate], were examined. The experimental results reveal that the enhancement in glass transition temperature (Tg) of BA-a/PU copolymers was clearly observed [i.e., Tg of the BA-a/PU copolymers in 60 : 40 BA-a : PU system for all isocyanate types (Tg beyond 230C) was higher than those of the parent resins (165C for BA-a and ,70C for PU)]. It was reported that the degradation temperature increased from 321C to about 330C with increasing urethane content. Furthermore, the flexural strength synergism was found at the BA-a : PU ratio of 90 : 10 for all types of isocyanates. The effect of urethane prepolymer based on TDI rendered the highest Tg, flexural modulus, and flexural strength of the copolymers among the three isocyanates used. The preferable isocyanate of the binary systems for making high processable carbon fiber composites was based on TDI. The flexural strength of the carbon fiber-reinforced BA-a : PU based on TDI at 80 wt % of the fiber in cross-ply orientation provided relatively high values of about 490 MPa. The flexural modulus slightly decreased from 51 GPa for polybenzoxazine to 48 GPa in the 60 : 40 BA-a : PU system. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

    Thermal and dynamic mechanical properties of organic,inorganic hybrid composites of itaconate-containing poly(butylene succinate) and methacrylate-substituted polysilsesquioxane

    Takenori Sakuma
    Abstract Itaconate-unit-containing poly(butylene succinate) (PBSI) was synthesized by the reaction of 1,4-butanediol, succinic acid, and itaconic acid in a molar ratio of 2.0 : 1.0 : 1.0, and the obtained PBSI was reacted with methacryl-group-substituted polysilsesquioxane (ME-PSQ) in the presence of benzoyl peroxide (BPO) at 130C to produce PBSI/ME-PSQ hybrid composites. The thermal and dynamic mechanical properties of the PBSI/ME-PSQ hybrid composites were investigated in comparison with those of PBSI cured at 130C in the presence of BPO. As a result, the hybrid composites showed a much higher thermal degradation temperature and storage modulus in the rubbery state than the cured PBSI (C-PBSI). The thermal degradation temperature and storage modulus of the hybrid composites increased with increasing ME-PSQ content. The glass-transition temperature, measured by dynamic mechanical analysis of the hybrid composites, somewhat increased with increasing ME-PSQ content. However, the glass-transition temperatures of all the hybrid composites were lower than that of C-PBSI. Although the IR absorption peak related to CC groups was not detected for C-PBSI, some olefinic absorption peaks remained for all the hybrid composites. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Kinetic study of the thermal degradation of poly(aryl ether ketone)s containing 2,7-naphthalene moieties

    Si-Jie Liu
    Abstract The degradation of poly(aryl ether ketone) containing 2,7-naphthalene moieties was subjected to dynamic and isothermal thermogravimetry in nitrogen and air. The dynamic experiments showed that the initial degradation temperature, temperature for 5% weight loss, and temperature corresponding to the maximum degradation rate of poly(aryl ether ketone) containing 2,7-naphthalene moieties were a little higher than those of poly(ether ether ketone) and almost independent of the 2,7-naphthalene moiety content. The thermal stability of poly(aryl ether ketone) containing 2,7-naphthalene moieties in air was substantially less than that in nitrogen, and the degradation mechanism was more complex. The results obtained under the isothermal conditions were in agreement with the corresponding results obtained in nitrogen and air under the dynamic conditions. In the dynamic experiments, the apparent activation energies for the degradation processes were 240 and 218 kJ/mol in nitrogen and air for the second reaction stage as the heating rate was higher than 5C/min. In the isothermal experiments, the apparent activation energies for the degradation processes were 222 and 190 kJ/mol in nitrogen and air, respectively. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Novel adamantane-containing epoxy resin

    Xiaoming Su
    Abstract A novel adamantane-containing epoxy resin diglycidyl ether of bisphenol-adamantane (DGEBAda) was successfully synthesized from 1,3-bis(4-hydroxyphenyl)adamantane by a one-step method. The proposed structure of the epoxy resin was confirmed with Fourier transform infrared, 1H-NMR, gel permeation chromatography, and epoxy equivalent weight titration. The synthesized adamantane-containing epoxy resin was cured with 4,4,-diaminodiphenyl sulfone (DDS) and dicyandiamide (DICY). The thermal properties of the DDS-cured epoxy were investigated with differential scanning calorimetry and thermogravimetric analysis (TGA). The dielectric properties of the DICY-cured epoxy were determined from its dielectric spectrum. The obtained results were compared with those of commercially available diglycidyl ether of bisphenol A (DGEBA), a tetramethyl biphenol (TMBP)/epoxy system, and some other associated epoxy resins. According to the measured values, the glass-transition temperature of the DGEBAda/DDS system (223C) was higher than that of the DGEBA/DDS system and close to that of the TMBP/DDS system. TGA results showed that the DGEBAda/DDS system had a higher char yield (25.02%) and integral procedure decomposition temperature (850.7C); however, the 5 wt % degradation temperature was lower than that of DDS-cured DGEBA and TMBP. Moreover, DGEBAda/DDS had reduced moisture absorption and lower dielectric properties. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

    Effect of molecular structure of hybrid precursors on the performances of novel hybrid zwitterionic membranes

    Junsheng Liu
    Abstract Three types of novel hybrid zwitterionic membranes were prepared via a coupling reaction between two silane-coupling agents in a nonaqueous system and a subsequent reaction with 1,4-butyrolactone to create ion pairs in the hybrid precursors. FT-IR spectra corroborated the corresponding reactions. The synthesized membranes were characterized by thermal analyses, ion-exchange capacities, streaming potentials, and pure water flux. Thermal analyses exhibited that the degradation temperature of the hybrid precursors decreased with an increase in zwitterionic extent because of the introduction of ion pairs. Ion-exchange capacity measurements revealed that the anion-exchange capacities and cation-exchange capacities were in the range of 0.023,0.05 and 0.32,0.58 mmol g,1, respectively. Streaming potentials displayed that when the membranes coated for one or three times, the isoelectric points were in the pH range of 6.6,7.58 and 6.58,7.7, respectively. The pure water flux showed that it could be affected by the coating times and the ingredients of these zwitterionic membranes. This difference in membrane's characteristics can be ascribed to the effect of molecular structure of the hybrid precursors. Both the Coulombic interactions of ion pairs between the polymer chains and the hydrophilicity of these membranes were proposed to clarify the above phenomena. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source]

    Functionalization of carbon nanofibers (CNFs) through atom transfer radical polymerization for the preparation of poly(tert -butyl acrylate)/CNF materials: Spectroscopic, thermal, morphological, and physical characterizations

    Marcos Ghislandi
    Abstract Vapor-grown carbon nanofibers (CNFs) were oxidized and functionalized for atom transfer radical polymerization (ATRP) of tert -butyl acrylate (t -BA) from the surface of the CNFs. The materials were characterized by solubility tests, Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy. The FTIR and electron microscopy results suggest that ATRP process was successfully used to graft poly(tert -butyl acrylate) (poly(t -BA)) chains from the surface of the fibers. Raman results strongly indicate the partial degradation of the graphitic layer of CNFs because of the chemical treatments. TGA results suggest that the presence of poly(t -BA) leads to a decrease of the initial degradation temperature of the fibers. XRD and electron microscopy results indicate that the microstructure of fibers was not destroyed because of the oxidation and functionalization processes. 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3326,3335, 2008 [source]

    Nonaqueous synthesis of nanosilica in epoxy resin matrix and thermal properties of their cured nanocomposites

    Tzong-Ming Lee
    Abstract Nonaqueous synthesis of nanosilica in diglycidyl ether of bisphenol-A epoxy (DGEBA) resin has been successfully achieved in this study by reacting tetraethoxysilane (TEOS) directly with DGEBA epoxy matrix, at 80 C for 4 h under the catalysis of boron trifluoride monoethylamine (BF3MEA). BF3MEA was proved to be an effective catalyst for the formation of nanosilica in DGEBA epoxy under thermal heating process. FTIR and 29Si NMR spectra have been used to characterize the structures of nanosilica obtained from this direct thermal synthetic process. The morphology of the nanosilica synthesized in epoxy matrix has also been analyzed by TEM and SEM studies. The effects of both the concentration of BF3MEA catalyst and amount of TEOS on the diameters of nanosilica in the DGEBA epoxy resin have been discussed in this study. From the DSC analysis, it was found that the nanosilica containing epoxy exhibited the same curing profile as pure epoxy resin, during the curing reaction with 4,4,-diaminodiphenysulfone (DDS). The thermal-cured epoxy,nanosilica composites from 40% of TEOS exhibited high glass transition temperature of 221 C, which was almost 50 C higher than that of pure DGEBA,DDS,BF3MEA-cured resin network. Almost 60 C increase in thermal degradation temperature has been observed during the TGA of the DDS-cured epoxy,nanosilica composites containing 40% of TEOS. 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 757,768, 2006 [source]

    High molecular weight monodisperse polystyrene microspheres prepared by dispersion polymerization, using a novel bifunctional macromonomer

    Hyejun Jung
    Abstract A novel bifunctional vinyl-terminated polyurethane macromonomer was applied to the dispersion polymerization of styrene in ethanol. Monodisperse polystyrene (PS) microspheres were successfully obtained above 15 wt % of macromonomer relative to styrene. The steep slope from the reduction of the average particle size reveals that the macromonomer can efficiently stabilize higher surface area of the particles when compared with a conventional stabilizer, poly(N -vinylpyrrolidone). The stable and monodisperse PS microspheres having the weight-average diameter of 1.2 ,m and a good uniformity of 1.01 were obtained with 20 wt % polyurethane macromonomer. The grafting ratio of the PS calculated from 1H NMR spectra linearly increased up to 0.048 with 20 wt % of the macromonomer. In addition, the high molecular weights (501,300 g/mol) of PS with increased glass transition and enhanced thermal degradation temperature were obtained. Thus, these results suggest that the bifunctional vinyl-terminated polyurethane macromonomer acts as a reactive stabilizer, which gives polyurethane-grafted PS with a high molecular weight. 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3566,3573, 2005 [source]

    Properties of covalently bonded layered-silicate/polystyrene nanocomposites synthesized via atom transfer radical polymerization

    Chung-Ping Li
    Abstract Covalently bonded layered silicated/polystyrene nanocomposites were synthesized via atom transfer radical polymerization in the presence of initiator-modified layered silicate. The resulting nanocomposites had an intercalated and partially exfoliated structure, as confirmed by X-ray diffraction and transmission electron microscopy. The thermal properties of the nanocomposites improved substantially over those of neat polystyrene. In particular, a maximum increase of 35.5 C in the degradation temperature was displayed by these nanocomposites. Additionally, the surface elastic modulus and hardness of these nanocomposites were more than double those of pure polystyrene. 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 534,542, 2005 [source]

    Physical Properties of PBMA- b -PBA- b -PBMA Triblock Copolymers Synthesized by Atom Transfer Radical Polymerization

    Luis Martn-Gomis
    Abstract The physical properties of well-defined poly(butyl methacrylate)- block -poly(butyl acrylate)- block -poly(butyl methacrylate) (PBMA- b -PBA- b -PBMA) triblock copolymers synthesized by atom transfer radical polymerization (ATRP) are reported. The glass transition and the degradation temperature of copolymers were determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC measurements showed phase separation for all of the copolymers with the exception of the one with the shortest length of either inner or outer blocks. TGA demonstrated that the thermal stability of triblock copolymers increased with decreasing BMA content. Dynamic mechanical analysis was used for a preceding evaluation of adhesive properties. In these block copolymers, the deformation process under tension can take place either homogeneously or by a neck formation depending on the molecular weight of the outer BMA blocks and on the length of the inner soft BA segments. Microindentation measurements were also performed for determining the superficial mechanical response and its correlation with the bulk behavior. Stress-strain curves for the different PBMA- b -PBA- b -PBMA specimens at room temperature and at 10 mm/min. [source]

    DGEBA monomer as a solvent for syndiotactic polystyrene

    Jaap Schut
    Abstract Syndiotactic polystyrene (sPS) has to be processed at high temperatures (i.e. >290C due to its melting point of 270C), which approaches its degradation temperature. We aim to facilitate the processing of sPS by lowering its melt temperature and viscosity with a curable epoxy/amine model system as reactive solvent, which will result in a thermoplastic-thermoset polymer blend. As a first step we therefore investigated the melting behaviour of sPS in epoxy monomer, established its phase diagram, and investigated the crystalline form of sPS in these mixtures. DGEBA epoxy monomer is found to be a solvent for syndiotactic polystyrene at temperatures above 220C. The DGEBA-sPS phase diagram was established by means of DSC, on the basis of crystallization and melting peaks. The form of the curve in the phase diagram indicates that DGEBA is a poor solvent for sPS. In WAXS studies of blends only the , crystalline form was detected, not the , form, thus no sPS-DGEBA polymer-solvent compounds (clathrates) were detected. However, DGEBA can still serve as a monomer for improved processing as it depresses the crystallization temperature by 20 to 60 K upon addition of 20 to 90 wt% DGEBA respectively, while a 16 to 45 K melting peak depression can be observed by adding 20 to 90 wt% DGEBA. [source]

    Effects of synthesis conditions on crystal morphological structures and thermal degradation behavior of hydrotalcites and flame retardant and mechanical properties of EVA/hydrotalcite blends

    POLYMER COMPOSITES, Issue 2 2007
    Longchao Du
    The effects of synthesis methods and reaction conditions on the crystal morphological structures and thermal degradation behavior of hydrotalcites have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), particle size analysis (PSA), and differential thermal analysis (DTA). The flame retardant and mechanical properties of ethylene,vinyl acetate (EVA) blends with the corresponding hydrotalcites have been estimated by limiting oxygen index (LOI), UL-94, and mechanical measurements. The results from the XRD, TEM, and PSA demonstrate that the hydrotalcites synthesized by ultrasound method have larger crystal sizes and particle size distribution than those by mechanical stirring method. Higher reaction temperature, longer dripping time, and lower solution concentration can increase the crystal and particle sizes of ultrasound-synthesized hydrotalcites, whereas the longer ultrasound aging time can increase the crystal sizes and decrease the particle sizes of hydrotalcites because of the smashing conglomeration. The DTA data give a positive evidence that the hydrotalcite samples prepared by mechanical stirring method with longer alkaline dripping time have higher thermal degradation temperature than those by ultrasound method, since the ultrasound-synthesized hydrotalcites have more lattice defects than stirring-prepared hydrotalcites. The data from LOI, UL-94, and mechanical tests show that the ultrasonic-synthesized hydrotalcites have better flame retardant properties, whereas the stirring-synthesized hydrotalcites have better tensile strength in the EVA/hydrotalcite blends. POLYM. COMPOS., 28:131,138, 2007. 2007 Society of Plastics Engineers [source]

    An optimization procedure for the pultrusion process based on a finite element formulation

    POLYMER COMPOSITES, Issue 3 2002
    R. M. L. Coelho
    Composite materials are manufactured by different processes. In all, the process variables have to be analyzed in order to obtain a part with uniform mechanical properties. In the pultrusion process, two variables are the most important: the pulling speed of resin-impregnated fibers and the temperature profile (boundary condition) imposed on the mold wall. Mathematical modeling of this process results in partial differential equations that are solved here by a detailed procedure based on the Galerkin weighted residual finite element method. The combination of the Picard and Newton-Raphson methods with an analytical Jacobian calculation proves to be robust, and a mesh adaptation procedure is presented in order to avoid integration errors during the process optimization. The two earlier-mentioned variables are optimized by the Simulated Annealing method with some constraints, such as a minimum degree of cure at the end of the process, and the resin degradation (the part temperature cannot be higher than the resin degradation temperature at any time during the whole process). Herein, the proposed objective function is an economic criterion instead of the pulling speed of resin-impregnated fibers, used in the majority of papers. [source]

    Effects of epoxy resin-modified zinc-ion-coated nanosilica on structural, thermal and dynamic mechanical properties of propylene-ethylene copolymer

    Chaganti Srinivasa Reddy
    Abstract This paper reports a comparative study of propylene,ethylene copolymer (EP) nanocomposites synthesized using zinc-ion (Zn2+)-coated nanosilica (ZNS) and the diglycidyl ether of bisphenol-A (DGEBA, an epoxy resin)-modified zinc-ion-coated nanosilica (EZNS) as nanofillers. These nanocomposites were prepared using the ,melt mixing' method at a constant loading level of 2.5 wt%. This loading level is much lower than that used for fillers in conventional composites. The EP nanocomposites were characterized using wide-angle X-ray diffractometer (WAXD), a thermo gravimetric analyzer (TGA), a differential scanning calorimeter (DSC), a dynamic mechanical analyzer (DMA) and scanning electron microscopy (SEM). DMA results showed a higher storage modulus for EP-epoxy-modified Zn2+ -coated nanosilica nanocomposite (EP-EZNS) with respect to EP and EP-Zn2+ -coated nanosilica nanocomposite (EP-ZNS). In addition, TGA thermograms showed an increase in degradation temperature of EP in the presence of EZNS. Copyright 2006 Society of Chemical Industry [source]

    Thermal and mechanical characterization of epoxy resins toughened using preformed particles

    J Day
    Abstract Preformed, multilayer particles have been used to toughen an epoxy resin. The particles were formed by emulsion polymerization and consist of alternate glassy and rubbery layers, the outer layer having glycidyl groups to give the possibility of chemical bonding of the particles in the cured resin. Two variants of this type of particle were used, termed GM(47/15) and GM(47/37); both types have an overall diameter of 0.5,m, but the former have a thicker rubbery layer. For comparison, acrylic toughening particles (ATP) with no surface functionality and a liquid carboxyl-terminated butadiene,acrylonitrile (CTBN) rubber were used as toughening agents. The epoxy resin system consisted of a commercial diglycidyl ether of bisphenol A (Shell Epon 828) with diamino-3,5-diethyl toluene as hardener, two commercial sources of which were used, namely Ethacure-100 (Albemarle SA) and DX6509 (Shell Chemicals). These hardeners contain a mixture of two isomers, namely 2,6-diamino-3,5-diethyltoluene and 2,4-diamino-3,5-diethyltoluene Thermogravimetry in nitrogen shows that the preformed toughening particles begin to degrade at 230,C, whereas the cured resin begins to degrade rapidly at 350,C. Thus, even though the particles are less thermally stable than the cured resin, their degradation temperature is well above the glass transition temperature of the resin, and their use does not affect the thermal stability of the toughened materials at normal use temperatures. The performance of the toughening agents was compared using Ethacure-100 as the hardener. The GM(47/15) and GM(47/37) toughening particles gave rise to a greater toughening effect than the ATP and the CTBN. For example, the fracture energies were: 0.26,kJ,m,2 for the unmodified resin; 0.60,kJ,m,2 for the resin toughened with CTBN; and 0.69,kJ,m,2 for the resin toughened with the GM(47/15) particles. The ultimate tensile stress of the unmodified epoxy resin was 43,MPa, which increased to 55,MPa when 20,wt% of GM(47/15) toughening particles were added. The toughness of resins cured with the DX6509 hardener were superior to those obtained with the Ethacure-100 hardener, most probably due to DX6509 producing a less-highly-crosslinked network. This highlights the sensitivity of the toughening process to the hardener used, even for hardeners of a similar nature. 2001 Society of Chemical Industry [source]

    A novel organic rectorite modified bismaleimide/diallylbisphenol A system

    Li Yuan
    Abstract 4,4,-Bismaleimidodiphenylmethane (BMIPM)/O,O,-diallylbisphenol A (BA) system was modified by organic rectorite (OREC) to develop a novel BMI/BA/OREC nanocomposite. The effect of OREC on the viscosity and reactivity of BMIPM/BA system was investigated. The mechanical properties of BMIPM/BA/OREC composites such as the flexural and impact strength were evaluated. The morphology of cured BMIPM/BA/OREC systems was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The hot water resistance of BMIPM/BA/OREC systems was discussed. The thermal property of BMIPM/BA/OREC systems was investigated using thermogravimetric analysis (TGA). The dynamic mechanical properties of BMIPM/BA/OREC systems were also measured. Results show that the addition of OREC has a significant influence on the reactivity of the BMIPM/BA system. Proper content of OREC can improve the flexural strength, impact strength, and hot water resistance of a BMIPM/BA system. The addition of OREC cannot decrease the thermal degradation temperature of cured BMIPM/BA system with a slight sacrifice of the glass transition temperature (Tg). Copyright 2008 John Wiley & Sons, Ltd. [source]

    Synthesis and photophysical properties of a novel semiconducting polymer

    Hongmin Huang
    Abstract An alternating copolymer containing triphenylamine (TPA) and cyano-substituted benzene moieties, TPA-CNPPV was synthesized using the Wittig reaction. The monomers and polymer were characterized by H-NMR, FT-IR and mass spectroscopy (MS). The polymer shows good solubility in common organic solvents and excellent film-forming ability. Thermogravimetric analysis (TGA) demonstrates that the polymer has a degradation temperature (TD) of 600C; differential scanning calorimetry (DSC) result indicates that the glass transition temperature (Tg) of TPA-CNPPV is 160C, suggesting high thermal stability. The photophysical properties of the light-emitting material were investigated in both solution and spin-coated film. Photo-isomerization of the polymer was investigated by UV-vis and fluorescence spectra. The interaction between TPA-CNPPV and C60 was studied by fluorescence quenching. Copyright 2004 John Wiley & Sons, Ltd. [source]

    Recycled PCB flour reinforced linear low-density polyethylene composites enhanced by water cross-linking reaction

    Chen-Feng Kuan
    Abstract Recycled printed circuit board (PCB) flour reinforced linear low-density polyethylene (LLDPE) composites were prepared successfully. Water cross-linking technique was adopted to improve the physical characteristics of the composites. Composites were compounded using a twin-screw extruder and treated with a coupling agent (vinyltrimethoxysilane, VTMOS) and a compatibilizer (polyolefin elastomer grafted with melaic acid, POE-g-MA). They were then moisture-cross-linked in hot water. The composite that was cross-linked in water exhibited better mechanical properties than the noncross-linked composite because of strong chemical bonding between the filler and the polyolefin matrix. When the PCB flour content reaches 60 wt% following 4 h of water cross-linking, the tensile strength and the flexural strength are increased by 18.8% (12.8,15.2 MPa) and 13.2% (21.9,24.8 MPa) respectively. Scanning electron microscopy (SEM) images of the fracture surfaces of water cross-linked composites indicated that good interfacial strength existed between the filler and the polyolefin matrix. Thermal analyses of water cross-linked composites indicated that the thermal degradation temperature and the heat deflection temperature (HDT) of the composite increased with the increasing of water cross-linking time. The HDT of the composite rose from 55.8 to 83 C. Copyright 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

    Comparison of Physicochemical Properties of New Ionic Liquids Based on Imidazolium, Quaternary Ammonium, and Guanidinium Cations

    Abstract More than 50 ionic liquids were prepared by using imidazolium, quaternary ammonium, and guanidinium cations and various anions. In these series, different cationic structures such as 1-benzyl-3-methylimidazolium [Bzmim]+, 1,3-dibenzylimidazolium [BzmiBz]+, 1-octyl-3-methylimidazolium [C8mim]+, 1-decyl-3-methylimidazolium [C10mim]+, tricapryl-methylammonium [Aliquat]+, benzyltriethylammonium [BzTEA]+, phenyltrimethylammonium [PhTMA]+, and dimethyldihexylguanidinium [DMG]+ were combined with anions, p -toluenesulfonate [TSA],, dicyanoamide [DCA],, saccharine (2-sulfobenzoic acid imide sodium salt) [SAC],, trifluoroacetate [TFA],, bis(trifluoromethanesulfonyl)imide [Tf2N],, trifluoromethanesulfonate [TfO],, and thiocyanate [SCN],. Important physical data for these ionic liquids are collated, namely solubility in common solvents, viscosity, density, melting point and water content. Apart from the viscosity, the Newtonian and non-Newtonian behavior of these ionic liquids is also disclosed. Stability of these ionic liquids under thermal, basic, acidic, nucleophilic, and oxidative conditions was also studied. The features of the solid,liquid phase transition were analyzed, namely the glass transition temperature and the heat capacity jump associated with the transition from the non-equilibrium glass to the metastable supercooled liquid. A degradation temperature of each ionic liquid was also determined. Comparisons of the properties of various ionic liquids were made. [source]

    Synthesis and electroluminescent properties of polyfluorene-based conjugated polymers containing bipolar groups

    Sheng-Tung Huang
    Abstract A bipolar dibromo monomer, bis-(4-bromophenyl)[4-(3,5-diphenyl-1,2,4- triazole-4-yl)-phenyl]amine (9), containing electro-rich triphenylamine and electro-deficient 1,2,4-triazole moieties was newly synthesized and characterized. Two fluorescent fluorene-based conjugated copolymers (TPAF, TPABTF) were prepared via facile Suzuki coupling from the dibromo bipolar monomer, 4,7-dibromo-2,1,3-benzothiadiazole (BTDZ), and 9,9-dioctylfluorene. They were characterized by molecular weight determination, IR, NMR, DSC, TGA, solubility, absorption and photoluminescence spectra, and cyclic voltammetry. The polymers showed good solubility in common organic solvents such as dichloromethane, chloroform, tetrahydrofuran, and dichlorobenzene at room temperature. They had glass transition temperatures (Tg) higher than 135 C and 5% degradation temperatures in nitrogen atmosphere were higher than 428 C. Single layer polymer light-emitting diodes (PLED) of ITO/PEDOT:PSS/polymer/metal showed a blue emission at 444 nm and Commission Internationale de I'Eclairage (CIE) 1931 color coordinates of (0.16, 0.13) for TPAF. The device using TPABTF as emissive material showed electroluminescence at 542 nm with CIE1931 of (0.345, 0.625), low turn-on voltage of 5 V, a maximum electroluminance of 696 cd/m2, and a peak efficiency of 2.02 cd/A. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6231,6245, 2009 [source]

    Kinetic analysis of thermo-oxidative degradation of PEEK/thermotropic liquid crystalline polymer blends

    M. Naffakh
    The thermal degradation behavior of blends of poly(aryl ether ether ketone), PEEK, with a thermotropic liquid crystalline polymer (TLCP), Vectra, were investigated in an oxidative atmosphere, using thermogravimetric analysis under dynamic conditions. The theoretical weight loss curves of the blends were compared with the experimental curves in order to explain the effect of blending on the thermal stability of the pure polymers. The thermo-oxidative degradation of PEEK/Vectra blends of different compositions takes place in various steps and the characteristic degradation temperatures and the kinetic parameters such as activation energy are strongly influenced by blending. Polymer blends based on this TLCP polymer had not been previously studied from kinetic viewpoint. POLYM. ENG. SCI. 46:129,138, 2006. 2005 Society of Plastics Engineers [source]

    Thermal and morphological properties of high-density polyethylene/ethylene,vinyl acetate copolymer composites with polyhedral oligomeric silsesquioxane nanostructure

    Patrcia Scapini
    Abstract The demand for improved properties of common polymers keeps increasing, and several new approaches have been investigated. In the study reported here, composites with a polymer matrix comprising a blend of high-density polyethylene with ethylene,vinyl acetate copolymer (EVA), and with polyhedral oligomeric silsesquioxane (POSS) as a nanostructure, were processed and characterized in terms of their thermal and morphological properties. For the preparation of the composites, the concentrations of the blend components (0, 50 and 100 wt%) and of the POSS (0, 1 and 5 wt%) were varied. X-ray diffraction results indicated that the presence of EVA in the composites led to the appearance of crystalline domains at lower POSS concentrations. Transmission and scanning electron microscopy showed that samples with 1 wt% of POSS had a homogeneous distribution in the polymer matrix with average dimensions of ca 150 nm. However, the formation of aggregates occurred in samples with 5 wt% of POSS. Differential scanning calorimetry and thermogravimetic analyses indicated that the POSS did not affect the melt and degradation temperatures of the polymer matrix. POSS underwent aggregation at higher concentrations during the composite processing, indicating a solubility limit of around 1 wt%. The presence of EVA in the composite favors POSS aggregation due to an increase in the polarity of the polymer matrix. Copyright 2009 Society of Chemical Industry [source]