Thermogravimetric Analysis (thermogravimetric + analysis)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Selected Abstracts

Synthesis of dendrimer,carbon nanotube conjugates

A. Garca
Abstract We describe the coupling between Carbon Nanotubes (CNTs) and a second-generation cyanophenyl-based dendrimer. The goal of our work is the synthesis of highly functionalized CNTs without provoking damage to the conjugated ,-system. One approach is the attachment of dendrimers with a high density of functional groups to the CNTs. These groups serve as anchor points for further reactions. With this aim, we have carried out a primary modification on CNTs by the use of 1,3 dipolar cycloaddition reaction. We have employed Single Wall Carbon Nanotubes (SWNTs) as well as Multi Wall Carbon Nanotubes (MWNTs) obtaining 238 ,mol and 511 ,mol of pyrrolidine groups per gram, respectively. The amount of amino groups introduced in the system was measured by the Kaiser test as well as thermogravimetric analyses. As a second step, dendrimer incorporation was performed by carbodiimide chemistry. Thermogravimetric Analysis, Raman Spectroscopy and Atomic Force Microscopy characterization techniques are reported for the characterization of the final CNT,dendrimer conjugate. The results show that the dendrimer has been attached covalently to the previously generated amine groups. Morphologically, the attached dendrimer with an estimated theoretical molecular length of 6.4 nm, generates a wrapping of 8 nm thick around the CNTs walls. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Preparation and properties of polyurethane/montmorillonite nanocomposites cured under room temperature

Hangbin Jiang
The polyurethane/C16C18 -MMT (the montmorillonite modified with cetyloctadecyldimethyl ammonium bromide) nanocomposites were synthesized by intercalative polymerization and cured under room temperature. The d -spacing and the dispersion of the C16C18 -MMT in the nanocomposites were measured by X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM). The mechanical and thermal properties of the nanocomposites were measured by Universal Testing System, Electric Anti-fold Instrument, Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC). It was found out that introducing C16C18 -montmorillonite (MMT) in the polyurethane (PU) displayed good mechanical properties and thermal stability. Rheology behavior in liquid state showed that the addition of the C16C18 -MMT to PU resulted in low gel time and high viscosity. POLYM. COMPOS. 27:470,474, 2006. 2006 Society of Plastics Engineers. [source]

Improvement of the interfacial compatibility between sugar cane bagasse fibers and polystyrene for composites

Edgar Garca-Hernndez
Sugar cane bagasse fibers were modified by surface treatments using either physical or chemical methods in order to improve their adhesion to polystyrene matrices. The surface treatment methods used were alkaline treatment, treatment with silane coupling agents, physical coating with polystyrene and grafting of polystyrene with and without crosslinker. Fiber modifications were monitored by Fourier Transform Infrared Spectroscopy (FTIR), Differential Thermal Analysis coupled with Thermogravimetric Analysis (DTA-TGA) and Scanning Electron Microscopy (SEM). On the other hand, the improvement of the adhesion between sugar cane modified fibers and polystyrene was assessed by micromechanical pull-out and by macromechanical Iosipescu tests. It was found, from Interfacial Shear Strength values (IFSS), that substantial improvements in fiber-matrix compatibility were achieved. According to micro- and macromechanical test results, the IFSS increased for all treated fibers as compared to non-treated fibers. Particularly, both the coating the fibers or grafting with polystyrene using crosslinker resulted in substantial adhesion improvement to the polystyrene matrix in comparison with the non-treated fibers and fibers treated by alkaline and silane methods only. Polym. Compos. 25:134,145, 2004. 2004 Society of Plastics Engineers. [source]

Effects of chemical composition and thermal stability of finishes on the compatibility between glass fiber and high melting temperature thermoplastics

P. Gao
Experimental studies were made on the surface characteristics of glass fibers with two different finishes. The effects of the chemical composition and thermal stability of the finishes on the compatibility between glass fibers and high melting temperature thermoplastics were investigated. Thermogravimetric Analysis (TGA) was used to characterize the composition of surface finishes and their thermal stability. The chemical composition of surface finishes was investigated using a combination of X-ray photoelectron spectroscopy (XPS) and Time-of-Flight secondary ion mass spectrometry (ToF SIMS). Static contact angle measurements were performed at room temperature to characterize the interfacial tension between the glass fibers and thermoplastics. The study provides a fundamental understanding on some important compatibility issues between thermoplastic resins and glass fiber related to composite fabrication and application. [source]

Self-Assembly of 1D to 3D Cadmium Complexes: Structural Characterization and Properties

Xing Li
Abstract Self-assembly reactions of 5-sulfoisophthalic monosodium salt (NaH2sipa), Cd(NO3)24H2O and 2,2'-bipyridine (or 4,4'-bipyridine) under hydrothermal condition give rise to four polymeric complexes, namely {[Cd3(sipa)2(2,2'-bpy)4(H2O)2]6H2O}n (1), {[Cd(sipa)(H-4,4'-bpy)(H2O)]2H2O}n (2); {[Cd2(sipa)(4,4'-bpy)3(H2O)3][Cd(sipa)(4,4'-bpy)(H2O)]8H2O}n (3),and {[Cd3(sipa)2(4,4'-bpy)4(H2O)2]3H2O}n (4), respectively. X-ray diffraction analyses reveal that complex 1 possesses a 1D rail-like chain structure, 2 is a 1D double chain, 3 has a 2D network consisting of an independent [Cd2(sipa)(4,4'-bpy)3(H2O)3]nn+ cationic layer and a [Cd(sipa)(4,4'-bpy)(H2O)]nn, anionic layer, and 4 is a novel 3D self-penetrating network constructed from two mixed bridging ligands. Thermogravimetric analyses (TGA) and fluorescent measurements of complexes 1,4 have also been performed. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Polymeric, Molecular, and Cation/Anion Arrangements in Chloro-, Bromo-, and Iododiruthenium(II,III) Carboxylate Compounds

M. Carmen Barral
Abstract The synthesis and characterization of the anhydrous compounds [Ru2X(,-O2CR)4] [R = CH2CH2OPh, X = Cl (1a), Br (2a), I (3a); R = CMePh2, X = Br (5a), I (6a)] and of the solvated complexes [Ru2X(,-O2CR)4(H2O)] [R = CH2CH2OPh, X = Cl (1b), I (3b); R = CMePh2, X = Cl (4b), Br (5b), I (6b)] are described. Thermogravimetric analyses have been used to confirm the anhydrous or solvated natures of the complexes. The crystal structures of 1b2MeOH, 3b0.5H2O, and 4b have been investigated by X-ray diffraction and none of them shows the usual polymeric arrangement reported for tetracarboxylatodiruthenium(II,III) compounds. The structure of 3b0.5H2O consists of cationic and anionic units, [Ru2(,-O2CCH2CH2OPh)4(H2O)2][Ru2I2(,-O2CCH2CH2OPh)4], and represents the first reported crystal structure of a tetracarboxylato(iodo)diruthenium(II,III) derivative. The structures 1b2MeOH and 4b each show the presence of discrete dinuclear molecules. The crystal structure of [Ru2Cl(,-O2CCMePh2)4(H2O)] demonstrates that diruthenium compounds with the same halide and carboxylate ligands may adopt polymeric or discrete molecular dispositions. Magnetic susceptibility measurements of the complexes in the 2,300 K range have been carried out. Complex 2a shows a strong antiferromagnetic coupling, consistent with the existence of linear chains in the solid state. The complexes [Ru2X(,-O2CR)4(H2O)] show weak through-space antiferromagnetic coupling, in accordance with non-polymeric structures. The magnetic behaviour of 1a, 3a, 5a, and 6a suggests a mixture of arrangements. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Epoxy,siloxane hybrid coatings by a dual-curing process

Giulio Malucelli
Abstract Coatings based on a hybrid organic,inorganic epoxy system were prepared by a dual-curing mechanism, via cationic photopolymerization in the first step at room temperature and a subsequent hydrolysis/condensation reaction of a trialkoxy-silane compound (sol,gel process) at high temperature. To this end, a high Tg epoxy resin (3,4-epoxycyclohexylmethyl-3,-cyclohexenyl-methyl adipate, UVR 6128) was added in increasing amounts to a precursor for the inorganic-like phase (3,4-epoxycyclohexylethyltrimethoxysilane, EETMOS). The mixture contained triphenylsulfoniumhexafluoroantimonate as a cationic photoinitiator. By this method, the strongly acid environment generated by the photolysis of the triarylsolfunium salt in the first step induces the hydrolysis of EETMOS alkoxy-silane groups. The films produced in the first step of the process were thermal treated to promote the condensation reactions of the siloxane moieties. The kinetics of the reactions of photopolymerization and condensation was investigated. It was found that the presence of EETMOS increases both the polymerization rate and the final consumption of epoxy groups. Thermogravimetric analyses performed in air have revealed an increased stability of the hybrid coatings with respect to the films produced from formulations without EETMOS. A significant increase in surface hardness was also observed for the hybrid coatings. The thermo-mechanical properties were found to be strongly affected by the temperature used in the thermally induced reactions in the second step. The hybrid coatings on a low-density polyethylene substrate were found to decrease the diffusivity of oxygen and to increase the oxygen solubility within the coating. 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:77,85, 2009; Published online in Wiley InterScience ( DOI 10.1002/adv.20149 [source]

Copper-mediated radical polymerization on a microcellular monolith surface

Laurence Moine
Abstract High-capacity microcellular monoliths were prepared by a two-step process, including the synthesis of a bromoester-functionalized scaffold by the copolymerization of a highly concentrated emulsion and an in situ surface polymerization of methyl methacrylate with atom transfer radical polymerization. The influence of various parameters, such as the feed ratio, the concentration of immobilized bromoester groups, and the presence of a spacer group on the poly(methyl methacrylate) loading, was studied. Monoliths with capacities of up to 7 mmol g,1 were obtained. Thermogravimetric analyses, scanning electron microscopy experiments, and mercury intrusion porosimetry measurements were used for the characterization of the final materials. 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1216,1226, 2004 [source]

Synthesis and polymerization of fluorinated monomers bearing a reactive lateral group.


Abstract The radical copolymerization in solution of vinylidene fluoride (VDF; or 1,1-difluoroethylene) with methyl 1,1-dihydro-4,7-dioxaperfluoro-5,8-dimethyl non-1-enoate (MDP) initiated by di- tert -butyl peroxide is presented. Six copolymerization reactions were investigated with initial [VDF]0/[MDP]0 molar ratios of 35/65 to 80/20. Both of these comonomers copolymerized in this range of copolymerization. Moreover, these comonomers homopolymerized separately under these conditions. The copolymer compositions of these random copolymers were calculated by means of 19F NMR spectroscopy, which allowed the quantification of the respective amounts of each monomeric unit in the copolymers. The Tidwell,Mortimer method was used for the assessment of the reactivity ratios (ri) of both comonomers, which showed a higher incorporation of MDP in the copolymers (rMDP = 2.41 2.28 and rVDF = 0.38 0.21 at 120 C). The Alfrey,Price Q and e values of the trifluoroallyl monomer MDP were calculated to be 0.024 (from QVDF = 0.008) or 0.046 (from QVDF = 0.015) and 0.70 (vs eVDF = 0.40) or 0.80 (vs eVDF = 0.50), respectively, indicating that MDP was an electron-accepting monomer. The thermal properties of these fluorinated copolymers were also determined. Except for those containing a high amount of VDF, the copolymers were amorphous. Each showed one glass-transition temperature (Tg) only, and with known laws of Tg's, Tg of the MDP homopolymer was assessed. It was compared to that obtained from the direct radical homopolymerization of MDP and discussed. Indeed, these two values were close (Tg = ,3 C). Thermogravimetric analyses were performed, and they showed that the copolymers were rather thermostable because the thermal degradation occurred at 280 C. 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3109,3121, 2003 [source]

Aromatic polybenzoxazoles containing ether,sulfone linkages

Sheng-Huei Hsiao
Abstract A series of poly(o -hydroxy amide)s having both ether and sulfone linkages in the main chain were synthesized via the low-temperature solution polycondensation of 4,4,-[sulfonylbis(1,4-phenylene)dioxy]dibenzoyl chloride and 4,4,-[sulfonylbis(2,6-dimethyl-1,4-phenylene)dioxy]dibenzoyl chloride with three bis(o -aminophenol)s including 4,4,-diamino-3,3,-dihydroxybiphenyl, 3,3,-diamino-4,4,-dihydroxybiphenyl, and 2,2-bis(3-diamino-4-hydroxyphenyl)hexafluoropropane. Subsequent thermal cyclodehydration of the poly(o -hydroxy amide)s afforded polyethersulfone benzoxazoles. Most of the poly(o -hydroxy amide)s were soluble in polar organic solvents such as N -methyl-2-pyrrolidone; however, the polybenzoxazoles without the hexafluoroisopropylidene group were organic-insoluble. The polybenzoxazoles exhibited glass-transition temperatures (Tg) in the range of 219,282 C by DSC and softening temperatures (Ts) of 242,320 C by thermomechanical analysis. Thermogravimetric analyses indicated that most polybenzoxazoles were stable up to 450 C in air or nitrogen. The 10% weight loss temperatures were recorded in the ranges of 474,593 C in air and 478,643 C in nitrogen. The methyl-substituted polybenzoxazoles had higher Tg's but lower Ts's and initial decomposition temperatures compared with the corresponding unsubstituted polybenzoxazoles. For a comparative purpose, the synthesis and characterization of a series of sulfonyl polybenzoxazoles without the ether group that derived from 4,4,-sulfonyldibenzoyl chloride and bis(o -aminophenol)s were also reported. 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2262,2270, 2001 [source]

A Study on the Metal Organic CVD of Pure Copper Films from Low Cost Copper(II) Dialkylamino-2-propoxides: Tuning the Thermal Properties of the Precursor by Small Variations of the Ligand,

R. Becker
Abstract Pure copper metal thin films were grown on SiO2/Si(100) substrates by metal,organic (MO) CVD in a horizontal cold-wall reactor employing the two metal,organic compounds, Cu(OCHMeCH2NR2)2, where R,=,Et (1) and R,=,Me (2) as precursors. Thermogravimetric analyses proved them to be convenient compounds for the deposition of copper without a reducing agent. Depositions were carried out at various substrate temperatures in the range 230,350,C. X-ray diffraction (XRD) indicated that the resulting films were highly crystalline and showed a strong (111) preferred orientation, which increased with increasing deposition temperature. Photoelectron spectroscopy (XPS) revealed that copper films deposited at 230,C and 260,C consisted solely of metallic copper with no detectable carbon, nitrogen, or oxygen contamination. Copper films obtained from 1 at 260,C had a resistivity of 2.16,,,,cm. [source]

A Novel 3-D Self-Penetrating Topological Network Assembled by Mixed Bridging Ligands

Xing Li
Abstract The assembly of 5-sulfoisophthalic acid (H3sipa) and 4,4,-bipyridine (bpy) with Cd2+ ions gave rise to a new polymeric complex {[Cd3(sipa)2(bpy)4(H2O)2]3H2O}n (1). X-ray diffraction analysis reveals that complex 1 has a 3-D self-penetrating network formed by the interlocking and interweaving of two types of one-dimensional chains comprising two kinds of Cd4(sipa)4 and Cd4(bpy)4 units, respectively. The sipa3, ligand serves as the connector and the Cd2+ ion as the node. Thermogravimetric analysis (TGA) and the luminescence property of 1 are discussed. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Flame retardancy finish with an organophosphorus retardant on silk fabrics

Jin-Ping Guan
Abstract The paper mainly deals with flame retardancy of silk fabrics treated with a commercial organophosphorus flame retardant [N-hydroxymethyl (3-dimethyl phosphono) propionamide (HDPP), also known as Pyrovatex CP], using the pad-dry-cure-wash method. The structures and properties of the treated and control sample are discussed. The Limiting Oxygen Index (LOI) value of the modified sample is above 30%. After 50 laundry cycles, it still has some flame retardancy left. HDPP and a cross-linking agent (HMM) were bound to silk fabrics which is confirmed by FT-IR spectra and amino analysis. The reaction degree of the flame retardant with silk is also high; almost all the tyrosine units have reacted, which can be confirmed by amino acid analysis. The reaction between flame retardant and silk only occurs in the amorphous region of silk fibre, which is confirmed by X-ray diffraction analysis and amino acid analysis. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis show that the flame retardant causes silk fabrics to decompose below its ignition temperature (600C) and formed carbonaceous residue or char when exposed to fire. The char behaves as a thermal barrier to fire, so silk fabrics show good flame retardancy. The treatment has a little effect on the whiteness of the silk fabrics and the tensile strength of treated silk fabrics slightly decreased; both effects are negligible. Copyright 2006 John Wiley & Sons, Ltd. [source]

Flame retardant properties of EVA-nanocomposites and improvements by combination of nanofillers with aluminium trihydrate

Gnter Beyer
Flame retardant nanocomposites are synthesized by melt-blending ethylene,vinyl acetate copolymers (EVA) with modified layered silicates (montmorillonites). Thermogravimetric analysis performed under different atmospheres (nitrogen and air) demonstrated a clear increase in the thermal stability of the layered silicate-based nanocomposites. The use of the cone calorimeter to investigate the fire properties of the materials indicated that the nanocomposites caused a large decrease in heat release. The char-formation is the main factor important for improvement and its function is outlined. Further improvements of the flame retardancy by combinations of nanofillers and traditional FR-additives on the basis of metal hydroxides were also studied. Copyright 2002 John Wiley & Sons, Ltd. [source]

Repellent studies with Aedes aegypti mosquitoes and human olfactory tests on 19 essential oils from Corsica, France

J. Drapeau
Abstract In order to reduce the risk of getting infected with any epidemic disease transmitted by mosquitoes, repellent products are often used to protect populations at risk. The repellent potential of 19 essential oils from the island of Corsica, France, was evaluated in a bio-assay with the mosquito Aedes aegypti, in order to assess the ,space repellent' properties of these oils. Lavendula stoechas, Helichrysum italicum (leaves) and Laurus nobilis oils showed a capability of reducing the attractivity of a human finger for yellow fever mosquitoes in a Y-tube olfactometer. In addition to the behavioural studies on mosquitoes, two tests on the olfactory perception of these 19 oils were performed, involving 25 female and 25 male human volunteers. The aspects studied were the ,hedonic dimension' of these oils and their acceptance as a final fragrance for a repellent formulation. The experiments yielded promising results concerning both aspects for three oils, from Calamintha nepeta, Laurus nobilis and Rosmarinus officinalis, with minor differences between male and female participants. Laurus nobilis oil was the only oil tested fulfilling both properties: a spatial repellent effect on Aedes aegypti and acceptance by the volunteers for its integration in a repellent product. Thermogravimetric analysis showed that Calamintha nepeta oil has a slower evaporation rate in comparison to the Laurus nobilis and Rosmarinus officinalis oils. Copyright 2009 John Wiley & Sons, Ltd. [source]

Synthesis and characterization of novel polyimide/SiO2 nanocomposite materials containing phenylphosphine oxide via sol-gel technique

Canan Kizilkaya
Abstract In this article, a series of novel polyimide/silica (PI/SiO2) nanocomposite coating materials were prepared from tetraethoxysilane (TEOS), ,-glycidyloxypropyltrimethoxysilane (GOTMS), and polyamic acid (PAA) via sol-gel technique. PAA was prepared by the reaction of 3,3,,4,4,-benzophenone tetracarboxylic dianhydride (BTDA) and bis (3-aminophenyl) phenyphosphine oxide (BAPPO) in N -methyl-2- pyrrolidone (NMP). BAPPO was synthesized hydrogenation of bis (3-nitrophenyl) phenyphosphine oxide (BNPPO) in the presence of Pd/C. The silica content in the hybrid coating materials was varied from 0 to 20 wt %. The molecular structures of the composite materials were analyzed by means of FT-IR and 29Si-NMR spectroscopy techniques. The physical and mechanical properties of the nanocomposites were evaluated by various techniques such as, hardness, contact angle, and optical transmission and tensile tests. These measurements revealed that all the properties of the nanocomposite coatings were improved noticeable, by the addition of sol-gel precursor into the coating formulation. Thermogravimetric analysis showed that the incorporation of sol-gel precursor into the polyimide matrix leads to an enhancement in the thermal stability and also flame resistance properties of the coating material. The surface morphology of the hybrid coating was characterized by scanning electron microscopy (SEM). SEM studies indicated that nanometer-scaled inorganic particles were homogenously dispersed throughout the polyimide matrix 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Properties of soy protein isolate/poly(vinyl alcohol) blend "green" films: Compatibility, mechanical properties, and thermal stability

Jun-Feng Su
Abstract Blend films from nature soy protein isolates (SPI) and synthetical poly(vinyl alcohol) (PVA) compatibilized by glycerol were successfully fabricated by a solution-casting method in this study. Properties of compatibility, mechanical properties, and thermal stability of SPI/PVA films were investigated based on the effect of the PVA concentration. XRD tests confirm that the SPI/PVA films were partially crystalline materials with peaks of 2, = 20. And, the addition of glycerol will insert the crystalline structure and destroy the blend microstructure of SPI/PVA. Differential scanning calorimetry (DSC) tests show that SPI/PVA blend polymers have a single glass transition temperature (Tg) between 80 and 115.0C, which indicate that SPI and PVA have good compatibility. The tension tests show that SPI/PVA films exhibit both higher tensile strength (,b) and percentage elongation at break point (P.E.B.). Thermogravimetric analysis (TGA) and water solubility tests show that SPI/PVA blend polymer has more stable stability than pure SPI. All the results reflect that SPI/PVA/glycerol blend film provides a convenient and promising way to prepare soy protein plastics for practical application. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Polypropylene/clay nanocomposites prepared by in situ grafting-melt intercalation with a novel cointercalating monomer

Pingan Song
Abstract Polypropylene (PP)/clay nanocomposites were prepared by melt-compounding PP with organomontmorillonite (OMT), using maleic anhydride grafted polypropylene (PP- g -MA) as the primary compatibilizer and N -imidazol- O -(bicyclo pentaerythritol phosphate)- O -(ethyl methacrylate) phosphate (PEBI) as the cointercalating monomer. X-ray diffraction patterns indicated that the larger interlayer spacing of OMT in PP was obtained due to the cointercalation monomer having a large steric volume and the d -spacing further increased with the addition of PP- g -MA, as evidenced by transmission electron microscopy. Thermogravimetric analysis revealed that the PEBI-containing PP nanocomposites exhibited better thermal stability than PEBI-free PP composites. Dynamic mechanical analysis demonstrated that the storage modulus was significantly enhanced, and the glass transition temperature (Tg) shifted slightly to low temperature with the incorporation of clay for PP/OMT hybrids. PEBI-containing PP/OMT composites gave a lower Tg value because of the strong internal plasticization effect of PEBI in the system. Cone calorimetry showed that the flame-retardancy properties of PP nanocomposites were highly improved with the incorporation of PEBI. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Synthesis and properties of organic/inorganic hybrid nanoparticles prepared using atom transfer radical polymerization

Tzong-Liu Wang
Abstract The synthesis of organic/inorganic hybrid materials was conducted by atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate (MMA) from the surface of silica colloids. Colloidal initiators were prepared by the functionalization of silica nanoparticles with (3-(2-bromoisobutyryl)propyl) dimethylethoxysilane (BIDS). Well-defined polymer chains were grown from the nanoparticle surfaces to yield individual particles composed of a silica core and a well-defined outer polystyrene (PS) or poly(methyl methacrylate) (PMMA) layer. Fourier transform infrared (FTIR) and solid state 13C and 29Si-NMR spectroscopy confirmed the successful modification of nanosilica surfaces. Subsequent grafting of polymers on silica surfaces by ATRP was also performed with success based on FTIR and NMR data. Scanning electron microscopy (SEM) and silicon mapping showed both hybrid materials were homogeneous dispersion systems. Energy dispersive X-ray spectrometer (EDS) analysis indicated that the BIDS initiator was covalently attached on surfaces of silica nanoparticles and ATRP of styrene and MMA were accomplished. Thermogravimetric analysis (TGA) results displayed higher thermal stabilities for both nanohybrids in comparison with the linear-type vinyl polymers. Contact angle measurements revealed the nanomaterials character for both silica-based hybrid materials. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Recycled PET nanocomposites improved by silanization of organoclays

Milan Kr, alk
Abstract Recycled PET/organo-modified montmorillonite nanocomposites were prepared via melt compounding as a promising possibility of the used beverage bottles recovery. According to our previous work, the three suitable commercial organoclays Cloisite 25A, 10A, and 30B were additionally modified with [3-(glycidyloxy)propyl]trimethoxysilane, hexadecyltrimethoxysilane and (3-aminopropyl)trimethoxysilane. The selected organoclays were compounded in the concentration 5 wt % and their degree of intercalation/delamination was determined by wide-angle X-ray scattering and transmission electron microscopy. Modification of Cloisite 25A with [3-(glycidyloxy)propyl]trimethoxysilane increased homogeneity of silicate layers in recycled PET. Additional modification of Cloisite 10A and Cloisite 30B led to lower level of delamination concomitant with melt viscosity reduction. However, flow characteristics of all studied organoclay nanocomposites showed solid-like behavior at low frequencies. Silanization of commercial organoclays had remarkable impact on crystallinity and melt temperature decrease accompanied by faster formation of crystalline nuclei during injection molding. Thermogravimetric analysis showed enhancement of thermal stability of modified organoclays. The tensile tests confirmed significant increase of PET-R stiffness with organoclays loading and the system containing Cloisite 25A treated with [3-(glycidyloxy)propyl]trimethoxysilane revealed combination of high stiffness and extensibility, which could be utilized for production of high-performance materials by spinning, extrusion, and blow molding technologies. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source]

Synthesis of Mo,W carbide via propane carburization of the precursor sulfide: Kinetic analysis

Tuan-Huy Nguyen
Abstract Thermogravimetric analysis (TGA) has been used to investigate the carburization kinetics of Mo,W sulfide using an H2:C3H8 feed mixture. The effect of heating rate over the range 1,10 K min,1 showed that up to four different carburized products may be formed but the critical (peak) temperature for formation of these species and the amount (peak height) of each species formed are highly dependent on the heating rate employed. The critical temperature increased linearly with heating rate for each of the four products. The four TGA peaks corresponding to the four phase transformation species are consistent with XRD identifiable species, namely; ,-Mo2C, ,-Mo2C, W and MoC1,x. Isothermal conversion,time data at three different temperatures are described by a reaction-controlled shrinking core model implicating a first-order dependency on the H2:C3H8 ratio. The reaction exhibited fractional order dependence on the metal sulfide concentration, the associated global activation energy estimated as 227 kJ mol,1 is representative of a non-catalytic gas,solid reaction. Copyright 2004 Society of Chemical Industry [source]

Radical copolymerization of vinylidene cyanide with 2,2,2-trifluoroethyl methacrylate: Structure and characterization,

Mustapha Raihane
Abstract A novel copolymer of vinylidene cyanide (VCN) and 2,2,2-trifluoroethyl methacrylate (MATRIF) was synthesized by bulk free radical process in a 52% yield from an equimolar comonomer feed. The copolymer's composition and microstructure were analyzed by FTIR, 1H- and 13C-NMR spectroscopy, SEC, and elemental analysis. The reactivity ratios calculated from both the Q-e Alfrey-Price parameters and the Jenkins' Patterns Scheme indicate a tendency to alternation in the copolymerization, the latter method suggesting that MATRIF homopropagation be slightly favoured (rV = r12 = 0.1, rM = r21 = 0.3). The molar incorporation of VCN in the copolymer was only 42 mol % according to the 9.0 wt % nitrogen content determined by elemental analysis, in good agreement with the value obtained by 1H-NMR. High-resolution 1H and 13C-NMR spectra were used to study the microstructure of the copolymer. As an example, the three well-resolved carbonyl resonances in the 13C-NMR spectrum were assigned to the MATRIF-centered triads VMV, VMM, and MMM, respectively, (V and M stand for VCN and MATRIF, respectively). The presence of VCN dyads (e.g., in VVM and VVV sequences) was shown to be marginal or absent altogether. Thermogravimetric analysis of poly(VCN- co -MATRIF) copolymer showed good thermal stability, and its main pyrolytic degradation taking place only above 368 C. A 4% weight loss at about 222 C suggested the presence of a few VCN homodyads, possibly inducing thermal depolymerization. 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source]

Cationic polymerization of L,L -lactide

gorzata Ba
Abstract Cationic bulk polymerization of L,L- lactide (LA) initiated by trifluromethanesulfonic acid [triflic acid (TfA)] has been studied. At temperatures 120,160 C, polymerization proceeded to high conversion (>90% within ,8 h) giving polymers with Mn , 2 104 and relatively high dispersity. Thermogravimetric analysis of resulting polylactide (PLA) indicated that its thermal stability was considerably higher than the thermal stability of linear PLA of comparable molecular weight obtained with ROH/Sn(Oct)2 initiating system. Also hydrolytic stability of cationically prepared PLA was significantly higher than hydrolytic stability of linear PLA. Because thermal or hydrolytic degradation of PLA starting from end-groups is considerably faster than random chain scission, both thermal and hydrolytic stability depend on molecular weight of the polymer. High thermal and hydrolytic stability, in spite of moderate molecular weight of cationically prepared PLA, indicate that the fraction of end-groups is considerably lower than in linear PLA of comparable molecular weight. According to proposed mechanism of cationic LA polymerization growing macromolecules are fitted with terminal OH and C(O)OSO2CF3 end-groups. The presence of those groups allows efficient end-to-end cyclization. Cyclic nature of resulting PLA explains its higher thermal and hydrolytic stability as compared with linear PLA. 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2650,2658, 2010 [source]

PS/PMMA mixed polymer brushes on the surface of clay layers: Preparation and application in polymer blends

Jian Zhang
Abstract Polystyrene (PS) and poly(methyl methacrylate) (PMMA) mixed polymer brushes on the surface of clay layers were prepared by using in situ free radical polymerization. Free radical initiator molecules with two quaternary ammonium groups at both ends were intercalated into the interlayer spacing of clay layers. The amount of polymer brushes grafted on the surface of clay layers can be controlled by controlling the polymerization time. Thermogravimetric analysis, X-ray diffraction, and high-resolution transmission electron microscope results indicated successful preparation of the mixed polymer brushes on the surface of clay layers. The kinetics of the grafting of the monomers was also studied. The mixed polymer brushes on the surface of clay layers were used as compatibilizers in blends of PS and PMMA. In the blends, the intercalated clay particles tend to locate at the interface of two phases reducing the interfacial tension. In the meanwhile, PMMA homopolymer chains tend to intercalate into clay layers. The driving force for the intercalation is the compatibility between homo-PMMA chains and PMMA brushes on the surface of clay layers. 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5329,5338, 2007 [source]

Surface covalent encapsulation of multiwalled carbon nanotubes with poly(acryloyl chloride) grafted poly(ethylene glycol)

Yan-Xin Liu
Abstract Multiwall carbon nanotube (MWNT) was grafted with polyacrylate- g -poly (ethylene glycol) via the following two steps. First, hydroxyl groups on the surface of acid-treated MWNT reacted with linear poly(acryloyl chloride) to generate graft on MWNT; secondly, the remaining acryloyl chloride groups were subjected to esterification with poly(ethylene glycol) leading the grafted chains on the surface of MWNTs. Thus obtained grafted MWNT was characterized using Fourier transform infrared spectrometer, transmission electron microscopy, and X-ray photoelectron spectroscopy. Thermogravimetric analysis showed that the weight fraction of grafted polymers amounted to 80% of the modified MWNT. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6880,6887, 2006 [source]

N,N -dimethylaminopyridine as initiator in the copolymerization of diglycidylether of bisphenol A with six-membered cyclic carbonates

Roser Cervellera
Abstract N,N -Dimethylaminopyridine (DMAP) was used as initiator to cure mixtures of diglycidylether of bisphenol A (DGEBA) and 1,3-dioxan-2-one (TMC) or 5,5-dimethyl-1,3-dioxan-2-one (DMTMC). The curing was studied by differential scanning calorimetry (DSC) and Fourier transform infrared in the attenuated-total-reflection mode (FTIR/ATR). FTIR/ATR was used to monitor the competitive reactive processes and to quantify the evolution of the groups involved in the curing. We observed the formation of five-membered cyclic carbonates and anionic carbonate groups that remain unreacted at the chain ends. The formation of these groups was explained by the attack of the anionic propagation species on the methylene carbon of the carbonate group, which leads to an alkyl-oxygen rupture. By performing the cure in the thermobalance we could evaluate the loss of CO2 produced in the samples containing carbonates. The kinetics were studied by DSC and analyzed with isoconversional procedures. The addition of carbonates slows down the curing rate. Thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) experiments were used to evaluate the properties of the materials obtained. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2873,2882, 2006 [source]

Frontal free-radical copolymerization of urethane,acrylates

Ting Hu
Abstract We report the first synthesis of urethane,acrylate copolymers via free-radical frontal polymerization. In a typical run, the appropriate amounts of the reactants (urethane,acrylate macromonomer and 2-hydroxyethyl acrylate) and initiator (ammonium persulfate) were dissolved in dimethyl sulfoxide. Frontal polymerization was initiated by the heating of the wall of the tube with a soldering iron, and the resultant hot fronts were allowed to self-propagate throughout the reaction vessel. Once it was initiated, no further energy was required for the polymerization to occur. The dependence of the front velocity and front temperature on the initiator concentration was investigated. The front temperatures were between 55 and 65 C, depending on the persulfate concentration. Thermogravimetric analysis indicated that the urethane,acrylate copolymers had higher thermal stability than pure frontally prepared polyurethane. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3018,3024, 2006 [source]

Synthesis of autophotosensitive hyperbranched polyimides based on 3,3,,4,4,-benzophenonetetracarboxylic dianhydride and 1,3,5-tris(4-aminophenoxy)benzene via end capping of the terminal anhydride groups by ortho -alkyl aniline

Huan Chen
Abstract Benzophenone-containing, anhydride-terminated hyperbranched poly(amic acid)s were end-capped by ortho -alkyl aniline in situ and then chemically imidized, yielding autophotosensitive hyperbranched polyimides. The polyimides were soluble in strong polar solvents, such as N -methyl-2-pyrrolidone, N -dimethylformamide, dimethylacetamide, and dimethyl sulfoxide. Thermogravimetric analysis revealed their excellent thermal stability, with a 5 wt % thermal loss temperature in the range of 527,548 C and a10 wt % thermal loss temperature in the range of 562,583 C. The strong absorption of the polyimide films in ultraviolet,visible spectra at 365 nm indicated that the hyperbranched polyimides were patternable. Highly resolved images with a line width of 6 ,m were developed by ultraviolet exposure of the polymer films. A well-defined image with lines as thin as 3 ,m was also patterned, but the lines were rounded at the edges. 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2026,2035, 2003 [source]

Synthesis and characterization of aromatic polyamides containing alkylphthalimido pendent groups

E. Ferrero
Abstract A series of polyisophthalamides containing pendent phthalimido groups and flexible side spacers were prepared from four novel diacids and three commercial aromatic diamines. These polyamides were prepared in high yields and with high molecular weights by direct polycondensation with triphenyl phosphite and pyridine as condensing agents. The weight-average and number-average molecular weights, measured by gel permeation chromatography, were 70,000,137,000 and 47,000,86,000 g/mol, respectively. The novel polyamides were amorphous and readily soluble and showed glass-transition temperatures of 150,240 C, as measured by differential scanning calorimetry. Thermogravimetric analysis showed that the 10% weight-loss temperatures in nitrogen were 355,430 C, a significant improvement in thermal stability having been observed with the increase in the side-chain length. A theoretical quantum mechanical study was successfully carried out to explain these results. Flexible and tough films, cast from polymer solutions, showed tensile strengths of 50,125 MPa. 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3711,3724, 2002 [source]

Monomer reactivity ratios of the 2-(3-mesityl-3-methylcyclobutyl)-2-hydroxyethyl methacrylate and styrene system from 1H NMR

Ibrahim Erol
Abstract 2-(3- Mesityl-3-methylcyclobutyl)-2-hydroxyethyl methacrylate (MCHEMA) was prepared from the reaction of methacrylic acid with the oxirane compound obtained from the chlorhydrin formed in the cyclization of 1-chloro-2,3-epoxy-5-methyl-5-hexene. Copolymers of MCHEMA and styrene were prepared in 1,4-dioxane solution at 60 C using 2,2,-azobisisobutyronitrile as the initiator. They were characterized by IR, 1H NMR, and 13C NMR spectra. Their compositions were determined by the 1H NMR technique. The monomer reactivity ratios were determined by the Fineman,Ross, Kelen, Tds, and Yezrielev,Brokhina,Roskin method. Thermogravimetric analysis of the copolymers was carried out under a nitrogen atmosphere. The glass-transition temperature of the copolymers as determined by differential scanning calorimetry agreed with the Flory,Fox relationship. 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1756,1763, 2002 [source]