To Thermogravimetric Analysis Research Articles

Effect of ultrasonication medium on the properties of copper nanoparticle-filled epoxy composite for electrical conductive adhesive (ECA) application

In this study, the relationship of three different media, (air, epoxy fluid, and chloroform solution) on the electrical, mechanical, and thermal properties of 5 vol.% copper nanoparticle (CuNP)-filled epoxy nanocomposite was investigated. Microscopic observation revealed that the CuNP ultrasonicated with chloroform solution exhibited the best filler distribution in the epoxy matrix. It showed high electrical conductivity of 7.65 × 10−3 S cm−1 and flexural properties, and low coefficient of thermal expansion (CTE) compared with the other two nanocomposites. However, CuNP prepared by chloroform medium showed inferior thermal property compared with the other two nanocomposites according to thermogravimetric analysis (TGA).

A simple aqueous metathesis reaction yields new lanthanide monothiophosphates

This paper describes the synthesis and characterization of two, new rare earth monothiophosphate materials, LaPO 3S· xH 2O and NdPO 3S· yH 2O, and their properties in comparison to the corresponding orthophosphates prepared by a similar aqueous metathesis reaction. Each of these new materials was found to exist in an amorphous phase similar to a corresponding orthophosphate mineral. The new rhabdophane-type oxythiophosphates were found to display reversible dehydration and rehydration under mild conditions. The materials were found to be thermally unstable. Disproportionation was found to occur at less than 450 °C under vacuum. Sulfur is lost during heating in air between 450 and 650 °C, according to thermogravimetric analysis (TGA) experiments, yielding the orthophosphate. The monothiophosphate hydrates display broad photoluminescence in the visible under excitation by a 325 nm laser. The compounds were also analyzed using differential thermal analysis, FT-IR and UV/vis/NIR spectroscopy.

Influence of lithium ions on the NLO properties of KDP single crystals

AbstractPotassium Dihydrogen Phosphate (KDP) and its isomorphous deuterated form are popular due to their applications in frequency converters and electro‐optic modulation. Different attempts have been made to dope KDP with inorganic additives, organic materials and amino acids. Since many of the metal ions possess more electro negativity which increases the non centrosymmetry, it is of interest to dope them in KDP. The influence of lithium ion (Li+) on NLO properties of KDP crystal has been studied in the present investigation. Single crystal of Lithium ion doped Potassium Dihydrogen Phosphate (KDP) was grown by slow evaporation technique. The enhancement in SHG efficiency after addition of ion Lithium (Li+) was observed by Kurtz Powder SHG test. It was found that the SHG efficiency of KDP after addition of Lithium ion is 1.33 times more than pure KDP. The crystal structure and cell parameters of grown crystal were determined by X‐ray diffraction. The Energy Dispersive X‐ray analysis (EDAX) gives the chemical composition of grown crystal. The functional groups were identified by FT‐IR spectral analysis. The presence of Lithium in the material of grown crystal was detected by Atomic absorption spectroscopy (AAS). The optical absorption and transmission studies were done by UV‐Visible spectral analysis. The grown crystal was subjected to thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Synthesis and Characteristics of Multi-Walled Carbon Nanotubes-Polyimide Nanocomposite Films

The polyimide/multi-walled carbon nanotubes (PI/MWNTs) nanocomposite film has been successfully synthesized in this study. The source of MWNTs is prepared by chemical vapor deposition (CVD) method. Then the MWNTs are washed with acid for purification before being added into the polymer matrix. The acid-modified procedure aids in dispersing MWNTs in N,N-dimethylacetamide (DMAc) solvent. Based on the results of field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), the MWNTs are embedded in PI and well-dispersed within the PI matrix. The dynamic mechanical analysis (DMA) shows that the storage modulus of nanocomposite film is increased by 68% with the addition of 1 wt% MWNTs into PI. The nanocomposite films start to decompose at or above 400 degrees C and lose 5% of its weight at 545 degrees C according to thermogravimetric analysis (TGA). Meanwhile, the electrical conductivity of the nanocomposite film with 3 wt% MWNTs, is raised more than 10 orders of magnitude from 10(-15) to 10(-5) S/cm.

Electrochemical behaviour of nano-sized spinel LiMn 2O 4 and LiAl xMn 2−xO 4 ( x=Al: 0.00–0.40) synthesized via fumaric acid-assisted sol–gel synthesis for use in lithium rechargeable batteries

Pristine spinel LiMn 2O 4 and LiAl x Mn 2− x O 4 ( x=Al: 0.00–0.40) with sub-micron sized particles have been synthesized using fumaric acid as chelating agent by sol–gel method. The synthesized samples were subjected to thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry (CV) and galvanostatic cycling studies. The TGA curve of the gel shows several weight-loss regions stepwise amounting to 55% till 800 °C attributed to the decomposition of the precursors. Calcination to higher temperatures (800 °C) yields pure-phase spinel (LiAl x Mn 2− x O 4), as it is evident from the high-intensity XRD reflections matching to the standard pattern. SEM and TEM studies confirm that the synthesized grains are of uniform regular surface morphology. FT-IR studies show stretching and bending vibration bands of Li–O, Li–Al–Mn–O. LiAl 0.1Mn 1.90O 4 spinel was found to deliver discharge capacity of 139 mA h/g during the first cycle with columbic efficiency of 97%. LiAl 0.1Mn 1.90O 4 spinel exhibits the high cathodic peak current indicating better electrochemical performance. Low doping ( x=0.1) of Al is found to be beneficial in stabilizing the spinel structure.

Study of Radiant Smoldering Ignition of Plywood Subjected to Prolonged Heating Using the Cone Calorimeter, TGA, and DSC

Maple plywood samples were heated in an oven at 180°C to a residual weight of 70%, 50%, and 30% of the virgin weight. The virgin plywood and the thermally pretreated samples were tested in a cone calorimeter over the range of 6 to 15 kW/m2 without the use of an ignitor. Tests were conducted until smoldering/glowing combustion was observed or for eight hours if ignition was not observed. The extent of thermal pretreatment of the plywood had no measurable effect on the minimum heat flux for smoldering ignition. At heat fluxes above the minimum for ignition, ignition times were reduced for thermally pretreated samples relative to virgin wood. This is consistent with the thermal pretreatment achieving the charring required as the first step in smoldering ignition and the reduction in thermal inertia resulting from charring. Samples of the virgin and pretreated wood were subjected to thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The chemical kinetics analysis of the virgin and pretreated samples showed no change in the chemical mechanism. The thermal pretreatment simply resulted in the samples being further along the reaction pathway at the start of the ignition test. The results are not consistent with the formation of a more reactive char species commonly referred to in the fire investigation lore as “pyrophoric carbon.”

New Broom Fiber (Spartium junceum L.) Derivatives: Preparation and Characterization

In the past decade interest in biopolymers has increased. Attempts were made to prepare new composite systems from biopolymers by binding different synthetic polymers to a biopolymer backbone. This paper reports the synthesis and characterization of derivatized broom fibers to prepare composites with either degradability or fireproofing properties. Synthetic strategies are described for the introduction of polymerizable functional groups or fluorine atoms on the glucose of cellulose chains of broom. The fibers containing polymerizable groups were copolymerized with dimethylacrylamide and styrene and, after that, investigated by optical polarizing microscopy (OPM) and scanning electron microscopy analysis (SEM). The materials containing fluorine were submitted to thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) for the purpose of verifying the fireproofing. Such derivatized biomaterials could be successfully used for applications in agriculture and in the packaging area.

Gas permeation properties of poly(2,5-dialkyl-p-phenyleneethynylene) membranes

Dipropynylbenzenes with alkyl groups (CH3C ≡ CRC6H2RC≡CCH3, R=n-C6H13, n-C8H17, n-C10H21, 1a–c, respectively) were polymerized with Mo(CO)6 to afford solvent-soluble poly(2,5-dialkyl-p-phenyleneethynylene)s (2a–c). The polymers (2a–c) had high molecular weight over 3×104, and gave free-standing membranes by solution casting method. According to thermogravimetric analysis (TGA), these poly(p-phenyleneethynylene)s showed high thermal stability (T0 ≥380 °C). The densities of membranes of poly(2,5-dialkyl-p-phenyleneethynylene)s (2a–c) were 0.936–0.965, and their fractional free volume (FFV) were relatively large (ca. 0.14–0.15). The oxygen permeability coefficients (PO2) of membranes of 2a–c were 4.88, 7.06, and 16.6 barrers, respectively.

Synthesis and Charge/Discharge Properties of Polyacetylenes Carrying 2,2,6,6‐Tetramethyl‐1‐piperidinoxy Radicals

The 2,2,6,6-tetramethyl-1-piperidinoxy (TEMPO)-containing acetylenic monomers HC[triple bond]CC(6)H(3)-p,m-(CONH-4-TEMPO)(2) (1), HC[triple bond]CC(6)H(3)-p,m-(COO-4-TEMPO)(2) (2), (S,S,S,S)-HC[triple bond]CC(6)H(3)-p,m-[CO-NHCH{COO-(4-TEMPO)}CH(2)COO-(4-TEMPO)](2) (3), (S,S)-HC[triple bond]CC(6)H(4)CO-NHCH{COO-(4-TEMPO)}CH(2)COO-(4-TEMPO) (4), HC[triple bond]CC(6)H(4)-p-OCO-4-TEMPO (5), HC[triple bond]CCH(2)C(CH(3))(CH(2)OCO-4-TEMPO)(2) (6), HC[triple bond]CCH(2)NHCO-4-TEMPO (7), and HC[triple bond]CCH(2)OCO-4-TEMPO (8) were polymerized to afford novel polymers containing the TEMPO radical at high densities. Monomers 1, 3-6, and 8 provided polymers with average molecular weights of 10 000-136 500 in 62-99 % yield in the presence of a rhodium catalyst, whereas monomers 2 and 7 gave insoluble polymers in 100 % yield. The formed polymers were thermally stable up to approximately 274 degrees C according to thermogravimetric analysis (TGA). All the TEMPO-containing polymers demonstrated reversible charge/discharge processes, whose discharge capacities were 21.3-108 A h kg(-1). In particular, the capacity of poly(1)-, poly(4)-, and poly(5)-based cells reached 108, 96.3, and 89.3 A h kg(-1), respectively, which practically coincided with their theoretical values.

The oxidative polycondensation of 2-[(4-pyridilmethylene)-imino]phenol by molecular O2 in alkaline medium: Synthesis and characterization

The polymer of 2-[(4-pyridilmethylene)-imino] phenol (2-PIP) has been formed from the oxidative polycondensation (OP) reaction by using molecular O2 as the oxidant in an aqueous alkaline medium between 60–90 °C. The optimum reaction conditions and the main parameters of the process were determined. The yield of polymer was found as 50.1%. The structures of synthesized monomer and polymer were confirmed by FT-IR, UV-vis, 1H-13C-NMR and elemental analysis. The characterization was made by TGA-DTA, size exclusion chromatography (SEC) and solubility tests. The 1H-13C-NMR data shows that the polymerization proceeded with C-C and C-O-C coupling system of ortho and para positions and oxyphenylene according to –OH group of 2-PIP. The molecular weight distribution values of the product were determined from SEC measurement. The number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of poly-2-[(4-pyridilmethylene)-imino]phenol (poly-2-PIP) were found to be 11350, 12600 g.mol-1 and 1.110, respectively. According to thermo gravimetric analysis (TGA), the carbon residues of 2-PIP and poly-2-PIP were found to be 18.17% and 45.10%, respectively, at 1000 °C.

Synthesis and properties of various poly(diarylacetylenes) containing siloxy and hydroxy groups

AbstractDiarylacetylene monomers (1b−f) containing siloxy and either naphthyl, fluorenyl, or biphenyl groups were polymerized with TaCl5–n‐Bu4Sn catalyst, and 1b, 1c, and 1f provided high molecular weight polymers. Free‐standing membranes of polymers 2b, 2c, and 2f were fabricated by casting from toluene solution. Desilylation of these polymer membranes was carried out with trifluoroacetic acid to afford poly (diarylacetylenes) membranes having hydroxy groups (3b and 3c). According to thermogravimetric analysis (TGA), both siloxy‐containing and hydroxy‐containing polymers exhibited high thermal stability, and the onset temperatures of weight loss in air were ∼370 °C and ∼430 °C, respectively. The CO2 permeability coefficients of these membranes were in the range of 65–640 barrers. The points of 3b and 3c in the PCO2 versus PCO2/PCH4 plot were located above Robeson's upper bound. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4487–4495, 2007

Synthesis and Properties of Substituted Polyacetylenes Having Cyclohexyl Groups

Disubstituted acetylenes containing cyclohexyl groups (RC≡CC6H4–p-cyclo-C6H11, R=Ph, p-Me3SiPh, p-tert-BuMe2SiOPh, Me, Cl, 1a–e, respectively) were polymerized with Ta- or Mo-based catalyst, and 1a, 1c, and 1e provided high molecular weight polymers. Free-standing membranes of poly(1a) and poly(1c) were fabricated from toluene solution. Hydroxy-containing membrane poly(2c) was prepared by desilylation of siloxy-containing poly(1c) using trifluroacetic acid. According to thermogravimetric analysis (TGA), the produced polymers exhibited high thermal stability, and the onset temperatures of weight loss in air were ∼340 °C. The oxygen permeability coefficients of these membranes were in the range of 17–230 barrers. The point of poly(2c) in the PCO2 vs. PCO2/PCH4 plot were located above Robeson’s upper bound.

Miscibility and Properties of Acid-Treated Multi-Walled Carbon Nanotubes/Polyurethane Nanocomposites

Nanocomposites based on polyurethane and acid-treatment multi-walled carbon nanotubes (A-MWNTs) are prepared by solution blending. The surface of the MWNTs was modified by acid treatment to incorporated functional groups. The modified MWNTs exhibited improved dispersion in organic solvents and miscibility with the PU matrix. The derivatives of MWNTs were characterized by Fourier transform infrared (FT-IR) spectroscopy, Transmission electron microscopy (TEM) and Raman spectroscopy. The thinning and defects of the A-MWNT from the surface etching of acid treatment can be clearly seen from TEM pictures and Raman spectra, respectively. The interaction and degree of miscibility between the MWNTs and the PU matrix is examined using FT-IR, modulated differential scanning calorimeter (MDSC), TEM and atomic force microscopy (AFM). The hydrogen bonding index (HBI) measured by FT-IR was employed to show the degree of interchange hydrogen bonding. Composites films with higher A-MWNT content exhibit higher HBI and the degree of miscibility is significantly improved. The resultant composites have higher tensile strength, higher Young’s modulus and lower elongation at break because of the rigid structure of A-MWNT and the increase in the number of hydrogen bonds among the composites. Incorporating A-MWNT in composites increases the mass of the residue at temperatures over 600 °C, according to thermo gravimetric analysis (TGA). An A-MWNT percentage of 20 wt %, the electric conductivity approached 6.2×10−2 S/cm.

Use of new hydroxytelechelic cis-1,4-polyisoprene (HTPI) in the synthesis of polyurethanes (PUs): Influence of isocyanate and chain extender nature and their equivalent ratios on the mechanical and thermal properties of PUs

AbstractNew segmented polyurethanes (thermoplastic-elastomers) based on previously described hydroxytelechelic cis-1,4-polyisoprene (HTPI), miscellaneous isocyanates and chain extenders at various equivalent ratios were prepared by the classical one-shot method. The influence of the nature of isocyanate and chain extender, as well as their equivalent ratios, on the mechanical and thermal materials behavior was investigated. Thus, a comparative assessment of material properties was performed. Microphase separation of hard and soft segments was observed by DMTA, DSC and AFM. Moreover, according to Thermogravimetric Analysis (TGA), linear relationships depending on the isocyanate and chain extender nature were found between the weight loss (%) and the percentages of hard segments. A classification of thermal stability in terms of weight loss was established. With the aim of a thermo-mechanical comparative study, polyurethane elastomers based on HTPI and isocyanates without chain extender, were also synthesized.

Synthesis and properties of poly(diphenylacetylenes) containing siloxy and halogen/methyl groups and their desilylated membranes

Diphenylacetylenes containing both siloxy groups and halogen or methyl substituents (p-tert-BuMe2SiOC6H4CCC6H3R2, R=m,p-Cl,Cl; m,m-Cl,Cl; m,p-Br,Br; m,m-Br,Br; m,p-Me,Me; m,m-Me,Me, 1a–f, respectively) were polymerized with TaCl5–n-Bu4Sn catalyst to give high molecular weight polymers (2a–f) in good yields. Free-standing membranes were fabricated by casting from toluene solution. Desilylation of these siloxy group-containing polymer membranes with trifluoroacetic acid (TFA) afforded poly(diphenylacetylene) membranes having hydroxy groups (3a–f). Polymers 2a–f were soluble in low polar solvents such as toluene and CHCl3, while 3a–f were insoluble in these solvents. According to thermogravimetric analysis (TGA), 2a–f and 3a–f exhibited high thermal stability (T0 ∼340 and ∼390°C, respectively). The gas permeability of the halogen-containing polymer membranes was higher than that of methyl group-containing ones. The PCO2/PN2 permselectivity ratios of polymer membranes 3a–f were in the range of 14–49. The points of 3a–f in the PCO2 vs PCO2/PN2 plot were located obviously above Robeson's upper bound.

Thermal transition of electrochemically synthesized polyaniline

The thermal stability of polyaniline (PAni) is of great importance in commercial applications. PAni and its emeraldine base form (PAni-EB) were electrochemically synthesized and subjected to thermogravimetric analysis (TGA) in inert atmosphere, which illustrated that the dopant HClO 4 could act as the oxidizing agent at elevated temperature and caused serious decomposition of PAni. Combined with differential scanning calorimetry (DSC), in-situ X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analyses, the crosslinking reaction among PAni-EB molecules at about 250 °C was characterized, and the kinetic parameters were calculated by applying different heating rates in the DSC measurement.

Synthesis and gas permeation properties of poly(diphenylacetylenes) having bulky alkyl/silyl and hydroxy groups

Novel diphenylacetylene monomers 1c– h possessing tert-butyl or trialkylsilyl and siloxy groups ( p-R-C 6H 4C CC 6H 4– p-OSiMe 2 t-Bu: 1c R = t-Bu, 1e R = SiMe 3, 1g R = SiMe 2 t-Bu; p-R-C 6H 4C CC 6H 4– m-OSiMe 2 t-Bu: 1d R = t-Bu, 1f R = SiMe 3, 1h R = SiMe 2 t-Bu) were polymerized with TaCl 5– n-Bu 4Sn catalyst. Monomers 1c and 1e gave high molecular weight polymers in good yields. Free-standing membranes of polymers 2c– f were fabricated by casting from toluene solution. Desilylation of membranes of polymers 2c and 2d with trifluoroacetic acid (TFA) yielded poly(diphenylacetylenes) having tert-butyl and hydroxy groups ( 3c and 3d). Polymers 2c– f and 2h were soluble in nonpolar solvents such as hexane, cyclohexane and toluene, while 3c and 3d were insoluble in these solvents. According to thermogravimetric analysis (TGA), 2c– f, 3c and 3d exhibited high thermal stability. The gas permeability of all the membranes in the present study was much higher than that of the corresponding polymers without bulky groups, indicating that incorporation of bulky groups into the polymers improves the gas permeability. The PCO 2/ PN 2 permselectivity ratios of polymers 3c and 3d were 23 and 14, respectively. The CO 2 permeability and CO 2/N 2 permselectivity of 3c and 3d were positioned above Robeson's upper bound line.

Synthesis and properties of halogen- or methyl-containing poly(diphenylacetylene) membranes

Novel diphenylacetylenes with both trimethylsilyl groups and other substituents (R 2C 6H 3C CC 6H 4- p-SiMe 3, R = m, p-Cl,Cl, m, m-Cl,Cl, m, p-Br,Br, m, m-Br,Br, m, p-Me,Me, m, m-Me,Me, 1a– f, respectively) were polymerized with TaCl 5– n-Bu 4Sn to produce solvent-soluble polymers ( 2a– f). Most polymers ( 2a– e) had high molecular weight over 1 × 10 6, and gave free-standing membranes by the solution casting method. Desilylation of these Si-containing polymer membranes was carried out with trifluoroacetic acid (TFA), which afforded solvent-insoluble desilylated polymer membranes ( 3a– e). According to thermogravimetric analysis (TGA), both Si-containing and desilylated polymers showed high thermal stability ( T 0 ≥ 420 °C). The fractional free volume (FFV) of both Si-containing and desilylated polymer membranes ( 2a– d, 3a– d) were fairly large (ca. 0.27–0.32), while the FFVs of membranes ( 2e, 3e) were rather small (0.28 and 0.24). The oxygen permeability coefficients ( P O 2 ) of 2a was as high as 5400 barrers, which is the largest among all the poly(diphenylacetylene) derivatives. Polymers 2b– d also exhibited high oxygen permeability, and their desilylated ones 3b– d retained similar high oxygen permeability. On the other hand, the P O 2 values of 2e and 3e were 1200 and 530 barrers, respectively, which are smaller than those of the halogen-containing polymers ( 2a– d and 3a– d).

The structure–activity relationship of fire retardant phosphorus compounds in wood

Sawdust of Scots Pine sapwood was chemically modified with various alkyl- and phenylchlorophosphorus compounds. The formation of covalent bonds was confirmed with solid state CP-MAS 13C NMR. According to thermogravimetric analysis (TGA), all phosphorus compounds decreased the temperature for the maximum rate of pyrolysis (from 350 °C to max. 240 °C) and increased the char formation (from 25% to max. 54%). Variation of the alkyl groups (C2–C8) had no significant effect. Phenylphosphates decrease the temperature of pyrolysis more efficiently than the alkyl analogues, due to higher thermal stability. The order in which the phenylphosphorus compounds affect the pyrolysis of the modified sawdust is consistent with their acidity order: organophosphate > organophosphonate ≫ organophosphinate. All phosphorus compounds used in this study reduce the equilibrium moisture content (EMC). Whereas the results obtained with the dialkyl phosphates are relatively poor, significant reductions in EMC can be achieved with the phenylphosphorus compounds.

Towards new precursors for ZnO thin films by single source CVD: the X-ray structures and precursor properties of zinc ketoacidoximates

Zinc complexes of pyruvic and glyoxylic acid oximes have been investigated as potential precursors for single source chemical vapour deposition (SSCVD) of ZnO thin films. The X-ray crystal structures of the complexes and of their –NOMe analogues reveal markedly different coordination and intermolecular bonding patterns. These structural differences, in conjunction with ligand substituent changes impart different responses to thermogravimetric analysis (TGA), and sublimation. The glyoxylic acid methyloxime Zn(O 2CCHN(OMe)) 2 · 2H 2O has volatility and thermolysis properties suitable for SSCVD of ZnO.