Initial Weight Loss Temperature Research Articles

A Study on Irradiated HDPE/Sericite Composites

The C=O and C-O groups were rapidly introduced onto the molecular chains of high density polyethylene (HDPE) by ultraviolet irradiation in ozone atmosphere and the contents of the C=O and C-O groups increased with increasing the irradiation time. The crystal form of irradiated HDPE in irradiated HDPE/sericite composites was still an orthorhombic structure. The melting temperature and crystallinity of the HDPE in irradiated HDPE/ sericite composites decreased with increasing the irradiation time. Compared with those of HDPE/sericite composites, the dispersion of sericite particles in the matrix and the interfacial interaction between the sericite particles and the matrix were improved for the irradiated HDPE/sericite composites. With increasing the irradiation time, the tensile strength and impact strength of irradiated HDPE/sericite composites increased, while its initial temperature of weight loss decreased. Compared with those of HDPE/sericite composites, the tensile strength and impact strength of HDPE irradiated for 15 min/sericite composites were enhanced from 27.5 MPa and 75 J/m to 31.2 MPa and 600 J/m, respectively, while its initial temperature of weight loss (in N 2 ) decreased from 454.7°C to 432.5 °C.

Preparation of heat-resistant branched poly(styrene-alt-NPMI) by ATRP with divinylbenzene as the branching agent

Heat-resistant branched poly(styrene-alt-NPMI) has been prepared via atom transfer radical polymerization (ATRP) of styrene (St) and N-phenyl maleimide (NPMI) with divinylbenzene (DVB) as the branching agent in anisole at 80°C. Gas chromatography (GC) was used to determine the conversion of the reactants. Triple detection gel permeation chromatography (TD-GPC) was used to analyze the copolymers. The results show that the polymerization yields primary chains predominately in the early stages and the formation of branched molecules occurs mainly when conversion is higher than 50%. As expected, higher dosage of DVB in our investigation range favors the formation of polymers with higher degree of branching. All the resulting branched poly(styrene-alt-NPMI)s have glass transition temperature (Tg) above 175°C, extrapolated initial weight loss temperature (Ti) above 410°C and statistic heat-resistant index above 200°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis and characterization of novel magnetic Fe3O4/polyurethane foam composite applied to the carrier of immobilized microorganisms for wastewater treatment

The objective of this work was to prepare novel magnetic Fe3O4/polyurethane foam (Fe3O4/PUF) composites applied to the carriers of immobilized microorganisms for toluene-containing wastewater treatment. The morphology and structure of Fe3O4/PUF composite were characterized by X-ray diffraction, Fourier transform IR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, and magnetic property measurement system. These morphological investigations revealed that Fe3O4 nano-particles were well dispersed into the matrix of PUF with nano-scale diameter particles. TG experiments indicated that the initial thermal weight loss temperatures of composite with the content of 2.5 wt% and 7.5% Fe3O4 were increased by 7 and 16 °C, compared with pure PUF. The degradation efficiency of toluene with magnetic PUF composite was much higher than that of pure PUF carrier, and the reason why the immobilization of microbial biomass of microorganisms on the magnetic PUF composite was much higher than that of the pure PUF. The prepared magnetic Fe3O4/PUF composite offered excellent thermal stability and medium paramagnetic properties. And this composite could not only increase the immobilized biomass of the microorganisms, but also enhance the COD removal efficiency of wastewater.

Heat treatment of a direct composite resin: influence on flexural strength

The purpose of this study was to evaluate the flexural strength of a direct composite, for indirect application, that received heat treatment, with or without investment. One indirect composite was used for comparison. For determination of the heat treatment temperature, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed, considering the initial weight loss temperature and glass transition temperature (Tg). Then, after photoactivation (600 mW/cm(2) - 40 s), the specimens (10 x 2 x 2 mm) were heat-treated following these conditions: 170 masculineC for 5, 10 or 15 min, embedded or not embedded in investment. Flexural strength was assessed as a means to evaluate the influence of different heat treatment periods and investment embedding on mechanical properties. The data were analyzed by ANOVA and Tukey's test (alpha = 0.05). TGA showed an initial weight loss temperature of 180 masculineC and DSC showed a Tg value of 157 degrees C. Heat treatment was conducted in an oven (Flli Manfredi, Italy), after 37 degrees C storage for 48 h. Flexural strength was evaluated after 120 h at 37 degrees C storage. The results showed that different periods and investment embedding presented similar statistical values. Nevertheless, the direct composite resin with treatments presented higher values (178.7 MPa) compared to the indirect composite resin (146.0 MPa) and the same direct composite submitted to photoactivation only (151.7 MPa). Within the limitations of this study, it could be concluded that the heat treatment increased the flexural strength of the direct composite studied, leading to higher mechanical strength compared to the indirect composite.

Molecular assemblies based on the template-directing effect of anionic polyoxometalate clusters and organic cationic flexibility

Molecular assembly processes by utilizing the template-directing effect of anionic polyoxometalate clusters and the flexible organic cation have achieved three hybrids: (H 2bpp)(Hbpp)[PMo 12O 40]·3DMF ( 1), (H 2bpp)(Hbpp)(bpp) 2 [PMo 9V 3O 40(VO) 2] 2 ( 2), and (H 2bpp) 2[ β-Mo 8O 26] ( 3) (bpp = 1,3-bis(4-pyridyl)propane). Three compounds were characterized using single crystal X-ray crystallography, elemental analysis, IR, XPS, EPR, voltammetric behavior and TGA. Crystal structural analyses revealed that compounds 1– 3 were all constructed from protonated organic bpp cations with different POM clusters: isolated α-Keggin P–Mo cluster in 1; dimer of bi-capped α-Keggin P–Mo–V anions linked through a {V 2O 2} unit in 2; β-octamolybdate isopolyanion in 3, respectively. All three assemblies demonstrated a higher thermal stability. The protonated bpp cations lost at temperature higher than 300 °C that the strong intermolecular interactions may account for the high initial temperature of weight loss. The electrochemistry property of compound 2 modified carbon paste electrode was also studied in 1 M H 2SO 4 aqueous.

A kinetic study of the thermal degradation of chitosan‐metal complexes

AbstractThe thermal degradation of metal complexes formed by chitosan with Cu(II), Ni(II), Co(II), and Hg(II), at different metal concentrations, was studied by thermogravimetric analysis in a nitrogen atmosphere over the temperature range 25–800°C. The results indicate that thermal degradation of chitosan and chitosan‐metal ion complexes could be of one or two‐stage reaction. In the thermal degradation of chitosan with metal complexes, the temperature of initial weight loss and the temperature of maximum weight loss rate decrease. Fourier transform infrared spectroscopy was used to probe the interaction of chitosan with metal ions. The bands of NH, CO, COC groups of chitosan are shifted or change their intensity in the presence of metal. These changes in the characteristic bands are taken as evidence of the influence of metal ions on the thermal stability of chitosan. Broido's method was employed to evaluate the activation energies as a function of the degree of degradation. The presence of metal ions provoked a decrease in the thermal stability of chitosan, which became more marked when the concentration of metal was increased. The dynamic study showed that the apparent activation energy values of the main stage of the thermal degradation of chitosan‐metal complexes decrease as the strength of the polymer‐metal interaction increases. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Studies on Coprocessing Vacuum Residue Oil With Plastics Using Thermogravimetric Analysis

Synergism and kinetics of plastic/vacuum residue oil blends pyrolysis were investigated in nitrogen and hydrogen atmosphere. From this comprehensive investigation, the results indicated that the higher temperature of initial weight loss of polyethylene plastics was decreased significantly by the addition of vacuum residue oil. Furthermore, the difference in weight loss, calculated as algebraic sums of those from each separate component, is about 10%. These experimental results show a significant synergistic effect during plastics and vacuum residue oil copyrolysis at higher temperatures. Kinetics data from thermogravimetric (TG) analysis fit well the first-order kinetics for both isolated materials and their blends.

A Study of PU/MMT Nanocomposites

The polyurethane (PU)/montmorillonite (MMT) composite prepared by in situ polymerization was a sort of intercalated nanocomposite. The silicate platelets were dispersed in the PU matrix on the nanoscale. The N,N-dimethylformamide (DMF) suspension containing the PU/MMT nanocomposite was stable for a long time, and the silicate platelets did not subside. With an increasing content of silicate, the tensile and tear strength of the PU/MMT nanocomposite increased, but the rate of increase diminished. Compared with that of pure PU, the temperature of initial weight loss of the PU/MMT nanocomposite in the first step decreased because of the acid catalytic action of the protonated silicate platelets, but the temperature of initial weight loss in the second step increased due to the barrier effect of the silicate platelets and the strong interfacial interaction between silicate platelets and the molecular chains of PU.

主鎖にカルバゾールを有する共役高分子の合成

We have synthesized novel conjugated polymer with a benzodioxane group and then polymerized them with a Ni-based reagent. A polymer was soluble in organic solvents such as chloroform, acetone and tetrahydrofuran. The obtained polymer had a number-average molecular weight of 2200, and a weight-average molecular weight of 3500. The fluorescence spectrum of the polymer showed photoluminescence peaks at 420 nm. Further, from the TGA measurements, it was shown that the polymer had high thermal stability with the temperature of initial weight loss 440°C.

Study on Polyurethane/MDI-Modified-Organic Montmorillonite Nanocomposites

Polyurethane (PU)/MDI-modified-organic montmorillonite (MOMMT) nanocomposites were prepared by in situ polymerization and intercalation technology. Compared with that of organic montmorillonite (OMMT), the interlayer spacing of MOMMT was increased from 1.50 nm to 2.05 nm because MDI was grafted on the surface of the silicate layers through reaction between MDI and -OH. The dispersion of silicate layers in PU/MOMMT nanocomposites was better than that of silicate layers in PU/OMMT nanocomposites. Compared with those of PU/OMMT nanocomposites, the tensile strength and tear strength of PU/MOMMT nanocomposites were increased, and the MOMMT showed a higher stiffened effect. Because of the improvement of the dispersion and interfacial interaction, the temperature of initial weight loss of PU/MOMMT nanocomposites was higher than that of PU/OMMT nanocomposites, so PU/MOMMT nanocomposites had better thermal stability.

Impact of ultraviolet radiation on HDPE and HDPE/STC blends

AbstractThe structure and properties of high‐density polyethylene (HDPE) ultraviolet irradiated in ozone atmosphere were studied by FTIR, XPS, GPC, XRD, DSC, TG, gel, and contact angle test. The oxygen‐containing groups such as CO, CO, and C(O)O were quickly introduced onto HDPE chains through ultraviolet irradiation in ozone atmosphere; their content increased with increase in the time of ultraviolet irradiation. Compared with those of HDPE, the molecular weight of the irradiated HDPE decreased and its distribution became wider. There was no gel in the HDPE irradiated in ozone atmosphere. After ultraviolet irradiation for short times in ozone atmosphere, the water contact angle of the irradiated HDPE decreased and its hydrophilicity was improved. The crystal shape of the irradiated HDPE was still an orthorhombic structure; its cell parameter and the face space did not alter, but its melting temperature decreased slightly. Compared with that of HDPE, the temperature of initial weight loss for irradiated HDPE decreased. The irradiated HDPE/sericite‐tridymite‐cristobalite (STC) blends were prepared. The dispersion and compatibility of the irradiated HDPE/STC blends were improved compared with those of HDPE/STC blends; thus its mechanical properties increased. Copyright © 2008 John Wiley & Sons, Ltd.

Synthesis, cure kinetics, and thermal properties of the Bis(3‐allyl‐2‐cyanatophenyl)sulphoxide/BMI blends

AbstractA novel allyl functionalized dicyanate ester resin bearing sulfoxide linkage was synthesized. The monomer was characterized by Fourier Transform Infrared (FT‐IR) Spectroscopy, 1H‐, and 13C Nuclear Magnetic Resonance (NMR) spectroscopy and elemental analysis. The monomer was blended with bismaleimide (BMI) at various ratios in the absence of catalyst. The cure kinetics of one of the blends was studied using differential scanning calorimetry [nonisothermal] and the kinetic parameters like activation energy (E), pre‐exponential factor (A), and the order of the reaction (n) were calculated by Coats‐Redfern method and compared with those calculated using the experimental Borchardt‐Daniels method. The thermal stability of the cured dicyanate, BMI, and the blends was studied using thermogravimetric analyzer. The initial weight loss temperature of dicyanate ester is above 380°C with char yield of about 54% at 800°C. Thermal degradation of BMI starts above 463°C with the char yield of about 68%. Inclusion of BMI in cyanate ester increases the thermal stability from 419 to 441°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Structure and Property of PU/MMT Nanocomposites by In-Situ Polymerization

A montmorillonite modified by octadecylammonium salt (OMMT) was prepared. A polyurethane (PU)/montmorillonite nanocomposite was synthesized by in-situ polymerization using the OMMT, poly(propylene glycol), 4,4-diphenylmethylate diisocyanate, and 1,4-butanediol. The MMT platelets were dispersed in PU matrix on a 10 ∼ 50 nm scale. Compared to that of pure PU, the tensile strength and tear strength of the PU/OMMT nanocomposites increased, respectively, and the MMT platelets dispersed on a nanometer scale enhanced the PU. The temperature of initial weight loss of the PU/OMMT nanocomposites was lower than that of pure PU because of the acid catalytic action of protonated MMT platelets in the first thermodegradation step. But its temperature of initial weight loss was higher than that of pure PU because of the barrier effect of the MMT platelets in the second thermodegradation step.

High Hole Mobilities in the Amorphous Films of 2,7-Di(9-carbazolyl)-9-(2-ethylhexyl)carbazole

Abstract 2,7-Di(9-carbazolyl)-9-(2-ethylhexyl)carbazole was synthesized and investigated as new effective hole-transporting material. The synthesized compound showed high thermal stability with the initial weight loss temperature of 400 °C. It forms glass with glass-transition temperature of 88 °C. Hole drift mobilities in the amorphous films of the newly synthesized compound exceeded 10−2 cm2 V−1 s−1 at high electric field, as characterized by the xerographic time of flight technique.

Study of nanocomposites prepared by melt blending TPU and montmorillonite

AbstractThe intercalated thermoplastic polyurethane (TPU)/montmorillonite (MMT) nanocomposites were prepared by melt blending TPU and organic octadecylammonium‐treated MMT (ODA‐MMT) at 150–155°C for 10 min. Compared with those of TPU/montmorillonite composites, the interface interaction and dispersion of TPU/ODA‐MMT nanocomposites were improved remarkably. The tensile strength and tear strength of the TPU/ODA‐MMT nanocomposites were higher than those of pure TPU, and the MMT platelets dispersed on the nanometer scale in TPU matrix had reinforce effect. Due to the “labyrinth” effect of the MMT platelets dispersed on the nanometer scale in the TPU matrix caused by the eximious barrier and strong interaction between the MMT platelets and TPU, the temperature of initial weight loss of the TPU/ODA‐MMT nanocomposites was higher than that of pure TPU and TPU/MMT composites in the second thermodegradation step. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Synthesis and properties of glass-forming phenothiazine and carbazole adducts

Charge-transporting and photoluminescent phenothiazine and carbazole adducts were synthesized and their thermal, optical, photophysical and photoelectrical properties were studied. The materials synthesized were found to constitute glasses with glass transition temperatures in the range of 63–78 °C. Their initial weight loss temperatures range from 334 to 362 °C. Steady state and time-resolved fluorescence spectrometry techniques have revealed energy transfer in the adducts of carbazole and phenothiazine and the existence of excimer forming sites in the films of 3-(10-phenothiazinyl)-9-ethylcarbazole and 3-(9-carbazolyl)-9-ethylcarbazole. The electron photoemission spectra of the materials were recorded and the ionization potentials of 5.38–5.87 eV were established. Time-of-flight hole drift mobilities of carbazole twin compound molecularly dispersed in bisphenol Z polycarbonate (1:2 by weight) approach 2 × 10 −5 cm 2/V s at high electric field.

Effect of cupric ion on thermal degradation of chitosan

The thermal degradation of chitosan and chitosan–cupric ion compounds in nitrogen was studied by thermogravimetry analysis and differential thermal analysis (DTA) in the temperature range 30–600°C. The effect of cupric ion on the thermal degradation behaviors of chitosan was discussed. Fourier transform-infrared (FTIR) and X-ray diffractogram (XRD) analysis were utilized to determine the micro-structure of chitosan–cupric ion compounds. The results show that FTIR absorbance bands of NH, CN, COC etc. groups of chitosan are shifted, and XRD peaks of chitosan located at 11.3, 17.8, and 22.8° are gradually absent with increasing weight fraction of cupric ion mixed in chitosan, which show that there are coordinating bonds between chitosan and cupric ion. The results of thermal analysis indicate that the thermal degradation of chitosan and chitosan–cupric ion compounds in nitrogen is a two-stage reaction. The first stage is the deacetylation of the main chain and the cleavage of glycosidic linkages of chitosan, and the second stage is the thermal destruction of pyranose ring of chitosan and the decomposition of residual carbon, in which both are exothermic. The effect of cupric ion on the thermal degradation of chitosan is significant. In the thermal degradation of chitosan–cupric ion compounds, the temperature of initial weight loss (Tst), the temperature of maximal weight loss rate (Tmax), that is, the peak temperature on the DTG curve, and the peak temperature (Tp) on the DTA curve decrease, and the reaction activation energy (Ea) varies with increasing weight fraction of cupric ion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

N-Propylpyridinium chloride-modified poly(dimethylsiloxane) elastomeric networks: Preparation, characterization, and study of metal chloride adsorption from ethanol solutions

An n-propylpyridinium chloride-modified PDMS elastomeric network, PDMS/Py +Cl −, was prepared from linear PDMS chains containing Si(CH 3) 2 OH end-groups cross-linked by 3-chloropropyltrimethoxysilane and posterior reaction with pyridine. PDMS/Py +Cl − material was structurally characterized by infrared spectroscopy (IR) and solid state 13C and 29Si NMR. Thermogravimetric analysis of the product showed good thermal stability, with the initial temperature of weight loss at 450 K. The ion-exchange capacity of the PDMS/Py +Cl − was 0.65 mmol g −1. Metal halides, MCl z [M = Fe 3+, Cu 2+, and Co 2+], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes MCl z + n n − . The nature of the anionic complex structure was proposed by UV–vis diffuse reflectance spectra. The species adsorbed were FeCl − 4, CuCl 2− 4, and CoCl 2− 4. The specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures. The trend in affinities of PDMS/Py +Cl − for the metal halides were found to be FeCl 3 > CuCl 2 ∼ CoCl 2.

Preparation, characterization, and prominent thermal stability of phase‐change microcapsules with phenolic resin shell and n‐hexadecane core

AbstractMicrocapsules with phenolic resin (PFR) shell and n‐hexadecane (HD) core were prepared by controlled precipitation of the polymer from droplets of oil‐in‐water emulsion, followed by a heat‐curing process. The droplets of the oil phase are composed of a polymer (PFR), a good solvent (ethyl acetate), and a poor solvent (HD) for the polymer. Removal of the good solvent from the droplets leads to the formation of microcapsules with the poor solvent encapsulated by the polymer. The microstructure, morphology, and phase‐change property as well as thermal stability of the microcapsules were systematically characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimety (DSC), and thermogravimetric analysis (TGA). The phase‐change microcapsules exhibit smooth and perfect structure, and the shell thickness is a constant fraction of the capsule radius. The initial weight loss temperature of the microcapsules was determined to be 330°C in N2 and 255°C in air, respectively, while that of the bulk HD is only about 120°C both in air and N2 atmospheres. The weight loss mechanism of the microcapsules in different atmosphere is not the same, changing from the pyrolysis temperature of the core material in N2 to the evaporation of core material caused by the fracture of shell material in air. The melting point of HD in microcapsules is slightly lower than that of bulk HD, and a supercooling was observed upon crystallization. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

The thermal properties of controllable diameter carbon nanotubes synthesized by using AB 5 alloy of micrometer magnitude as catalyst

We have synthesized multi-wall carbon nanotubes by catalytic chemical vapour deposition (CCVD) method using an AB 5 hydrogen storage alloy with diameter ranging from 38 to 150 μm as a catalyst. The H 2 uptake capacity of the carbon nanotubes prepared using an AB 5 alloy as a catalyst is about 4 wt.% through to the pressure of 8 MPa at room temperature. Differential thermal analysis–thermogravimetric analysis (DTA–TGA) technique has been applied to investigate the effect of the diameters of the AB 5 alloy catalyst of micrometer magnitude and the technique conditions in the CCVD process on the thermal properties of carbon nanotubes. As the catalyst diameter increases from 38 to 150 μm, the average diameter of the prepared carbon nanotubes increases and the diameter distribution also enlarges. Electron microscope, Raman spectrum and thermal analysis all indicated that the catalyst sizes affect the diameter and the thermal properties of the carbon nanotubes. When the catalyst diameter increases, the initial weight loss temperature and the differential thermal peak temperature of the carbon nanotubes increases, which shows that the lager the diameter of the carbon nanotubes is, the higher the oxidation temperature, and the better the anti-oxidizablity. However, if the diameter of the catalyst is larger than 100 μm, the anti-oxidizablity does not rise anymore but tend to be invariableness. In the CCVD preparation process, the anti-oxidizability of the carbon nanotubes increases, when raising the ratio of the hydrogen gas in the reaction gas in our experimental range (4:1, 3:1, and 2:1, respectively).