Thermal Stability Degradation Research Articles

Alkyd resins based on waste PET for water-reducible coating applications

Simultaneous glycolysis and neutral hydrolysis of waste PET flakes obtained from grinding post-consumer bottles was carried out in the presence of xylene and an emulsifier at 170 °C. The product was separated from ethylene glycol (EG), water, and xylene by filtration, and was extracted by water at boiling point thrice. The remaining solid was named water insoluble fraction (WIF). The filtrate was cooled to 4 °C, and the crystallized solid obtained by filtration was named water soluble crystallizable fraction (WSCF). These fractions were characterized by acid value (AV) and hydroxyl value (HV) determinations. WSCF and WIF were used for preparation of the water-reducible alkyd resins. Three long oil alkyd resins were prepared from phthalic anhydride (PA; reference alkyd resin) or depolymerization product of the waste PET (PET-based alkyd resin), glycerin (G), fatty acids (FA), and glycol (EG; reference alkyd resin) or depolymerization product of the waste PET (PET-based alkyd resin). Film properties and thermal degradation stabilities of these alkyd resins were investigated. Physical properties (drying times and hardness) and thermal degradation stabilities of the PET-based alkyd resin is better than these properties of the reference alkyd resin.

Alkyd resins synthesized from postconsumer PET bottles

Simultaneous glycolysis and neutral hydrolysis of waste PET flakes obtained from grinding postconsumer bottles was carried out in the presence of xylene and an emulsifier at 180 °C. The product was separated from EG, water and xylene by filtration and was extracted by water at boiling point three times. The remaining solid was named water insoluble fraction (WIF). The filtrate was cooled to 4 °C and the crystallized solid obtained by filtration was named water-soluble crystallizable fraction (WSCF). These fractions were characterized by acid value (AV), hydroxyl value (HV) determinations. WSCF and WIF were used for preparation of the alkyd resins. Three long oil alkyd resins were prepared from phthalic anhydride (PA) (reference alkyd resin) or depolymerization product of the waste PET (PET-based alkyd resin), glycerin (G), sunflower oil fatty acids (SOFA) and glycol (EG) (reference alkyd resin) or depolymerization product of the waste PET (PET-based alkyd resin). Film properties and thermal degradation stabilities of these alkyd resins were investigated. Physical properties (drying times, hardness and abrasion resistance) and thermal degradation stabilities of the PET-based alkyd resins are better than these properties of the reference alkyd resin.

Thermal and physical properties of flame-retardant epoxy resins containing 2-(6-oxido-6 H-dibenz〈 c, e〉〈1,2〉oxaphosphorin-6-yl)-1,4-naphthalenediol and cured with dicyanate ester

2-(6-oxido-6 H-dibenz( c, e)(1,2)oxaphosphorin-6-yl)-1,4-naphthalenediol (DOPONQ) was prepared by the addition reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) with 1,4-naphthoquinone. The phosphorus-containing diol (DOPONQ) was used as a reactive flame retardant by an advancement reaction with the diglycidyl ether of bisphenol-A epoxy (DGEBA) resin at various stoichiometric ratios. DOPONQ-containing advanced epoxy was separately cured with various dicyanate esters to form flame-retardant epoxy/cyanate ester systems. The effect of the phosphorus content and dicyanate ester structure on the curing characteristic, glass transition temperature, dimensional stability, thermal stability, flame retardancy, and dielectric property was studied and compared with that of the control advanced bisphenol-A epoxy system. The DOPONQ-containing epoxy/cyanate ester systems exhibited higher glass transition temperatures as well as better thermal dimensional and thermal degradation stabilities. The flame retardancy of the phosphorus-containing epoxy/dicyanate ester system increased with the phosphorus content, and a UL-94 V-0 rating could be achieved with a phosphorus content as low as 2.1%.

Synthesis, Spectroscopic and Thermal Investigations of O‐Phd and P‐Phd Bridged Binuclear Manganese (III) Schiff Base Complexes Derived from Pyrazolone Base Ligands

Acyl pyrazolone and their derivatives are an important class of chelating compounds called heterocyclic β‐diketones. β‐diketones have played, and continue to play, a key role in coordination compounds that have found wide application in several fields, from new materials to catalysts, as precursors for CVD in the microelectronic industry and as potential antitumourals. Due to variety of application of this class of ligand, there are studies on metal complexes of many researchers, including ours. We herein report the structural variability of pyrazolone moiety and its chelating nature with manganese (III) ions, in mononuclear and binuclear complexes. The mononuclear complex [Mn(PMFP)(bipy)(OAc)]ClO4 and [Mn(PMFP‐Me) (bipy)(OAc)]ClO4 was prepped by reaction of Mn(OAc)3 · 2H2O with ligand PMFP or PMFP‐Me (where PMFP=5‐Hydroxy‐3‐methyl‐1‐phenyl‐1H‐pyrazole‐4‐carbaldehyde; PMFP‐Me=5‐hydroxy‐3‐methyl‐1‐p‐tolyl‐1H‐pyrazole‐4‐carbaldehyde; bipy=2,2′bipyridyl). The corresponding binuclear complexes were prepared by bridging molecule, o‐phD or p‐phD (o‐phD= where o‐phenelene diamine or p‐phD=p‐phenelen diamine). Both the ligand PMFP and PMFP‐Me were characterized by elemental analysis and 1H‐NMR, GC‐MS, FT‐IR spectroscopic study. The resulting complexes have been characterized by elemental analysis, magnetic susceptibility and conductometry measurements and spectroscopic methods FT‐IR, electronic spectra and mass spectrometry. All the complexes were electrolytic in nature and consist of 1∶2 electrolytes in solution. Electronic spectral and magnetic susceptibility measurements indicate square pyramidal geometry around manganese (III) ion. TGA and DSC determined thermal stability, heat capacity and activation energy of thermal degradation for these complexes.

Influence of Functionalization of Multi-Walled Carbon Nanotubes on the Properties of Ethylene Vinyl Acetate Nanocomposites

Commercially available multiwalled carbon nanotubes (MWNT) were chemically modified by amine, acid and silane and their ethylene vinyl acetate (EVA) based nanocomposites were prepared. Unmodified and modified nanotubes were characterized by thermogravimetry, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. Early degradation of modified nanotubes from the thermogravimetry study proved the presence of functional groups on nanotube surface. Increase in D-band to G-band ratio and a shift in radial breathing mode peaks from the Raman spectra indicated the generation of surface defects due to functionalization and variation in van der Waals force of attraction between nanotube aggregates on modification. The unmodified nanotubes improved the tensile strength by 30% with 4 weight% of filler. Amine modification imparted further increase in strength due to the presence of functional groups on the nanotube surface and the subsequent better dispersion of the nanotubes in the polymer matrix. The silane treatment imparted maximum improvement in various properties of the nanocomposites. The nanotubes provided better thermal degradation stability and also higher thermal conductivity to virgin EVA. The results were well supported by the morphological as well as swelling study of the various samples.

Synthesis, spectral, thermal, and antibacterial investigation of mixed ligand complexes of oxovanadium(IV)

Novel mononuclear mixed-ligand oxovanadium(IV) complex [VO(PMFP)(Bipy)]ClO4 was prepared by the condensation of VOSO4 · 5H2O with ligands 1-phenyl-3-methyl-4-formyl-2-pyrazolin-5one (PMFP) and 2,2′-bipyridyl (Bipy). The corresponding Schiff bases were prepared by the condensation of [VO(PMFP)(Bipy)]ClO4 with ethylenediamine, ethanolamine, and glycine. All the compounds have been characterized by elemental analysis, magnetic susceptibility, X-ray crystallography, conductometry measurement, 1H NMR, FT-IR, ESR, electronic spectra, and mass spectrometry. Electronic spectra and magnetic susceptibility measurements indicate distorted octahedral stereochemistry of the oxovanadium(IV) complexes. Thermal stability, kinetic order, heat capacity, and activation energy of thermal degradation of these complexes were determined by TGA and DSC. The presence of one coordinate water molecule is suggested from the IR and TGA studies. Hamiltonian and bonding parameters were found from ESR spectra, indicating that the metal-ligand bonding is partial covalent. Antibacterial screening is reported for the ligand and complexes of oxovanadium(IV).

Organic–inorganic hybrid boron‐containing phenol–formaldehyde resin/SiO2 nanocomposites

AbstractThe organic–inorganic hybrid boron‐containing phenol–formaldehyde (BPFR) resin/SiO2 nanocomposites was synthesized in‐situ from boric acid, phenol, and tetramethoxysilane. The structure of BPFR modified and the distributions of silicon element were studied by Fourier‐transform infrared spectroscopy, energy dispersive X‐ray spectrometry, and transmission electron microscope, respectively. The glass transition temperature (Tg) was determined by torsional braid analysis. The results show that silicon element distribution is homogeneous, and the size of nanosilica is about 40–60 nm. The thermal stability and kinetics parameters of thermal degradation were determined by thermogravimetry analysis (TGA). TGA results show that the resin modified has higher heat resistance property when the additive quantity of SiO2 was 3 wt%. The temperature of 5% weight loss is 487.7°C, which is 12.4°C higher than that of common BPFR. The residual ratio of 3 wt% SiO2/BPFR was 62.3% at the temperature of 900°C, which is 11.2% higher than that of common BPFR. The mechanics loss peak Tp of 3% SiO2/BPFR is 33°C higher than common BPFR. Fiberglass‐reinforced BPFR modified by 3 wt% SiO2 has better mechanical and dielectric properties than that of common BPFR. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers

Ethylene vinyl acetate/expanded graphite nanocomposites by solution intercalation: preparation, characterization and properties

Nanodimensional reinforcing agents are introduced to polymer matrices to improve properties at very low loading. Natural graphite (NG) as such is not reinforcing in nature. But when modified to expanded graphite (EG) by high temperature heat treatment, this may be used as reinforcing nanofiller. In the present study, ethylene vinyl acetate (EVA) was reinforced with EG by solution intercalation, and the composite properties were compared with those of the virgin polymer and NG filled composite. The tensile strength exhibited an improvement of 35% with 4 wt% EG addition, while the modulus at 100% elongation was increased by 150% with respect to the control EVA. Another interesting feature was that unlike the conventional fillers, addition of EG did not reduce the elongation at break, due to the lubricating action of graphite. However, at a high loading of 8 wt%, the tensile strength showed a lower value, due to the agglomeration of graphite platelets. The storage modulus also showed increment with the addition of graphite without much change in the glass transition temperature. In addition to these, the EVA-EG nanocomposites exhibited high thermal conductivity and thermal degradation stability as compared to the virgin polymer. About 4 wt% of EG shifted the temperature of maximum rate of degradation by 14 °C towards higher temperature. These results were well supported by the swelling and morphological studies. The NG filled composite exhibited inferior properties to EVA-EG nanocomposites.

Kinetics of Curing and Thermal Degradation of POSS Epoxy Resin/DDS System

Polyhedral oligomeric silsesquioxanes epoxy resin (POSSER) was prepared from 3-glycidypropyl-trimethoxysilane (GTMS) and tetramethylammonium hydroxide (TMAH) by hydrolytic condensation. POSSER was characterized using Fourier-transformed infrared spectroscopy (FTIR), 1H-NMR, and liquid chromagraphy/mass spectrometry (LC/MS). The epoxy value of POSSER is 0.50 mol/100 g. The LC/MS analysis indicated that T10 is the majority and contain some amount of T8, besides, a trace T9 also exists. The curing kinetics of POSSER with 4,4′-diaminodipheny sulfone (DDS) as a curing agent was investigated by means of differential scanning calorimetry (DSC). The curing reaction order n is 0.8841 and the activation energy Ea is 61.06 kJ/mol from dynamic DSC analysis. Thermal stability and kinetics of thermal degradation were also studied by thermal gravimetric analysis (TGA). TGA results indicated that the temperature of POSSE/DDS system 5% weight loss is approximately 377.0°C, which is higher by 12.6°C than that of pure POSSER, and the primary degradation reaction (300–465°C) followed first order kinetics; the activation energy of degradation reaction is 75.81 kJ/mol.

Influence of the hard-to-soft segment ratio on the adhesion of water-borne polyurethane adhesive

Three water-borne polyurethane dispersions were synthesised by the pre-polymer mixing process. Different hard segment contents in the polyurethanes were obtained by varying the diisocyanate/macroglycol (NCO/OH) molar ratio. A decrease in the NCO/OH ratio produced an increase in the mean particle size and in the pre-polymer viscosity, as well as a decrease in the molecular weight of the polyurethane. On the other hand, the lower the NCO/OH ratio, the more crystalline the polyurethane and the lower the resistance to flow at high temperature. Lower NCO/OH ratios improved the thermal degradation stability of the polyurethane. Finally, a high initial adhesion to PVC was obtained in all joints produced with the aqueous polyurethane dispersions and the final adhesion increased as the NCO/OH ratio in the water-borne polyurethane adhesive decreased.

Thermal and Morphological Studies of Acrylonitrile–Butadiene (NBR) Latex Reinforced Jute Nonwoven Fabric Composites

A series of composites was fabricated by impregnating jute nonwoven fabric in a bath of acrylonitrile-butadiene (NBR) latex. Thermogravimetric analysis of the jute, NBR and their composites were performed in order to establish the thermal stability and mode of thermal degradation. Thermal degradation of the jute fabric and composites was found to proceed in two steps, unlike NBR. All the composites were stable to 280°C. A degradation kinetic parameter was obtained for each stage of degradation of the jute, NBR and their composites, using Broido, Coats-Redfern and Horowitz-Metzger methods. The activation energy (Ea) of the composites for the thermal degradation process lay in the range 39-129, 35-130 and 20-142 kJ/mol for the Broido, Coats-Redfern and Horowitz-Metzger method respectively. Cryogenically fractured specimens were used to analyse the surface morphology of the jute fabric and composites by scanning electron microscopy.

Effect of alkyl quaternary ammonium on processing discoloration of melt-intercalated PVC-montmorillonite composites

The effects of alkyl quaternary ammonium on the processing thermal stability of poly (vinyl chloride)/alkyl quaternary ammonium modified montmorillonite (PVC/OMMT) composites were investigated. PVC/sodium montmorillonite (MMT) composites were prepared for comparison. The intercalated PVC/OMMT composites exhibited a non-terminal rheological behavior, and showed better mechanical properties and higher thermal degradation stability than the PVC/MMT composites. However, under identical melt processing conditions, the PVC/OMMT composites were observed to discolor from light yellow to pink with increasing OMMT content, while the PVC and PVC/MMT composites kept good processing stability. It is suggested that the decomposition of alkyl quaternary ammonium modifier and the following catalytic effects on the dehydrochlorination of PVC were the main reasons for the discoloration of the PVC/OMMT composites. Discoloration of all the composites was investigated by UV–visible spectroscopy, yellowness index and haze measurement. All the composites were characterized and tested using wide angle X-ray diffraction, transmission electron microscopy, infrared spectroscopy, solution 1H nuclear magnetic resonance spectroscopy, tensile testing, notched Izod impact testing and thermogravimetric analysis as well as ARES rheometrics.

Curing reaction of molybdenum–phenolic resins

AbstractThe curing behavior and curing reaction kinetics of novel molybdenum–phenolic resins were studied with differential scanning calorimetry and thermogravimetry methods, the thermal degradation properties of the cured products were studied with thermogravimetry, and the mechanism of the curing reaction was investigated with Fourier transform infrared. When the mixing ratio of the molybdenum–phenolic resin (with 12% molybdenum) to the curing agent was 100/10 (w/w), the curing temperature and activation energy were at a minimum, the thermal degradation stability of the cured product was optimal, and the temperature corresponding to the maximum extent of curing was 200°C. The curing mechanism was similar to that of conventional phenolic systems. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1410–1415, 2003

Correlation between the tacticity and content of labile nondefect structures in poly(vinyl chloride)

AbstractThe content of mm isotactic triads taking the GTTG− conformation for samples of poly(vinyl chloride) (PVC) fractions of different tacticities was measured through a substitution reaction with sodium benzenethiolate. This quantity changed linearly with the ratio of rmmmrx to mmmmrx (x = m or r), as accurately determined by 13C NMR spectroscopy. In a comparison of this correlation and that obtained between the thermal degradation stability and overall isotactic content, as studied previously, some novel evidence for the GTTG− conformation of a few mm triads, termini of isotactic sequences no shorter than one heptad as specific labile sites in PVC, was obtained. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3944–3949, 2002

Investigation of thermal stability and kinetics of thermal degradation of meridional isomers of aminocarboxylato cobalt(III) complexes

The thermal properties of some mixed complexes of cobalt(III) containing tetradentate ethylenediamine- N, N′-di-3-propionate (eddp) ligand and several amino acids were investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC). The thermal stability derived from decomposition temperatures was discussed in terms of amino acid present. It was shown that the processes of thermal decomposition of these complexes are multi-step degradation processes. Some of these can be separated into individual steps. The corresponding kinetic and thermodynamic parameters of these processes were determined, and the possible mechanisms were discussed.

High-resolution thermogravimetry of liquid crystalline copoly(p-oxybenzoate-ethylene terephthalate-m-oxybenzoate)

Thermotropic liquid crystalline terpolymers consisting of three units of p-oxybenzoate (B), ethylene terephthalate (E), and m-oxybenzoate (M), were investigated through high-resolution thermogravimetry to evaluate their stability and kinetic parameters of thermal degradation in nitrogen and air. Overall activation energy data of the first major decomposition was calculated through three calculating methods. Thermal degradation occurs in three major steps in both nitrogen and air. Three kinds of degradation temperatures (T d , T m1 , T m2 ) are slightly higher and the first maximum weight-loss rates are slightly lower in nitrogen than in air, suggesting a higher thermostability in nitrogen. The thermal degradation temperatures range from 450 to 457°C in nitrogen and 441 to 447°C in air and increase with increasing B-unit content at a fixed M-unit content of 5 mol %. The temperatures at the first maximum weight loss rate range from 452 to 466°C in nitrogen and 444 to 449°C in air and increase slightly with an increase in B-unit content. The first and second maximum weight-loss rates are maintained at almost 9.2-10.8 and 4.0-6.1%/min in nitrogen (11.2-12.0 and 3.9-4.2%/min in air) and vary slightly with copolymer composition. The residues after the first major step of degradation are predicted on the basis of the complete exclusion of ester and ethylene groups and hydrogen atoms and compared with those observed experimentally. The char yields at 500°C in both nitrogen and air are larger than 42.6 wt % and increase with increasing B-unit content. However, the char yields at 800°C in nitrogen and air are different. The activation energy and In(pre-exponential factor) for the first major decomposition are slightly higher in nitrogen than in air and increase with an increase in B-unit content at a given M-unit content of 5 mol %. There is no regular variation in the decomposition order with the variation of copolymer composition and testing atmosphere. The activation energy, decomposition order, and In(preexponential factor) of the thermal degradation for the terpolymers are located in the ranges of 212-263 kJ mol -1 , 2.4-3.5, 33-41 min -1 , respectively.