Search

Abstract: A new pyrolysis–GC/MS system incorporating with on-line micro-ultraviolet (UV) irradiation was developed to make rapid evaluation of the synergistic material deterioration during UV irradiation under thermal and oxidative atmospheres. The basic effectiveness of the system was demonstrated by polystyrene, polypropylene and polycarbonate as the test samples. The volatile products evolved during deterioration of the polymers were analyzed on-line by thermal desorption GC/MS, and then the residual degraded polymers were analyzed by evolved gas analysis (EGA) and/or Py–GC/MS to obtain specific thermograms and pyrograms. Based on these results, the deterioration mechanism of the polymeric materials during irradiation under thermal and oxidative atmosphere can be evaluated using a sub-milligram polymer sample within a relatively short period of time. [Copyright &y& Elsevier]

Nylon 6-clay hybrid (NCH) was characterized by temperature-programmed pyrolysis (TPPy) techniques such as TPPy-mass spectrometry and TPPy-gas chromatography mainly focusing on the interaction between nylon 6 molecule and the surface of silicate monolayers in the NCH samples, which leads to the superior properties of the hybrid nanomaterials. Pyrolysis profile of nylon 6 matrix in the NCH samples was gradually shifted to lower temperature region with increase in the clay content. The yields of main pyrolysis products such as ε-caprolactam from the NCH samples decreased with increase in the clay content, whereas those of the nitrile compounds significantly increased. These results suggested that the clay surface accelerate cis-elimination reaction of nylon 6 matrix in the NCH samples to form the nitrile compounds rather than intramolecular amide exchange to ε-caprolactam. Based on the changes in pyrolysis behaviors of nylon 6 matrix in the NCH samples, the interaction between positively charged NH proton of nylon 6 molecules and negatively charged clay surface was proposed which would stabilize the six-membered transition state during pyrolysis. [ABSTRACT FROM AUTHOR]

The flame retardant mechanism for silicone rubber induced by adding ppm order of a platinum compound, platinum (0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex was studied by analytical pyrolysis techniques and alkaline hydrolysis gas chromatography. The thermal degradation measurement of the flame retardant silicone rubber sample (FR-SR) indicated that a considerable amount of methane was evolved from the FR-SR sample at around 400–800 °C while formations of cyclic siloxanes were fairly suppressed in comparison with that from the control SR sample. On the other hand, on the gas chromatogram of the hydrolysis products from the FR-SR residue samples thermally treated over 400 °C, significant amounts of characteristic products reflecting the cross-linking structures generating from methylene-bridge and trifunctional siloxane structures in the polymer chains were observed. These results suggest that the thermal decomposition of the FR-SR material is strongly suppressed by the formation of the cross-linking structures induced by the platinum compound during combustion, which leads to its flame retardancy. [Copyright &y& Elsevier]

Abstract: A pyrolysis-GC/MS system incorporating with micro-UV irradiator (Xe–Hg lamp) was applied to the evaluation of the weatherability of the acrylic coating paints for house exterior walls. The deterioration of the materials during UV irradiation under thermal, and oxidative atmosphere was evaluated within a relatively short period of time with evolved gas analysis-mass spectrometry (EGA-MS) using a sub-milligram polymer sample. The EGA-MS thermograms indicated that both micro-UV irradiator with Xe–Hg lamp and weather meter with metal halide lamp caused similar photo, thermal, and oxidative degradation to the coating paint samples. Strong correlations between the results obtained by the UV/Py-GC/MS and that obtained by conventional weathering test using metal halide lamp was observed. It was suggested that UV/Py-GC/MS method could be used for compensating the conventional method by reducing the test period. [Copyright &y& Elsevier]

Abstract: The determination of trace organophosphonates which are used in cooling towers as a scale inhibitor usually involves extraction and/or concentration of the target components prior to analysis. The extracts are analyzed using chromatographic or spectroscopic methods. This methodology is not only cumbersome but also results in poor data quality. This work presents a novel approach for the rapid and sensitive determination of trace amounts of an organophosphonate: 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) in aqueous solution. This method is based upon reactive pyrolysis-GC/MS in the presence of tetramethyl ammonium hydroxide (TMAH). Approximately 10μL of the aqueous sample containing a trace amount of HEDP and 1μL of 25% a methanol TMAH solution was placed in the sample cup. The cup was then dropped into the furnace which was at 350°C. The heat initiated the hydrolysis of the organophosphonate followed by the methylation of the hydrolysates. Trimethylphosphate (TMP) was detected by GC/MS. The level of TMP is related to the level of the phosphonate, HEDP in the aqueous sample. Using an external standard calibration curve, it was possible to make a rapid estimation of mg/L levels of organophosphate. [Copyright &y& Elsevier]

As a novel method for analytical pyrolysis of polymers, pyrolysis-fractography (Py-F) was developed. In this method, the pyrolyzates generated when a polymer is instantaneously pyrolyzed at 600 °C are introduced together with the carrier gas into a short length of deactivated stainless steel capillary tube equipped in the gas chromatographic oven. By a programmed heating the oven temperature is linearly raised, so that the pyrolyzates are fractionated, and a fractogram is obtained using a mass spectrometer or a flame ionization detector. The fundamental study was conducted using polyethylene, and this method was applied to elucidate the pyrolysis behavior of such nitrogen containing polymers as polyurethane and melamine formaldehyde resin. As a result, the Py-F method was proved to be useful in analyzing the pyrolysis behavior of polymeric materials, such as a nitrogen-containing polymer, that generates highly polar components upon pyrolysis. [Copyright &y& Elsevier]

Reactive pyrolysis-gas chromatography (Py-GC) in the presence of oxalic acid was applied to the determination of degree of substitution (DS) in N-carboxyethylated chitin derivatives. On the obtained pyrogram, characteristic products, such as methylacrylate, ethylacrylate and acrylic acid originating from the carboxyethyl branches of the chitin derivatives, were clearly observed together with those from the N-acetyl-d-glucosamine units, such as acetonitrile, acetic acid and acetamide. On the basis of relative yields of these characteristic products, the DS values were precisely evaluated. The results by reactive Py-GC also supported the validity of the results obtained by 1H NMR that the mono-alkylation onto the amino group of the original chitin was favorable for the derivatization of the samples. [Copyright &y& Elsevier]

Compositional analysis of UV-cured resins consisting of multi-component acrylic esters was studied by pyrolysis–gas chromatography (Py–GC) in the presence of organic alkali, tetramethylammonium hydroxide (TMAH). The pyrograms of the UV-cured resins formed from ethylene oxide modified bisphenol A diacrylate (EBADA) contained specific products such as methyl acrylate (MA) and various dimethyl ethers of ethylene oxide modified bisphenol A reflecting the numbers of ethylene oxide units in the original EBADA. Meanwhile the pyrograms of the UV-cured resins comprised of acrylated polyfunctional aliphatic alcohols such as pentaerythritol triacrylate (PETA) and dipentaerythritol hexacrylate (DPEHA) contained methyl ethers reflecting the structure of the original alcohols. In addition, considerable amounts of pyrolyzates with non-methylated hydroxyl groups were also detected for aliphatic alcohol moieties. The compositions of the UV-cured resins containing multi-component acrylic esters were also analyzed based on the relative yields of the characteristic pyrolyzates of each acrylic ester. For calibration purpose, a series of UV-cured standard samples, which contained known amounts of the individual acrylic ester and neopentylglycol diacrylate (NPGDA) used as an internal standard, were measured. The compositions of the multi-component UV-cured resins determined using this approach showed good agreement with the theoretical values estimated from the feed composition. [Copyright &y& Elsevier]

Presents a quantitative analysis of detailed lignin monomer composition by pyrolysis-gas chromatography. Contribution of the lignin acetylation procedure; Determination of the dehydrogenative polymers; Accuracy of the preacetylation in analyzing the detailed lignin monomer composition.

A novel solid-phase extraction element is developed for sorptive enrichment of dilute analytes from liquid samples with high extraction efficiencies due to its larger amounts of polydimethylsiloxane (PDMS) absorbent than the conventional syringe type of solid-phase microextraction (SPME). The extraction element is made of titanium (Ti) open tubular tube (30 mm×1.2 mm i.d.×1.6 mm o.d.) coated with a chemically bonded layer of PDMS (500 μm in thickness). The extraction element combined with thermal desorption–gas chromatography–mass spectrometry using a pyrolysis–gas chromatography–mass spectrometry system was used to extract and analyze a typical herbicide, bethrodine in water samples over a concentration range from 2.5 to 2.5×104 ng/l. Thus obtained calibration curve showed good linearity for the tested whole concentration range with regression coefficient of 0.992. Detection limit of 0.5 ng/l level was achieved and the reproducibility of the measurements for bethrodine at 10 ng/l level was found to be fairly good with relative standard deviation below 7.5%. [Copyright &y& Elsevier]