Py GC MS Research Articles

Characterization of coal particles in the soil of a former rail yard and urban brownfield: Liberty State Park, Jersey City (NJ), USA

From the 1850's until the 1960's, the Central Railroad of New Jersey was among several major railways shipping anthracite and bituminous coal to the New York City area, transferring coal from railcar to barge at its extensive rail yard and port facility in Jersey City. The 490 ha Liberty State Park was developed on the site after the rail yard closed, but a ca. 100 ha brownfield zone within the park remains off limits to visitors pending future remediation. As part of an environmental forensic and industrial archeological investigation of this zone, the present study characterizes anthracite and bituminous coal particles present in abundance in the soil by scanning electron microscopy (SEM) and pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS). A simple pretreatment procedure employing density separation improved the analytical results. This detailed information about the nature of contaminants at the site will help to inform the remediation effort in the public interest.

Characterization of bio-oil and biochar from pyrolysis of waste corrugated cardboard

As the most abundant municipal solid waste, corrugated cardboard (CCB) is a suitable resource for thermochemical conversion into various solid and liquid products. CCB samples were pyrolyzed at three temperatures (350, 400, and 450 °C) and their pyrolysis products (bio-oil and biochar) were characterized and analyzed. Thermogravimetric analysis (TGA) was utilized to study the thermal degradation behavior of CCB. CCB and biochar samples were subjected to proximate, ultimate, lipid and carbohydrates analyses, and Py–GCMS to characterize their chemical components. The highest biochar yield was 75% at 350 °C, and the highest bio-oil yield was 47% at 450 °C. The biochar physical and chemical properties were also assessed using calorific values, specific surface area, Fourier-transform infrared (FTIR) and Raman spectroscopies, and x-ray diffraction (XRD). Biochar was found to have low ash and nitrogen contents. The bio-oil was characterized by the combination of GCMS, high-performance liquid chromatography (HPLC), and electrospray ionization mass spectrometry (ESI–MS). The molar mass distribution and an estimate of monomer/oligomer ratio were determined from ESI-MS data. The bio-oil contained a complex mixture of pyrans, furans, phenols, and cyclopentenes. Levoglucoson was abundantly found in the bio-oil, suggesting the suitability of cardboard pyrolysis products for further processing into fuels.

Assessment of aqueous cleaning of acrylic paints using innovative cryogels

Waterborne acrylic paints have been widely used by artists since their development in the late 50s. Their cleaning, i.e., the removal of mainly airborne dust and grime, is a challenging operation, because acrylics are very sensitive to solvents in a wide range of polarity. Even if aliphatic and low-molecular weight aromatic hydrocarbons are less prone to interact with the hydrophilic components of the acrylic paint layer, the use of water is necessary since it grants better cleaning performances. In this paper, three acrylic commercial paints from Liquitex® (USA) were selected and characterized using Fourier Transform Infrared spectroscopy (FT–IR) and pyrolysis – gas chromatography – mass spectrometry (Py-GC–MS). The removal of artificial soil from these paint films was carried out using novel highly retentive PVA-based cryogels that have been recently developed to avoid the uncontrolled wetting of water-sensitive artistic surfaces. Their cleaning efficiency was evaluated using Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). Finally, an ATR-FTIR and 2D FTIR Imaging study about the residues left by the gels was carried out by comparing the cryogel with a Velvesil Plus® emulsion, a gel-like silicone polyether copolymer used in the recent past to create a stable water-in-oil emulsion, and still available on the market to conservators. In conclusion, the cryogel granted a safe and satisfactory cleaning action and a residue-free soil removal from acrylic paint films, overcoming the drawbacks of traditional cleaning methods.

Pyrolysis kinetic behavior and Py-GC–MS analysis of waste dahlia flowers into renewable fuel and value-added chemicals

To explore the bioenergy potential, kinetic and pyrolysis behavior of waste dahlia flowers (DF), model-free methods and Py-GC–MS were used. Kinetic characteristics of DF biomass were estimated by adopting four model-free methods, Kissinger-Akahira-Sunose (KAS), Ozawa-Flynn-Wall (OFW), Friedman, and Distributed Activation Energy (DAEM). Further, functional groups, the presence of mineral matter in DF biomass, and mineral compounds present in the inorganic residue were analyzed using FTIR, EDX, and XRF. Physicochemical analysis results confirmed its bioenergy potential for conversion into renewable fuel and valuable chemicals. The kinetic results of DF biomass showed that activation energy varied with conversion value, and the thermodynamic analysis indicated multiple step pyrolysis. FTIR analysis confirmed the presence of hemicellulose, cellulose, and lignin in biomass. EDX and XRF analysis also revealed the presence of various useful mineral matter, which had a positive effect during pyrolysis. Py-GC–MS results confirmed that at a lower temperature (500 °C), the formation of ester, nitrogen containing compounds and acid were higher, while at higher temperatures (550 °C and 600 °C), the formation of oxygenated compounds were reduced and the production of hydrocarbons and alcohols increased.

Millennial-scale changes in the molecular composition of Posidonia australis seagrass deposits: Implications for Blue Carbon sequestration

Seagrass ecosystems are recognised for their role in climate change mitigation, due to their capacity to form organic-rich sediments. The chemical recalcitrance of seagrass organs is one characteristic driving carbon storage, but the molecular background of this feature is poorly understood. We assessed molecular composition changes of Posidonia australis sheaths (SH) and roots plus rhizomes (RR) along a sediment core, encompassing 3200 cal. yr BP, by means of nuclear magnetic resonance spectroscopy (13C NMR), conventional analytical pyrolysis (Py-GC–MS) and thermally assisted hydrolysis and methylation (THM-GC–MS). Significant trends with depth (age) in the composition of both SH and RR remains of P. australis were observed from all methods. In general terms, polysaccharides become depleted (degraded) and lignin enriched (selectively preserved) as age increases, and the minor constituents cutin, suberin and condensed tannin are also preferentially depleted during ageing in both fractions. Molecular changes with ageing were smaller in SH, especially regarding polysaccharides, indicative of a superior stability compared to RR. The molecular changes observed are most pronounced within the first 75 cm of the record, which reflects the recalcitrance of P. australis detritus once it is buried below that depth (corresponding to approximately 700 cal. yr BP). The capacity of P. australis to act as a long-term carbon sink seems to be mainly related to the resistance of buried lignocellulose materials to decomposition. The results on diagenetic effects on the molecular fingerprint of seagrass detritus contribute to our understanding of carbon sequestration in Blue Carbon ecosystems. Furthermore, data comparison of the methods applied using principal component analysis (PCA) allowed us to identify consistencies, discrepancies and complementarities.

In vitro cytotoxicity studies of industrial Eucalyptus kraft lignins on mouse hepatoma, melanoma and Chinese hamster ovary cells

Kraft lignin is a polyphenolic compound generated as a by-product from the kraft pulping process in large quantities annually worldwide. In addition to its commercial availability, its structural features make it worth to be considered in the pharmaceutical area. The present study was carried out to evaluate in vitro antioxidant and cytotoxic properties of kraft lignin on mouse hepatoma MH-22A, melanoma B16 (tumor cells) and Chinese hamster ovary (CHO, non-cancerous) cells. Moreover, several analytical techniques were used in order to elucidate the chemical structure of isolated industrial lignins (FT-IR, GPC, Py-GC–MS, 2D HSQC NMR). Results revealed high phenolic content in their composition, high-condensed structure and high phenolic hydroxyls group content. DPPH and ABTS⁎+ radical scavenging assays demonstrated their strong antioxidant activity, which was higher than found for commercial antioxidant (BHT). Kraft lignins act cytotoxically inducing apoptosis- and necrosis-like processes on both on tumor and normal cells. However, the results evidenced that MH-22A cells showed greater sensitive behavior than B16 and non-cancerous CHO cells, which were more tolerant of kraft lignin.

Py-GC-MS of hydrochars produced from brewer’s spent grains

The aim of the study was to understand pyrolysis behavior and analyze the influence of hydrothermal carbonization (HTC) pretreatment on the volatile matter released during pyrolysis of hydrochars, produced from brewer’s spent grains (BSG). The Py-GC–MS was used to analyze the pyrolysis products. The measurements were conducted for three hydrochars produced from BSG at different HTC conditions: (i) 180 °C, 4 h; (ii) 220 °C, 2 h; and (iii) 220 °C, 4 h, and the precursor BSG. The sample was pyrolyzed in the sequence at 300, 400, 500, and 600 °C with a heating rate of 500 °C min−1 and residence time 15 s. Pyrolysis of BSG resulted in more phenolic compounds than hydrochars produced at mild conditions (HTC-180-4 and HTC-220-2). Pyrolysis of high-temperature hydrochar (HTC-220-4) showed the highest share of phenols due to the conversion of furan rings into benzene rings during HTC. Hydrochars (HTC-180-4 and HTC-220-2) produced more furans, and other cyclic oxygen compounds compared to the initial biomass. A significant amount of N-compounds was detected at low pyrolysis temperature for spent grains due to weakly bonded proteins into the biomass structure. However, hydrochars were characterized by fewer N-compounds compared to BSG because of the Maillard reaction occurred during hydrothermal pretreatment leading to more stable N-heterocycles structures. Increased severity during the HTC resulted in a higher share of N-compounds found during Py-GC–MS.

Thermal profile of 4,4′-dinitrocarbanilide determined by thermogravimetry–differential scanning calorimetry–mass spectrometry (TG–DSC–MS) and pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS)

Nicarbazin is an anticoccidial used in poultry production. Its residue of concern left in chicken meat is 4,4′-dinitrocarbanilide (DNC) whose content can be reduced through meat thermal processing. Thermal analysis techniques can be considered to elucidate how DNC degradation proceeds. This study aimed to investigate the thermal behavior of DNC using TG–DSC–MS and Py–GC–MS. TG–DSC–MS data showed that DNC decomposition occurs in a single step (252–280 °C) as an endothermic event (ΔH of 670 J g−1). Fragments detected at m/z 43, 44 and 65 indicated the release of isocyanic acid, carbon dioxide and 4-nitroaniline as breakdown products. In addition, Py–GC–MS analysis confirmed that DNC is thermally degraded above 250 °C generating 4-nitrophenyl isocyanate and 4-nitroaniline as the major pyrolysis products. Findings obtained from thermal analysis herein are useful to better comprehend the DNC disappearance after submitting chicken meat to heat processing.

Exploring the composition of macromolecular organic matter in Arctic Ocean sediments under a changing sea ice gradient

Arctic sea ice has been affected by climate change, leading to reductions in summer sea ice extent over the past few decades, impacting nutrient dynamics, ocean temperature fluxes and the biological communities present in the ocean. Marine organic matter is a complex mixture of differentially degraded terrestrial and marine organisms from a range of sources and time periods. In this study pyrolysis-gas chromatography-mass spectrometry (Py-GC–MS) has been used to quantify the solvent-insoluble component of marine organic matter in surface sediments to gain a more holistic understanding of the macromolecular composition at five stations along a south to north transect in the Arctic Barents Sea, east of Svalbard (depths 288–334 m.b.s.l). Two methods were compared to identify the effectiveness of rapid screening, in contrast to grouping similar pyrolysis products. There were changes in macromolecular composition of marine surface sediments across the S-N transect using both methods, highlighting the varying benthic and pelagic communities north of the Polar Front and across the variable sea ice margin, corresponding to differing biological communities (e.g. fish, phytoplankton, ice algae, zooplankton). All five stations across the changing sea ice transect were interpreted as having primarily marine surface sediment macromolecular signatures, given their locations far from major terrestrial inputs and the more subtle changes when compared with previous investigations on the East Siberian Artic shelf. Fluctuations in macromolecular compositions across the transect included increasing N-containing compounds (including pyridines) and n-alkene/n-alkane doublet pyrolysis products from sediments collected in stations with the greatest average ice cover. If the future position of the Polar Front moves northwards then deposition of labile organic matter which appears to be efficiently processed will move further north, meaning greater deposition of organic carbon under areas of open ocean. Future research needs to understand how this OC will be buried and if it is regionally significant, given anticipated weakening stratification and a more Atlantic influenced northern Barents Sea.

Study on the ancient putty from the site of the Ming Dynasty (1368–1644 CE) Baochuanchang Shipyard, Nanjing, China

In 2003, the excavation of the ancient site Baochuanchang Shipyard was carried out in Nanjing, China and this shipyard was believed to have been the workshop where the huge vessels of Zheng He's fleet were built and maintained. Several pieces of ancient putty were found here, and a small piece was sampled and analyzed in this paper to study its components and structure. The results of X-ray diffraction (XRD) showed that the putty was mainly composed of calcite (CaCO3), while pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS) analysis indicated that tung oil was used in making the putty. In addition, plant fibers inside the putty were identified as jute by the means of polarizing microscope and scanning electron microscope (SEM) analysis. These findings confirmed the putty as the so-called chu-nam putty, which was a traditional sealing material used in ancient shipbuilding. Moreover, the surface morphology of the putty was obtained by SEM, and pore size distribution was measured by gas adsorption-desorption analysis. The analytical results suggested that the putty was quite compact, which could perform well in sealing huge wooden ships. This research revealed the shipbuilding skills of the Baochuanchang Shipyard. It may provide reference for studying Zheng He's vessels and make further a contribution to the conservation and restoration of ancient wooden ships of the Ming Dynasty.

Catalytic pyrolysis of lignin over hierarchical HZSM-5 zeolites prepared by post-treatment with alkaline solutions

The application of hierarchical HZSM-5 zeolite catalysts in the catalytic fast pyrolysis (CFP) of lignin was investigated using a pyrolyzer coupled with gas chromatography-mass spectrometry (Py-GC–MS). A series of modified HZSM-5 zeolites were prepared by the post-treatment desilication of commercial HZSM-5 zeolite with varying concentrations of sodium hydroxide (NaOH) solutions (0.1 – 0.5 mol/L) and the following solutions: 0.3 mol/L of sodium aluminate (NaAlO2), 0.3 mol/L of sodium carbonate (Na2CO3), and 0.3 mol/L of tetrapropylammonium hydroxide (TPAOH). The catalyst samples were characterized by XRD, XRF, TEM, N2 adsorption–desorption, and NH3-TPD techniques. The crystallinity, the SiO2/Al2O3, the morphology, the pore properties, and the density of acid sites of the HZSM-5 zeolites were changed after alkali treatment. The alkali treatment improved the catalytic performance of HZSM-5 zeolite for cracking bulky oxygenates released from lignin (such as guaiacol, syringol, and their derivatives from the pyrolysis of lignin) to produce aromatic hydrocarbons. The HZSM-5 zeolite treated with 0.3 mol/L NaOH was the optimal choice for the catalytic fast pyrolysis of lignin for producing aromatic hydrocarbons.

Investigation of pathways for transformation of N‑heterocycle compounds during sewage sludge pyrolysis process

This study investigated the transformation of N‑heterocycle compounds during sewage sludge pyrolysis process. The reaction pathways for evolution of the products especially the N-containing organics such as amino acids‑N were analyzed in detail. NH3 is the main N-containing gaseous product during the pyrolysis and its concentration was increased with the increasing temperature. Phenolic compounds, hydrocarbons and heterocyclic compounds were the main component in liquid products. The in situ FT-IR study showed that the labile inorganic ammonium salt decomposition proceeded to completion below 500 °C. Above 500 °C N‑heterocycle compound was formed and then it was decomposed, while above 600 °C nitrile started to decompose. NH3 formation main originates from the decomposition of N‑heterocyclic compounds and nitrile. Proteins during the pyrolysis, as verified by XPS, were mainly converted into inorganic nitrogen. In addition, the Py-GC–MS results showed that large amount of N‑heterocyclic compounds were found in amino acid‑N pyrolysis products. The transformation paths for the amino acids with different chemical structures were distinct. Except N‑heterocyclic amino acids, long chain aliphatic amino acid also can form N‑heterocyclic compounds through cyclization. In addition, the decomposition of the intermediates of N‑heterocyclic compounds form small molecular compounds or while the polymerization of the intermediates forms macromolecule compounds. The amino acids with heterocycle structure were disrupted to form heterocycle and aliphatic intermediate. The plausible mechanism of sewage sludge pyrolysis was proposed.

Mechanistic insight in the selective delignification of wheat straw by three white-rot fungal species through quantitative 13C-IS py-GC\u2013MS and whole cell wall HSQC NMR

BackgroundThe white-rot fungi Ceriporiopsis subvermispora (Cs), Pleurotus eryngii (Pe), and Lentinula edodes (Le) have been shown to be high-potential species for selective delignification of plant biomass. This delignification improves polysaccharide degradability, which currently limits the efficient lignocellulose conversion into biochemicals, biofuels, and animal feed. Since selectivity and time efficiency of fungal delignification still need optimization, detailed understanding of the underlying mechanisms at molecular level is required. The recently developed methodologies for lignin quantification and characterization now allow for the in-depth mapping of fungal modification and degradation of lignin and, thereby, enable resolving underlying mechanisms.ResultsWheat straw treated by two strains of Cs (Cs1 and Cs12), Pe (Pe3 and Pe6) and Le (Le8 and Le10) was characterized using semi-quantitative py-GC–MS during fungal growth (1, 3, and 7 weeks). The remaining lignin after 7 weeks was quantified and characterized using 13C lignin internal standard based py-GC–MS and whole cell wall HSQC NMR. Strains of the same species showed similar patterns of lignin removal and degradation. Cs and Le outperformed Pe in terms of extent and selectivity of delignification (Cs ≥ Le >> Pe). The highest lignin removal [66% (w/w); Cs1] was obtained after 7 weeks, without extensive carbohydrate degradation (factor 3 increased carbohydrate-to-lignin ratio). Furthermore, though after treatment with Cs and Le comparable amounts of lignin remained, the structure of the residual lignin vastly differed. For example, Cα-oxidized substructures accumulated in Cs treated lignin up to 24% of the total aromatic lignin, a factor two higher than in Le-treated lignin. Contrarily, ferulic acid substructures were preferentially targeted by Le (and Pe). Interestingly, Pe-spent lignin was specifically depleted of tricin (40% reduction). The overall subunit composition (H:G:S) was not affected by fungal treatment.ConclusionsCs and Le are both able to effectively and selectively delignify wheat straw, though the underlying mechanisms are fundamentally different. We are the first to identify that Cs degrades the major β-O-4 ether linkage in grass lignin mainly via Cβ–O–aryl cleavage, while Cα–Cβ cleavage of inter-unit linkages predominated for Le. Our research provides a new insight on how fungi degrade lignin, which contributes to further optimizing the biological upgrading of lignocellulose.

Molecular characterization and atomistic model of biocrude oils from hydrothermal liquefaction of microalgae

Hydrothermal liquefaction (HTL) converts wet biomass into biocrude oils that can serve as a green substitute to fossil crude oil for several applications, i.e., biofuel or additive for asphalt. However, the use of biocrude oils in such applications has been limited by a lack of detailed characterization of its molecular components. This hinders the establishment of molecular models for biocrude oil that can be used to establish computationally the links between HTL parameters, chemical composition of biocrude, and its macroscopic properties and applications. Understanding such links would significantly reduce the need of expensive and time-consuming trial-and-error HTL experimentation. Here, we present the first molecular model of biocrude oil from microalgae derived from a detailed analytical characterization by pyrolysis gas chromatography mass spectrometry (Py-GC–MS) with non-negative matrix factorization (NNMF), supported by an extensive literature research. The selected molecules are then characterized by conceptual density functional theory (DFT) calculations. These are then used to evaluate the reactivity and intermolecular interactions of biocrude oil in upgrading and oxidative ageing processes, which are the most relevant for its aforementioned application as biofuel or as additive for asphalt. The results show that the properties of the light fraction of biocrude oil favor its use for biofuel. In the case of additive for asphalt pavement, the light fraction is less prone to oxidative ageing, while the heavy fraction might still be useful to provide the rheological properties required for asphalt concrete.

The effect of the grinding process on pore structures, functional groups and release characteristic of flash pyrolysis of superfine pulverized coal

Due to the superiority on the reduction of pollutant emissions by applying superfine pulverized coal with air-staged combustion and oxygen-enriched combustion, it has attracted more and more attention. Grinding process plays a crucial role in the variation of the physicochemical properties of raw coal. In this paper, the different scales of pore structures changing with particle size were investigated. The varying principle of pore structures during the grinding process was discussed. Our results indicate that as the particle size decreases, it has more developed pore structures and especially the concentration of micro-pores increases, which provide larger specific surface area and porosity that are beneficial to heat and mass transfer. Furthermore, the effect of particle size on the distributing characteristic of flash pyrolysis products by PY-GC–MS is studied, combining the analysis of carbon containing functional groups. Particle with smaller size has a larger content of oxygen containing functional groups and less concentration of CC and CH. Compared to HN coal, the proportion of aliphatic compounds in total release quantity is higher in NMG coal. In addition, the concentration of oxygen-bearing organic compounds first increases and then reduces, and it reaches to the maximal at around 14 µm.

Catalytic fast pyrolysis with metal-modified ZSM-5 catalysts in inert and hydrogen atmospheres

The objective of this work was to determine the impact of hydrogen-activating metals on catalytic fast pyrolysis over ZSM-5 with and without hydrogen addition. Ga-, Ni-, Cu-, Co-, and Pt-modified ZSM-5 catalysts with metal-to-aluminum molar ratios of 2 were prepared by incipient wetness method. The catalysts were evaluated for hydrocarbon and oxygenate yields and for deactivation by analytical pyrolysis (Py-GC–MS), and post-reaction catalysts for characterization were prepared in a larger fixed-bed reactor. In inert atmosphere, there was a linear correlation between both the hydrocarbon yield and coke formation and density of strong acid sites, and the main impact of the metals was occlusion of active sites in ZSM-5, leading to proportional reductions in hydrocarbon and coke yields. With the addition of hydrogen, several metals (Pt, Ni, Cu, Co) activated hydrogen and further reduced coke formation, leading to improvements in the ratio of hydrocarbons to coke. No metal-modified catalyst out-performed fresh unmodified ZSM-5 in terms of hydrocarbon yield; however, Ni/ZSM-5 and Cu/ZSM-5 in hydrogen produced comparable hydrocarbon yields to ZSM-5 while reducing coke formation.

Characterisation of the products of low temperature pyrolysis of Victorian brown coal in a semi-continuous/flow through system

Two Victorian brown coal samples, a run-of-mine Loy Yang coal (LY) and a Loy Yang light lithotype (LL), were subjected to pyrolysis at 420–460 °C and 330–460 °C, respectively, under a continuous nitrogen flow. The process produced condensed products in two phases, oil and aqueous, as well as solid residue and gaseous products. An increase in the condensed product yields with increasing temperature was observed for both coals, with LL achieving higher yield than LY at a given temperature (e.g. 26.3 wt% vs 19.5 wt% at 460 °C). The condensed products were characterized by 1H and 13C NMR as well as GC–MS. Abundant triterpenoid polycyclics and aliphatic hydrocarbons were found in the oils from both coals produced at lower temperatures, whilst the yield of aromatics significantly increased with increasing pyrolysis temperature. Analyses of the solid residues by FTIR, solid state 13C NMR and flash pyrolysis GC–MS (Py-GC–MS) also revealed an increasing aromaticity of the residues at higher temperatures. Py-GC–MS analysis identified compound groups released by flash pyrolysis at 650 °C and the results were found to correspond to those of GC–MS for the oil.

Environmental petroleum pollution analysis using ramped pyrolysis-gas chromatography–mass spectrometry

In response to the Deepwater Horizon oil spill, critical research has tracked the changes in petroleum hydrocarbons with environmental weathering. There are limitations, however, whereby single analytical techniques cannot always identify the wide breadth of petroleum and petroleum-derived compounds. We explore the analytical capabilities of ramped pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS) to evaluate environmental samples of petroleum hydrocarbons from the Deepwater Horizon oil spill. We show that bulk flow Py-GC–MS can quantify the overall degree of petroleum hydrocarbon weathering. Furthermore, thermal slicing Py-GC–MS can quantify specific compounds in the “thermal desorption zone” (50–370 °C), as well as characterize pyrolyzed fragments from non-GC-amenable petroleum hydrocarbons (including oxygenated hydrocarbons) in the “cracking zone” (370–650 °C). Our data also suggest an increase in thermochemical stability, concentration of oxygenated products and complexity of high molecular weight and/or polar components with advanced weathering. This analysis not only elucidates weathering trends in Deepwater Horizon oil over several years, but also illustrates the analytical capacity of this method for future petroleum hydrocarbon investigations, filling a void in research connecting Py-GC–MS and environmentally weathered oil samples.

Thermal decomposition of polyimides containing phosphine-oxide units

This work details analyses of the thermal decomposition behaviour of three phosphine-oxide containing aromatic processable polyimides. The polymers exhibited high thermal stability with initial decomposition temperatures in the range of 473–483 °C and a char residue at 900°C in the domain of 48.58–58.38%. The values of non–isothermal decomposition kinetic parameters were determined using the Friedman isoconversional method, as recommended by the Kinetics Committee of the International Confederation for Thermal Analysis and Calorimetry (ICTAC). The data evidenced a complex decomposition process of the main chain, being probably initiated by the cleavage of the weaker PC bonds, followed by the decomposition of the macromolecular backbone. The volatile products formed during the thermal decomposition of polyimides were analysed by TGA-FTIR. All spectra evidenced peaks associated with water, CO2, CO and aliphatic and aromatic decomposition products predominant from 500° to 800 °C. By using Py-GC–MS studies the fragments originating from the thermal decomposition of the polyimides up to 600 °C were identified. Based on these data, it was suggested that the thermal decomposition pathways of the three polyimides undergoes the same mechanism. Additionally, an oversimplified decomposition mechanism for the polyimides was proposed. The morphology of the char residue obtained after TGA experiments showed a continuous and dense structure. The EDX mapping identified the C, N, O and P atoms uniformly dispersed in the residual char surface.

Release and flammability evaluation of pyrolysis gases from carbon-based composite materials undergoing fire conditions

In the event of fire, composite materials can be exposed to high heat flux leading to a significant release of smoke and toxic fumes that can contribute to the growth of the fire. This can be problematic in the aerospace industry where strict fire regulations are imposed for designated fire zones. Research has therefore been carried out in recent years to estimate the volatile emissions and self-ignition risk during the development phase of composite parts. In the present study, gaseous emissions and lower flammability limits (LFL) were evaluated during the degradation of three carbon-reinforced composites. The thermoplastic polyetherketoneketone (PEKK), belonging to the polyaryletherketone (PAEK) family, which is known for its high-temperature stability, was compared with two thermosetting resins: a classic phenolic resin and a fire improved epoxy. The former is well known and already used as thermal protection whereas the latter could be used as ablative protection for internal thermal insulation. Gaseous emissions were measured using an analytical pyrolyser (heated platinum filament) coupled with a gas chromatograph and a mass spectrometer (Py-GC–MS) for four different temperatures: 360, 450, 590 and 750 °C. From the suspected species given by the pyrolysis experiments, the LFLs were determined by means of a Quantitative Structure-Property Relationship. The classification of the three materials in terms of combustibility (degradation temperature and mass loss) and ignitability (gaseous emissions and lower flammability limit) revealed superior performances of PEKK composites. The benefit of the fire treatment on the carbon-epoxy was demonstrated by a higher value of LFL whereas the carbon-phenolic resin had a lower mass loss even if it presented a lower degradation temperature.