Study on pyrolysis behaviors of L-tyrosine-based phthalonitrile resin

The pyrolysis behaviors of l-tyrosine-based phthalonitrile(TPN) resin were investigated by thermogravimetric-Fourier transform infrared spectrometry-mass spectrometry (TG-FTIR-MS) and Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The small molecules produced during pyrolysis process of TPN resin were tracked in real time by TG-FTIR-MS. The larger molecules (m/z > 40) from fast pyrolysis at 900 °C of the TPN resin using Py-GC/MS were identified. From TG-FTIR-MS and Py-GC/MS results, the production pathways of pyrolysis products such as CO₂, CO, NH₃, benzonitrile and phenol were analyzed. The possible pyrolysis mechanism of TPN resin under non-oxidizing gaseous environment was proposed. The results of this study provide the useful information for designing the molecular structure of l-tyrosine-based polymers which possessing high thermal stability.     

Mass spectrometric techniques for characterizing low-molecular-weight resins used as paint varnishes

The molecular structure of three low-molecular-weight resins used as paint varnishes has been characterized by use of an approach based on three different mass spectrometric techniques. We investigated the ketone resin MS2A, the aldehyde resin Laropal A81, and the hydrocarbon resin Regalrez 1094, now commonly used in restoration. To date, the molecular structures of these resins have not been completely elucidated. To improve current knowledge of the chemical composition of these materials, information obtained by gas chromatography–mass spectrometry (GC/MS), pyrolysis–gas chromatography–mass spectrometry (Py/GC/MS), and electrospray ionization mass spectrometry (ESI–Q–ToF) was combined. Analysis, in solution, of the whole polymeric fraction of the resins by flow-injection ESI–Q–ToF, and of the non-polymeric fraction by GC–MS, enabled us to identify previously unreported features of the polymer structures. In addition, the Py–GC/MS profiles that we obtained will help to enhance the databases currently available in the literature. The proposed approach can be extended to other low-molecular-weight resins used as varnishes in conservation.     

Mass spectrometric methodology for the analysis of highly oxidized diterpenoid acids in Old Master paintings

Diterpenoid resins from larch and pine trees and the corresponding fractions in a >100-year-old wax-resin adhesive and varnish and a 200-year-old resin/oil paint sample were analysed with by gas chromatography/mass spectrometry (GC/MS) using several off-line and on-line derivatization methods. The main resin compounds were highly oxidized abietic acids. Important products found are hydroxydehydroabietic acids (OH-DHAs), 7-oxoDHA, di-OH-DHAs and 15-OH-7-oxoDHA. The last two compounds have not been reported to occur in artworks before. Larixyl acetate, an important marker from larch resins, was found to be still present in high amounts in the adhesive. A large number of mass spectra of the different oxidation products and larixol and larixyl acetate are presented and their fragmentation behaviour under electron impact conditions is discussed. An index for the degree of oxidation (IDOX) of the abietic acids is presented as an indicator of the degree of oxidation of the matrix in which the resin is present. The IDOX was 0.10, 0.67, 0.81 and 0.76 for the fresh resins, the dark-aged adhesive, the aged varnish and the resin/oil paint, respectively (measured with pyrolysis (Py)-tetramethylammonium hydroxide (TMAH)-GC/MS). Py-TMAH-GC/MS and direct temperature-resolved mass spectrometry are reliable, valuable and fast techniques for the assessment of the presence and degree of oxidation of diterpenoid resins. Copyright 2000 John Wiley & Sons, Ltd.     

AP-U resin as modifying additive for polymeric formulations

The interaction of a number of phenol compounds with silica filler of polymer compositions (highly dispersed amorphous silicas) was studied by the pyrolysis gas chromatography mass spectrometry. AP-UBS modifier was tested in protector, facing, and breaker rubber mixtures.     

压力对塔里木原油四组分热解性能的影响

压力对深层油藏原油热化学过程的影响尚存在较大争议,为研究其在油藏原油热解成气过程中的作用机理,我们在450℃、5~40 MPa压力下对塔里木原油四组分(饱和分、芳香分、胶质和沥青质)进行了封闭体系的热解实验,通过气相色谱(GC)和气相色谱/质谱(GC/MS)分别对原油四组分热解反应的气体产物及饱和分热解过程的液态产物进行了分析。结果表明,在450℃、24 h及不同压力下,沥青质热解产气率高于胶质、芳香分和饱和分;四组分的气相热解产物中,C1的产率明显高于C2~C5组分。增大压力抑制沥青质、胶质及芳香分的热解产气过程而促进饱和分的热解产气过程。随压力的增大,饱和分热解的液态产物的主峰组分碳数先减小,再增大。压力低于20 MPa时,饱和分热解过程中以裂解反应为主;高于30 MPa时,增大压力有利于缩合反应。研究结果可为认识深层油藏原油的稳定程度及天然气的成因提供一定的理论参考。     

Fast gel permeation chromatography–mass spectrometry method for polymer and additive analysis

This study presents gel permeation chromatography (GPC) coupled with mass spectrometry (MS) as a suitable method to evaluate molecular weight distribution, oligomeric structure, and additives of commercial polystyrene resins in just 4?min. The chromatogram recorded by ultraviolet (UV) detection gives information on the high molecular mass fractions, while the mass detector provides knowledge on the chemical structure and concentration of oligomers and additives. A good agreement for the average molecular weights of the broad polystyrene reference SRM 706 and an excellent correlation with the expected isotope distributions for oligomers and additives were obtained using this fast GPC–UV–MS method.     

Hyphenation of Curie-point-pyrolysis high-resolution gas chromatography with several spectroscopic methods for the analysis of cured epoxy resins

The coupling of Curie-point pyrolysis (Py) with gas chromatography (GC) and mass spectrometry (MS) or Fourier transform infrared spectroscopy (FTIR) has been widely reported. The approach reported in this paper combines chromatographic separation with eluent monitoring by use of three different spectroscopic detectors (MS, FTIR and Atomic Emission Detector [AED]). The features of these detectors, with different selectivities, are shown for the analysis of cured epoxy resins. Besides characterisation of major resin constituents by identification of the pyrolysis products, the usefulness of the AED is also revealed by the detection of minor compounds (such as coupling agents) in cured epoxy resins.     

不同氛围下绿原酸的热解行为及其裂解产物中苯酚含量分布规律研究

采用热重分析法(TGA)及在线裂解气相色谱-质谱联用仪(Py/GC - MS)研究了烟草中绿原酸在不同氛围下的热解行为及其含量分布规律.先用TGA确定了绿原酸在氮气氛围中的主要热失重区间,选取4个典型的温度点,再结合卷烟在高温燃烧区的3个温度点,分别在惰性(氦气)和有氧(含9％氧气的氮氧混合气)氛围中进行热裂解实验,对...     

Thermal degradation mechanisms of liquid crystalline aromatic polyesters studied by pyrolysis–gas chromatography/mass spectrometry

The thermal degradation mechanisms of liquid crystalline aromatic polyesters (LCPs) prepared from p-hydroxybenzoic acid (PHB), biphenol (BP), and terephthalic acid (TA) were studied by pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS). The LCP containing deuterated terephthalate units and the LCPs that have different comonomer ratios were examined. On the basis of the pyrolysis products determined, the origin of the main pyrolysis products (benzene, phenol, biphenyl, phenyl benzoate, etc.) from the corresponding comonomer units were estimated and their thermal degradation mechanisms were eventually discussed in detail.     

Py-GC/MS characterization of a wild and a selected clone of Arundo donax,and of its residues after catalytic hydrothermal conversion to high added-value products

Two analytical procedures based on gas chromatography and mass spectrometry were used to study the compositions of a wild population and a selected clone (Torviscosa) of giant reed (Arundo donax L.), one of the most promising biomass both in terms of energy and fine chemicals production. Gas chromatography/mass spectrometry (GC/MS) was used to characterize and quantitatively determine the monosaccharide composition. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), using hexamethyldisilazane (HMDS) as a derivatising agent, was used to characterize the lignocellulosic polymers. Analytical pyrolysis was also used to study the composition of residues left after the catalytic hydrolysis used to convert cellulose to levulinic acid and hemicellulose to furfural.GC/MS allowed us to determine the monosaccharide composition and polysaccharide content of the giant reed samples, highlighting that there was no significant difference between the wild population and the selected clone. GC/MS also highlighted that the giant reed leaves have a higher percentage (roughly 60%) of polysaccharide material than the stalks, which contain approximately 50%.Py-GC/MS, following the disappearance of the pyrolysis products of polysaccharides, showed that 150 °C and 190 °C are the best temperatures to obtain the complete catalytic conversion of hemicellulose and cellulose, respectively. Analytical pyrolysis also highlighted that in the course of catalytic hydrothermal conversion a partial depolymerisation of lignin was obtained. In particular, the formation of lignin units containing free phenol groups via the cleavage of the β-aryl ether bonds was demonstrated. The presence of these free phenols in the lignin network suggests the possible exploitation of lignin residues as antioxidant components or in high value biopolymer industries rather than the traditional use as low-value fuel for energy production.     

Studies on structure characterization of tryptophan melanin: Comparison between filament and curie-point pyrolysis gas chromatography/mass spectrometry

Structural studies of a synthetic melanin, obtained by means of performic acid oxidation of tryptophan, were carried out by pyrolysis gas chromatography/mass Spectrometry (Py-GC/MS). To identify the best pyrolysis conditions, both Curie-point pyrolysis and filament pyrolysis were employed and the effects of pyrolysis temperatures and times were studied. Using the first approach, various compounds were identified: toluene, ethylbenzene, styrene, indole, methylindole, ethylindole, phenol, cresol and ethylphenol. Using filament pyrolysis some interesting differences could be observed. Whereas toluene, ethylbenzene, phenol, cresol and methylindole were found, neither indole nor ethylindole was detected. Instead, new pyrolysis products were evident, such as methylpyrrole and indolin-2-one. Hence filament pyrolysis seems to activate different thermal decomposition pathways of the melanin under study. It is suggested that tryptophan melanin is a polymer containing indole and hydroxyindole derivatives as subunits.     

Study on the photostability of guaiazulene by high-performance liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry

The photostability of guaiazulene (1,4-dimethyl-7-isopropylazulene; GA), a natural azulenic compound used in cosmetic and health-care products, as well as in pharmaceutical preparations, was investigated in solution (methanol, ethanol, acetonitrile), by different techniques: gas chromatography/mass spectrometry (GC/MS) and high-performance liquid chromatography combined with atmospheric pressure chemical ionization mass spectrometry and UV detection (LC/APCI-MS and HPLC/UV). A solar simulator (xenon-arc lamp) was used as UV-A radiation source. The study involved: monitoring compound decomposition, identifying products of photodegradation (PPs), assessing the role of oxygen and evaluating the kinetics of the process. Minor PPs are volatile compounds and were characterized by GC/MS, while oligomeric polyoxygenated compounds, tentatively characterized on the basis of MS and MS/MS spectra, were found to be the main photoproducts. The photodegradation was found to be enhanced by the presence of oxygen; nevertheless, determination of the singlet oxygen quantum yield for GA gave a lower value than that for the reference standard Rose Bengal. The obtained results and the developed stability-indicating methods (GC/MS and LC/MS) are of interest for stability studies and/or quality control purposes of GA as raw material or cosmetic products.     

聚亚苯基苯并二噻唑与聚亚苯基苯并二噁唑的热分解

用高分辨裂解气相色谱 质谱（ＨＲＰｙＧＣ ＭＳ）研究了聚亚苯基苯并二噻唑、聚亚苯基苯并二唑的热分解行为,鉴定了相应裂解产物的组成、分布及其与高分子结构的关系,并用热重法（ＴＧ）测定了它们的热分解反应动力学参数,提出了其热分解反应机理     

Thermal degradation behaviors of epoxy resin/POSS hybrids and phosphorus–silicon synergism of flame retardancy

Epoxy resin (EP)/polyhedral oligomeric silsesquioxane (POSS) hybrids were prepared based on octavinyl polyhedral oligomeric silsesquioxane (OVPOSS) and phosphorus‐containing epoxy resin (PCEP). The PCEP was synthesized via the reaction between bisphenol A epoxy resin (DGEBA) and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO). The structure and morphology of PCEP/OVPOSS hybrids were characterized by Fourier transform infrared spectroscopy and transmission electron microscopy. Differential scanning calorimetry revealed that the PCEP/OVPOSS hybrids possessed higher glass transition temperatures than that of PCEP. The thermal stability of the PCEP/OVPOSS hybrids was studied using thermogravimetric analysis (TGA). The TGA results illustrated the synergistic effect of phosphorus–silicon of flame retardancy: phosphorus promotes the char formation, and silicon protects the char from thermal degradation. The thermal degradation mechanism of the PCEP/OVPOSS hybrids was investigated by real time Fourier transform infrared spectra and pyrolysis/gas chromatogram/mass spectrometry (Py‐GC/MS) analysis. It was found that OVPOSS migrated to the surface of the matrix and then sublimed from the surface in nitrogen; whereas, the vinyl groups of OVPOSS were oxidated to form a radical trap which could react with pyrolysis radicals derived from PCEP to form the branched and crosslinked structure in air. The combustion behaviors of the hybrids were evaluated by micro combustion calorimetry. The addition of OVPOSS obviously decreased the value of peak heat release rate and total heat release of the hybrids. Moreover, scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy were used to explore the char residues of the PCEP and the hybrids. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 693–705, 2010     

Analysis of keto-enol tautomers of curcumin by liquid chromatography/mass spectrometry

Keto-enol tautomers of curcumin were confirmed by reversed-phase liquid chromatography(RPLC)/ hybrid quadrupole ion trap/time-of-flight mass spectrometry(QIT/TOFMS).Tautomers gave different MS/MS spectra in negative mode.Different mass spectra were also obtained by hydrogen/deuterium exchange LC/MS/MS in positive mode.Our results suggest that enol form is the major form in the solution(water/acetonitrile).     

Thermal degradation and pyrolysis study of brominated butyl rubber‐based damping material

This paper deals with the thermal stability and decomposition behavior of brominated butyl rubber‐based damping material (BRP). The raw materials, butyl rubber matrix (IIR) and brominated phenolic resin (PF), were also investigated as control. IIR shows one decomposition stage, while PF shows four weight loss stages. Flynn‐Wall‐Ozawa calculation indicates that BRP has thermal stability between IIR and PF. Thermogravimetric analysis–Fourier transform infrared (TGA‐FTIR) and pyrolysis–gas chromatography/mass spectrometry (GC/MS) were used to investigate the volatile products under nitrogen atmosphere. As expected, BRP shows combined thermal decomposition behavior of both IIR and PF. The degradation mechanism of BRP was proposed, which is not significantly influenced by the incorporation of PF. The application stability of BRP is worth to be noticed since the post‐cure effect, that is, the free radicals remained from vulcanization would cause additional cross‐linking when stored at 80°C to 120°C.     

Study of ageing of ketone resins used as picture varnishes by pyrolysis–silylation–gas chromatography–mass spectrometry

This contribution presents a research aimed at the study of the commercial products Laropal K80, Keton N and MS2A, ascribed to ketone resins prepared as thin films, in an attempt to reproduce the pictorial layers and protective finishes that are commonplace in contemporary paintings. For this purpose, a new method based on “online” silylation–pyrolysis using hexamethyldisilazane as a derivatisation reagent in pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) has been proposed. This procedure leads to the unambiguous identification of such varnishes and improves direct Py–GC–MS. Chemical changes due to the degradation effect of environmental agents have been especially considered. To that end, three different accelerated ageing processes were applied to a series of specimens prepared from the studied commercial products: thermal, UV light and ageing in an SO₂-polluted chamber. Chemical changes due to UV light ageing of Keton N resin are in good agreement with those previously reported in the literature.     

Thermal degradation mechanism of flame retarded epoxy resins with a DOPO-substitued organophosphorus oligomer by TG-FTIR and DP-MS

A novel phosphorus-containing oligomeric flame retardant, poly(DOPO substituted hydroxyphenyl methanol pentaerythritol diphosphonate) (PDPDP) was synthesized and applied to flame retarded epoxy resins. The thermal degradation behaviors of flame retarded epoxy composites with PDPDP were investigated by thermogravimetric analysis (TGA), thermogravimetric analysis/infrared spectrometry (TG-FTIR) and direct pyrolysis-mass spectrometry (DP-MS) techniques. The identification of pyrolysis fragment ions provided insight into the flame retardant mechanism. The results showed that the mass loss rate of the EP/PDPDP composites was clearly lower than pure EP when the temperature was higher than 300 °C in air or nitrogen atmosphere. The results also suggested that the main decomposition fragment ions of the EP/PDPDP composite were H₂O, CO₂, CO, benzene, and phenol. The incorporation of PDPDP can reduce the release of combustible gas and induce the formation of char layer, hence the fire potential hazard was reduced.     

酚醛树脂分子量及分布场解吸质谱表征方法研究

酚醛树脂分子量及分布的表征方法有很多,如蒸气压渗透法(VPO)、气相色谱、高压液相色谱和凝胶渗透色谱等,但由于酚醛树脂存在众多异构体,这些方法均有一定限制性.场解吸质谱(FD-MS)方法的特点是只给出样品固有组分的分子峰,不产生碎片离子峰,用于酚醛树脂的表征,可以直接得出树脂所有固有组分的分子离子峰值,及树脂不同缩合度组分的相对含量,非常适用于组份繁多的酚醛树脂的的分子量及分布表征研究.以苯酚、甲酚及甲醛等原料分别制备了Resole型苯酚-甲醛树脂、Novolac型苯酚-甲醛树脂、Novolac型甲酚树脂及混酚-甲醛树脂,利用FD-MS对制备的几种不同类型酚醛树脂的分子量及分布进行了研究.结果表明,通过FD-MS谱图分析还可以得到树脂缩聚程度、原料种类、树脂特性等信息,对于鉴别及剖析各种类型酚醛树脂方便有效.     

裂解同时烷基化气相色谱/质谱鉴定醇酸树脂

 用裂解同时烷基化气相色谱-质谱联用技术（SPM-GC-MS）对不同类型的醇酸树脂进行分析研究,将衍生化试剂四甲基氢氧化胺与样品同时裂解,经高效毛细管气相色谱分离,质谱鉴定,可区分醇酸树脂中的多元醇、多元酸、植物油类型,由此对改性醇酸树脂作结构鉴定。与直接裂解-气相色谱-质谱联用技术比较,具有样品前处理快速、简单,用量少,灵敏度高,定性准确,谱图直观等特点。