High-resolution Pyrolysis-gas Chromatography Research Articles

Quantitative analysis of the higher fatty acids in acetone solutes (AS) from raw natural rubber and their impacts on the structure and properties of NR/silica composites

Traditionally, non-isoprene components as higher fatty acids in raw NR (natural rubber) were neglected in composites. Here, linoleic acid (LA), stearic acid (SA) in acetone solutes (AS) from different raw NR were analyzed quantificationally by high resolution pyrolysis gas chromatography mass spectrometry (HRPyGC–MS) firstly, where the relative amounts of LA and SA in AS were arranged as AS-STR (Standard Thailand Rubber) > AS-WF > AS-SMR (Standard Malaysia Rubber) > AS-MRSS (Myanmar Smoked Sheet Rubber). The impacts of LA and SA on the structure and properties of NR/silica composites were also investigated. Consequently, the mechanical and dynamical properties of composites were improved significantly by increasing the amount of LA or SA. Further, LA performed better than SA on decreasing the low rolling resistance of composites. Finally, esterification reaction, hydrogen bond between −COOH and Si-OH in NR/silica/LA and NR/silica/SA systems both were verified via Fourier transformation infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The present findings provide a new introspection about regulating the quality of raw NR from the hevea brasiliensis planting.

Application of high resolution pyrolysis gas chromatography/mass spectrometry (HRPGC/MS) for detecting Listeria monocytogenes.

The characteristic of Listeria monocytogenes' pyrolysis product was found by fingerprint analysis of high resolution pyrolysis gas chromatography and mass spectrometry (HRPGC/MS), which hold a great potential to rapidly detect L. monocytogenes with the application of selected ion monitoring (SIM). Food products (beef and milk) contaminated by L. monocytogenes and uncontaminated were evaluated. The retention time of the characteristic peak of pyrolysis product was 19.056min, the ion of m/z were 54, 98. The results showed that the peak at retention time 19.056min was detected in agricultural products that contaminated by L. monocytogenes, while the result of the uncontaminated food, there is no peak at the retention time 19.056min. Qualified by the retention time of chromatographic and mass spectrometry, it can eliminate the interference induced by different types of agricultural products. The results prove united technologies of HRPGC/MS and SIM is not only reliable, reproducible, but also a new method for rapid detecting L. monocytogenes in food products.

Thermal properties of the polyimide foam prepared from aromatic dianhydride and isocyanate

A new type of polyimide foam (PIF) was prepared successfully based on a one-pot process by the reaction of a first solution and a second solution. The first solution comprised pyromellitic dianhydride (PMDA), N, N-dimethyl formamide (DMF), methanol, polyethylene glycol and water. The second solution contained polyaryl polymethylene isocyanate (PAPI). The thermal properties of the polyimide foam were thoroughly investigated by thermogravimetry–Fourier transform infrared spectroscopy (TG–FTIR) and high-resolution pyrolysis gas chromatography–mass spectroscopy (PyGC–MS) at various temperatures. The results of TG–FTIR indicated that polyimide foam was thermally stable and experienced a weight loss of less than 2% before the scanning temperature reached 280.7 °C. It showed a two-stage degradation process during the whole decomposition. The major decomposition products were carbon dioxide (CO2), carbonic oxide (CO) and methyl formate. The results of PyGC–MS indicated that no pyrolysis products were indentified when the test temperature was 250 °C. Certain pyrolyzates such as oxygen, carbon dioxide and methyl formate was identified as the pyrolysis temperature increased. According to the degradation behaviors and the structure and relative content of pyrolysis products, a proposed pyrolysis mechanism of polyimide is presented in this article.

Thermal stability and degradation products analysis of benzocyclobutene-terminated imide polymers

Benzocyclobutene-terminated imides were prepared and fully characterized with 1H NMR, MS, and FT-IR. The thermal degradation of polymers was investigated by using thermogravimetric analyzer (TGA) and high-resolution pyrolysis-gas chromatography–mass spectrometry (HR-Py-GC–MS). TGA showed that thermal degradation of the polymer was a single-stage process in N 2, whereas a three-stage degradation in air atmosphere. The major involved products were found to be CO 2, naphthalene and naphthalene derivatives. Degradation mechanism of the polymer was suggested and the relationship between structures of the polymer and degradation products was also discussed.

Characterization of structure of comblike polymer by pyrolysis gas chromatography and Fourier transform infrared spectroscopy

AbstractThe characterization of branching in comblike polymers using high‐resolution pyrolysis gas chromatography (HRPGC) and Fourier transform infrared spectroscopy (FTIR) is investigated. The branching type can be identified from characteristic peaks of monomer and a group of dimers in pyrograms derived from α‐ and β‐scission of branched atoms. By resolving the overlapping bands between 2800–3000 cm−1, the relative absorbance of CH2 can be used to calculate the average branch length L. This method is helpful in evaluating the property of drag‐reduction agents. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 359–363, 2001

Thermal decomposition of amide and imide derivatives of maleated polyethylene

The thermal decomposition behavior of six derivatives of maleated polyethylene was investigated by high-resolution pyrolysis gas chromatography–mass spectrometry. The results revealed that substituents attached to maleated polyethylene as amides formed from secondary amines were significantly less stable than imides formed from primary amines. Morpholine amide and N-methylaniline amide derivatives of maleated polyethylene underwent significant decomposition at 160 °C and substantial decomposition at 200 °C. In contrast, the imide derivatives of maleated polyethylene were stable for long periods of time at elevated temperatures. Following 2 min of heating, the first traces of decomposition were detected at 200 °C for the 2-aminoanthrancene imide derivative, at 255 °C for the 2-phenethylamine imide, and at 280 °C for the 9-aminomethylphenanthrene imide. With the exception of the 9-aminomethylphenanthrene imide, all other derivatives decomposed to form the corresponding amine as the single most significant volatile product. The most likely explanation for this result is that the polymer contained small amounts of succinamic acid that did not close to form the imide. We concluded that the imide was stable even to 315 °C and that the amine was lost from β-carboxyamide groups present in the sample. In the 9-aminomethylphenanthrene imide derivative, we observed no loss of amine. Instead, we observed an alternative fragmentation process yielding 9-methyl phenanthrene. The dependence of the thermal stability of these various derivatives of maleated polyethylene has important implications for the design of reactive-blending strategies for polyolefins with other functional polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 730–740, 2000

High-resolution pyrolysis–gas chromatography with a movable reaction zone

A new device was constructed for pyrolysis–gas chromatography and it was laboratory tested. The device enables the thermal degradation of polymers inside a capillary pre-column and transfer of the reaction zone into a column oven. The pyrolysis procedure described protects the thermally sensitive compounds prior to pyrolysis, prevents the process of irreversible condensation of high-boiling pyrolysis products during the chromatographic process and eliminates extracolumn effects on the peak broadening.

Analysis of bone marrow from patients with acute leukemia by high resolution pyrolysis-gas chromatography

The mononuclear cells and plasma in bone marrow from 30 subjects with leukemia, 12 subjects with hematological disease, four subjects with multiple myeloma, one subject with malignant histiocytosis and 18 normal subjects were analyzed by high-resolution Py-GC(HR Py-GC). In the present study, the samples were pyrolyzed using CDS 122 pyroprobe at 770 °C, coupled on-line to a model HP 5890A gas Chromatograph with a fused silica capillary column coated with PEG 20M. The results showed that the pyrograms of the leukemia cases were significantly different from those of the other hematological diseases and normal subjects. A characteristic peak with the same retention time in the pyrograms of the leukemia, multiple myeloma and malignant histiocytosis samples was found. In contrast, this characteristic peak did not appear in the pyrograms of other hematological diseases and normal subjects. The pyrograms of the different subtypes of leukemia were also different. Variation in the pyrograms of six cases of mononuclear cells and plasma from different stages of treatment were closely related to changes in the effectiveness of the treatment. All pyrograms of the plasma from the leukemia, other hematological diseases and normal controls showed similar results to those of the mononuclear cells. Therefore, 36 clinical samples of the different subtypes of acute leukemia were identified by the method, 35 cases were diagnosed (97.2%). The technique appears to provide a simplified and reproducible method as a rapid diagnostic tool and dynamic observation of acute leukemia.

Characterization of epoxy resins cured with dicyandiamide in the presence of imidazole catalysts by high-resolution pyrolysis—gas chromatography

Epoxy resins cured with dicyandiamide (DCDA) in the presence of various imidazole catalysts were characterized by high-resolution pyrolysis-gas chromatography (HR-Py—GC) with simultaneous detection by a nitrogen phosphorus detector (NPD) and a flame ionization detector (FID). Sharp peaks of the nitrogen-containing degradation products characteristic of the various imidazole catalysts were observed, along with those of DCDA in the pyrograms obtained, by use of NPD. The observed characteristic peaks of the imidazole catalysts in the pyrograms obtained by use of both NPD and FID were successfully correlated to the contents of the imidazole catalysts in the epoxy resins.

Investigation of the detection limit for the determination, by pyrolysis‐capillary GC, of the thickness of ultra thin PMMA layers coated on to PET film

AbstractThe determination of nanometer thick layers of poly(methyl methacrylate) coated on to the surface of poly(ethylene terephthalate) film has been investigated by high resolution pyrolysis gas chromatography without sample pretreatment or modification of the instrumentation used. A good linear relationship was observed between the quantity of the characteristic pyrolysate and the thickness of the poly(methyl methacrylate) layer; the detection limit was sufficient to enable the quantitation of poly(methyl methacrylate)‐to‐poly(ethylene terephthalate) film thickness ratios of 1:20000 in composite materials.

Characterization of poly(2,6-dimethyl-1,4-phenylene ether) by high resolution pyrolysis-gas chromatography (HR-Pyg.c.)

Pyrograms of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) samples were obtained by on-line high resolution pyrolysis-gas chromatography (HR-Pyg.c.). Characteristic peaks on the pyrograms (up to trimers) were assigned by using gas chromatography-mass spectrometry (g.c.-m.s.) and retention time data. The analysis of a series of fractions of varying molecular weight from a given PPE sample suggested that HR-Pyg.c. would be a powerful technique for characterization of the end groups of PPE when 13C-n.m.r. was used to take reference data for these end groups.

High-resolution pyrolysis-gas chromatography for the study of epoxy resins cured with prepolymers of varying molecular weight

Epoxy resins cured with prepolymers of varying molecular weight were studied by high-resolution pyrolysis-gas chromatography. Various phenols and the glycidylethers of bisphenol A characteristic of the prepolymer backbone were observed in the pyrograms of the prepolymers. In addition, pyrolysates characteristic of the curing agents were also observed in cured resin systems. In both cases, the peak intensities changed as a function of the molecular weight of the original prepolymers. The molecular weights of the original prepolymers were calculated from the peak intensities of the characteristic products for the uncured prepolymers and the cured resins.

Characterization of Vulcanized EPDM Rubbers by High-Resolution Pyrolysis Gas Chromatography

Abstract Pyrolysis gas chromatography (PyGC) is a powerful tool to give unique information of high polymers. Especially, PyGC is favorable for the practical analysis of insoluble polymeric materials such as vulcanized rubbers. In the previous paper, the structures of commercially available unvulcanized ethylene-propylene-ethylidenenorbornene rubbers (ENB-EPDMs) were investigated by high-resolution PyGC. The observed high-resolution pyrograms of the unvulcanized EPDMs were correlated to the ENB content. In addition, several peaks of the characteristic degradation products were interpreted in terms of the sequence distribution and the ethylene-propylene composition. In this work, vulcanized ENB-EPDMs (V-EPDMs) cured with two types of vulcanizing agents were studied using high-resolution PyGC. Characteristic pyrolysis products formed at 650°C were separated by the high-resolution capillary column, and the resulting pyrograms were interpreted in terms of ENB content in the vulcanized rubber samples. In addition, thermal degradation behavior of the ENB units in V-EPDMs was investigated.

Characterization of poly(styrene—dimethylsiloxane) block copolymer by high-resolution pyrolysis—gas chromatography/mass spectrometry

Two poly(styrene—dimethylsiloxane) block copolymers with different compositions were studied by high-resolution pyrolysis—gas chromatography using a modified column system and a self-made fused silica capillary column, and their pyrolyzates were identified by pyrolysis capillary gas chromatography/mass spectrometry. The pyrolysis mechanism of these copolymers was discussed and their compositions were characterized on the basis of qualitative and quantitative analysis of the pyrolysis products. The results show that this is a convenient and reliable method for the characterization of this type of copolymer.

Structural Characterization of Ethylene-Propylene-Diene Rubbers by High-Resolution Pyrolysis Gas Chromatography

Abstract Ethylene-propylene-diene rubbers (EPDMs) are now used for various purposes because of their excellent resistance to ozone, weather, and heat. Therefore, many kinds of EPDMs are provided as commercial polymers. Consequently, reliable methods for the structural characterization of EPDM have been needed in the fields of material development, process control, and quality assurance of the cured products. The iodine value method is generally used to determine the diene content in EPDMs. However, it is too time consuming to be a routine method. Until now, spectroscopic methods such as IR and NMR are generally used for the study of the composition and the sequence length distributions in EPDMs. Levine and Haines determined the content of ethylidenenorbornene (ENB) in ethylene-propylene-ethylidenenorbornene rubbers (ENB-EPDMs) by IR. Florence and Loustalot investigated ethylene-propylene-1.4-hexadiene rubbers by NMR. However, these spectroscopic methods often encountered the difficulties in the analysis of vulcanized rubbers since they were insoluble and usually contained many kinds of additives such as curing agents, plasticizers, stabilizers, and fillers. On the other hand, owing to the recent development of excellent pyrolyzers and highly efficient fused-silica capillary columns, pyrolysis-gas chromatography (PyGC) has become a powerful tool to give unique information about structures of high polymers. Furthermore, PyGC is advantageous to the practical analysis of insoluble polymeric materials such as vulcanized rubbers.

Characterization of Polymerization Reagents Incorporated into Poly(methyl methacrylate) Chains by Pyrolysis-Gas Chromatography

High-resolution pyrolysis-gas chromatography was successfully applied to characterize the end groups of poly(methyl methacrylate) (PMMA) prepared by radical polymerization. Although PMMA mainly depolymerized to the monomer at elevated temperatures, some of the minor peaks on the pyrograms could be assigned to the products associated with the end groups derived from both the initiation reactions caused by benzoyl peroxide (BPO) and the chain transfer reactions to dodecanethiol and solvent. Two kinds of BPO-initiated chain ends were clearly distinguished. It was confirmed that phenyl-initiated polymer chains rather than benzoyloxy-initiated ones were preferentially formed in solution polymerization, whereas the latter pre-dominated in bulk polymerization. Moreover, the characteristic peak intensities could be correlated to the amounts of polymerization reagents in the feed. In addition, dodecanethiol formed from thiol-incorporating chain ends was selectively detected without interference from any other pyrolysis products by using a sulfur-specific flame photometric detector.

Characterization of chloromethyl-substituted polystyrene networks by high-resolution pyrolysis-gas chromatography

Characterization of chloromethyl-substituted polystyrene networks by high-resolution pyrolysis-gas chromatography

Studies on Curing Process of Epoxy Resins by High-Resolution Pyrolysis-Gas Chromatography

The curing processes of epoxy resins cured with a dicarboxylic acid anhydride or in the presence of an imidazole catalyst were studied by high-resolution pyrolysis-gas chromatography. The yields of the pyrolyzates with epoxide groups decreased with increase in the degree of curing, while those of various phenols characteristic of prepolymer skeleton increased. Additionally, the yields of low boiling pyrolyzates such as ethylene oxide, propylene, acrolein and acetone also specifically changed with the degree of curing. The obtained results are discussed in comparison with the results from other techniques such as glass transition temperature measurements and FT-IR.

Studies on thermal degradation of epoxy resins by high-resolution pyrolysis-gas chromatography

The optimum pyrolytic conditions for thermosetting epoxy resin samples were first empirically studied. On the basis of the optimized pyrolytic conditions, epoxy prepolymers and epoxy resin samples cured with and without curing agents, such as diamine and dicarboxylic acid anhydride, were studied using high-resolution pyrolysis-gas chromatography. In addition to some intact prepolymer molecules, various degradation products characteristic of the prepolymers, up to diglycidyl ether of bisphenol A, were detected on the pyrograms of the prepolymers. On the other hand, various phenols characteristic of the prepolymers and a variety of pyrolyzates characteristic of the reacted curing agents, including intact dicarboxylic acid anhydride, were observed on the programs of the cured resin samples. The potential of this technique for studying the curing process of the epoxy resins is discussed.

Studies on thermal degradation behaviour of anionically copolymerized styrene-divinylbenzene copolymers by high-resolution pyrolysis-gas chromatography

Anionically and radically copolymerized styrene-divinylbenzene copolymers with comparable divinylbenzene contents have been synthesized and studied by high-resolution pyrolysis-gas chromatography. The considerable differences in thermal degradation behaviour observed between both copolymer systems were interpreted on the basis of differences in the expected network structures for the corresponding copolymer systems. In addition, thermogravimetric analysis was carried out to evaluate the thermal degradation behaviour of the copolymers.