Application of Pyrolysis-Gas Chromatography in Explosive and Propellant Analysis

Applications of pyrolysis-gas chromatography and pyrolysis capillary gas chromatography in explosive and propellant analysis are reviewed, including the identification of explosives and propel- lants, the investigation of the thermal decomposition of nitrocellulose (NC), cyclotetramethylene tetranitramine (HMX)and cyclotrimethylene trinitramine (RDX), and the study of the wear- reducing mechanism of polyurethane additive in propellant gain.

Molecular Structures and Mechanical Properties of Microbe Rapid Coagulation Natural Rubber

In this work,molecular structures,dynamic mechanical properties and glass transition temperatures of microbe coagulated natural rubber（NR） samples were analyzed by using pyrolysis gas chromatography-mass spectrometry（py-GC/MS）,rubber process analyzer（RPA） and dynamic mechanical thermal analysis（DMA）.And the cross-linked network structures and mechanical properties of the corresponding NR vulcanizates were further determined by using nuclear magnetic resonance（NMR） crosslink density spectrometer（XLDS-15） and universal testing machines.The results show that NR raw rubber produced by rapidly coagulated with microorganism exhibits a simple molecular structure composition and good dynamic mechanical properties,and the corresponding NR vulcanizates possess the aggregation structure of high cross-linked density,a high glass transition temperature of-61.5 ℃ and high mechanical properties（tensile strength reaches 25.2 MPa）,as compared with that coagulated with acetic acid.

Pyrolysis Study of Waterborne Polyurethane

The thermal degradation of synthetic waterborne polyurethane（PU） based on toluenediisocyanate（TDI） was investigated by pyrolysis-gas chromatography/mass spectrometry（Py-GC/MS） and thermogravimetry（TG）.The degradation profiles of cast films obtained from dispersions were evaluated.More than 20 characteristic volatile pyrolyzates reflecting the structure and pyrolysis mechanisms of the polymer have been identified by on-line MS.In helium atmosphere,the synthesized products of polyurethane were pyrolyzed at 350,450,550,650 and 750 ℃ respectively,and the thermal decomposition products were analyzed on line using GC/MS.The product analysis reveals that the pyrolyzates distribution of the polyurethane depends strongly on the pyrolysis temperature.Based on the Py-GC/MS data,the thermal degradation mechanism of the polyurethane is discussed.

Chemical-Structural Changes of Organic Matter in a Semi-Arid Soil After Organic Amendment

A 9-month incubation experiment using composted and non-composted amendments derived from vine pruning waste and sewage sludge was carried out to study the effects of the nature and stability of organic amendments on the structural composition of organic matter (OM) in a semi-arid soil.The changes of soil OM,both in the whole soil and in the extractable carbon with pyrophosphate,were evaluated by pyrolysis-gas chromatography and chemical analyses.By the end of the experiment,the soils amended with pruning waste exhibited less organic carbon loss than those receiving sewage sludge.The non-composted residues increased the aliphatic-pyrolytic products of the OM,both in the whole soil and also in the pyrophosphate extract,with the products derived from peptides and proteins being significantly higher.After 9 months,in the soils amended with pruning waste the relative abundance of phenolic-pyrolytic products derived from phenolic compounds,lignin and proteins in the whole soil tended to increase more than those in the soils amended with sewage sludge.However,the extractable OM with pyrophosphate in the soils amended with composted residues tended to have higher contents of these phenolic-pyrolytic products than that in non-composted ones.Thus,despite the stability of pruning waste,the composting of this material promoted the incorporation of phenolic compounds to the soil OM.The pyrolytic indices (furfural/pyrrole and aliphatic/aromatic ratios) showed the diminution of aliphatic compounds and the increase of aromatic compounds,indicating the stabilization of the OM in the amended soils after 9 months.In conclusion,the changes of soil OM depend on the nature and stability of the organic amendments,with composted vine pruning waste favouring humification.

Pyrolysis behaviors of oil sludge based on TG/FTIR and PY-GC/MS

Pyrolysis is an alternative technology for oil sludge treatment.Thermogravimetric Analysis-Fourier Transform Infrared Spectroscopy and Pyrolysis-Gas Chromatography/Mass Spectrometry were employed to investigate the pyrolysis process and products of oil sludge.The pyrolysis process was divided into five stages:drying and gas desorption,oil volatilization,main pyrolysis,semicoke charring,and mineral decomposition.The main reaction temperatures ranged from 497.6 K to 753.2 K.The products were mainly composed of pairs of alkane and alkene(carbon number ranges from 1 to 27).The mechanisms consisted of random chain scission followed by end chain scission at high temperatures with volatilization occurring during the whole process.This study is useful not only for the proper design of a pyrolysis system,but also for improving the utilization of liquid oil products.

Temperature dependency of VOCs release characteristics of asphalt materials under varying test conditions

Asphalt pavement is increasingly used in paving and roofing.However,the release of volatile organic compounds(VOCs)from asphalt harm both the environment and humans.Various methods were applied to characterize the VOCs for better understanding and inhibiting.However,asphalt VOCs have huge heating temperature dependency,which makes the asphalt VOCs’characterization complicated.In this research,three kinds of heating conditions,thermal gravimetric(TG)analyzer,pyrolysis(PY)analyzer,and thermal desorber(TD),were compared to determine the temperature dependency of VOC release characteristics.Gas chromatography and mass spectrometer(GC-MS)were then coupled for VOC detection.Results indicated that the TG heating condition can surely simulate the volatilization of VOCs from some asphalt that is not in contact with air(no oxygen)during the actual construction process,while PY and TD represent the substances released by the asphalt due to the boiling point at a certain temperature and under the actual construction process,respectively.The components detected by TG heating condition are both large and small molecules,while PY and TD heating condition will detect large molecules or small molecules,respectively.The VOC composition results under various heating conditions reflect the chemical reaction law of asphalt molecules in the heating process.When heating asphalt binders to a higher temperature,macromolecular substances will gradually crack and oxidize into small molecular substances,sulfides and nitrides.With the increase of temperature,the change trend of VOC components under different conditions is different.

Thermal degradation of organo-soluble polyimides

The thermal degradation behavior of two organo-soluble polyimides was investigated by high resolution pyrolysis-gas chromatography/mass spectrometry. The pyrolyzates of the polymers at various temperatures were identified and characterized quantitatively. The relationship between the polymer structure and pyrolyzate distribution was discussed. The kinetic parameters of the thermal degradation were calculated based on thermogravimetric measurements. Finally, the thermal degradation mechanism for the polymers was suggested.