GC-MS

Crighton (1976) carries out a comparision of thermogravimetry and pyrolysis/gas chromatography to determine their effectiveness for the characterization of textiles. He finds that the former is more versatile, and hence perferable, since it is capable of permitting the observation of characteristic curves from a wide range of substances to be accomplished. Th same author later points out that thermogravimetry also has the advantage of being more accurately reproducible because of its slow and controlled heating rate and is there ore able to give the experimenter more positive control of the degradation conditions.

Urbas (1977), however, does not share this opinion and prefers to use pyrolysis/gas chromotography for the quantitative determination of the pyrolysis products of acrylic, nylon and carbon fibers prepared from viscose.

Perlstein (1983) also prefers the latter method of analysis, mainly because of its higher specificity. He points out diagnostic peaks in the pyrograms of each fibre, which can be used to identify single fibre types or, more particularly, fiber blends quantitatively in a mixture. The peaks that can be recognized include those derived from hydrocarbons, aldehydes, ketones, acids, and simple or complex cyclic organic compounds, and different fibres or components of fibre blends are identifiable from the presence or intensity of these various diagnostic peaks in their pyrograms.

Hughes, Wheals, and Whitehouse (1978) describe a process for the pyrolysis/mass spectroscopy of many fibers, including all kinds of nylon, cellulose acetate, triacetate, polyester, acrylic, modacrylic, polyolefin, poly(vinylidene chloride), poly(vinyl chloride), polystyrene, and natural fibers, Qiana, aramid fibers such as Nomex, Kevlar. They compare the method with electron-spin resonance for use in forensic characterization of fibers and find it preferable because it is more sensitive (since sample sizes as small as 5 mg can easily be analysed).

 

Editor P.W. Harrison, Textile Degradation, Textile Progress, V. 21, No. , The Textile Institute, Manchester, 1991

 

C. Westphal et al (2001) used Py-GC/MS to show microstructure of polymers and in life time studies of polymers it was shown to be a versatile tool to show extent of degradation. They identified at 400 and 500C PLA acetaldehyde, acrylic acid, lactoyl acrylic acid, two lactide isomers and cyclic oligomers up to pentamer by fractionated Py-GCMS (pyrolysis gas chromatography mass spectrometry).

 

S. Villar-Rodil et al (2001) studied the pyrolysis behavior of Nomex [poly(m-phenylene isophtalamide)] fibers under argon using thermoanalytical and infrared spectroscopic methods to get direct information on the progressive changes undergone by the solid material and its carbon fiber residues. The TGDTADRIFTS combination of techniques used in this work is suitable to identify changes taking place in Nomex fibers during pyrolysis. After moisture release, Nomex undergoes changes reflected in TG (thermogravimetry), DTG and DTA (differential thermal analysis) curves near 317C, that may be due to rupture of hydrogen bonds, which are only accompanied by broadening of N---H streching band in the DRIFTS (Diffuse reflectance infrared Fourier transform spectroscopy) spectrum of Nomex pyrolyzed at 360C.

The latest works are reviewed on analytical and applied pyrolysis of polymers, copolymers and blends. Improved identification, component analysis and structural elucidation were performed on several new polymers and copolymers. Various additives, catalysts and residual oligomers were analysed in plastics and the emission of toxic compounds under pyrolysis and combustion were monitored. The development of analytical pyrolysis methods (pyrolysis on line coupled to gas chromatography, mass spectrometry and/or infrared spectroscopy) is closely related to the advances in instrumental chemical analysis and to their combination possibilities. Publications on applied pyrolysis are concerned with the conversion of polymeric precursors into high performance materials (e.g. carbon fibers and ceramics) and the production of useful chemicals (e.g. monomers or fuels) from polymer wastes. In both analytical and applied pyrolysis, knowledge about the chemical reactions taking place is essential. M. Blazson (1997) reviewed the thermal decomposition mechanism of polyolefins, polystyrenes, acryl polymers, polyesters, polyethers, formaldehyde resins, polyamides, sulfur- and silicon-containing polymers.

In his paper, the following subjects dealing with polymers pyrolysis will be covered:

-         Methodology development for analytical pyrolysis of polymers;

-         Analytical applicaitons for new polymers or new materials containing polymers;

-         Production of high performance materials from oplymeric precursors

-         Pyrolytic recycling of polymers or polymer containing materials

-         Thermally induced reaction mechanisms in polymers

The leterature is listed as following;

Bibliography of analytical pyrolysis applications, (Wampler, 1989): Condensation polymers, polyolefins, and polydienes, vinyl polymers, polystyrenes.

Thermal analysis using MS, (Morelli, 1990): Instrumentation, chemical kinetics

Analytical Py-MS, (Boon, 1992): Synthetic polymers, pyrolysis mechanism.

Polymer microstructure by Py-GC/MS, (Zaikin, Mardanov, and Plate 1993):Copolymer sequencing, brnching of macromolecules.

Analysis of synthetic polymers and rubbers (Smith et al, 1993-1995): Pyrolysis techniques, mass spectroscopy, thermal analysis, thermal, thermo-oxidative, thermo-catalytic degradation,

Degradation of butyl rubber (Dubey, Pandey, and Rao, 1995): Resins and paints,

Pyrolysis-field ionisation mass spectroscopy (Wilcken, Schulten,1996): Reactivity of functional groups.

Thermal degradation of condensation polymers (Montaudo, Puglisi,1992) Ionic processes, free radical processes, molecular rearrangements

Polymer routes to silicone carbid (Laine, Babonneau, 1993): Precursor synthesis and processing, pyrolytic transformation

Carbogenic moleculer sieves (Foley, 1995): Polymeric precursors

Synthesis of advanced ceramics (Riedel, 1995): Polymeric precursor, processing to ceramic.

He reported differently the polymer identification with analysis of volatiles in polymers. This is performed either by gas chromotography or by mass spectrometry applying Py-GC or Py-MS technique.