Filament pyrolysis

Fast screening techniques, such as temperature-resolved in-source filament pyrolysis and laser-assisted pyrolysis, benefit from the high cycle time and mass accuracy of FUCR-MS [214]. An additional advantage of FUCR-MS in the study of pyrolysis processes is that MS can be readily used for structural identification of desorption and pyrolysis products. 

Direct pyrolysis in the ion source of a mass spectrometer (QMS) was used to analyse PE/(dicumylperoxide, Santonox R) and PVC/DIOP [259]. In-source PyMS is an analytical tool for fast analysis of flame retardants in unknown mixtures of polymers [223, 265], Heeren and Boon [224] used in-source filament pyrolysis FTMS for high-speed, broadband screening of additives in polymeric household appliances. 

MS with ionization at lower energies, etc.) were proven less reproducible than the work done on synthetic polymers and using either Curie-point or filament pyrolysis and standard GC/MS or MS analysis. 

By scanning the temperature in a filament pyrolyser, the technique allows the separation of non-polymeric impurities from a polymer or composite material. Time-resolved filament pyrolysis has a series of useful applications as an analytical tool or even in some structure elucidations. As an example, it can be used [48] to differentiate the existence of more labile groups in a polymer structure. A typical variation of the total ion trace in a time-resolved pyrolysis MS for a composite material is shown in Figure 5.4.3. 

Figure 5.4.3. Total ion trace (TIT) of a time-resolved filament pyrolysis MS for a composite material.

Besides probe pyrolysis, a filament pyrolysis technique, usually called Desorption Chemical Ionization (DCI) is also used. The polymeric material is deposited on a filament, which is rapidly heated to the degradation temperature. The pyrolysis occms very close to the electron beam, and therefore EXZI is often referred to as an "in-beam" pyrolysis. ... 

The high molecular weight DOC samples were analyzed by Py-MS using the in-source platinum filament pyrolysis technique. The filament, bearing a 1- to 20-(tg sample, was heated at 15°C/sec to a final temperature of 800°C. The mass spectrometer collected one scan/sec over the m/z range of 20 to 800 amu for 1.5 nun. 

Figure 7 Automated resistively heated filament pyrolysis using quartz sample tubes, front view, and side view of the pyrolysis chamber. 1, Quartz tubes 2, sample carousel 3, optical sensor for locating tubes 4, funnel to guide tubes into inlet valve 5, inlet valve 6, quartz chamber 7, heating filament 8, outlet valve 9, GC online valve 10, connection to GC injector.

Although FTIR can readily be utilised for the analysis of pyrolysates, and has some advantages over PyMS and TVA, a disadvantage of PyFTIR is the lower sensitivity relative to mass spectrometry. This explains the limited usage of this complementary technique. The sensitivity of pyrolysis-IR spectroscopy is surpassed by pyrolysis-laser photoacoustic spectroscopy, a combination of filament pyrolysis and CO2 laser photoacoustic detection [838]. 

Sharp and Paterson [41] used a Perkin Elmer filament pyrolysis unit fitted in a Perkin Elmer Ell gas chromatograph (pyrolysis temperature control 250-550 °C). The gas chromatographic column used is a 1.7 m x 3 mm od stainless steel column packed with 30% m/m silicone oil (Embaphase) on acid washed Celite, operated at 80 "C with a helium flow rate of 30 ml/min. The column effluent is split in the ratio 2 1 between a flame ionisation detector and an API MS12 mass spectrometer equipped with a glass fit type of molecular separator at 150 C. Mass spectra are scanned from m/e 200 to 20 at 8 seconds per decade under standard electron bombardment conditions, electron energy 70 eV, emission current 500 pA, accelerating voltage 8 kV and source temperature 200 °C. 

The consensus of opinion is that, particularly in the cases of those polymers such as the polyolefins where complex pyrograms are produced, filament pyrolysis is the preferred method. For the purposes of fundamental studies, pyrolysis at a variety of temperatures and heating rates is preferred. Smaller sample weights of the order of 1-2 mg are preferred as these prevent or reduce the occurrence of secondary side... 

Two procedures have been described, (I) flash filament pyrolysis (Section 6.3.1) and (ii) heating the polymer in a micro-reactor and collecting the total volatiles produced, (Section 6.3.2). In yet another more recent approach, the pyrolyser probe method discussed below, the polymer is placed in a quartz tube which is then inserted into a platinum coil heater element. The coil heater is switched on to release the pyrolysis products which are then directly swept into the gas chromatograph. 

This Curie point filament pyrolysis technique enables unknown polymers to be identified. 

Figure 2 Schematic representation of the parameters that determine the heating profile in filament pyrolysis, namely temperature rise time (TRT), equilibrium temperature (Tgq) and total heating time (THT).

Polysulfones, polyphenylene sulfone Filament pyrolysis with MS flame ionisation GC detection Varied SOj Kinetics of SO2 production on sequential pyrolysis [42]... 

Figure 1.2 (A) Filament pyrolysis - gas chromatogram of PVC (a) biphenyl, (b) methyl naphthalene, (c) naphthalene, (d) methylindene, (e) tetralin, (f) methyl indene, (g) indene, (h) indane, (i) styrene, (j) o-xylene, (k) ethylbenzene, (1) toluene, (m) benzene. (B) Filament pyrolysis - gas chromatography of polyvinylidene chloride, (a) tetra-chlorostyrene, (b) trichlorostyrene, (c) 1,3,5 trichlorobenzene, (d) w-dichlorobenzene, (e) trichlorobutadiene, (f) chlorobenzene, (g) vinyldene-chloride. [Source Author s own files)...

In this Curie point filament pyrolysis technique the polymer is pyrolysed at a controlled temperature and the pyrolysis products passed into a gas chromatograph. Relative retention data and peak height ratio data obtained when compared with data obtained from known polymers provide a means of identifying the unknown polymer. 

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