Gas chromatography, pyrolysis PGC

For compounds of high molecular mass, however, the formation of derivatives does not help to solve the problem of in volatility. This difficulty may be overcome by breaking the large molecules up into smaller and more volatile fragments which may then be analysed by gas-liquid chromatography, i.e. by using the technique known as pyrolysis gas chromatography (PGC). 

Major methods involved with the generation of information about thermal property behavior of materials include thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), differential thermal analysis (DTA), torsional braid analysis (TBA), thermal mechanical analysis (TMA), and pyrolysis gas chromatography (PGC). 

One of the simplest techniques is pyrolysis gas chromatography (PGC) in which the gases resulting from the pyrolysis of a polymer are analyzed by gas chromatography (GC). This technique may be used for qualitative and quantitative analysis. The latter requires calibration with known amounts of a standard polymer pyrolyzed under the same conditions as the unknown. 

Chemical, Physical, and Mechanical Tests. Manufactured friction materials are characterized by various chemical, physical, and mechanical tests in addition to friction and wear testing. The chemical tests include thermogravimetric analysis (tga), differential thermal analysis (dta), pyrolysis gas chromatography (pgc), acetone extraction, liquid chromatography (lc), infrared analysis (ir), and x-ray or scanning electron microscope (sem) analysis. Physical and mechanical tests determine properties such as thermal conductivity, specific heat, tensile or flexural strength, and hardness. Much attention has been placed on noise /vibration characterization. The use of modal analysis and damping measurements has increased (see Noise POLLUTION AND ABATEMENT). 

The methods described in this section can in principle only be used to determine the average composition of a certain copolymer sanple. Among the numerous ways to determine the chemical composition we mention IR spectroscopy, ultraviolet spectroscopy (UV), NMR spectroscopy, and pyrolysis gas chromatography (PGC). 

The choice of packed or capillary pyrolysis gas chromatography (PGC) is generally a matter of personal requirements. The type and range of samples to be analysed, the... 

Pyrolysis may be defined as the thermal transformation of a compound (single entity) into another compound or compounds, usually in the absence of oxygen. In modem pyrolysis the sample decomposition is rigidly controlled. One shonld keep in mind that pyrolysis gas chromatography (PGC) is an indirect method of analysis in which heat is used to change a compound into a series of volatile prodncts that should be characteristic of the original compound and the experimental conditions. 

Pyrolysis gas chromatography (PGC) was one of the first combination gas chromatographic techniques, yet it is still plagued by problems of accuracy and repeatability of pyrolysis conditions and laboratory-to-laboratory reproducibility. There are three major devices for PGC (1) heated wire or ribbon, (2) tube furnace, and (3) Curie point filament. The heated wire or ribbon apparatus uses resistive heating to provide flash pyrolysis from ambient temperature to 1400°C. It can be controlled to reach the maximum temperature in milhseconds or at some fixed rate, and the device can hold the top temperature for a settable fixed time. These high-precision devices can be placed directly in the injection port (for vertical injection ports). The temperature reading should be checked from time to time to ensure accuracy. 

SMA resins swell and eliminate carbon dioxide when heated at 200 C. The resultant soft, brown-colored resins are soluble in acetone, as well as hydrocarbons, to which it imparts a brilliant white fluorescence under ultraviolet light. Pyrolyzed polymer also dissolves in aqueous potassium hydroxide to produce a fluorescent solution.Sequence analysis and microstructure of SMA-type resins can be studied by pyrolysis/gas chromatography (PGC). Styrene yields are generally extremely low by the PGC technique. In a truly alternating copolymer it might be expected to be zero. For a copolymer showing 51.5 wt. % styrene, the styrene yield was 3.6%. 

---