Oxygen bomb combustion plastics

The first step in analysing plastics for metals content in polymers by ICP-AES technique is that they must be prepared in solutions that are suitable for nebulization. There are four general methods applicable for sample preparation for metal analysis by ICP-AES and they are solvent dissolution of some plastics dry ashing using a muffle furnace acid digestion using a microwave oven and oxygen bomb combustion. 

Digestion of samples using high pressure oxygen bomb combustion is an excellent technique for sample preparation, particularly trace metal analysis. This technique can be applied to most plastics provided that small sample ( 0.25 g) of fine grain sizes of plastics are used. The solutions obtained are clean and easily analysed for metal content against standards prepared in the same solution added to bomb. 

Table 4.10 Results of analysis of selected plastic materials for listed metals by ICP-AES after microwave acid digestion (A), dry eishing to 650°C with PTSA (B) or high pressure oxygen bomb combustion (C)...

The major differences between the fluorine and oxygen combustion calorimetry methods arise from the exceptional reactivity and toxicity of fluorine. The substances studied by oxygen combustion calorimetry are normally stable when kept inside a bomb at 298.15 K and under 3 MPa of O2. Oxygen- and moisture-sensitive compounds can also be studied because various types of containers are available to prevent their reaction with O2 prior to ignition. Common examples are glass ampules, which are inert toward the combustion process and, more commonly, Melinex bags or polyethene ampules, which burn cleanly to CO2 and H2O. As carbon dioxide and water are also generated in the combustion of the sample, no extra complexity is introduced in the analysis of the final state of the bomb process by the use of those plastic containers. 

Inside the pressurized oxygen atmosphere of a bomb calorimeter, most organic matter, including food, fabrics, and plastics, will ignite easily and burn rapidly. Some samples of matter may even explode, but the strong walls of the calorimeter contain the explosions. Sample sizes are chosen so that there is excess oxygen during the combustion reactions. Under these conditions, the reactions go to completion and produce carbon dioxide, water, and possibly other compounds. 

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