TABLE OF CONTENTS Non-metallic elements such as boron, halogens, nitrogen, oxygen, phosphorus and sulfur, can occur in polymers either as major constituents or as impurities or as components of low-percentage additions of additives containing the element, for example, the addition of 0.5% dilauryl thiodipropionate antioxidant to a polymer during processing will introduce parts per million concentrations of sulfur into the final polymer. Another source of non-metallic elements in polymers is catalyst residues and processing chemicals.
It is advisable when commencing the analysis of a polymer to determine the content of various non-metallic and metallic elements first. Initially, these tests could be qualitative, simply to indicate the presence or absence of the element. All that is required here is that the test is of sufficient sensitivity such that elements of importance are not missed. If an element is found in these tests, it may then be necessary to determine it quantitatively as discussed next. The analytical methods used to determine elements should be sufficiently sensitive to determine about 10 ppm of an element in the polymer, i.e., should be able to detect in a polymer a substance present at 0.01% and containing down to 10% of the element in question.
This requirement is met for almost all the important elements by the use of optical emission spectroscopy and X-ray fluorescence spectrometry (XRFS). XRFS is applicable to all elements with an atomic number greater than 12. Using these two techniques, all metals and non-metals down to an atomic number of 15 (phosphorus) can be...
