The development of methods for examining stabilizers in polymers and their conversion products

Abstract

In the field of stabilizer analysis today there is a need for the analytical determination of the decomposition or transformation products of the stabilizers in polymer systems including their reaction products with the polymers. For the solution of such a complex analytical task, separation problems are at the centre of modern scientific work. These separation problems are subdivided into two partial processes, namely (a) separation of the low molecular substances from the polymer; (b) separation of the mixture of low molecular substances.Selective stage extractions and gel permeation chromatography are particularly favourable. The well-known method of the precipitation of the polymer from diluted solutions needs a more thorough scientific consideration of the solvent-precipitant effects on the stability of the reaction products of stabilizers or their fragments with the polymer.Thin-layer chromatography (TLC) has brought the greatest success, multistage processes here also offer prospective possibilities for the separation of complex systems. Gas chromatography (GC) is less important. Liquid chromatography (LC) with new high-efficiency carrier materials having particle diameters in the micro range will be most important in the future.Structure examinations of the decomposition products of the stabilizers in principle correspond to the classical organo-analytical concepts after separation processes. The most important of the decomposition products of the stabilizers were those of the tin compounds and those of stabilizers based on urea. All toxic substances were detectable by TLC.Structure examinations of stable transformation products of the nitrogencontaining antioxidants with u.v. and i.r. spectrometry are demonstrated in relation to the most discussed mechanism of the inhibition reaction. An analytical scheme for oxidized vulcanizates in the presence of secondary and tertiary mono-and diamines is given at the end to demonstrate the necessity of combining largely selective separation processes with all analytical detection and determination processes of high sensitivity for a successful overall analytical process.