Analysis of Natural and Synthetic Rubber by Infrared Spectroscopy

Abstract

Abstract This report describes an investigation of the applicability of infrared spectro-scopic methods to the quantitative determination of the elastomer composition of industrial rubber products. Generally satisfactory techniques for obtaining a valid spectrum of the elastomer content of any rubber specimen have been developed and evaluated and have been applied to the development of detailed analytical procedures for the identification and qualitative analysis of elastomer mixtures, to the quantitative analysis of natural-GR-S blends, and to the determination of the nitrile content of nitrile copolymers. An accuracy corresponding to ° 1 per cent average error has been obtained in these determinations. The methods can be extended to analogous problems with a minimum of alteration, and the same order of accuracy can be expected in general. A discussion of the correlations between spectral absorption and molecular structure is also included. Infrared spectroscopy is finding increasing application as a means for the identification of organic materials and the analysis of complex mixtures. Spectroscopic methods are not only rapid and generally conservative in sample requirements, but the results are often more specific than those obtained by chemical analysis, distillation, etc., and in many cases furnish detailed structural information of importance to research and development. The advantages of infrared analysis are that : (1) the spectrum of a molecule is a unique physical property which is not altered by any changes in which molecular identity is maintained, and (2) the individual features of the spectrum relate in a definite manner to the chemical bonds comprising the molecule and can thus be interpreted, regardless of the total configuration.