Characterization of elastomeric materials by NMR-microscopy.
This review reflects a long experience with the application of NMR-imaging methods to elastomeric materials. The experimental techniques, used to obtain parameter selective NMR images (T1, T2, T1 rho-images), are described in detail and the methods required for the data analysis are explained. A special emphasis is put on the analysis of experimental errors within the framework of NMR-imaging. In order to make parameter selective images generally useful their information should be correlated to material properties, so that images of the material properties can be obtained. This is demonstrated for the case of crosslink density, which is certainly one of the molecular properties in rubber materials, exhibiting the main influence on mechanical and other material properties. Sulfur cured and carbon black filled technical rubbers with different degree of crosslink density and oxidative aging were investigated using parameter selective in aging techniques. The image data were analyzed by means of gaussian and multiexponential fitting procedures, revealing spatially resolved NMR relaxation parameters. The further interpretation of these parameters was based on physical models describing molecular motions in crosslinked polymers.