The Analysis of Pigment Dispersion in Rubber by Means of Light Microscopy, Microradiography, and Electron Microscopy

Abstract

Abstract The significance of these dispersion studies can be summarized as follows: 1) A simple but highly versatile liquid nitrogen freeze technique makes it possible to microtome pigment loaded rubber stocks into thin (0.05–0.1 microns, e.g.) cross sections for examination by means of light microscopy, microradiography or electron microscopy. All of the common elastomers including polybutadiene and silicone rubber have been successfully sectioned for each of these techniques. Thus the state of dispersion can readily be traced from coarse pigment agglomerates, a few hundred microns in size, down to the ultimate particles which can be below 20 millimicrons. 2) Through the use of one of the techniques described or by the coordinated use of all of them (“dispersion in depth”), most dispersion problems can be resolved. A very complete analysis of this type is often necessary to explain pigment effects upon reinforcement. 3) The effects of varied dispersion quality can now be studied directly using special x-ray and electron microscope tensile specimen holders with which small rubber specimens can be examined under strain. Actually these procedures have a greater scope than simply measuring dispersion. The reinforcing capabilities of different pigments in a variety of polymers may be compared by the use of these techniques.