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Measurements of linear swelling in solvent of small test pieces provide a useful means of investigating anisotropy in vulcanized products and components whose small size precludes the use of conventional tests on dumbbells, etc. Anisotropy has been found to be present in molded components. The extent of this is related to the material flow in the mold before or during vulcanization. There also appears to be an effect of flow on crosslink density. In this preliminary investigation the contribution of each of the various factors, e.g., filler- filler structure, polymer gel, polymer-filler interaction, tendency to prevulcanize, has not been established.

A procedure is described for the identification and semi‐quantitative estimation of plasticizers in the mixtures commonly used in the formulation of plastics, especially polyvinyl chloride. It involves chromatographic separation followed by infra‐red spectroscopy.

A test for estimating the dispersion of carbon black in rubber compounds is described. It works by examining the freshly cut surface of a specimen at low magnification in dark field illumination. Roughness of the surface related to the presence of carbon black causes increased reflection under dark field illumination. The illumination of each field of view is examined as 100 subdivisions and the relative values of these readings give a numerical estimate of the dispersion. Details of how this is done and the corrections applied to the results are described. A second paper reports some initial results obtained with the test. The test works well for certain elastomers, notably NR and SBR. The biggest advantage of the test is its ability to work rapidly and cheaply on small zones at relatively high magnification. This opens up the possibility of detailed studies of macroscopic variations in dispersion, done in reasonable times and at reasonable costs.