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Conditions were established for dispersing clay nanolayers into both cis-1,4-polyisoprene (synthetic) natural rubber (NR) and epoxidized natural rubbers (ENR) having 25 or 50 mol % epoxide. The clay was a sodium montmorillonite and was used as a pristine layered silicate or as organically modified layered silicates to make the galleries more hydrophobic and thus more compatible with the elastomers. The chemical modifications were carried out using an ion-exchange reaction with alkyl ammonium cations. Incorporation of the clays into the elastomers was achieved by mixing the components themselves in a standard internal blender or by mixing dispersions of them in toluene or methyl ethyl ketone. X-ray diffraction results indicated intercalation of NR and ENR into the silicate interlayers, followed by exfoliation of the silicate layers into the elastomer matrices. Of primary interest was the effect of the intercalated and exfoliated clays on the mechanical properties of the elastomers. The reinforcing effects obtained were found to depend strongly on the extent of the dispersion of the silicate layers into the rubber matrices.

Interfacial tensions (IFT) between low salinity surfactant solutions of sodium dodecylbenzenesulfonate (SDBS) and sodium dioctylsulfosuccinate (Aerosol OT or AOT) and different oil phases were measured using the spinning drop method. The oil phases were either n-heptane, a 1:1 mixture of n-heptane and toluene or crude oils. The IFT was strongly affected by variation of the salinity and especially by the presence of calcium. IFT values between SDBS solutions and heptane, as well as all four crude oils, decreased when adding sodium and calcium. IFTs down to 32 μN/m for crude oil were measured in the presence of AOT solutions with low salinity electrolyte. In the IFT region below 1 mN/m the presence of small amounts of calcium could lower the IFT by more than 1 order of magnitude compared to solutions containing only sodium chloride with the same ion strength.

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