Melt compounded epoxidized natural rubber/layered silicate nanocomposites: structure-properties relationships

Epoxidized natural rubber (ENR)-layered silicate composites were produced by melt compounding and sulfur curing. Pristine (sodium bentonite and sodium fluorohectorite) and organophilic modified silicates (organoclays with primary amine and quaternary ammonium modifications) were introduced in 10 parts per hundred rubber (phr) in the recipes and their effect on the curing and (thermo)mechanical properties determined. The dispersion state of the silicates was studied by X-ray diffraction and transmission electron microscopy. Fastest curing and best mechanical properties were found for the ENR containing the organoclay with primary amine modification. This organoclay was partly exfoliated, partly intercalated and partly confined (reaggregated). Due to the high shearing during compounding the pristine fluorohectorite was also intercalated by ENR. The complex dispersion state of the layered silicates was well reflected in the glass transition relaxation, which showed multiple peaks. Intercalation/exfoliation of the silicates were best displayed in stiffness- and strength-related mechanical parameters.