Effect of coupling agent on surface free energy of organic modified attapulgite (OAT) powders and tensile strength of OAT/ethylene-propylene-diene monomer rubber nanocomposites

Experimental measurements of tensile strength reveal that unmodified attapulgite has low reinforcing effect, and a dramatic increase of the tensile strength was observed as soon as the attapulgite was modified by coupling agent. When the coupling agent content was 3%, both Si-AT and Ti-AT had maximum tensile strength (16.86 MPa for Si-AT and 18.32 MPa for Ti-AT). When the coupling agent content was over 3%, the tensile strength began to decrease. Presumably, the fillers started to disrupt the mechanical integrity and continuity of the bulk rubber materials at high loading levels. The two curves of elongation at break exhibited reversed trends, indicating that silane could decrease elongation at break and titanate could increase elongation at break.