Role of stearic acid in preparing EPDM/clay nanocomposites by melt compounding

EPDM/organic clay (OC) nanocomposites were prepared by melt blending. XRD results showed that if OC mixed with EPDM matrix, macromolecule chains are difficult to intercalate into the layers while stearic acid (SA) could easily intercalate into the OC interlayers under pretreating conditions (S-OC) and expand the interlayer spacing 2.6 nm of OC to a wider distance of 3.9 nm; EPDM could not further expand the distance of S-OC during the followed mixing process and the structure SA intercalating into OC is kept. TEM observation showed S-OC improved the dispersion of OC in EPDM, and FT-IR results indicated the esterification reaction occurred between carboxyl groups of SA and hydroxyl groups of OC, which was believed to be the driving force of SA intercalation. The tensile strengths of the nanocomposites are improved with increasing amount of SA, and the stresses at low strain are almost the same, due to the physical interaction between OC and EPDM macromolecules.