ABSTRACT: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. [doi:10.1295/polymj.PJ2006085] KEY WORDS Organoclay / Rubber / Stearic Acid / Intercalation / Nanocomposites / Since the researchers at Toyota central research laboratories successful prepared PA6/clay nanocomposites for the first time, 1 as a new kind of materials, polymer/clay nanocomposite have caught much attention through the world. Compared with pure materials and traditional composites, polymer/clay nanocomposites exhibit increased modulus and strength, improved heat resistance, outstanding gas barrier properties, and decreased flammability.
2-4For rubbers/layer nanocomposite, there are mainly three kinds of preparation methods: latex, 5 solution 6 and melt compounding.
7Considering industrialization, melt compounding is one of the feasible preparation techniques, in which polymer is directly intercalated into organoclay (OC) in the molten state to prepare nanocomposites. The driving force of the intercalation is determined by physical and/or chemical interactions between polymers and OC.At the same time, as one of the widely used and fast growing synthetic rubbers, Ethylene-propylene-diene terpolymer (EPDM) finds applications in automotive weather-strapping and seals, radiator, electrical insulation, roofing membrane, tubing, belts, and other general-purpose applications because of its excellent resistance to heat, oxidation, ozone, weathering, and microbial attack, attributed to the stable and saturated polymer backbone structure. 8 This motivated us to develop rubber/clay nanocomposites based on EPDM.For nonpolar saturated EPDM matrix, the functional oligomers, with polar telechelic groups as a compatibilizer, e.g., EPDM grafted by maleic anhydride [9][10][11] or glycidyl methacrylate, 12 were used to improve the interfacial interaction. In addition, there are hydroxyl groups 13,14 on the surface of clay layer, carboxylic acids have been used to intercalate into clay gallery to modify the clay. 1,15 Stearic acid (SA), usually used as a kind of additives for rubber sulfur vulcanization, is an acidic ingredient like maleic anhydride, and c...