Effect of organoclay reinforcement on the properties of styrene-butadiene rubber

Figure 2 :- TEM images of (a) unmodified clay and (b-d) modified clay with DBSA,NPE and mixed DBSA/NPE surfactants, at a magnification of 25,kx.

TEM images of (a) unmodified clay and (b-d) modified clay with DBSA,NPE and mixed DBSA/NPE surfactants, respectively. Figure 2(a) showed unsatisfactory aggregation of silicates. The result is thought to be the phenomenon caused by the reaggregation between polar silicates. The particle size of the agglomerated particles lies in between 135-226 nm. Contrary to the result it was possible to observe nanostructure of silicate in the prepared organoclays as shown in Figure 2 (b-d). It is considered to be the result of using DBSA as anionic surfactant with respect to the nonanionic NPE surfactant. The surfactant anions enter the interlayer space as ion pairs with protons (H3O+ions). This led to less polar surface of silicate and consequently the lowering of silicate-silicate interaction. Organically modified clay with mixed surfactants was found to have the least average particle size (i.e. 4nm) as observed in Figure 2(d) with better rubber-filler interaction. Such pattern was well correspond to the result of increased d-spacing of silicates by the used surfactants as compared with unmodified clay, as previously observed at the XRD data in Figure 1(a). Thus, TEM provided evidence of surfactant intercalation inside the clay galleries.