NR-OMt nanocomposites

Morphological analysis of NR-OMt nanocomposites. (Reproduced with permission of John Wiley and Sons.)... 

Much effort has gone into preparing rubber-clay nanocomposites based on NR as described in the earlier section. However, the dispersion of such nanoclays in non-polar NR matrices was very poor. In this section we would like to outline the preparation and characterization of NR-clay nanocomposites in the presence of certain eompatibilizers added into the system externally. For instance, Teh et al. prepared NR-OMt nanocomposites by a melt compounding method. ENR 25 and ENR 50 were used as compatibilizers. Pristine MMT was modified with oetadecyltrimethylamine and abbreviated as MMT-ODTMA. The amount of organoclay was only 2 phr while the amount of ENR was varied. NR-MMT-ODTMA showed mostly intercalated structure of the... 

In a study by Modhusoodanan et al.y nanocomposites based on NR and organomodified clay were produced by melt-mixing technology. The dispersion of these silicates was studied by XRD and TEM (Figure 8.9). The greatest interlayer distance (3 nm) was observed in the case of OMt-filled NR nanocomposites. 

The effectiveness of organoclay in NR was observed and reported by Carli et They evaluated the technical feasibility of NR nanocomposites with Cloisite 15A, a commercial organoclay to substitute conventional silica (Si02) filler. TEM analysis indicated that the OMt was homogeneously dispersed in the rubber matrix. A shift of the characteristic peaks to lower angles was observed in XRD, attributed to the intercalation of the OMt by macromolecular rubber chains. Based on the mechanical properties of the compounds they concluded that 50 phr of silica can be replaced by 4 phr of OMt with a reduction in the filler content by 12.5 times, without adversely affecting the tensile properties of the final material even after ageing. 

TEM investigation was carried out to examine directly the intercalation of rubber chains and the state of dispersion of the EOMt into the NR matrix. Figure 8.17 shows TEM micrographs of NR nanocomposites with both OMt and EOMt. The thickness of most EOMt tactoids was 7-8 nm and the length about 80-200 nm and these numbers were invariant to the EOMt loading. 

The achievement of a high degree of exfoliation of layered clay minerals in nonpolar rubber matrices, such as NR, is still a major issue. This chapter presents a brief overview of studies of clay reinforcement in NR both in micro and nano scale. Although quite a lot of studies have been reported in the field of NR reinforcement with simple organoclay (OMt), plenty of scope still exists to improve the dispersion of MMT followed by property enhancement. Better dispersion and improvement in dilferent properties was observed in the case of EOMt-filled NR nanocomposites. 

---