Melt compounding/intercalation nanocomposites

The morphology of rubber-based nanocomposites also seems to change in the presence of compounding ingredients [89, 90]. HNBR, when melt-compounded with organo-modified sodium montmorillonite clays (o-MMTs) prior to sulfur curing, resulted in the formation of nanocomposites with exfoliated or intercalated structures. In stark contrast, under similar conditions HNBR compounded with unmodified sodium montmorillonite clays (NA) formed microcomposites [90]. This was traced to its reactivity with the sulfur in the presence of amine-type organomodifiers. 

Intercalated and partially exfoliated PVC-clay nanocomposites were produced by melt blending in the presence and absence of DOP and characterised by X-ray diffraction and transmission electron microscopy. The effects of various factors, including volume fraction of clay, plasticiser content, melt compounding time and annealing, on nanocomposite structure and the thermal and mechanical properties of the nanocomposites were also examined. It was found that the best mechanical properties were achieved at 2% clay loading and 5 to 10% DOP loading. 18 refs. 

Pluta [49] studied the structure and properties of PLA/MMT nanocomposites and showed an effective enhancement of MMT dispersion with prolongation of the blending time (from 6 to 30 min). They stressed that this was possible due to strong interaction between PLA-MMT and shearing forces during melt compounding. The nanostructure was induced by the intercalation followed by tactoids formation and exfoliation of MMT, as confirmed by TEM analysis and XRD. The studies performed also clearly revealed the influence of MMT s dispersion in the PLA matrix on the physical properties of the nanocomposites formed as the improved MMT s dispersion (at their constant concentration) had increased the thermal stability of the nanocomposites under oxidative and nonoxidative conditions was improved with MMT s dispersion. Besides that, the crystallization ability of PLA also improved with incorporation of MMT. 

As the hydrophilic clay is incompatible with polypropylene, compatibilization between the clay and PP is necessary to form stable PP nanocomposites. There are two ways to compatibilize the clay and PP. In the first approach, the enthalpy of the interaction between the surfactant and the clay is reduced. In the second approach, a compatibilizer, such as maleic anhydride grafted PP (PPgMA) can be used( Manias et al.,2001). The clay is melt compounded with the more polar compatibilizer to form an intercalated master batch. The master batch is then compounded with the neat PP to form the PP nanocomposite. 

Polymer nanocomposites are generally prepared by three methods solution intercalation, in-situ polymerisation or melt compounding. 

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... 

Several methods including melt compounding, solution-based process, and in-situ polymerization could be used for the preparation of PET/clay nanocomposites. In-situ polymerization involves swelling of clays in a liquid monomer, or a monomer solution, followed by polymerization initiated thermally or by the addition of a suitable compound in the presence of intercalated/exfoUated days. It is considered as one of the best methods to produce polymer nanocomposites based on day because relativdy small-sized monomers could be easily intercalated into day layers before polymerization. Then, further polymerization between days could easily lead to weU-dispersed clay in the polymer matrix. Furthermore, day could be added into the redpe for the polymerization process thus, no further process is needed to reahze industrial application. 

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