Organoclay layer separation

VanderHart and co-workers [37] used solid-state NMR ( H C) spectroscopy for the first time as a tool to study the morphology, surface chemistry and to a very limited extent the dynamics of exfoliated PCN. This method uses the reduction in the spin-spin relaxation time,, of a nanocomposite when compared with the neat system, as an indicator for the organoclay layer separation. It was shown that the paramagnetic Fe " ions in the crystal lattice of the montmorillonite provide an additional relaxation mechanism of the protons. The additional relaxation depends on average Fe - H distance, which is determined by clay concentration and dispersion of clay in the matrix. 

X-ray diffraction (XRD) was used to measure the organoclay layer separation after compounding. An X-ray unit from Pan Analytical was used with CuXa as the X-ray source. 

It is observed from this figure that there are a lot of small dark lines preferably oriented in a north-south direction. Here, the organoclay is distributed evenly in the whole rubber matrix. Some small dark clusters are shown enlarged in Fig. 29b. These structures are formed due to the separation of the polar XNBR phase from the nonpolar S-SBR matrix. Furthermore, exfoliated layers of organoclay are visible in the interface between the two polymer phases, which obviously promotes a better compatibility between XNBR and S-SBR phases. Figure 29c displays the ... 

Aliphatic polyester layered silicate nanocomposites based on poly(e-caprolactone) (PCL) and on plasticized poly(L-lactide) (PLA) have been prepared first by melt blending of the respective polymer matrix with different (organo-modified) montmorillonites. It has been demonstrated that melt blending with organo-modified clay such as Cloisite 20A, 25A or SOB, yields intercalated nanocomposites with the possibility of partial exfoliation. Even at low organoclay content, substantial improvement of thermal stability, gas barrier properties and physical-mechanical performances have been noticed. However, melt blending of natural montmorillonite with PCL or neat (non plasticized) PLA leads to microphase-separated compositions. 

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