Molecular weight effect exfoliated

Alexandre et al. [98] reported the preparation of PE/clay nanocomposite using Ti-based constrained geometry catalyst (CGC) catalyst. The MMT and hectorite were initially treated with TMA-depleted MAO and then intercalated with the CGC catalyst. Finally, addition of ethylene resulted in the formation of high molecular weight and exfoliated PE/clay nanocomposites. The vinyl groups were chemically linked to the sDicate surface when copolymerized was carried out with ethylene inside the clay galleries using the nickel catalyst (Fig. 9). This method not only results in the effective exfoliation of the layered silicate but also in polyethylene chains that are chemically bonded to silicate surface. 

Blends made by extrusion have created difficulties and show a degradation of the molecular weight with development of colour. Processing leads to more exfoliation of platelets in the clay that causes two competing effects. A reduction of the peak heat release rate (HRR) because of the exfoliated platelets, versus degradation processes that increase the peak HRR. The dominant effect in low ash and/or low shear situations is reduction of peak HRR. The opposite is true with high ash or high shear since the peak increases. 

D-B transition temperature, and the effect of elastomer MFI on the D-B transitirMi temperature becomes less prominent with the increased PP molecular weight as seen in Fig. 17.18. The nanocomposites based on the high-octene-content elastomer ( 39 wt%) also lead to a lower D-B transition temperature compared with nanocomposites based on the elastomer with low octene content ( 28 wt%). The toughening mechanism was not explored for this system a more detailed study in this area would further enhance the understanding of the role of organoclay in elastomer-toughened nanocomposites with partially exfoliated clay particles. 

The extent of nanofiller dispersion and matrix properties have a significant effect on the overall blend properties, for example, highly exfoliated MMT particles in the polyamide matrix can make it brittle, whereas partially exfoliated clay particles in extruder-made thermoplastic olefin nanocomposites can lead to significant improvements in impact strength depending on the PP molecular weight and elastomer MFI. 

Fornes et al. [8] studied the effectiveness of an extensive array of quaternary ammonium ion surface treatments on montmorillonite in regard to exfoliation efficiency in the higher and lower molecular weight nylon 6... 

Pandey, R.B. and Farmer, B.L. (2008) Exfoliation of a stack of platelets and intercalation of polymer chains Effects of molecular weight, entanglement, and interaction with the polymer matrix. J. Polym. Sci. Part B Polym. Phys., 46, 2696-2710. 

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