Rubber nanocomposites grafting

Work done by Gong et al. [66] is similar to the work by Maruyama et ah, above. They functionalize butyl rubber with succinic anhydride to improve the compatibility of butyl rubber with an organoclay. Barrier performance of the rubber nanocomposite increases with the amount of succinic anhydride modification. In a companion publication [67], butyl rubber is functionalized by grafting maleic anhydride onto the polymer chain with peroxide. The same organoclay is utilized in this work as well to form the rubber nanocomposite. Barrier performance of the butyl rubber is significantly enhanced. 

This is another important and widely used polymer. Nanocomposites have been prepared based on this rubber mostly for flame-retardancy behavior. Blends with acrylic functional polymer and maleic anhydride-grafted ethylene vinyl acetate (EVA) have also been used both with nanoclays and carbon nanotubes to prepare nanocomposites [65-69]. 

TPV nanocomposites of LLDPE/reclaimed rubber with nanoclay and 1 wt.% MA-grafted PE and curative were prepared using a Brabender internal mixer at 170°C (Razmjooei et al., 2012). Contents of the reclaimed rubber, nanoclay, and compatibilizer were varied up to 30, 7, and 21 wt.%, respectively. The blends without the compatibilizer were also prepared. Morphological, thermal, and mechanical properties of the nanoclay-reinforced TPV nanocomposites indicated intercalation and partial exfoliation by the high-shear stress during mixing with the reclaimed rubber. Vulcanization of rubber phase led to an increase of viscosity. The size of rubber particles in TPV was reduced with the addition of nanoclay and compatibilizer. 

High impact polystyrene (HIPS) is a blend of PS that has been polymerized in the presence of polybutadiene. This leads to PS chains with grafted polybutadiene, as well as some free PS and PB, and the resultant polymer blend has improved impact strength. HIPS/MMT nanocomposites were formed though in-situ bulk polymerization in the presence of polybutadiene [86]. Intercalated nanocomposites with improved thermal stabihty were formed although the dispersion was different in the PS matrix phase compared to the rubber phase. 

Among the clay nanocomposites, MC (fully maleic anhydride grafted IIR mixed with clay at 5 phr) had the highest number of stable bonds. Figure 9 also shows the increase in the number of stable bonds (increased Payne effect) with the rate of grafting and amount of MA-g-llR (maleic anhydride grafted HR). This is attributed to the increased specific surface area with the increase in MA-g-IIR content, which can improve the number of bonds and thus the filler-rubber bond formation. The same conclusion was drawn from the analysis of the unstable bonds as well. 

Chow WS, Abu Bakar A, Mohd Ishak ZA, Karger-Kocsis J, Ishiaku US. Effect of maleic anhydride-grafted ethylene-propylene rubber on the mechanical, rheological and morphological properties of organoclay reinforced polyamide 6/polypropylene nanocomposites. Eur Polym J 2005 41 687-96. 

In recent years, some works have focused on the possibility of using silica nanoparticles as a com-patibilizer for polymer blends. Blends of PP and dynamically vulcanized EPDM rubber are called TPVs. Wu et al. [114] prepared nanocomposites of TPV/SiOj. The CTAB-treated SiO was melt-blended with TPV in the presence of MA grafted PP (mPP), which acted as a function ized com-patibilizer. During melt blending, CTAB and mPP tethered themselves onto the TPV backbone by a grafting reaction. The strong interaction caused by the grafting reaction improved the dispersion of silica in the TPV matrix. 

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