Clays organo modifier

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. 

On the other hand, Bhattacharya et al. have reported the plasticization effect of organically modified layered silicates on dynamic mechanical properties [13]. In this work, nanocomposites of SBR have been prepared using various nanofillers like modified and unmodified montmorillonite, SP, hectorite etc. It has been observed that the Tg shifts to lower temperature in all the nanocomposites, except for systems from hectorite and NA. This is due to the fact that clay layers form capillaries parallel to each other as they become oriented in a particular direction. Due to wall slippage of the unattached polymer through these capillaries, the Tg is lowered, which could be even more in the absence of organo-modifiers [13]. A similar type of plasticization effect is also noted in the case of the low... 

The clay is first dispersed in water or an aqueous system (to form a suspension) and the modifier that has been pre-dissolved in water (or an aqueous system) is then gradually (drop-wise) added to the clay suspension. The organo-modifier will be anchored onto the surface of the clay platelets immediately after it is added but further stirring for some more time up to a few hours may be needed to achieve homogeneous and complete ion exchange. Some representative modifiers (in both cationic and anionic form) that have been used as surface treatment for the clays in the literature are shown in Figure 11.9. 

Figure 2.2 Schematic illustration of exfoliated organo-modified clays with immobilized enzyme molecules.

Pluta et al. investigated PLA/MMT nanocomposites by studying the dispersions of modified and unmodified MMT prepared by melt blending. XRD showed that the good affinity between the organo-modified clay and the PLA was sufficient to form an intercalated structure in the nanocomposite. TGA showed that... 

The two factors shown below affect the physical properties of a polypropylene clay nanocomposite made by compoimding polypropylene and organo-phiUc clay using modified polypropylene as a compatibihzer [16,36]. They also affect the dispersibility of sihcate layers in this nanocomposite ... 

The knowledge of the angle 20 helps to define the size of the pack of the aluminous silicate consisting of the clay layer and interlayer space. The size of such pack increases in a row from initial silicate to polymeric nanocomposite according to the increase in the interlayer space. The average size of that pack for montmorillonite is 1.2-1.5 nanometers but for organo-modified one varies in the range of 1.8-3.5 nanometers. 

Richards, S. Bouazza, A. (2007). Phenol adsorption in organo-modified basaltic clay and bentonite. Applied Clay Science, vol. 37, pp. 133-142. ISSN 0169-1317. 

The DSC curves for thermoset epoxy with different weight fraction of organo-modified nano-clay are shown in Figure 9.11. The onset temperature of the curing and the temperature of the exothermal peak for neat resin are 115°C and 155 C, respectively. The addition of 5 wt% nano-clay in epoxy matrix reduces the onset temperature to 84°C and peak exothermal temperature to 143°C. The catalytic effect of the nano-clay on the crosslinking reaction of epoxy resin is responsible for the reduction. 

Furthermore, the introduction of organo-modified clays in an epoxy resin was found to lead to the formation of a stronger interface with E-glass fibers, with an increase of the interfacial shear strength of around of 30% for a filler content of 5 wt% [11]. 

Finally, a further strategy to obtain stable and exfoliated polyolefin nanocomposites involves the use of an organo-modifier containing a terminal double bond. The comonomer anchored within the silicate layers of MMT allows one to graft the polymer chains to the clay. 

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