Layered silicates organic modification

Keywords Layered double hydroxides Layered silicates Nanocomposites Organic modification Reinforcement Rubber Rubber curatives... 

The nature of the changes in adsorption and separation properties of layer silicates with the expanding structural cell, caused by the modification, depends on the size of modifying organic cation. 

New methods to improve the separation properties of the organomontmorillonites can also be proposed. For example, it was shown in Section 4 that the introduction of Cs+ cations into the exchange complex of layer silicates, followed by the modification of the mineral by long-chain organic cations, results in the development of surface micropores on side faces of the adsorbent particles. This, in turn, leads to the increase of the adsorption sites, where the chromatographic separation of hydrocarbons takes place. 

Polyurethane/clay-based nanocomposites are already being used for automobile seats and it also exhibit superior flame retardancy. Phenolic resin impregnated with montmorillonite clay was already identified as the resin for manufacturing rocket ablative material with MMT. The nanolevel dispersion of clay platelets leads to a uniform char layer that enhances the ablative performance. The formation of this char was slightly influenced by the type of organic modification on the silicate surface of specific interactions between the polymer and the silicate platelets surface, such as... 

The results obtained on two sets of PA nanocomposites containing silicates with different organophilization confirmed published results that layered silicates promote the formation of the y modification of PA. Partial exfoliation was achieved with both fillers, the extent of which differed slightly in the two cases. The mechanical properties of the composites depend very much on the type of organic compound used for the treatment of the silicate. Stiffness and heat deflection temperatures increased with composition, the tensile strength increased compared to the neat polymer, but its composition dependence was completely different in the two cases. Deformability decreased with increasing filler content, while the composition dependence of the impact resistance was very dissimilar in composites containing... 

The first section of the book deals with the thermal stability of layered silicates and polymer nanocomposites. Chapter 1 provides an overview of layered silicates as fillers, organic surface modification of such layered silicates, and thermal stability considerations in relation to the surface modification molecules ionically exchanged on the filler surface. Chapter 2 provides in-depth information on the mechanisms of thermal degradation of layered silicates modified with ammonium and other thermally stable filler surface modifications. Chapter 3 provides the example of generating thermally stable polystyrene... 

These materials, unlike the other nanophase materials described in this chapter, are nano-sized in only one dimension and thereby act as nanoplatelets that sandwich polymer chains in composites. Mont-morillonite (MMT) is a well-characterized layered silicate that can be made hydrophobic through either ionic exchange or modification with organic surfactant molecules to aid in dispersion [5,23]. Polymer-layered silicates may be synthesized by exfoliation adsorption, in situ intercalative polymerization, and melt intercalation to yield three general types of polymer/clay nanocomposites. Intercalated structures are characterized as alternating polymer and siHcate layers in an ordered pattern with a periodic space between layers of a few nanometers [13], ExfoHated or delaminated structure occurs when silicate layers are uniformly distributed throughout the polymer matrix. In some cases, the polymer does not intercalate... 

Ray et al. [268] also found that the biodegradability of polylactides in bionanocomposites depends completely on both the nature of pristine layered sihcates and surfactants used for the modification of layered silicate. Based on this behavior, they reported that composite biodegradabihty can be controlled by a judicious choice of the organically modified layered silicate (OMLS). 

---