Polymer Nanocomposites silica nanotubes

PDMS nanocomposites with layered mica-type silicates were also reported.374 A two-step sol-gel process of the in situ precipitation of silica led to the development of siloxane-based nanocomposites with particularly high transparencies.3 5 Some unusual nanocomposites prepared by threading polymer chains through zeolites, mesoporous silica, or silica nanotubes were reviewed.3 6 Poly(4-vinylpyridine) nanocross-linked by octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane was reported.377... 

Nanofillers may be nanoclays, carbon nanotubes (single or multiwall) (CNTs), silica, layered double hydroxides (LDHs), metal oxides, etc., offering the promise of a variety of new composites, adhesives, coatings, and sealant materials with specific properties [32-37]. Among the fillers mentioned, nanoclays have attracted most of the academia and industry interest, due to their abrmdance as raw materials and to the fact that their dispersion in polymer matrices has been studied for decades [38]. In fact, there are three major polymer nanocomposites categories in terms of nanofiller type that are expected to compile the global nanocomposites market in 2011 nanoclay-reinforced (24%), metal oxide-reinforced (19%), and CNTs-reinforced (15%) ones [39-41]. 

Over the last 2 decades, there has been an increasing interest in the development of one-dimensional nanomaterials, such as carbon nanotubes (Ounaies et al., 2003), bacterial nanofibers (Yano et al., 2005), silica nanotubes (Miyaji et al., 2003), and titanium dioxide nanotubes and nanowires (Yuan and Su, 2004). These new materials have relatively large specific surface areas and high aspect ratios hence, they are suitable for use as reinforcements, chemical probes, sensors, hydrogen storage, displays, and templates. One-dimension material/polymer nanocomposites allow us to take advantage of the extraordinary properties of one-dimension nanomaterials. 

The term polymer nanocomposite (PNC) has evolved, since the first reports in the early 1990s to refer to a multicomponent system, where the major constituent is a polymer or blend thereof and the minor constituent exhibits a length scale below 100nm [1-3], The minor constituent is usually an inorganic filler, called nanofiller, nanoload, or, improperly, nanoparticle. The most commonly used are layered silicates (clays), carbon nanotubes (CNTs), and metals and various metal oxides (silica, titania, zirconia, zinc oxide, etc.). 

Polymer nanocomposites represent a rapidly expanding research area. Nanocomposites refer to a class of reinforced polymer with a low percentage of well dispersed nanopartieles. These materials often demonstrate notable improvement in properties such as mechanic characteristics, tensile strength, heat and chemical resistance. Nanoparticles can be classified based on how many dimensions are on the nanoscale. The first type is plate-like (e.g. nanoclays) that has a thickness in the nanometer range and lateral dimensions in the sub-micron or micron range. Two types of nanoclay, 20A (Southern Clay) and MHABS (a surface modified clay 20A), are used in our research. The second type has two dimensions in the nanometer range, such as carbon nanofibers (CNF) or carbon nanotubes. The third type has three dimensions in the range of nanometer, such as spherical silica particles. The latter type of nanoparticle is not used in our study. 

Based on their dimensions, which are in the nanometre range, three types of fillers can be distinguished. Isodimensional nanoparticles (NP), such as spherical silica NP have three nanometric dimensions. Nanotubes or whiskers are stretched constructions in which two dimensions are in the nanometre range and the other dimension is larger. When only one dimension is in the nanometre range, the composites are termed polymer-layered crystal nanocomposites, and are obtained by the complete intercalation of the polymer inside the galleries of layered host crystals [2]. 

The wide assortment of polymer systans (polypropylene, poly(methyl methacrylate) [PMMA], polyepoxide, polystyrol, PC, etc.) is used as a polymeric matrix for nanocomposites production (Ray and Okamoto 2003). The most well-known fillers of polymeric matrix are nanoparticles (silica, metal, and other organic and inorganic particles), layered materials (graphite, layered aluminosilicates, and other layered minerals), and fibrous materials (nanofibers and nanotubes) (Thostenson et al. 2005). Nanocomposite polymer materials containing metal or metal oxide particles attract growing interest due to their specific combination of physical and electric properties (Rozenberg and Tenne 2008, Zezin et al. 2010). Nanocomposites on the base of layered materials... 

In the last decade, considerable progress was observed in the field of PO/compatibil-izer (predominantly on the base of PO-g-MA)/organo-surface-modified clay nanocomposites. Polyethylene (PE), polypropylene (PP), and ethylene-propylene (EP) rubber are one of the most widely used POs as matrix polymers in the preparation of nanocomposites [3,4,6,30-52]. The PO silicate/silica (other clay minerals, metal oxides, carbon nanotubes, or other nanoparticles) nanocomposite and nanohybrid materials, prepared using intercalation/exfoliation of functionalized polymers in situ processing and reactive extrusion systems, have attracted the interest of many academic and industrial researchers because they frequently exhibit unexpected hybrid properties synergisti-cally derived from the two components [9,12,38-43]. One of most promising composite systems are nanocomposites based on organic polymers (thermoplastics and thermosets). 

The addition of nanoparticles to synthetic rubber resulting in enhancement in thermal, stiffness and resistance to fracture is one of the most important phenomena in material science technology. The commonly used white filler in mbber industry are clay and silica. The polymer/clay nanocomposites offer enhanced thermo mechanical properties. Bourbigot et al. observed that the thermal stability of polystyrene (PS) is significandy increased in presence of nanoclay [75]. Thermal and mechanical properties of clays multiwalled carbon nanotubes reinforced ethylene vinyl acetate (EVA) prepared through melt blending showed synergistic effect in properties [76]. 

The development of nanoparticles with different sizes and shapes, including spherical particles such as silica, platelets such as layered silicates, and carbon nanotubes have been used as fillers in elastomeric matrices to improve their properties like mechanical and barrier. The interaction of the polymer chains with the filler particles is also cmcial in controlling the performance of nanocomposites. 

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