Polymer/clay-based nanocomposites

In the past decade, clay-based polymer nanocomposites have attracted considerable attention from the research field and in various applications. This is due to the capacity of clay to improve nanocomposite properties and the strong synergistic effects between the polymer and the silicate platelets on both a molecular and nanometric scale [2,3], Polymer-clay nanocomposites have several advantages (a) they are lighter in weight than the same polymers filled with other types of fillers (b) they have enhanced flame retardance and thermal stability and (c) they exhibit enhanced barrier properties. This chapter focuses on the polymer clay-based nanocomposites, their background, specific characteristics, synthesis, applications and advantages over the other composites. 

Condesation polymer-MMT based nanocomposites were formed, while polymerizing bifunctional monomers in the presence of organophilic modified clay containing active groups capable of forming a bond between the clay and... 

The most commonly studied polymer nanocomposites are clay-based nanocomposites, mainly with montmorillonite (MMt) as layered silicate filler (Scheme 15.12). Upon incorporation of organomodihed clays (organoclays) into a polymer matrix, two nanomorphologies (Scheme 15.13) can be obtained, either intercalation of the polymer chain in between the clay platelets keeping the stacking of the sheets, or exfoliation of the clay platelets with a disordered dispersion of the inorganic sheets in the polymer. 

Besides clay-based nanocomposites, there has been huge discussion on the metallic and semiconductor-based hybrid materials. The ability of polymer materials to assemble into nanostructures describes the use of polymers providing exquisite order to nanoparticles. Finally, a discussion on potential applications of polymer—nanoparticle composites with a special focus on the use of dendrite polymers and nanoparticles for catalysis should follow (Polymer-Nanoparticle Composites Part 1 (Nanotechnology), 2010) (Figure 1.15). 

H. Sh. Xia, M. Song, Characteristic length of dynamic glass transition based on polymer/clay intercalated nanocomposites. Thermo. Acta 2005, 429, 1. 

Paul and Robeson [35] have reviewed polymer nanotechnology including a study of polymer matrix-based nanocomposites and exfoliated clay-based nanocomposites. 

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... 

In the chapter Dispersion of Inorganic Nanoparticles in Polymer Matrices Challenges and Solutions, the synthesis, properties, and applications of nanoparticles their surface modification and preparation of polymer-inorganic nanocomposites are reviewed in detail. The chapter Recent Advances on Fibrous Clay-Based Nanocomposites reviews recent results on nanocomposite materials derived from the fibrous clay silicates sepiolite and palygorskite and combined with diverse types of polymers, from typical thermoplastics to biopolymers such as polysaccharides, proteins, lipids, and nucleic acids. The chapter Nanohybrid Materials by Electrospinning highlights recent progress and current issues in the production of... 

Recent developments in polymer nanotechnology include the exfoliated clay nanocomposites, CNTs, carbon nanofibers, exfoliated graphite, nanocrystalline metals, and a host of other filler modified composite materials. Polymer matrix-based nanocomposites with exfoliated clay are discussed in this section. Performance... 

The present chapter is devoted mainly to the phase morphology reported for silicate clay-based nanocomposites. Many of the selected TEM photomicrographs show exfoliated and intercalated states of clay in various polymer matrices. 

Paul and Robeson et al. [139] have published an extremely informative review on the properties of exfoliated nanoclay-based nanocomposites. These have dominated the polymer literature, but there are a large number of other significant areas of current and emerging interest. This review details the technology involved with exfoliated clay-based nanocomposites and also includes other important areas, such as barrier properties, flammability resistance, biomedical applications, electrical/electronic/optoelectronic applications, and fuel cell interests. The important question of the nanoeffect of nanoparticles or fiber inclusion relative to their large-scale counterparts is addressed relative to crystallization and glass transition behavior. Other polymer (and composite)-based properties derive benefits from the nanoscale filler or fiber addition, and fhese questions are addressed. 

Composites are widely used in such diverse areas as transportation, construction, electronics and consumer products. They offer unusual combinations of stiffness, strength and weight that are difficult to attain separately from the individual components. The advent of nanoscience and nanotechnologies has continuously provided the impetus pushing for the development of materials with fascinating properties and a rich variety of applications. Polymer-clay (PC) nanocomposites represent a new class of materials based on reinforcement of polymeric materials by dispersion of nano-scale clay particles at molecular level in the polymer matrix. Because of their nanometer size features, nanocomposites possess unique properties typically not shared by their more conventional miaocomposite counterparts and therefore offer new technology and business opportunities. 

The phyllosilicate particles present a very high aspect ratio of width/thickness, in the order of 10-1000 and the complete exfoliation of the layered silicate in the polymer matrix is the main goal for the successful development of clay-based nanocomposites. For very low concentrations of particles, the total interface between polymer and layered silicates is much greater than that in conventional composites. Depending on the strength of the interfacial interaction, four types of morphology are possible in nanocomposites (Fig. 2) [24] ... 

So far, most polymer nanocomposites contain only one type of nanofiller. Recent studies revealed that combination of clay and Si02 has a more enhanced effect on the polymer matrix. In this chapter, we discuss the structure and properties of clay- and silica-based polymer nanocomposites prepared by in situ emulsion polymerization, especially polyacrylonitrile (PAN)-clay-silica ternary nanocomposites. The chapter consists of three parts (1) synthesis and structure of polymer-clay-silica nanocomposites (2) thermal properties of polymer-clay-silica nanocomposites and (3) mechanical properties of polymer-clay-silica nanocomposites. 

Many different polymers have already been used to synthesize polymer-clay nanocomposites. In this section, an overview of the advances that have been made during the last 10 years in the intercalation and the delamination of organoclay in different polymeric media is given. The discussion mainly covers the work involving thermoset nanocomposites along with a brief discussion about thermoplastic-based nanocomposites. 

PP is probably the most thoroughly investigated system in the nanocomposite field next to nylon [127-132]. In most of the cases isotactic/syndiotactic-PP-based nanocomposites have been prepared with various clays using maleic anhydride as the compatibilizer. Sometimes maleic anhydride-grafted PP has also been used [127]. Nanocomposites have shown dramatic improvement over the pristine polymer in mechanical, rheological, thermal, and barrier properties [132-138]. Crystallization [139,140], thermodynamic behavior, and kinetic study [141] have also been done. 

Darder, M. and Ruiz-Hitzky E. (2007) in Clay-Based Polymer Nanocomposite, Clay Minerals Society, Vol. 14... 

Concerns regarding the toxicity and environmental effects of polymer-based nanocomposites, such as those derived from clay nanoparticles or carbon nanotubes, throughout their life cycle, from formulation, polymerisation, compounding, fabrication, use, disposal and degradation, are described. The potential of nanoparticles to enter the body by skin contact or inhalation is discussed. Accession no.927669... 

The effect of polymer-filler interaction on solvent swelling and dynamic mechanical properties of the sol-gel-derived acrylic rubber (ACM)/silica, epoxi-dized natural rubber (ENR)/silica, and polyvinyl alcohol (PVA)/silica hybrid nanocomposites was described by Bandyopadhyay et al. [27]. Theoretical delineation of the reinforcing mechanism of polymer-layered silicate nanocomposites has been attempted by some authors while studying the micromechanics of the intercalated or exfoliated PNCs [28-31]. Wu et al. [32] verified the modulus reinforcement of rubber/clay nanocomposites using composite theories based on Guth, Halpin-Tsai, and the modified Halpin-Tsai equations. On introduction of a modulus reduction factor (MRF) for the platelet-like fillers, the predicted moduli were found to be closer to the experimental measurements. 

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