Nanocomposites polymeric, manufacturing

RECENT ADVANCES IN POLYMERIC NANOCOMPOSITES STRUCTURE, MANUFACTURE, AND PROPERTIES... 

Nanophase materials feature a three-dimensional structure and a domain size of less than 100 nm. They are usually produced by compaction of a nanoscale powder and are characterized by a large number of grain boundary interfaces in which the local atomic arrangements are different from those of the crystal lattice [11.2]. Nanocomposites, in contrast, consist of nanoparticles that are dispersed in a continuous matrix, creating a compositional heterogeneity of the final structure. The matrix is usually either ceramic or polymeric. Only the manufacturing of ceramic nanocomposites applies the principles of agglomeration (Section 6.7). 

Polymeric nanocomposites are a class of relatively new materials with ample potential applications. Products with commercial applications appeared during the last decade [1], and much industrial and academic interest has been created. Reports on the manufacture of nanocomposites include those made with polyamides [2-5], polyolefins [6-9], polystyrene (PS) and PS copolymers [10, 11], ethylene vinyl alcohol [12-15], acrylics [16-18], polyesters [19, 20], polycarbonate [21, 22], liquid crystalline polymers [8, 23-25], fluoropolymers [26-28], thermoset resins [29-31], polyurethanes [32-37], ethylene-propylene oxide [38], vinyl carbazole [39, 40], polydiacethylene [41], and polyimides (Pis) [42], among others. 

The manufacturing methods for PLA nanocomposites include intercalation of polymer from solution, polymer melt intercalation and intercalation of a suitable monomer and subsequent in situ polymerization. 

Sodium montmorillonite (Na-MMT) was originally modified with pro-tonated amino acids with different numbers of carbon atoms and subsequently swollen with e-caprolactam. Then it underwent polymerization to produce nylon-6 polymer-clay nanocomposite [18]. Later, this technique was also extended to manufacture other thermoplactics. One advantage of this in-situ polymerization technique is the tethering effect, which enables the organic chemical such as 12-aminododecanoic acid (ADA) situated at the surface of the nanoclays to link with nylon-6 polymer chains during polymerization. 

T. Kuila, S. Bose, P. Khanra, N.H. Kim, K.Y. Rhee, J.H. Lee, Characterization and properties of in situ emulsion polymerized poly(methyl methacry-late)/graphene nanocomposites. Composites Part A Applied Science and Manufacturing, 42 (11), 1856-1861, 2011. 

Preparation of polymer-day nanocomposites by in situ polymerization (sometimes called intercalative polymerization or polymerization compounding) circumvents the enthalpic and entropic barriers that prohibit the intercalation of nonpolar polyolefins into polar clays. Since supported olefin polymerization catalysts are desirable anyway in high-volume polyolefin manufacturing (see Section 5.1.1), the design of clay-supported catalysts to prepare nanocomposites can achieve both goals at once. In the late 1990s, researchers... 

A viable process for manufacturing polyolefin-clay nanocomposifes by in situ polymerization requires adequate catalytic activity, desirable polymer microstructure, and physical properties including processibility, a high level of clay exfoliation fhaf remains stable under processing conditions and, preferably, inexpensive catalysf components. The work described in the previous two sections focused on achieving in situ polymerization with clay-supported transition metal complexes, and there was less emphasis on optimization of polymer properties and/or clay dispersion. Since 2000, many more comprehensive studies have been undertaken that attempt to characterize and optimize the entire system, from the supported catalyst to the nanocomposite material. The remainder of this chapter covers work published in the past decade on clay-polyolefin nanocomposites of ethylene and propylene homopolymers, as well as their copolymers, made by in situ polymerization. The emphasis is on the catalyst compositions and catalyst-clay interactions that determine the success of one-step methods to synthesize polyolefins with enhanced physical properties. 

Styrene-butadiene copolymers are extremely important to the rubber industry. They are particularly important in tire manufacture. Styrene-butadiene polymer is produced by emulsion polymerization and solution polymerization. Most of the volume is by emulsion polymerization. This affords the opportunity to prepare polymer nanocomposites by several avenues. One can blend an aqueous dispersion of the nanoparticles with the styrene-butadiene latex before flocculation to produce the rubber crumb, disperse an organically treated nanoparticle in the styrene-butadiene solution polymer before the solvent is stripped from the polymer, disperse the organically treated nanoparticles into the monomers, or prepare the rubber nanocomposite in the traditional compounding approach. One finds all of these approaches in the literature. One also finds functional modifications of the styrene-butadiene polymer in the literature designed to improve the efficiency of the dispersion and interaction of the nanoparticles with the polymer. 

There are different manufacturing processes for the production of nanostructured polymeric blends. Peponi et al. reviewed [16] bottom-up and top-down processes for nanostructured polymers and advanced polymeric-based nanocomposites. Nanostrac-tured thermoplastics blends are reported under bottom-up matrix nanocomposites whereas nanostructured thermoplastic nanocomposites are introduced under top-down approaches. Polymer nanotechnologies are characterized by top-down processes including ingredients such as polymer and nanoparticles. They are introduced... 

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