Nano-composite

Nano-composites are the subject of intense research for a number of properties such as improved barriers to gas, higher mechanical strength, and improved flame retardancy. Plate-like particles of special clays, one nanometre (one billionth of a metre) thick by 1000 nanometres in diameter, are being studied as FRs in plastics by the US National Institute for Standards and Technology (NIST), Gaithersburg, Maryland. Initial research showed that the addition of as little as 5% of nano-sized clay particles could produce a 63% reduction in the 

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Poly(Lactic Acid) as a Biopolymer-Based Nano-Composite... 

Clays have long been used as fillers in polymer systems because of low cost and the improved mechanical properties of the resulting polymer composites. If all other parameters are equal, the efficiency of a filler to improve the physical and mechanical properties of a polymer system is sensitive to its degree of dispersion in the polymer matrix (Krishnamoorti et ah, 1996). In the early 1990s, Toyota researchers (Okada et ah, 1990) discovered that treatment of montmorillonite (MMT) with amino acids allowed dispersion of the individual 1 nm thick silicate layers of the clay scale in polyamide on a molecular. Their hybrid material showed major improvements in physical and mechanical properties even at very low clay content (1.6 vol %). Since then, many researchers have performed investigations in the new field of polymer nano-composites. This has lead to further developments in the range of materials and synthesizing methods available. 

Therefore, the clay should be modified before it can be used to make a nano-composite. After all, these stacks of clay platelets are larger than one nanometer in every dimension. 

Nano-composites (NCs) are materials that comprise a dispersion of particles of at least one of their dimentions is 100 nm or less in a matrix. The matrix may be single or multicomponent. It may include additional materials that add other functionalities to the system such as reinforcement, conductivity and toughness (Alexandre and Dubois, 2000). Depending on the matrix, NCs may be metallic (MNC), ceramic (CNC) or polymeric (PNC) materials. Since many important chemical and physical interactions are governed by surface properties, a nanostructured material could have substantially different properties from large dimensional material of the same composition (Hussain et ah, 2007). 

Polymer layered-silicate day nano-composites (PLCN) attracted lately major interests into the industry and academic fields, since they usually show improved properties with comparison by virgin polymers or their conventional micro and macro-composites. Improvements induded increase in strength, heat resistance (Giannelis, 1998), flammability (Gilman, 2000) and a decrease in gas permeability (Xu et ah, 2001) as well as an increase in biodegradability (Sinha et al., 2002). 

However, the field of polymer day silicate has only started to speed up recently, mixing the appropriate modified layered silicate with synthetic layered silicates has long been known (Theng, 1979). The interest in these materials came from two important findings, first has been reported by Toyota research group of a Nylon-6 (N6)/Na-MMT nano-composites (Okada et ah, 1990) where very small amounts of layered silicate loadings resulted in the improvements of thermal and mechanical properties and second the findings of Vaia et ah (1993) about the... 

Micro-composites are formed when the polymer chain is unable to intercalate into the silicate layer and therefore phase separated polymer/clay composites are formed. Their properties remain the same as the conventional micro-composites as shown in Figure 2(a). Intercalated nano-composite is obtained when the polymer chain is inserted between clay layers such that the interlayer spacing is expanded, but the layers still bear a well-defined spatial relationship to each other as shown in Figure 2(b). Exfoliated nano-composites are formed when the layers of the day have been completely separated and the individual layers are distributed throughout the organic matrix as shown in Figure 2(c). 

The nano-scale structures in polymer layered-silicate nano-composites can be thoroughly characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD is used to identify intercalated structures. XRD allows quantification of changes in layer spacing and the most commonly used to probe the nano-composite structure and... 

These tactoids are responsible for the particular geometrical structures formation in the blends, which leads to the formation of superstructures in the thickness of the blended film. The Young s modulus of the hybrid is increased by this kind of structural feature. After that, the preparation of intercalated PLA/ OMMT nano-composites with much improved mechanical and thermal properties was reported by Bandyopadhyay et al. (1999). 

In the matrix of PLA/ polycaprilactone (PCL)/OMMT nano-composites, the silicate layers of the organoclay were intercalated and randomly distributed (Zhenyang et at, 2007). The PLA/PCL blend significantly improved the tensile and other mechanical properties by addition of OMMT. Thermal stability of PLA/PCL blends was also explicitly improved when the OMMT content is less than 5%wt. Preparation of PLA/thermoplastic starch/MMT nano-composites have been investigated and the products have been characterized using X-Ray diffraction, transmission electron microscopy and tensile measurements. The results show improvement in the tensile and modulus, and reduction in fracture toughness (Arroyo et ah, 2010). 

PLA/PCL-OMMT nano-composites were prepared effectively using fatty amides as clay modifier. The nano-composites shows increasing mechanical properties and thermal stability (Hoidy et al, 2010c). New biopolymer nano-composites were prepared by treatment of epoxidized soybean oil and palm oil, respectively plasticized PLA modified MMT with fatty nitrogen compounds. The XRD and TEM results confirmed the production of nanocomposites. The novelty of these studies is use of fatty nitrogen compoimds which reduces the dependence on petroleum-based surfactants (Al-Mulla et al., 2011 Al-Mulla et ah, 2011 Al- Mulla et ah, 2010c). 

Plasticized PLA-based nano-composites were prepared and characterized with polyethylene glycol and MMT. It is reported that the organo-modified MMT-based composites show the possible competition between the polymer matrix and the plasticizer for the intercalation between the alumino-silicate layers (Paul et ah, 2002). 

Alexandre, M. and Dubois, P. 2000. Polymer-layered silicate nano-composites preparation, properties and uses of a new class of materials. Materials Science and Engineering 28 1- 63. 

In this chapter, a brief introduction will be given mainly to the DEC, CNx, multilayer films and nano-composite coatings. Detailed and comprehensive introduction of the conventional thin solid coating technique is not the objective of this chapter. Readers are referred to relevant publications to attain the knowledge in this area. 

D-TEM was introduced into rubber technology field in 2004 by the authors of this chapter [4]. In a recent review of 3D-TEM applied in materials science field [5], only two papers were cited on polymeric samples—one on block copolymers [6] and the other on rubbery composites with conventional and in situ silica [4]. Starting from the latter, 3D-TEM measurements have been carried out on rubbery nano-composites [7-16], and this recent and very important topic is described in this review. 

The morphology of the agglomerates has been problematic, although some forms of network-like structures have been assumed on the basis of percolation behavior of conductivity and some mechanical properties, e.g., the Payne effect. These network stmctures are assumed to be determining the electrical and mechanical properties of the carbon-black-filled vulcanizates. In tire industries also, it plays an important role for the macroscopic properties of soft nano-composites, e.g., tear. 

This fascinating product will still continue to develop to accommodate new applications, safety, health and environment (SHE) issues, advantages of novel materials like nano-composites, plasma-surface-modified carbon black, development of computer simulation techniques, and finally to develop a cybernetic or thinking tire. 

Arefian NA, Shokuhfar A, Vaezi MR, Kandjani AE, Tabriz MF (2008) Sonochemical synthesis of SnO/ZnO nano-Composite the effects of temperature and sonication power. In Ochsner A, Murch GE (eds) Defect and diffusion forum, vol 273-276, Diffusion in solids and liquids III., pp 34-39... 

Layered materials are of special interest for bio-immobilization due to the accessibility of large internal and external surface areas, potential to confine biomolecules within regularly organized interlayer spaces, and processing of colloidal dispersions for the fabrication of protein-clay films for electrochemical catalysis [83-90], These studies indicate that layered materials can serve as efficient support matrices to maintain the native structure and function of the immobilized biomolecules. Current trends in the synthesis of functional biopolymer nano composites based on layered materials (specifically layered double hydroxides) have been discussed in excellent reviews by Ruiz-Hitzky [5] and Duan [6] herein we focus specifically on the fabrication of bio-inorganic lamellar nanocomposites based on the exfoliation and ordered restacking of aminopropyl-functionalized magnesium phyllosilicate (AMP) in the presence of various biomolecules [91]. 

Freeman, B.D., High Temperature Nano-Composite Membranes for Hydrogen Production for Fuel Cells, Final Report, TCEQ/NTRD Grant Contract 582-5-65591-0002, August 2006. 

Optical Effects Manifested by PAMAM Dendrimer Metal Nano-Composites... 

The remaining sections outline recent findings on the optical properties of metal-dendrimer nano-composites. The sections have been organized into areas of interest related to the fabrication as well as photophysical properties of these new and important materials. The first section discusses some of the important issues concerning the fabrication of these novel materials and their chemical characterization. The second section discusses the linear and nonlinear optical properties of these materials. The third section provides details related to the ultrafast emission properties of gold- and silver-dendrimer nanocomposites. 

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