Processing nano-composites

The key components of polymeric nano-composites are water-swellable synthetic and natural layered silicates such as montmorillonites (the main 

The are two basic ways of making polymer/clay hybrids. Direct polymerization in the presence of clay platelets has been used successfully for polyamides and for epoxy and other resins. But, at a less exotic and more flexible level, compounding offers an economic way of modifying polypropylene - in theory - and there has been some active development of processes to produce polypropylene/clay hybrids by melt mixing. 

To achieve the high level of dispersion required, slurry processes are being developed both as a means of opening up the fine clay particles and separating the plate-like layers, and also to incorporate sub-microscopic particles of calcium carbonate into polypropylene. The filler is introduced as a slurry in 2 5% water at the start of the process and with polypropylene in powder form. During plasticizing, the water content of the slurry vaporizes and is vented by the usual degassing aperture. 

Researchers at Dresden University and at Elf Atochem s research and development centre at Serquigny, France, have been working on modification of a standard Werner and Pfleiderer in which, rather than adding the filler to the melt, the filler is brought in at the beginning of the process, as a slurry in water, and mixed with a powdered form of polypropylene. 

Multiaxial impact total energy. 3 mm, 4.3m.s-, 2 3°C 1 BO (ductile) 35 (semi-ductile) 74 (ductile) 

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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]. 

The metal oxides prepared by conventional baking or by the CVD method are, in general, chemically stable, crystalline materials, and show excellent mechanical, electrical, optical, and physical properties. Flexible porous gel films obtained by the surface sol-gel process are totally different. In this chapter, we described a new preparative method for ultrathin metal oxide films by stepwise adsorption of various metal alkoxides. We named this method the surface sol-gel process. Structural characterization of the gel films thus obtained, the electrical property, and formation of nano-composites with organic compounds, were also explained. The soft porous gel contains many active hydroxyl groups at the surface and interior of the film. This facilitates adsorption of organic compounds, and consequent preparation of ultrathin metal oxide/polymer nano-composite films and organization of functional small molecules. In the nano-composites, proper selection of polymer components leads to the design of new materials with unique electrical, optical, and chemi-... 

Mg-5at.%Nb nano-composite processed by reactive milling. Journal of Alloys and Compounds, 376, 251-256. 

Luo, C, Zuo, X, Wang, L, Wang, E, Song, S, Wang, J, Fan, C, Cao, Y. 2008. Flexible carbon nanotube-polymer composite films with high conductivity and superhydrophobicity made by solution process. Nano Lett 8 4454-4458. 

If two or more types of different materials are mixed up and treated in defined conditions (varying with temperature, pressure, and other chemical and physical processes), a composite material with a clear interfacial boundary will be obtained. If a major part of the produced composite consists of polymer, then it is called a polymeric composite. A polymeric composite material is one of the most developed areas of modern science and technology. In addition to composite materials, modern science and technology use nano-sized materials. Such composites are called nanocomposites, whose main attraction is related to very high operation properties, such as flexibility, elasticity, recycling, hardness, resistance to abrasion, and optical and electrical transmission [9]. 

N.A., Alexander, M., Vaia, R.A., 2004. Remotely actuated polymer nancxomposites—stress-recovery of carbon-nanotube-filled thermoplastic elastomers. Nat Mater. 3, 115-120. Copyright 2004, Macmillan Publishers Ltd. (B) Reproduced with permission from reference Yu, A., Meiser, F., Cassagneau, T., Caruso, F., 2004. Fabrication of polymer-nanopartide composite inverse opals by a one-step electrochemical co-deposition process. Nano Lett 4, 177-181. Copyright 2004, American Chemical Society. (C) Reproduced with permission from reference Fie, X., Shi, Q., Zhou, X., Wan, C., Jiang,... 

Yu, A., Meiser, E, Cassagneau, T, Caruso, E, 2004. Fabrication of polymer-nanoparticle composite inverse opals by a one-step electrochemical co-deposition process. Nano Lett. 4,177-181. 

Fibers have been widely used in polymeric composites to improve mechanical properties. Cellulose is the major substance obtained from vegetable fibers, and applications for cellulose fiber-reinforced polymers have again come to the forefront with the focus on renewable raw materials. Hydrophilic cellulose fibers are very compatible with most natural polymers. The reinforcement of starch with ceUulose fibers is a perfect example of a polymer from renewable recourses (PFRR). The reinforcement of polymers using rigid fillers is another common method in the production and processing of polymeric composites. The interest in new nanoscale fillers has rapidly grown in the last two decades, since it was discovered that a nanostructure could be built from a polymer and layered nanoclay. This new nanocomposite showed dramatic improvement in mechanical properties with low filler content. Various starch-based nano-composites have been developed. 

A nylon 66 clay nanocomposite was produced using the dry-compound method [26]. Co-intercalation organophihc clay was used as the clay base. Na-montmorillonite was first processed using hexadecyl trimethyl ammonium ions and epoxy resin. It was then kneaded using a twin screw extruder to make a clay nano composite. As the amount of clay that was added increased, the amount of y (gamma) phases increased. This is thought to be due to the strong interactions between the nylon 66 chains and the sinface of the clay layers. 

The dispersion of clay platelets (exfoliation and intercalation level of the silicate layers) and surface area of silicate platelets have the potential to alter the rheological behavior of the nanocomposites. In-situ polymerized nano composites exhibit more exfoliated structure than the composites prepared by the melt blending technique. Irrespective of the processing parameter, the nanocomposites show shear thinning behavior at high shear rate (Figure 9.14), whereas the pristine polyamide exhibits Newtonian behavior (i.e., the viscosity remains almost the same). It has also been reported that the polymer nanocomposite possesses higher steady shear viscosity than pristine polyamide at low shear rates. 

Table 9.12 Mechanical properties of neat polyamide, in-situ processed and melt-blended nano composites. Reprinted from [61] with permission from Elsevier.

Coiai, S., Scatto, M., Bertoldo, M., Conzatti, L., Andreotti, L., Sterner, M., Passaglia, E., Costa, G., and Ciardelli, R 2009. Study of the compounding process parameters for morphology control of LDPE/layered silicate nano-composites. e-Polymers, no. 050 1-18. http Hwww.e-polymers.org/ journal/papers/scoiai 280509.pdf... 

Chowdhury, M. and Stylios, G. (2011) Process optimization and alignment of PVA/EeCl 3 nano composite fibres by electrospinning. /. Mater. ScL, 46, 3378-3386. 

Polymer/CNF nano composites can be prepared by different routes, including in situ polymerization, solution processing and melt mixing. The latter is the most common, given its simplicity and high 5deld, the compat-... 

Processing and properties of polymeric nano-composites. Polym. Eng. Sd.,... 

In recent years, with the development of small-size fabrication techniques, new types and classes of high performance ceramic materials, consisting of, e.g., nano-composite structures and devices, layered structured ferroelectrics, multilayered functional devices, etc., have attracted considerable attention because of their improved mechanical/functional properties. Concurrent to processing developments, multiple complementary metrology tools are required for the evaluation of nano-scale mechanical and functional characteristics of the materials [1-3]. 

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