Clay-nanocomposite thin films

Kim et al. [14] modified Nafion 117 membranes by means of layer-by-layer deposition of clay-nanocomposite thin films. Membranes containing 20 nanocomposite bilayers exhibited a reduction in methanol permeability by -50%, while the proton conductivity remained unchanged. Unfortunately, no fuel cell performance was reported for this membrane material. A three layer membrane system consisting of a sulfonated poly(ether ether ketone) film sandwiched between two recast Nafion films was studied by Yang and Manthiram [33], where the middle layer was either... 

Figure 7.32 Typical indentation load-displacement curves for pristine PU and its two types of PU nanocomposite thin films with different clay concentrations. Reproduced from Ref. [43] with permission.

Polymer matrix nanocomposite is the most important type of nanocomposite in which the performance of a polymer matrix can be enhanced by appropriately adding nanoparticulates to it [12] and good dispersion of the filler can be achieved [ 12]. A imiform dispersion of nanoparticles leads to a very large matrix/filler interfacial area, which changes the molecular mobility, the relaxation behavior and the consequent thermal and mechanical properties of the material. A polymer matrix could be reinforced by much stiffer nanoparticles [13,14] of ceramics, clays, or carbon nanotubes, etc. Recent research on thin films (thickness < 50 micrometer) made of polymer nanocomposites has resulted in a new and scalable synthesis technique increasing the facile incorporation of greater nanomaterial quantities [15]. Such advances will enable the future development of multifunctional small scale devices (i.e., sensors, actuators, medical equipment), which rely on polymer nanocomposites. 

The PP-g-HMA nanocomposites, with 1, 3, and 5wt% of an MMT modified by cation exchange with cetyl pyridinium chloride, were prepared in xylene solution at 120°C for 6h. The powdery products were sandwiched between cover glasses and melted at 200°C to form thin films, which were then cooled with a rate of 20°C min i. The XRD and TEM analyses showed that the nanocomposites possess a mixed exfoliated/intercalated morphology, with a level of exfoliation that increases as the clay loading is lowered. Since PP-g-HMA contains more than one functional group per chain, the structure of the nanocomposites is probably similar to that of Figure 3.8c. 

Aranda P, Harder M, Femandez-Saavedra R, Lopez-Bianco M, Ruiz-Hitzky E (2006) Relevance of polymer- and biopolymer-clay nanocomposites in electrochemical and electro-analytical applications. Thin Solid Films 495 104-112... 

Tun9 S, Duman O (2010) Preparation and characterization of biodegradable methyl cellulose/ montmorillonite nanocomposite films. Appl Clay Sci 48 414 24 Turbak AF, Snyder FW, Sandberg KR (1983) Microfibrillated cellulose, a new cellulose product properties, uses, and commercial potential. J Appl Polym Sci Appl Polym Symp 37 815-827 Ung T, Liz-Marzan LM, Mulvaney P (2002) Gold nanoparticle. Thin Films Colloid Surf A 202 119-126... 

Kim et al [102,103] reported that the toughness of polyamide 12/clay and polyamide 6/clay nanocomposites was enhanced due to the occurrence of some energy dissipating events. They performed in situ tensile tests on thin films of these nanocomposites hi a transmission electron microscope and observed that the major deformation process in these materials was micro-void formation inside the stacked silicate layers. Since the clay interlayer strength is weaker than the clay/matrix interfacial strength, delamination or interlayer debonding... 

Barrier films of exfoliated clay-polymer composites have been a subject of considerable investigation with some commercial utility (e.g., barrier layer for termis balls).The thin exfoliated clay platelets dispersed in a polymer matrix present a tortuous diffusion path for gas molecules similar to that observed in Figure 12 for biaxially oriented polymer blends. The advantages of exfoliated clay modification for barrier properties are the retention of transparency and low cost. A novel approach utilizing nanocomposites involves dispersion of the exfoliated clay in a water emulsion or suspension and coating a desired substrate. This approach has been commercialized by IntMat for tennis balls, tires, and food packaging applications. For exceptional barrier properties, and where transparency is not required, metalized polymer films or aluminum foil polymer film laminates are usually employed. 

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