Many attempts have been made to fabricate various types of inorganic nanoparticle-filled polymers (filler/polymer nanocomposites) by a mechanical or chemical approach. However, these approaches require modification of the nanofiller surfaces and/or complicated polymerization reactions, making them unsuitable for industrial-scale production of the nanocomposites. The author and coworkers have proposed a simple melt-compounding method for the fabrication of silica/polymer nanocomposites, wherein silica nanoparticles without surface modification were dispersed through the breakdown of loose agglomerates of colloidal nano-silica spheres in a kneaded polymer melt. This review aims to discuss experimental techniques of the proposed method and its advantages over other developed methods.

A novel method for the fabrication of silica/perfluoropolymer nanocomposites was investigated, whereby nano-sized silica particles without surface modification were dispersed uniformly through mechanical breakdown of loosely packed agglomerates of silica nanoparticles with low fracture strength in a polymer melt during direct melt-compounding. The method consists of two stages. The first stage involves preparation of the loose silica agglomerate, and the second stage involves melt-compounding of a completely hydrophobic perfluoropolymer, poly(tetrafluoroethyleneco-perfluoropropylvinylether), with the loose silica agglomerates prepared in the first stage. In the first stage, the packing structure and the fracture strength of the silica agglomerate were controlled by destabilizing an aqueous colloidal silica solution with a mean primary diameter of 190 nm via pH control and salt addition. In the next stage, the silica/perfluoropolymer nanocomposite was fabricated by breaking down the prepared loose silica agglomerates with low fracture strength by means of a shear force inside the polymer melt during melt-compounding.

A new approach for the preparation of organic/inorganic nanocomposites was investigated in which nano-sized silica particles without surface modification were dispersed by the mechanical smashing of strength-controlled porous silica agglomerates in molten resin during direct melt-compounding. The method consists of two stages. The first stage involves preparation of the strength-controlled agglomerated silica nanoparticles with pore structure, and the second stage involves meltcompounding of a thermoplastic resin with the silica agglomerates prepared in the first stage. In the first stage, on the basis of the theory of stability of an aqueous colloidal silica solution, the pore structure and the fracture strength of the silica agglomerate could be controlled by pH-control and electrolyte ion-addition to the colloidal solutions of silica nanoparticles. In the next stage, primary silica nanoparticles could be dispersed in some matrix resins such as a poly(ethylene-ran-vinyl alcohol) and polystyrene uniformly by the proposed mechanical approach by the use of the high shear stress acting on porous silica agglomerates inside these melt-compounded resins. Organic/inorganic nanocomposites 983 Dimensionless Interaction Energy, E T / kT Distance between Two Particle Surfaces, H / nm Conditions of colloidal silica solution KBr-addition pH-control Figure 4. Effects of KBr-addition and pH-control on dimensionless energy versus distance profile of DLVO interaction between two silica particles with d p,Silica ¼ 12 nm at the beginning stage of the evaporation step of aqueous solvent at 353 K. Organic/inorganic nanocomposites 987 Figure 11. SEM micrographs of selected areas of silica nanoparticle-dispersed PS composites (volume fraction of silica, V f,Silica ¼ (a) 0.025, (b) 0.049 and (c) 0.098). Bright spots in the circles are examples of dispersed primary silica particles.

The rate of Sb elimination from molten copper by the use of Na 2 CO 3 slag was measured at 1523 K. The results obtained under the present experimental conditions show that Sb in molten copper is eliminated in a tri-valent or a penta-valent form, depending on the oxygen concentration at the slag-metal interface, and its elimination rate increases with increasing initial oxygen concentration in molten copper. The overall elimination rate of Sb is affected by the stirring condition of the molten copper, which indicates a rate control by mass transfer in that phase. The mass-transfer coefficients of Sb and oxygen in molten copper at 1523 K without external stirring were determined, respectively, to be based on the mass balances of Sb and oxygen in the molten copper and slag phases and the equilibrium relation of the Sb elimination reaction at the slag-metal interface. k m,Sb ϭ 4.0 (Ϯ0.9) ϫ 10 Ϫ5 m # s Ϫ1 and k m,O ϭ 1.3 (Ϯ0.3) ϫ 10 Ϫ4 m # s Ϫ1

The protection mechanism of a living body and man-made materials can be classified into two categories. One is a passive protection by which the body and materials are guarded by simple chemicals such as light absorbents, and the other is an active protection that repairs with metabolic reactions the internal injury suffered by many kinds of deterioration factors from the outside. Polyphenylene -ether was selected as a man-made material in which the metabolic reaction can be achieved in the atmosphere (21% of oxygen) and at room temperature (20 -40 8C). The polymer introduces oxygen as an energy source, transports it with copper-complex and repairs the scission point of the chain. Such active protections were attempted for several polymers and some advantages and problems were elucidated. In this paper, the mechanisms of active protections in some plastics are reviewed and are also compared with protection systems of a living body, which provide us with very useful information on the development of advanced materials. q