Abrasion silica-modified

The ability of organically modified ceramics based on alumina, zirconia, titania, or silica (and mixtures of each) to function as abrasion-resistant coatings has also been studied (62). For example, polycarbonate, when coated with an epoxy—aluminosilicate system, experiences a significant reduction in the degree of hazing induced by an abrader, as compared to uncoated polycarbonate. 

Abrasive particle properties can be attributed to the method or process used to generate the particles. The surface properties can be altered or modified by varying the physical conditions (temperature, pressure, time) or chemical composition of the initial reactants. This section will survey the various preparation techniques for silica, alumina, and diamond. 

Sol-gel techniques were used to prepare porous, organically modified silica materials. The introduction of organic groupings was carried out with alkoxysilanes as precursors methyl and propyl amino groups were used. The results show that high-porosity materials can be synthesized the microstructure strongly depends on reaction conditions such as composition, solvent, catalyst type, and concentration. Microstructure tailoring affects mechanical as well as adsorption properties, and custom-made materials such as abrasives and adsorbents with special properties were synthesized. 

For example, the abrasion-resistant coatings based on a silicone-silica hybrid (33) have provided a scratch- and mar-resistant finish for polycarbonate as well as metals. The chemistry involved is discussed by Vincent, Kimball and Boundy (3iL). The coating consists of polysiloxane and silane-modified submicron silica particles, microscopically dispersed in the solution. The coating is then cured at elevated temperatures. Currently, this type of abrasion resistant coating is marketed in the U.S. by Dow Corning and General Electric Company. 

This homogenous distribution of the hard, silane-modified fumed silica particles results in extremely scratch- and abrasion-resistant formulations. An indication of the performance of this system is given in Fig. 7. 

Figure 9.9 shows the OCP curves during a pohsh—stop— pohsh cycle in 0.065 mol/dm OA + 5 wt% H2O2 with the addition of 3 wt% coUoidal silica at pH values 1.5, 3.0, and 8.0. At both pH 1.5 and pH 3.0, the increase in the OCP value was nearly the same when the pohshing was stopped. This implies the presence of a similar type of modified surface film on copper substrate that can be easily abraded by the mechanical action of the pad and the abrasives. No significant change was observed in the OCP values for copper in the slurry at pH 8.0 similar to what was observed in Figure 9.8. 

Numerous researches have been conducted to modify abrasive particles for scratch reduction. Mixed abrasive slurry and various dispersants were used for the development of hne slurries [44,45] slurries made of abrasives with soft polymer coating are also proposed [46] polymer-core silica-shell composite abrasives were reported too [47]. However, most of these modified/composite abrasive slurries remain experimental and have not received wide industrial acceptance yet, because of challenges in particle control and difficulty in cleaning the residual abrasives. 

As far as the latter systems are concerned, in order to enhance activity or abrasion resistance of a sol-gel titania film, silica can be added, which may substantially modify its performance even at low concentrations. 

Additives such as fillers, oils, and various resins are added into the SBS block polymers to modify the properties and to adjust cost of the compound. The addition of mineral fillers, such as silica, calcium carbonate, and clay, improve tensile strength (at low concentration), resistance to abrasion, and crack growth as well as increases compound viscosity. The addition of oils generally acts as a plasticizer. This leads decreased tensile strength, hardness, and abrasion resistance however, it also increases flowability of the compound. Plasticizers such as naphthenic or paraffinic oils are compatible with polybutadiene, however, not with... 

Bauer F, Ernst H, Hirsch D, Naumov S, Peking M, Sauerland V and Mehnert R, Preparation of scratch and abrasion resistant polymeric nanocomposites by monomer grafting onto nanoparticles, 5(a) - Application of mass spectroscopy and atomic force microscopy to the characterization of silane-modified silica surface , Macromol Chem Phys 2004 205(12) 1587-93. 

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