Filler system, double

Vaterite is thermodynamically most unstable in the three crystal structures. Vaterite, however, is expected to be used in various purposes, because it has some features such as high specific surface area, high solubility, high dispersion, and small specific gravity compared with the other two crystal systems. Spherical vaterite crystals have already been reported in the presence of divalent cations [33], a surfactant [bis(2-ethylhexyl)sodium sulfate (AOT)] [32], poly(styrene-sulfonate) [34], poly(vinylalcohol) [13], and double-hydrophilic block copolymers [31]. The control of the particle size of spherical vaterite should be important for application as pigments, fillers and dentifrice. 

Typical liquid systems require doses between 10 and 50 kGy. They consist of binders (prepolymers) with acrylic (H2C=CH-CO-0-) double bonds in the main chain (polymaleates and polyfumarates) and of monomers, usually acrylates used as reactive thinners. Other ingredients added to the formulation may be pigments, dyes, fillers, flatting agents, and additives to improve film and surface properties and attain the required performance criferia. ... 

Some of the unusual properties of a solid propellant results from its basic composition. The two general categories of double-base and composite rubber binder propellants have many subcategories, but no exhaustive compilation will be attempted here. Most modem propellants consist of a deformable binder phase and a crystalline salt filler, such as ammonium perchlorate and usually a powdered metallic fuel such as aluminum. Table I gives some typical compositions for both composite rubber-based and composite double-base systems. 

Still, it is important that fillers interact with the polymer (binder) for various reasons. One is the rheological characteristic of paints. Figure 19.5 shows that many processes may affect how a filler behaves in the system. The simple drying of aluminum hydroxide prior to use contributes to an increased paint viscosity. It should be noted that aluminum hydroxide loses water at 220°C, therefore drying at 80 C may only remove the water adsorbed on the surface of particles. But this is apparently sufficient to increase the interaction with the binder since, when the partially dried filler is added, viscosity almost doubles. Similarly, treatment with 1% triethoxymethacryloylpropylsilane, MPS, contributes to an increased viscosity. This data shows that the same filler can be readily modified to give a variety of different results. 

Unsaturated polyester resins are mainly made by condensing a dibasic acid (1,2-propanediol) with an anhydride (maleic or phthalic anhydrides), by forming ester linkages between the dibasic acid (or their anhydrides) and glycols. Then a reactive monomer (mostly styrene or vinyl toluene, MMA or diallyl phthalate) is used to crosslink the system when needed. Unsaturated denotes the uncompleted chemical activity (double bond) in the original structure, which are used for crosslinking afterwards. In this context, an excess of styrene as the crosslinker (10 to 50 %) is usually added to have it ready in the system, as well as to reduce the viscosity. There are also certain accelerators used (such as, cobalt naphthenate or tertiary amines like dimethyl aniline) to facilitate the cure at ambient temperatures. In addition, there may be pigments, fillers, various inhibitors, accelerators, stabilisers and flame retardants, added to the system. Polymerisation is activated whenever a catalyst (i.e., benzoyl or methyl-ethyl-ketone peroxide) is added. 

For the N22 CMC system, remaining open porosity in the CVI SiC matrix was filled by room-temperature infiltration of SiC particulate or slurry casting, followed by the melt-infiltration (MI) of silicon metal near 1400°C. This yielded a final composite with 2% closed porosity within the fiber tows and 0% porosity between the tows. The final composite system (often referred to as a slurry-cast MI composite) typically displayed a thermal conductivity about double that of a full CVI SiC composite system in which the CVI matrix process was carried to completion. Also the composite did not require an oxidation-protective over-coating to seal open porosity. Decreasing the porosity of the hybrid matrix also increased the N22 CMC elastic modulus, which in turn contributed to a high proportional limit stress. However, since the filler contained some low-modulus silicon, the modulus increase was not as great as if the filler were completely dense SiC. 

The Cetex Institut fur Textil- und Verarbeitungsmaschinen gemeinniitzige GmbH based in Chemnitz, Germany, has been developing new areas of application for the 3D contour warp knitting process oti double-bar Raschel machines since 1997. The objective, to enable the incorporation of directly oriented thread systems into the base fabric (filler thread, weft thread), was reached (Anmi., 1997b). 

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