Glass, powder filler

Gl ss-Ionomers. Glass-ionomers show fluoride release at levels that are usually higher than those found in composite materials. The fluoride is found within the aluminosihcate glass, which is melted with fluoride fluxes and ground to form powder filler. The fluoride is added as calcium fluoride [7789-75-5] aluminum fluoride [15098-87-0] and sodium fluoride [7681-49-4] in a combined proportion of approximately 20% by weight in the final powder (284,285). 

Very often particles are blended into polymers, in thermoplasts as well as in thermosets and in synthetic rubbers. This is done for various reasons the aim may be stiffness, strength, hardness, softening temperature, a reduction of shrinkage in processing, reduction of thermal expansion or electric resistance, or, simply, to reduce the price of the material. The fillers used are wood flour, carbon black, glass powder, chalk, quartz powder, mica, molybdene sulphide, various metal oxides, etc. etc. 

Note The remainder of the composit consisted of 80 wt% filler consisting of barium- aluminum-boron silicate glass powder, silicon dioxide-zirconium dioxide, and ytterbium fluoride. For dental composites lower viscosities are preferred because of their flowability. 

Calcium Carbonate, Calcium Silicate, Powdered Aluminium, Copper Alumina, Flint Powder, Carborundum, Silica, Molybdenum Disulphide Chopped Glass Mica, Silica, Powdered or flaked Glass Metallic Filler or Alumina Colloidal Silica, Bentonite Clay Improved Thermal Conductivity Improved Machinability Improved Abrasion Resistance Improved Impact Strength Improved Electrical Conductivity Improved Thixotropic Response... 

The most frequently used fillers are glass powder, lithium aminosilicate, and glass-ceramic. Figure 19.14 shows that properties of dental composites are enhanced by the use of silanes. Treatment with silane also improves water resistance. ... 

An alternative to the use of antistatic additives is the incorporation of electrically conductive fillers or reinforcements into the polymer to make the whole structure conductive. Typical additives that are used for this purpose include aluminum, steel, or carbon powders, and metal-coated glass fibers or carbon fibers. Powdered fillers are generally less expensive than fibers. Maintaining the desired fiber distribution during processing is also problematic. 

Question by J. W. Mark, Argonne National Laboratory Was the glass fabric primarily a reinforcement, or did it serve by virtue of its low expansion coefficient as a filler much like glass powder ... 

Glasses are used in a wide variety of dental products. Glass powders are used as fillers in composite resin materials. These glasses must have very fine particle sizes, and typically contain strontium or barium to aid in... 

Additive type Calcium carbonate calcium silicate powdered aluminum or copper Alumina flint powder carborundum silica molybdenum disulphide Chopped glass Mica silica powdered or flaked glass Metallic fillers or alumina Colloidal silica Bentonite clay... 

The role of the fillers in composite resins is to reinforce their mechanical properties and provide a blended material whose overall properties make it suitable for the clinical repair of teeth. A limited range of materials has been used, with greater emphasis on variations in the particle size and size distribution than on chemical composition. Early materials were filed with powdered quartz, whereas modem composites are more likely to be filled with finely divided barium silicate or a radio-opaque silicate glass [8]. Filler loadings are typically of the order of 55% by volume, as they were in Bowen s original formulation [9]. 

The greater effect is caused by glass fiber and fabrics while powdered fillers are less effective. The behavior of PTFE is highly anomalous. In several cases there is reasonable agreement between the theoretical predictions and experimental data. However, general agreement can be reached when due consideration of particle size and shape, interfacial area and the polarity of polymers and fillers are taken into account. 

The thermal expansion of plastics can be increased by the incorporation of reinforcing agents or fillers into the formulation. Thns, the incorporation of ceramic powder filler into polytetraflnroethylene (PTFE) rednces the coefficient of thermal expansion. On the other hand, the incorporation of 20% glass fiber into epoxy resins will increase the coefficient of cubical expansion from 0.5 mn/mn/°C x 10" to 2.0 mn/mn/°C x 10. Reinforcanent of perfluoroalkoxyethylene improved the heat distortion temperature at 0.45 MPa from 24 C to lOO C and at 1.8 MPa from 30°C to 58°C. This was accompanied by a nominal increase in tensile strength. 

The curves of dependence of the relative free energy of PS and PMMA filled with glass powder on the effective thickness of the interlayer between two filler particles are given in Figure 3.4. The values AF/ kT were calculated according to the formula ... 

The above discussion shows that filler also affects the structure of the amorphous region by changing the degree of crystallinity and the ratio between the amorphous and crystalline parts. The study of crystallization of oligoester in the presence of glass powder shows that from the values of energetic parameters of nucleation at various thicknesses of the interlayer, the ratio of specific volumes of amorphous and crystalline phases, Va/Vc, may be calculated. This value is related to the free energy of nuclei surface, Oi, by the empirical ratio ... 

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