Volume filler

AH markets, except paper, have been adversely affected by the downturn in the automotive and constmction industries in the early 1990s. Most large-volume fillers are sufficiently diversified so that their growth trends foUow GNP. There are some exceptions. Table 4 gives 1992 price information on specific fillers, including some physical properties and manufacturing processes. 

Premeasured Volume Filler. The second method is to fill a premeasured volume. For containers that do not allow the product to be visible for comparison, such as a composite can for shortening, the filler transfers a premeasured volume of product into the container. There are three types of premeasured volume fillers. 

For a piston premeasured volume filler, the fill cycle consists of an intake stroke and a discharge stroke (Figure 9). During the intake stroke, the piston rises and draws product from the supply tank into a calibrated cylinder, which measures the volume of product. When the cylinder is fuU, the intake port closes and the discharge port opens. The fill takes place as the piston moves downward and delivers the premeasured volume of product into the container below. Most fillers are mechanically operated and simple. These fillers can handle a wide range of product viscosities and a broad range of speeds (15). 

Count may be achieved electronically (breaking a beam of light) or mechanically by counting devices such as slat, revolving disc, column fillers, or lever trip. Volumetric fillers may be the piston principle coupled with non-returnable valves whereby the product is drawn into a cylinder and then ejected via a filling nozzle. Alternatively, gravimetric volume fillers... 

FIGURE41.4 Microstructureofa dental composite. Miradapt [Johnson Johnson] 50% by volume filler barium glass and colloidal silica [Park and Lakes, 1992],... 

Figure 13.7b shows the imaginary part of the dielectric modulus, M", versus/of a PA-11/BT 700-nm nanocomposite at 72°C for volume fractions / = 0.03,0.1, and 0.2. The maximum of M" decreases when the filler content increases, due to the increase in permittivity e. The filler content does not affect the frequency dependence of the three relaxations. However, the ratio between the maximum value of the a -mode versus the maximum value of the a-mode increases with increasing filler content, indicating the interphase effects between the polymer and the nanoparticles. The low-frequency relaxation associated with the MWS phenomena become more pronounced with increasing volume filler fraction compared to the other relaxations. This evolution is attributed to the increase in interfacial effects around the particles. 

CaCOj and CB are the two largest volume fillers consumed in thermoplastics and elastomers. Before functions (5) and (6) are discussed, further discussion on the functional effects of titanates on these two fillers and a host of other inorganics/ organics in thermoplastics, as noted by the author and other investigators, is instructional. 

Volume filler (per hundred volumes rubber) Mooney viscosity MLl+4, 100°C Throughput (g/min) Die swell " (%) ... 

The influence of the volume filler concentration on the dynamic modulus was considered on the basis of analysis of propagation of waves in the two-phase medium. For this case, the following expression was derived ... 

Figure 14.16 Fat injection as a volume filler through the perioral area. (A) Preoperative (B) postoperative - after 9 months...

The starch remains in granular form in the plastic matrix and so may act as a filler. On mixing, starch enhances the biodegradability of the synthetic polymer, mainly because of the increase in polymer surface created after consumption of the starch by microorganisms. The mechanical properties are dependent on such factors as filler volume, filler particle size and shape, and the degree of adhesion of the filler to the polymer matrix. 

In Figure 5.23 the finite element model predictions based on with constraint and unconstrained boundary conditions for the modulus of a glass/epoxy resin composite for various filler volume fractions are shown. 

Filler particle si2e distribution (psd) and shape affect rheology and loading limits of filled compositions and generally are the primary selection criteria. On a theoretical level the influence of particle si2e is understood by contribution to the total energy of a system (2) which can be expressed on a unit volume basis as ... 

Because of the diversity of filler particle shapes, it is difficult to clearly express particle size values in terms of a particle dimension such as length or diameter. Therefore, the particle size of fillers is usually expressed as a theoretical dimension, the equivalent spherical diameter (esd), ie, the diameter of a sphere having the same volume as the particle. An estimate of regularity may be made by comparing the surface area of the equivalent sphere to the actual measured surface area of the particle. The greater the deviation, the more irregular the particle. 

For large amounts of fillers, the maximum theoretical loading with known filler particle size distributions can be estimated. This method (8) assumes efficient packing, ie, the voids between particles are occupied by smaller particles and the voids between the smaller particles are occupied by stiH smaller particles. Thus a very wide filler psd results in a minimum void volume or maximum packing. To get from maximum packing to maximum loading, it is only necessary to express the maximum loading in terms of the minimum amount of binder that fills the interstitial voids and becomes adsorbed on the surface of the filler. 

True Density or Specific Gravity. The average mass per unit volume of the individual particles is called the tme density or specific gravity. This property is most important when volume or mass of the filled composition is a key performance variable. The tme density of fillers composed of relatively large, nonporous, spherical particles is usually determined by a simple Hquid displacement method. Finely divided, porous, or irregular fillers should be measured using a gas pycnometer to assure that all pores, cracks, and crevices are penetrated. 

Bulk Density. Bulk density, or the apparent density, refers to the total amount of space or volume occupied by a given mass of dry powder. It includes the volume taken up by the filler particles themselves and the void volume between the particles. A functional property of fillers in one sense, bulk density is also a key factor in the economics of shipping and storing fillers. 

When determining bulk density, a distinction should be made between loose bulk density and tap density, eg, ASTM B527-81. The latter is a measure of the influence of settling on filler volume at constant mass. 

Plastics. In the plastics industry, the term filler refers to particulate materials that are added to plastic resins in relatively large, ie, over 5%, volume loadings. Except in certain specialty or engineering plastics appHcations, plastics compounders tend to formulate with the objective of optimizing properties at minimum cost rather than maximizing properties at optimum cost. Table 2 fists typical plastic fillers and their uses. 

Fire Resista.nce. Many fillers, particularly inorganic oxides, are noncombustible and provide a measure of passive fire resistance to filled plastics by reducing the volume of combustible matter in the filled composition. Depending on their density, they may also serve as insulation. 

Electrically conductive mbber (13) can be achieved by incorporation of conductive fillers, eg, use of carbon or metal powders. These mbbers exhibit volume resistivities as low as lO " H-cm. Apphcations include use in dissipation of static charge and in conductive bridging between dissimilar electronic materials under harsh operating conditions. 

Spheres. HoUow spherical fillers have become extremely useflil for the plastics industry and others. A wide range of hoUow spherical fillers are currently available, including inorganic hoUow spheres made from glass, carbon, fly ash, alumina, and 2h conia and organic hoUow spheres made from epoxy, polystyrene, urea—formaldehyde, and phenol—formaldehyde. Although phenol—formaldehyde hoUow spheres are not the largest-volume product, they serve in some important appHcations and show potential for future use. 

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