Disk molding

Other uses for coal-tar pitch include production as a binder for foundry cores, as a sealant for dry batteries, and in the manufacture of clay pigeons. PeUeted pitch used as the binder in foundry cores is a hard pitch suppHed as spherical granules which are formed by a spray-cooling process. Clay pigeons consist of disks molded from a mixture of hard pitch and a mineral filler such as clay or limestone dust. 

Requirements of special performance of plasticizers used in the injection molding process are seldom. In optical disk molding, the material requites mote plasticization during processing than ditring the product use. For this reason carbon dioxide was used as an additional plasticizer. Primary plasticizers were selected in such a manner that they will facilitate dissolution of carbon dioxide in melt. Figitre 14.17 shows that the more carbon dioxide dissolves, the lower is the glass transition tern-process, melt viscosity is decreased and... 

One example of the compression-molding process is outlined in Table 12.7 [28]. Polyamide-imide powder particles with a maximum particle size of 150 jm and a median particle size in the range of 10 to 50 pm are preheated in an oven for 1 to 24 h at 260 to 316°C. The purpose is to increase molecular weight and complete the imidization processes, both of which create water and can lead to voids in the compression-molded article. The compression-molding schedule depends on the size and geometry of the mold. A pressure-molding schedule for a 14.0 cm X 1.6 cm disk mold is shown in Table 12.8, where the mold temperature is set in the range of 315 to 329°C. 

Figure 13.7. Radial flow in a center-gated disk mold. (Not a possible solution as shown.)...

The mandibular fossa is an oval depression in the temporal bone just anterior to the external auditory meatus. It is bounded anteriorly by the articular tubercle, laterally by the zygomatic process, and posteriorly by the tympanic plate. The close proximity of the mandibular fossa to the external auditory meatus allows fingers placed in the meatus of each ear to palpate condylar motion as it rotates and glides in the fossa. Occasionally, a small ridge of bone (the postglenoid tubercle) forms a prominence at the posterior border of the fossa. The shape of the mandibular fossa does not exactly conform to the mandibular condyle. The articular disk molds the two surfaces together. 

Differentiating Eq. (8.7) with respect to Q and equating to zero yields the expression for the minimum pressure gradient Po, mm for center-gated disk mold cavity filling. 

Determine the velocity field and the pressure distribution for the flow of an incompressible Newtonian fluid between two disks as shown in Figure 2.13. Flows similar to this occur in several polymer processes including injection molding in a center-gated disk mold or compression molding. 

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