Granular Resin Processing

There are three basic steps for processing granular resins ... 

Chemical Applications. The chemical processing industry uses large amounts of granular and fine powder PTFE. Soft packing appHcations are manufactured from dispersions, and hard packings are molded or machined from stocks and shapes made from granular resin. 

Granular PTFE resins are most frequently processed by compression molding using a technique similar to that common in powder metallurgy and by ram extrusion. Each of these processes requires a specific type of granular resins. 

Shellac, Bleached, Wax-Free, occurs as an amorphous, light yellow, granular resin. It is obtained from lac, the resinous secretion of the insect Laccifer (Tachardia) lacca Kerr (Fam. Coccidae). Shellac, Bleached, Wax-Free, is obtained by the same process as that described in the monograph for Bleached Shellac, except that, in addition, wax is removed by filtration. Its solubility is the same as that of Bleached Shellac. Shellac, Bleached, Wax-Free, is usually dissolved in a suitable solvent for application to food products. 

Pelletized granular resins can be obtained by agglomeration of fine-cut resins. The agglomeration process increases the powder flow and apparent density. The goal of this process is to make the small PTFE particles adhere together. Essentially, there are two processes of agglomeration namely, dry and wet techniques [24]. 

PTFE is produced by free-radical polymerization mechanism in an aqueous media via addition polymerization of tetrafluoroethylene in a batch process. The initiator for the polymerization is usually a water-soluble peroxide, such as ammonium persulfate or disuccinic peroxide. A redox catalyst is used for low temperature polymerization. PTFE is produced by suspension (or slurry) polymerization without a surfactant to obtain granular resins or with a perfluori-nated surfactant emulsion polymerization) to produce fine powder and dispersion products. Polymerization temperature and pressure usually range from 0 to 100°C and 0.7 to 3.5 MPa. 

Extrusion coloring n. the method of adding colorants to a plastic compound by dryblending the colorant with the solid granular resin, extruding the mixture into strands, and cutting these strands into pellets for use in subsequent processing operations. 

Except for a small introduction in the section on aqueous dispersions, high MW PTFE is one perfluoroplastic which is not covered in this chapter. This is because, in the strictest sense, resins of high MW PTFE are not melt processible. Granular PTFE resins are processed by sintered metal technology techniques. PTFE fine powders are processed by paste extrasion techniques. The structures created with the use of these resins can be quite similar to melt processible perfluoroplastic parts or can be very... 

A diagram of the injection molding process is shown in Figure 6.22. The extruder is similar to other fabrication techniques where the granular resin enters a hopper, where the material is transferred to a heated barrel and a reciprocating screw moves the molten plastic to the molding cavity. The molding cavity is unique to this process. The molten polyethylene is forced xmder pressure into a closed mold that is continually cooled. After the molded part cools, the mold opens and the fabricated part is ejected from the mold. An injection molded article can usually be identified by the ejector pin marks that are usually present on the molded part. 

The conditioning process has been fully qualified to meet the requirements of Technical Guide 26 and to ensure the transportability of the conditioned waste according to IAEA Safety Guides in particular appropriate tests were made on the cement+waste matrix and on the final conditioned waste concrete shields will be added to the drums obtained from granular resins and sludges to meet IAEA requirements for transportation. 

First the granular resin was compounded into pellets along with stabilizing additives and the pellets thus made were then used for the powder-pellet mixture experiments under the same process conditions used during the powder conversion step. The experiments were run in the order shown in Table 1. 

Polymer Suspensions. Poly(ethylene oxide) resins ate commercially available as fine granular soHds. However, the polymer can be dispersed in a nonsolvent to provide better metering into various systems. Production processes involve the use of high shear mixers to disperse the soHds in a nonsolvent vehicle (72—74). 

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