Granular resins

The discovery of PTFE (1) in 1938 opened the commercial field of perfluoropolymers. Initial production of PTFE was directed toward the World War II effort, and commercial production was delayed by Du Pont until 1947. Commercial PTFE is manufactured by two different polymerization techniques that result in two different types of chemically identical polymer. Suspension polymerization produces a granular resin, and emulsion polymerization produces the coagulated dispersion that is often referred to as a fine powder or PTFE dispersion. 

Poly etrafluoroethylene is manufactured and sold in three forms granular, fine powder, and aqueous dispersion each requires a different fabrication technique. Granular resins are manufactured in a wide variety of grades to obtain a different balance between powder flows and end use properties (Pig. 1). Pine powders that are made by coagulating aqueous dispersions also are available in various grades. Differences in fine powder grades correspond to their usefulness in specific appHcations and to the ease of fabrication. Aqueous dispersions are sold in latex form and are available in different grades. A variety of formulation techniques are used to tailor these dispersions for specific appHcations. 

Property Granular resin Fine powder ASTM method... 

Electrical Applications. The largest application of PTFE is for hookup and hookup-type wire used in electronic equipment in the military and aerospace industries. Coaxial cables, the second largest appHcation, use tapes made from fine powder resins and some from granular resin. Interconnecting wire appHcations include airframes. Other electrical appHcations include computer wire, electrical tape, electrical components, and spaghetti tubing. 

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. 

Overbraided hose liners are made from fine powder resins by paste extmsion, and thread-sealant tapes are produced from fine powder by calendering. Fabricated gaskets are made from granular resins and pipe liners are produced from fine powder resins. Fibers and filament forms are also available. 

Granular quicklime, 75 27 Granular resins, 73 291-292 fabrication of, 73 299-300 Granulated sugar, refined, 23 481 Granulation, 70 272-273... 

Colestipol and cholestyramine are available as granular preparations. A gradual increase of dosage of granules from 4 or 5 g/d to 20 g/d is recommended. Total dosages of 30-32 g/d may be needed for maximum effect. The usual dosage for a child is 10-20 g/d. Granular resins are mixed with juice or water and allowed to hydrate for 1 minute. Colestipol is also available in 1 g tablets that must be swallowed whole, with a maximum dose of 16 g daily. Colesevelam is available in 625 mg tablets. The maximum dose is six tablets daily. Resins should be taken in two or three doses with meals. They lack effect when taken between meals. 

Suspension polymerization either little or no dispersion agent is used and vigorous agitation is maintained. A precipitated resin, commonly referred to as granular resin, is produced. 

Property Granular Resin Fine Powder ASTM Meth... 

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, occurs as an off white to tan, amorphous, granular resin. Shellac is obtained from lac, the resinous secretion of the insect Laccifer (Tachardia) lacca Kerr (Fam. Coc-cidae). Shellac, Bleached, is obtained by dissolving the lac in aqueous sodium carbonate, followed by bleaching with sodium hypochlorite, precipitation of the bleached lac with a dilute sulfuric acid solution, and drying. It is freely (though very slowly) soluble in alcohol, insoluble in water, and slightly soluble in acetone and in ether. Shellac, Bleached, is usually dissolved in a suitable solvent for application to food products. 

Fine-cut granular resins resnlting from size redaction of the snspension polymer have a typical average particle size 20 pm to 40 pm. The small particle size of hne-cnt PTFE imparts the highest possible mechanical properties to articles made from grannlar resins. Fine-cnt resins (powders) have poor flow and low apparent density... 

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]. 

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