Document JJnMz3Nek8J0e47Q96Km7y43a

'-Jit DU PORT DE .NEMOURS (E.'I . ) AST COMPANY ^CTLMINGTON, DEL. POLYCHEMTCALS DEPT. TEFLON TETRAFLUOROETHYLENE RESINS PROPERTIES,' USES. ' ' 1 9 5 ? SD.'-, ' x ' __________ _____ rT p l\S >0 P7 D S , I 57 PLAINTIFFS EXHIBIT WCD-93 nr r j i dielectric properties chem ical inertness ,_A _tc* ^ U` \ - ! weatherresistance PROPERTIES :! / /y /s ' Ii USES Polychemicais department e. i. du pont de nemours a co. (inc.) wiimington , Delaware / > J P r o d u c ts m a d e f r o m D u P o n t T H 3FEd M ' te tr a flu o r o e th l ti :1 v"' / Copyright 1957, E . 1. du P ont de N em ours de Co. (Inc.) 1 .1i 4 water absorption lets than 0.01 % > ns offer th is unexcelled com bin ation of properties. y . coefficient of friction DIELECTRIC PROPERTIES--Low power factor, low dielectric constant, high volume and surface resistivity, good dielectric strength . . . all constant over a wide range of frequencies and temperatures. CHEMICAL INERTNESS--Inert to nearly all chemicals and solvents. Exceptions to this include attack by the alkali metals under certain conditions. At elevated temperatures and pressures, halogens and certain halogenated chemicals and solvents may affect it. HEAT RESISTANCE--Capable of continuous service at 500F. TOUGHNESS AND FLEXIBILITY--Remain tough even at extremely low temperatures. LOW COEFFICIENT OF FRICTION--Unique slippery surface re sists adhesion to most materials. MOISTURE ABSORPTION--Less than 0.01% by ASTM test. WEATHER-RESISTANCE--Absolutely no recorded change in properties after 10 years of outdoor exposure, . / ' / ... . Table of C on ten ts _ p age H istory.............................................. ............ 3 G eneral Characteristics....................... 3 M anufacture............................................... 5 Co*mpositions................................................ 6 U s e s ............................................................... . 7 Electrical Applications................................. 7 Chemical Equipment Applications........... 9 Mechanical Applications.............................. 12 Non-Adhesive Applications......................... 13 P roperties.................................................... 15 Thermal Properties.............................. 15 Mechanical Properties.................................. 15 Friction Properties........................................ 16 Non-Adhesive Property................................ 16 Chemical Properties...................................... 17 Electrical Properties...................................... 17 Other Properties.......................... 18 Safety Precautions.T..................................... 18 Use of Additives with " Teflon" tetrafluoroethylene resins........... ................ 19 Standard Products Made of " Teflon" tetrafluoroethylene resins........................... 23 Fabricating Techniques.................................. 25 Coloring " Teflon" . tetrafluoroethylene resins........................... 28 Bibliography.................................................... 60 PROPERTIES n iiF E tetrafluoroethylene resins USES " Teflon' is a registered trademark of the Du Pont Company. "Teflon' tetrafluoroethylene resins have a combination of electrical, chemical, and thermal properties unmatched by any other single material. These properties have established "Teflon" tetrafluoroethyl ene resins as outstanding materials for use in electrical insulation at high frequencies ' and high temperatures; as a gasket and packing material in the chemical processing industries; and in many other applications. History General Characteristics "Teflon" tetrafluoroethylene resins are mem bers of the fluorocarbon family, and an out growth of the same Du Pont research that led to the development of the "Freon"1 series of refrigerants. The commercial production of "Freon" refrigerants, compounds consisting of fluorine, carbon, and (usually) chlorine, began in 1931. Further research on this family of products led to the laboratory discovery of the first tetrafluoroethylene resin in 1938. Semi plant production of "Teflon"tetrafluoroethylene resins began in 1941; and the first commercial plant, at Parkersburg, West Virginia, started operation in 1950. Continuing research has resulted in the development of a variety of tetrafluoroethylene resins, and in the continual improvement of fabricating techniques. 1O rganic Chem icals D ep artm en t, D u P o n t C om pany. Fabricated shapes of "Teflon" tetrafluoroethyl ene resins are tough, flexible in thin sections, and fairly rigid in massive pieces. They main tain their useful mechanical properties at tem peratures in the range from --450F. up to 500 F. or more. Their surfaces manifest an extremely low coefficient of friction, and al most nothing sticks to them. However, by special treatments (discussed on page 27) these surfaces can be made fo accept conventional industrial adhesives. "Teflon" tetrafluoroethyl ene resins are almost completely inert to chem ical attack, being affected only by such sub stances .as liquid alkali metals and fluorine. The low-loss electrical characteristics of the resins remain essentially constant, regardless of frequency, over a wide range of temperature. / 3 "Teflon" tetrafluoroethylene resins are unique materials, differing in important re spects from conventional thermoplastic and thermosetting resins. In their usual state at ordinary temperatures, they tend to be opaque, crystalline, and malleable. On being heated above 620F., they become transparent, am orphous, and relatively intractable, fracturing if severely deformed. They return to the opaque, crystalline malleable state on being cooled below 620 F. In the particular forms supplied to process ors, "Teflon" tetrafluoroethylene resins can be aggregated into dense coherent shapes at tem- peratures below 620F. by means of various "cold-forming" techniques. The cold-formed products then can be strengthened, if desired, by a process called "sintering," which involves heating the pre-formed resin at temperatures above 620F., and cooling below 620F. The sintered products may then be further shaped by various post-forming techniques, most readily at temperatures approaching but be low the 620F. transition temperature. Cold forming, sintering, and post-forming are the techniques most commonly employed in the processing of "Teflon" tetrafluoroethylene resins into useful articles. . 4 FIG U RE 1-- Some of the more important steps in the manufacture of "Teflon molding powder chlorpdrtluflrem M han*- filra (lw ra tlt)rl w m o n o m tt hyd roch lo ric ocid I i: POLYMERIZATIONKETTLE. tf- flTCFLO N " MOLDING POWDER hyd roch lo ric ocid Manufacture The manufacture of a "Teflon"molding powder is illustrated in the flow sheet (Figure 1). Fluorspar ( calcium fluoride) and sulfuric acid are reacted to give hydrogen fluoride, which is reacted, in turn, with chloroform to give chlorodifluoromethane. This is converted by pyrolysis to gaseous tetrafluoroethylene mono mer. The monomer is subsequently poly merized under high pressure and temperature. The polymer consists of long straight-chain molecules packed closely together. This struc (1) CaF2 + H2SO<- (lluorepar) > 2HF + CaSO< (hydrortn fluoride) (2) 2HF + CHCla - (chloioform) -> CHCIFj 4- 2HCI (chlorodifluoromothine) (3) 2CHCIF2 (pyrolyili) > CF2CF2 4- 2HCI ftetrafluorosthylsn* monomar) (4> r p F1 J" F F F F F 1 n| C = C -------- H - C - C - C - C - C - Lf fJ L F F F F F Jx *Teflon" molding powder ture and the strong chemical bond between carbon and fluorine in the molecule impart exceptional resistance to heat and chemicals. "Teflon" tetrafluoroethylene resins manu factured by the Du Pont Company are avail able as powder and as aqueous dispersion. The "Teflon" powders are used in molding and ex trusion processes. The "Teflon" aqueous dis persions are used in coating, film-casting, impregnating, and the production of composi tions containing additives. 5 Compositions The Polychemicals Department of the Du Pont Company supplies "Teflon" tetrafluoroethylene resins as a series of powders and aqueous dis persions. The basic characteristics of each are described below. Granular Molding Powders. These are sup plied in different granulations, tailored to spe cific uses. The general-purpose molding pow der is a white granular powder with a particle size of about 30 mesh. Its bulk density is about 500 grams per liter. It is processed by molding, and by special ram and screw extru sion techniques. Other Powders. Special powders are sup plied for the extrusion of articles of thin cross section. When compounded with an extrusion aid such as naphtha, they can be readily ex truded as tape, tubing, wire insulation, and shapes. Aqueous Dispersions. These are hydropho bic colloids with negatively charged particles. They contain 30-60% solids by weight and are stabilized with non-ionic wetting agents. The dispersions are normally supplied with a pH of 10 0.5. "Teflon" tetrafluoroethylene resins are con verted into tape, sheets, rods, tubes, coated fabrics, coated wire, wire enamels, molded parts, etc., by a number of manufacturers. \ Uses Electrical Applications--Because of their unique combination of electrical, thermal, and me chanical properties, "Teflon" tetrafluoroethylene resins are used extensively by the electrical industry, particularly in insulation for use at high frequencies and high temperatures. Tetrafluoroethylene resins offer many ad vantages for such uses, permitting improved design in many cases and providing unexcelled performance. The polymers can be made into thin, flexible insulation in many instances where such an insulation would previously have been impossible. In some types of elec trical equipment, it permits miniaturization and compactness of design. Because of its resiliency and toughness, the use of compo nents molded of "Teflon" tetrafluoroethylene resins frequently simplifies installation. Tape made from the resins is easy to handle, con forms well to corners and odd shapes, and is readily adaptable to automatic wrapping op erations. Wire and Cable. Tetrafluoroethylene resins are used for the insulation of many types of wires and cables. Specific fields of application include motors, generators, and transformers of all types; and aircraft, automotive, com munications, electronics, locomotive, and ma rine equipment. Wire insulated with enamels made from the polymer is used in fractional motors, elec tronic transformers, thermocouples, and con trol equipment (such as aircraft controls). The primary advantages contributed by "Teflon" tetrafluoroethylene resins in wire of this type are high service temperature and low power loss they make possible. Wire with insulation of medium thicknesses is used in electronic applications (as hook-up wire), distribution and power transformers, and aircraft, integral, and traction motors; and under corrosive conditions (as in chemical plants). Thick-walled insulations made of "Teflon" tetrafluoroethylene resins are used in coaxial cables for radar and television, and on wire designed for use under conditions of high voltages and high temperatures. The excel lent dielectric characteristics of these products over the full frequency range make them out standing for these Applications. Motors and Generators. Articles made of "Teflon" tetrafluoroethylene resins give out standing performance in many sizes and types of electric motors and generators, especially when service temperatures are too high for other dielectrics, when ruggedness and de pendability are paramount, or when motors 7 must operate in corrosive atmospheres. Tape made from the resins is particularly suitable for use in motors and generators. Uses include conductor insulation for armature or field, coil wrappers, slot liners, taping of coils, lead insulation, and coil separators within slots. These uses are illustrated in Figures 2-6. In addition to these uses in tape-wrapped constructions, fine wire coated with enamels made from one of the polymers is used in syn chronous and fractional motors, and wire insulated by extrusion or calendering (as well as by tape-wrapping) is used in integral and traction motors. A motor will tend to run more coolly with an insulation of a "Teflon" tetrafluoroethylene resin than with other materials. Although the thermal conductivity of these resins is lower than that of some conventional insulating materials, the heat transfer of an insulation made of "Teflon" tetrafluoroethylene resins is better because it is a compact, solid structure. Transformers and Coils. With the develop ment of new fabricating techniques for the resins, it is now possible to design transformers capable of operating at hot-spot temperatures as high as 550 F. Tetrafluoroethylene resins also permit considerable simplification of de sign and reduction in size of equipment, as compared to the use of sealed containers con taining liquid or gas dielectrics. The polymers are used in transformers as conductor, layer, and ground insulation, and for coil separators. This insulation is applied by a variety of methods, depending on the requirements of the particular application. For electronic transformers, the wire is coated with enamel made from a tetrafluoroethylene resin. For distribution transformers (Figure 7), the wire is insulated by extrusion or calendering, or taped constructions can be used. Such con structions as that shown in Figure 7 can be fused after assembly, excluding air and pro viding a compact coil unit. For power transformers, tetrafluoroethylene resin is used as conductor and layer insulation in the forms of tape and laminates made from glass cloth coated with the aqueous dispersion. Laminates provide high resistance to cutthrough and abrasion. Capacitors. Tetrafluoroethylene resins are giving outstanding service in electronic and line capacitors where ambient temperatures are high and minimum power loss is essential. They are used as the dielectric in wrapped capacitors. Two layers of cast tape are used between conductor plates for the electronic capacitors, while two layers of shaved or extruded tape are used in the line types. Much higher dielec tric strength can be achieved by use of two layers than by a thicker single layer. Power Distribution Equipment. Because ar ticles made of it have resistance to heat, weather, and moisture, and a low loss factor, "Teflon" tetrafluoroethylene resins are particu larly suitable for use in power distribution equipment. These uses include insulation for 8 W RAPPING TAPE FIGURE 5--Slot liners CONDUCTOR FIGURE 6--Conductor insulation for armature or field wire and cable, and insulation for motors, gen erators, and transformers. The use of laminates of glass fabric coated with "Teflon" aqueous dispersion is also important in components for power distribution equipment. Electronics Equipment. "Teflon" tetrafluoroethvlene resins are used in electronics equip ment as molded components, tape, and ex truded insulation. The excellent dielectric properties of these resins, even at ultra-high frequencies, and their moisture-resistance are particularly important in the electronics field. Heat-resistance is frequently essential, too, especially with the present trend to minia turization of electronics equipment, which re sults in increased operating temperatures. Components molded of "Teflon" tetrafluoroethylene resins include tube sockets, inserts for coaxial connectors, coaxial spacers, bases for sub-assemblies, terminals, and small stand off insulators. A variety of types and sizes of high-temperature hook-up wires for electronic appliances are insulated with "Teflon" tetrafluoroethvlene resins for their combination of properties not otherwise obtainable in a thin, flexible jacket. Such insulation is either ex truded or tape-wrapped. Other uses of tape made from a "Teflon" tetrafluoroethylene resin include layer insula tion and coil separators. Thin film cast from the dispersion is used for electronic capacitors, and for wrapping small components. Lam inates of glass fabric coated with "Teflon" dis persion are used for terminal boards, bases for printed circuits, and sub-assembly mount ing boards. Chemical Equipment Applications --The first commercial use of a "Teflon" tetrafluoroethyl ene resin was a gasket exposed to a boiling mixture of sulfuric and nitric acids. It proved so successful in this case that it has since been employed in hundreds of applications in the most difficult services encountered in the vthemical industry. In many instances, "Teflon" tetrafluoroethylene resins have been found to be the only materials that would give satis factory performance. In others, they have reduced maintenance requirements, lowered replacement costs, reduced wear on pistons and shafts, increased productive capacity EN D PLATE FIGURE 7--Distribution transformer coil 9 through less down-time, and permitted simpli fication of design. The use of these resins also frequently improves the quality of the prod ucts being processed because they do not con taminate materials being processed. Caskets. All types of gaskets are made of "Teflon" tetrafluoroethylene resins. For some uses, solid gaskets give satisfactory service. Many other applications are better served by one of a variety of jacketed and spiral-wound gaskets. Envelope gaskets, in which a filler is en closed in a shield made of a "Teflon" resin (Figure 8), are used where bolting pressures are limited, as in the case with comparatively fragile pipe made from ceramics, glass, or car bon, and glass-lined equipment. Spirally-wound gaskets and gaskets made from asbestos and glass cloth impregnated with "Teflon" dispersion are used in highpressure installations. Thus the unique proper ties of "Teflon" tetrafluoroethylene resins are applied to such gasket applications as pipe joints, valve bodies, reaction kettles, steam couplings, pump bodies, packaging closures, and containers for compressed gases. Gaskets made of "Teflon" tetrafluoroethylene resins have been used successfully in contact with bromine, chlorine, sulfur dioxide, con centrated sulfuric acid, aqua regia, thionylchloride, organic solvents of all types, and FILLER FIGURE 8--Envelope gasket made with a "Teflon" tetrafluoroethylene resin many, many other corrosive materials. Packings. Packings made from these resins are also supplied in many forms. Solid rings are completely impervious to gases and liquids, and have the advantage of simplicity. They are used singly or in series. Tapered wedge rings molded from a "Teflon" tetrafluoroethyl ene resin have an advantage over solid rec tangular rings in some cases, because they can be seated with lower gland forces. Braided packings are made of twisted rib bons of one of the polymers usually in com bination with asbestos yarn. These packings are'suitable for valves and low-speed shafts, and have the advantage of convenience for ready installation in stuffing boxes of various sizes. "Plastic" packings consisting of a shredded "Teflon" tetrafluoroethylene resin and a binder are easily shaped in the stuffing box. These packings will seal at low gland pressure. A variety of special shapes such as cup-andcone rings and "V" rings are also made of tetrafluoroethylene resins. The "V" ring, for example, is designed to provide a seal with a minimum gland pressure between parts having comparatively little relative motion. Packings made of asbestos braid impreg nated with "Teflon" aqueous dispersion pro vide the chemical-resistance of "Teflon" tetra fluoroethylene resins, while maintaining the strength and resiliency of asbestos fibers. An example of the use of one of the poly mers in high-speed packings is shown in Figure 9. Here, the packing rings are made by shredding a molded piece of "Teflon" tetra fluoroethylene resin and adding a small amount of binder (graphite, mica, or other low-friction modifier) to the shreddings to provide the nec essary combination ol form-stability, resiliency, and abrasion-resistance. As in the case of gaskets, packings made of the resins have given excellent service in many types of chemical equipment--pumps, valves, agitators, etc. --handling the most corrosive materials. In fact, cases have been reported in which pump packings made of "Teflon" tetra fluoroethylene resins have outlasted conven- 10 FIGURE 9--Stuffing box packed vith a " Teflon" tetrafluoroethylene resin tional packings by over 300 times. Valve Components. Valve components made of tetrafluoroethylene resins give outstanding performance and long service life, providing important savings in labor, material, and pro duction down-time. Gaskets and packings were among the earli est applications of these resins in valves. When made of "Teflon" tetrafluoroethylene resins these parts normally outlast the valve itself, permit miniaturization of packing glands, and require less torque to open and close the valve. The use of tetrafluoroethylene resins in valve seats and discs frequently permits inter changeability of valve parts and simplification of design, and improves operating characteris tics (Figure 10). The resiliency of these poly mers is an important factor in their use as a material for valve seats, providing tight, leak proof seating. "Teflon" molding powders have also been employed as materials for a liner in plug cock valves (Figure 11). In this application, their use prevents freezing of the plug cock in the body, and eliminates the need for intricate and costly design usually involved in lubricated valves. Tetrafluoroethylene resins have proved suc cessful in diaphragms for valves of the Saun ders type. Some diaphragms for pressurecontrolled valves are made either from these resins alone or glass cloth impregnated with "Teflon" aqueous dispersion. Pump Components. Gaskets and packings made of tetrafluoroethylene resins are used satisfactorily in countless pump applications handling corrosive chemicals under extremely seyere conditions. In mechanical seals (Figure 12), they elimi nate the possibility of scoring the shaft, and offer an excellent combination of chemicalresistance and flex life. "Teflon" tetrafluoroethylene resins are also giving excellent performance in impellers. This rapidly moving component is frequently the FIGURE 10--Valve with packing and seat of " Teflon" molding powder FIGURE 11--Plug valve with liner of a " Teflon" tetrafluoroethylene resin FIGURE 12--Mechanical seal of a " Teflon" tetrafluoroethylem li first element of a pump to fail, because of cor rosion and erosion accelerated by the imping ing of corrosive fluids. Tetrafluoroethylene resins provide a Jiigh degree of resistance to this effect (Figure 13). They are compounded with powdered glass and similar additives for applications of this type, for dimensional stability. In a similar manner, bearings made of com pounded tetrafluoroethylene resins are used in the same pump. The use of these resins for bearings and impellers has greatly extended the range of chemicals that can be handled by the single pump. Another type of pump impeller is the dia phragm. In this application, "Teflon" tetra fluoroethylene resins are used without being compounded, giving excellent flex life. Pipe and Tubing. Several types of pipe and tubing are made of tetrafluoroethylene resins. These include: (1) tubing made from laminate of glass im pregnated with "Teflon" aqueous dispersion-- ' both with and without a lining of solid tetra^ fluoroethylene resin; (2) thin-wall tubing made from an unsup ported "Teflon" molding powder, tetrafluoro ethylene resin with an overbraid of wire or cloth, and a compounded "Teflon" molding powder; (3) pipe (in standard sizes) made of both solid and compounded tetrafluoroethylene resin; (4) metal pipe lined with thin-wall tubing made of "Teflon" extrusion compound. Mechanical Applications--A new, and poten tially large, field of application for "Teflon" tetrafluoroethylene resins is that of mechanical parts, primarily bearing surfaces. Of particular importance in this use is its low coefficient of friction. Its form-stability under load is en hanced by use of the proper reinforcing agents, while other properties remain substantially unchanged. In some cases, the chemical inert ness of tetrafluoroethylene resins are employed. The use of "Teflon" tetrafluoroethylene resins as a bearing in pumps, noted under Chemical Equipment Applications, is an excel lent example of the combination of properties offered by these resins. In this use, chemical inertness plus unusual frictional properties have provided a bearing whose service cannot be matched by those made of other materials. A bearing made of "Teflon" molding powder compounded with an inorganic material is used on the rolls of a textile twisting machine to make possible the elimination of lubricants and the resulting contamination of goods by oil. This is a half-sleeve bearing which runs on a shaft of cast iron or hardened steel. The shaft turns at about 100-200 r.p.m., and the INLET (oullt In r.m o v.d 1 ^ / FIG U RE 13-- Pump with impeller and bearings of a "Teflon" molding powder 12 be.lring is subjected to loads of about 175 lb./sq.in. Tests indicate that the reinforced coinposition operates satisfactorily without lubricants, and under greater loads and speeds than are normal in textile operations. Tests are now underway to develop speed anl load data on "Teflon" tetrafluoroethylene __resins compounded with various reinforcing \ materials. Where difficult bearing applications 1 are encountered, and particularly where cor I rosion or high temperatures present a problem, i or where normal lubricants cannot be used, these resins compounded with reinforcing agents may provide the answer. Non-Adhesive Applications--The unique non adhesive property of articles made of "Teflon" tetrafluoroethylene resins is utilized in a var iety of operations in which sticky materials are - - handled.; By covering the critical surfaces of processing equipment with a tetrafluoroethyl- / ene resin, the following advantages are real- j ized: J ^ (1) reduction in time required for cleaning, (2) reduction in waste of materials, (3) elimination of ingredients added to re duce stickiness, (4) improvement of product quality, (5) improvement of operating efficiency. "Teflon" tetrafluoroethylene resins are ap plied to surfaces for nonadhesive purposes as a solid film or extruded or molded shape, which can be attached to the equipment by mechanical means; as a finish, applied directly to the substrate by use of a primer coat and multiple spraying and fusing operations; or as a glass cloth impregnated with "Teflon" aque ous dispersion. fn general, "Teflon" molding powders are used as tape or sheet when the surface is sub jected to hard mechanical usage and may require periodic resurfacing; or where resili ency is needed; or where, because of size or other considerations, it is not feasible to apply a finish. . A finish (made from "Teflon" dispersion) is used where a thin film (e.g., 4 to 8 mils) is desired over a metal substrate. Glass cloth impregnated with "Teflon" dis persion is used where it is necessary to com bine flexibility with strength and dimensional stability in a thin film. On bread-sheeting rolls, "Teflon" tetrafluoro ethylene resins eliminate the need for accu rately ground scrapers, otherwise needed to strip the sticky dough from the sheeting rolls. They reduce or eliminate the use of dusting flour to reduce sticking, and make it possible to produce bread of improved quality because a thinner sheet is rolled. The use of tape made of tetrafluoroethylene resin on heat-sealer plates of wrapping ma chines eliminates sticking of packaging ma terials to the sealer plates, and prevents build up of foreign matter on the plates. Other uses in packaging machinery include guides, dead plates, and hoppers of packaging machines to reduce cleaning and improve operating effi ciency. Tetrafluoroethylene resins are also used for their non-adhesive characteristics in a variety of other applications in food-processing equip ment, especially machinery used in the prep aration and handling of candy; in the rubber and plastics industries, to prevent sticking to molds and platens; and in industries in which glue is handled extensively. __ -- 13 m T A B L E 1-- Properties of molded " Teflon" tetrafluoroethylene resins 'J PROPERTY UNITS A.S.T.M. METHOD ____________* Tensile strength, 73F. ______________________ Elongation, 73F. Flexural strength, 73F. Ib./sq.in. % Ib./sq.in. Flexural modulus, 73F. Ib./sq.in. Impact strength, Izod, --40F. ft.-lb./in. 73F. ft.-lb./in. Hardness, Durometer at 1% offset, 73F. Ib./sq.in. Coefficient o f linear thermal expansion per F., 73-- 140F. Thermal conductivity, 0.18 in. B.T.U./hr./sq.ft./F./in. Specific heat B.T.U./lb./F. Deformation under load, 122F., 1200 Ib./sq.ln., 24 hrs. 122F., 2000 Ib./sq.in., 24 hrs. Heat-distortion temperature, 66 Ib./sqJn. Dielectric strength, short-time, 0.080 in. % % F- / v/mil Surface arc-resistance sec Volume resistivity ohm-cm. Surface resistivity, 100% R.H. megohms Dielectric constant, 60 to 3 x 109 cycles Dissipation factor, 60 to 3 x 109 cycles ""- Water-absorption . Flammability % in./min. " Specific gravity Resistance to weathering Static or kinetic coefficient of friction against polished steel D638-- 52T D638-- 52T D790-- 49T D747-- 50 D256-- 47T D256--47T D 676-- 49T D695-- 52T D69-- 44 (2) D621-- 51 D621-- 51 D648B-- 45T Dl 49--44 D495--48T D257-- 52T D257-- 52T Dl 50--54T Dl 50-- 54T D570--42 D635-- 44 D792-- 50 (5) 1,500-- 3,000(1) 100--200 did not break 50,000-- 90,000 2.0-- 3.0 2 .5 -- 4.0 D50-- D60 700-- 1,200 5.5 x 10-J \7 0.25 4--8 25 250 400-- 500(3) (4) > 1 0'* >10" 2.1 <0.0003 <0.01 / nonflammable 2.1-- 2.3 excellent (6) 0.04 D ata shown a ra avurag values and should not b e used for specifications. (1) Tensile strength in oriented film may b e as high as 15,000 Ib./sq. in. (2) M easured by Cenco-Fitch apparatus. ' (3 ) Value is 1000*2000 volts/mil in thicknesses of 12 to 5 mils, 4 0 0 0 volts/mil for Va mil. (4) Does not track. (5) Various methods used. (6 ) Unaffected by 10 years' exposure in Florida. ' 14 feMptitfM Properties Properties of "Teflon"tetrafluoroethylene resins are given in Table 1. These are representative values, measured on typical molded specimens essentially free of internal stresses. The proper ties of the various fabricated forms will depend to some extent on method of fabrication. Thermal Properties--Articles made from tetra fluoroethylene resins have exceptional thermal stability, and are suitable for continuous serv ice at 500F. The effect of heat on these resins, with respect to weight loss on continued ex posure, is shown in Table 2. The stability of "Teflon" tetrafluoroethylene resins is illustrated by the weight loss at 600 F.--only about 0.0002% per hour. Tetrafluoroethylene resins also maintain good properties at extremely low temperatures. Mechanical Properties -- Tetrafluoroethylene resins are relatively flexible, and, as has been noted, retain their flexibility and toughness over a wide range of temperatures. High elongation is evidence of their exceptional toughness. The behavior of these resins under compres sion is shown in Figure 14. They flow under initial application of load. After a short time there is no further change, unless the load is changed or the temperature raised. "Teflon" tetrafluoroethylene resins have an appreciable degree of elasticity, and have a perfect plastic memory, or tendency to return to their original shape when heated. When a deforming load is removed, with no change in ] 32 TEMPERATURE, WEIGHT LOSS, C. F. %/hour 204 400 0.0002 (1) 24 Load Removed 260 500 316 600 360 680 390 734 0.0002 (1) 0.0002 II) 0.001 (2) 0.006 (2) O 1* u Long Time Loading, 1000 L b./Sq. In. At 25C., Partially Confined Specimen, 0.5" High, 1.15" D iam eter e* < ______ 420 788 0.09 (2) (1) Test conducted on granular molding pow der. (2) Test conducted on molded sheet. 40 120 160 200 240 280 320 TIME, h ours TABLE 2-W eight loss of "Teflon" tetrafluoroethylene resins at various temperature* FIGURE 14--Typical compressive stress deformation data fot "Teflon" tetrafluoroethylene resins 15 SHiiaUtnaMllHMilljHitfUiiHiiilHIHiiiHilliliMillfelift temperature, there is some recovery, as shown in Figure 14, page 15. If the temperature is raised after removal of load, more complete recovery is effected, and heating to the transi tion temperature (620F.) will restore the original dimensions. (This property of plastic memory is used to advantage in making tight joints between these resins and metal. A com ponent made of a "Teflon" tetrafluoroethylene resin is pressed into a metal assembly at a low temperature in such a manner that there is some deformation of the component. As the temperature is increased and the component of "Teflon" tetrafluoroethylene resin tends to re cover its original shape, a tight joint is pro duced. ) "Teflon" tetrafluoroethylene resins can be "oriented,"as indicated by the fact that they do not recover completely when a deforming load is removed (at normal temperatures). Whether deformed by a tensile or compressive force, internal stresses are introduced that will re main unless relieved by heating. Such internal stresses, often termed orientation, have a marked effect on the physical properties of these resins. This is typified by molded sheets that aie cold-rolled to increase length and width with a corresponding reduction in thick ness. Rolling of sheet stock increases tensile strength and reduces the tendency to deform under compressive load. On the other hand, when sheets processed in this manner are heated, without physical restraint, they shrink in length and width and increase in thickness, because of the stress-relief that takes place. Any article of "Teflon" tetrafluoroethylene resins may contain internal stresses. To obtain maximum dimensional stability, it is neces sary to remove such stresses by heating at a temperature above that which will be en countered in service, before finishing to the final dimensions. Friction Properties --"Teflon" tetrafluoroethyl ene resins have an extremely low coefficient of friction. Coefficients of friction as low as 0.04 have been measured at high loads. The coef ficient of friction is independent of tempera ture in the range of 77F. to 572 F. However, 1 a drop in the coefficient of friction is quite apparent as the temperature is reduced to below the room temperature transition point (about 70F.) of these resins. In actual practice, thin films of a "Teflon" tetrafluoroethylene resin are transferred to sur faces sliding or rotating against it until the surface itself is coated with the resin. Thus, the condition becomes one of a "Teflon" tetra fluoroethylene resin sliding against a "Teflon" tetrafluoroethylene resin. The static coefficient for these resins is equal to the dynamic value. Hence "Teflon" tetrafluoroethylene resins do not exhibit a stick-slip type of motion. Further, the value for tetrafluoroethylene resins is lower than those of graphite and molybdenum disulfide (0.09-0.12). Conse quently, conventional low-friction additives such as these materials are not needed to en hance the friction properties of "Teflon" tetra fluoroethylene resins. Non-Adhesive Property --A unique property of "Teflon" tetrafluoroethylene resins, related to their low friction characteristics, is the fact that few materials tend to stick to their surface. This property is utilized in a variety of opera 16 tions in which sticky materials are handled, as shown in the illustration on page 16. Chemical Properties--"Teflon" tetrafluoroethylene resins have practically universal chemical inertness. Of the chemicals encountered in commercial practice, only alkali metals such as sodium, halogens such as fluorine and some halogen compounds show any sign of attack on these resins. Even with these, special con ditions such as elevated temperatures or pres sures or both are required for a noticeable ef fect. "Teflon" tetrafluoroethylene resins have been tested in many boiling solvents, including a variety of halogenated hydrocarbons, ketones, esters, and alcohols, without swelling or change in weight. It has been immersed in boiling aqua regia, and in hydrofluoric, nitric, and sulfuric acids with no change in weight or properties. It is equally resistant to attack by alkalies in all concentrations. Fluorine and chlorine trifluoride will react with it at ele vated temperatures and pressures. Although tetrafluoroethylene resins are successfully used in chlorine and bromine service, under cer tain conditions the halogens and halogenated compounds may affect them. In addition to its outstanding chemical inert ness, tetrafluoroethylene resins are relatively impermeable to many chemicals. The permea bility of films of "Teflon" tetrafluoroethylene resins to a number of compounds is given in Table 3. These permeability values are very low. Metal coated with a thin layer of a "Teflon" tetrafluoroethylene resin is consider ably superior in chemical resistance to un coated metal. However, on long immersion, materials such as hydrochloric acid may dif fuse through the film and attack the metal sub strate. In the case of thick coatings, the rate of permeability is so low as to be negligible. The permeability property of tetrafluoro ethylene resins is sensitive to their density or crystallinity. Table 3 gives permeability rates at 30 C. for samples of low void content of both low and high density. Some of these data have been extrapolated to correct for crystallinity and thickness. TABLE 3--Permeability data on "Teflon" tetrafluoroethylene resins TYPICAL PERMEABILITIES Gat or Vapor Permeability, gm./lOO (q.in./day (corrected to 1 mil thickness) Specific gravity o f "Teflon'' ` tetrafluoroethylene resins 2.14 2.22 nitrogen, 86F. air, 86F. carbon dioxide, 86F. hydrogen chloride, 86F. benzene, 167F. steam, 334F. 1.1 1.5 10.0 0.03 0.5 140 0.13 0.2 0.8 0.004 . 0.07 15 Liquids at Room Temperature Permeability, gm./lOO sq.in./day* - (corrected to 1 mil thickness) acetic acid, glacial nitric acid, 70% hydrochloric acid, 37% benzene . water * 0.33 0.45 1.5 0.2 . 0.3 ; ''Teflon" tetrafluoroethylene resins densities unknown. it/ . Electrical Properties--The electrical properties of "Teflon" tetrafluoroethylene resins are ex ceptional. Their dissipation factor is less than 0.0003 over the entire spectrum measured to date, 60 cycles to 3,000 megacycles. Their volume resistivity is greater than 1018 ohmcm., even after prolonged soaking in water. ("Teflon" tetrafluoroethylene resins have less than 0.01% water absorption by A.S.T.M. test.) Their surface resistivity is greater than 1017 ohms/sq. even at 100% relative humidity. Tetrafluoroethylene resins also have excel lent arc-resistance. On exposure to an arc, material made of the resins is decomposed to a vapor which leaves no carbonized path, regardless of tim(T of exposure to the arc. Short-time dielectric strengths are high. These values range from 500-4,000 volts per mil, depending on thickness. However, recom mended working stresses are in the range of 50-100 volts per mil, typical voltages used in motor and generators. The electrical properties of "Teflon" tetra fluoroethylene resins are essentially unchanged 17 at temperatures up to at least 480 F. Other Properties--"Teflon" tetrafluoroethylene resins are unaffected by either outdoor weath ering or moisture. Samples exposed in Florida for over ten years are completely unchanged The water - absorption of these resins by A.S.T.M. test is less than 0.01%. "Teflon" tetrafluoroethylene resins are non flammable. Safety Precautions--Because of its excellent heat-stability, the electrical and mechanical properties of "Teflon"tetrafluoroethylene resins are not degraded by the high temperatures to which they may be subjected during normal processing operations and in use. However, these temperatures often exceed the point at which small quantities of gaseous decomposi tion products are evolved. Some of these gases are harmful, and must be eliminated by ade quate ventilation. This is so simple and effec tive that very few problems resulting from the heating of these resins are encountered today. Animal feeding tests clearly show that "Teflon" tetrafluoroethylene resins are harm less when taken internally in reasonable quan tities. Other animal tests have shown that they do not produce skin irritation. These labora tory results are substantiated by the fact that no such cases arising from the handling of these resins during the 18-year history of its development, manufacture, and use, are known to the Du Pont Company. Dust from "Teflon" tetrafluoroethylene res ins, such as might arise from unheated mold ing powder, is also innocuous. However, when tetrafluoroethylene resins are heated above 400F., small quantities of harmful compounds are given off. Conse quently, adequate ventilation must be pro vided at such temperatures. Tetrafluoroethylene resins are extremely stable to heat, as shown in Table 2, page 15, which gives the weight lost by granular mold ing powder at various temperatures. The weight loss of tetrafluoroethylene resin extru sion powders is still small, but somewhat higher than that of the granular material. Sheets and other items molded from these powders show slightly lower losses, because of the lower surface area afforded by molded articles. The pyrolysis of tetrafluoroethylene resins does not become rapid until the tem perature exceeds 735F. Precautions. During the processing of "Teflon" tetrafluoroethylene resins, safety pre cautions should be observed in any sintering operation, and in any incidental local heating of these resins, such as may occur during ma chining operations with high-speed tools, the grinding of metal parts coated with them, or the sawing of sheets. In such operations, ex haust ducts must be located over the equip ment. In machining operations, water-cooling is also advisable. Exhausts must have sufficient suction to eliminate the possibility of any cross draft from open doors or windows. In addi tion to exhaust ventilation directly over the processing machinery, ventilation should also be provided in the rooms housing the equip ment. A typical good installation would be one in which 8,500 cu.ft. of air per minute is provided to a room in which 25 pounds of the resins are processed per hour. Proper educa tion of operating personnel is also imperative. One further point deserves consideration. It has. been pointed out that dust from unheated tetrafluoroethylene resins is, by itself, innocu ous. There is the possibility, however, that this dust, or dust from machine turnings, etc., can contaminate cigarettes or other forms of smok ing tobacco carried in the pockets of operating personnel. If this should happen, the polymer would be decomposed when the tobacco was smoked, and the fumes would be inhaled. It is suggested that the^carrying of cigarettes or tobacco into areas where they could become contaminated with these resins should be pro hibited. Since workers with tetrafluoroethylene resins on their hands could transfer this to cigarettes in smoking, they should be advised to wash their hands before smoking. Further details on health hazards involved in heating "Teflon" are given in Polychemicals Department Information Bulletin No. X-59b. 18 Use o f Additives with "Teflon" tetrafluoroethylene resins The value of "Teflon" tetrafluoroethylene resins in some applications can be considerably enhanced by the use of additives. Such modi fication improves certain mechanical proper ties of these resins, and permits compositions based on them to be tailored to a wide variety of chemical, mechanical, and electrical ap plications. In general, "Teflon" tetrafluoroethylene resins can be compounded to increase these properties: resistance to deformation under load by a factor of 10, resistance to wear by rotating shafts, by as much as 500 times, stiffness by a factor of 4 to 5, thermal conductivity by a factor of 5 to 10, compressive strength by a factor of 3 to 4, hardness by about 10%. Furthermore, the modified compositions re tain these outstanding properties of uncom pounded "Teflon" tetrafluoroethylene resins: low coefficient of friction, heat-resistance (up to 500F.), excellent outdoor durability, non-flammability, zero water-absorption, excellent electrical properties (at low addi tive loadings), high flexural strength. Elongation and impact strength of tetra fluoroethylene resins are adversely affected by the addition of modifiers, but in most instances these changes do not impair the usefulness of the product. The modified compositions can be molded and extruded in the same equipment used for uncompounded resins. Commercial uses of compounded "Teflon" tetrafluoroethylene resins include pump impellers and bearings; liners for plug valves used in steam lines; valve seats and packings; textile-machinery parts ("saddle" bearings); resistors; mounting boards for electronic and electrical parts; and pipe. ! ; Additives --Any material which can tolerate 19 TABLE 4--Typical additives suitable for use with ''Teflon'' tetrafluoroethylene resins MATERIAL Asbestos Blue asbestos Bronze Calcium fluoride Coke flour Glass fiber Graphite * ........------------------ - - ..... TYPE 7M Canadian-- fines Blue African--long staple MO-8802 powder technical fluorspar GC calcined petroleum coke flour; 55-65% through 200 mesh chopped, milled 1/3 2* GP-38 Acheson, 98.5% through 200 mesh SUPPLIER Roybestos Manhattan Company New York, New York Roybestos M anhattan Company New York, New York M etal Disintegrating Co., Inc. Elizabeth, New Jersey Grasselli Chemicals Departm ent Du Pont Company Wilmington, D elaw are National C arbon Division Union C arbide and C arbon Corp. New York, New York Owens-Coming Fiberglas Corp. Philadelphia, Pennsylvania National Carbide*Division Union C arbide and Carbon Corp. New York, New York The choice of a specific additive and concentration depends on the needs of the particular application for which the composition is in tended. As a general rule, the ad ditive should be used in the smallest particle size in which it is available, to obtain the maximum physical proper ties. However, exceptions may be found in the cases of materials of extremely fine particle size. Zircon "G " milled (gray white); fineness less than 44 microns Titanium Alloy Mfg. Div. National Lead Company N iag a ra Falls, New York Properties of Compounded "Teflon" Tetrafluoroethylene the processing temperatures required for tetrafluoroethylene resins can be used. This temperature requirement eliminates organic additives, but most inorganic materials are sufficiently heat-stable. Types of additives that are generally suitable include metallic copper and bronzes, glass fiber, graphite, coke flour, molybdenum disulfide, clay, talc, silica, asbestos, and calcium fluoride powder. Specific materials that have been used with "Teflon" tetrafluoroethylene resins are listed in Table 4. Resins --The physical prop erties of compounded tetrafluoroethylene res ins depend on the additive, the amount of additive, uniformity of the blend, and molding and annealing techniques. The data which fol low, and the accompanying curves (Figure 15) are typical values, and suggest the range of properties that may be obtained. When com paring properties achieved with different ad ditives, it is important that comparisons be made on stocks having equal volume loadings of additive. FIG U R E 15-- Properties of compounded "Teflon" tetrafluoroethylene resins TEN SILE STRENGTH, lb ./ i*. In. The tensile strength of the composition is not changed to any great extent with increas ing concentrations of additive until high load ings (about 50% by volume, and more) are reached (Figure* 15a). Elongation, on the other hand, decreases rapidly with addition of addi tive (Figure 15b). Flexural modulus (modified A.S.T.M. D790) increases sharply with increased concentration of additive beyond 10%, reaches a maximum, and then declines (Figure 15c). This property varies appreciably with molding technique; maximum modulus is obtained by baking in the mold. At proportions of additive generally used, the compositions are too tough to permit meas urement of flexural strength by the usual test (modified A.S.T.M. D790). At extremely high loadings, flexural strength decreases as addi tive content is increased (Figure 15d). Like elongation, impact strength is de creased with addition of modifier (Figure 15e). In many applications, high impact values are not required; for others, it will be necessary to use low loadings. Compressive strength is increased consider ably by the addition of modifier (Figure 15f). Resistance to deformation under load is im proved to an even greater extent. The follow ing are typical values: Additive %Additive (by volume) %Deformation Under Load 2,000 lb./sq.in. 122F., 24 hrs. none .......... .......... 0 ........ .............. 25 coke flour .. ..........33.3......... coke flour .. .......... 66.7......... .............. 0.5--1.3 asbestos .. . ..........50 ......... .............. 0.3 graphite . . . ..........25 ......... .............. 1.7 graphite .. . ..........50 ......... .............. 1.3 Resistance to creep, important in applica- tions in which the "Teflon" tetrafluoroethylene resins are subjected to a sustained load, is im proved in a similar manner. Modified compositions are harder than un compounded, though the increase is small at lower loadings (Figure 15g). At higher load ings, hardness can be increased substantially. Although the values for the coefficient of friction vary slightly depending on both addi tive and loading, these differences have little practical significance at usual levels. Conse quently, compounded products can be consid ered as having the same low friction character istics as the unmodified "Teflon" tetrafluoro ethylene resins. No scoring of steel shafts occurs even with hard materials such as glass fibers, though more severe abrasives such as zircon and carborundum should be avoided. The most striking advantage of modified () IMPACT STRENGTH 3.00 4 -- C O N T R O L 20 30 40 50 50 70 80 90 A D D IT IV E. % (f) COMPRESSIVE STRENGTH (9) HARDNESS so 60 G LA SS FIB E R ,*'* T ---- ^ -- A SBESTO S C O KE FLOUR CO N TRO L 50 0 W 20 30 40 50 50 70 80 90 A D D IT IV E, % (h) LINEAR THERMAL EXPANSION 0 10 20 30 40 50 50 70 80 90 A D D IT IV E. % IM P A C T STRENGTH, IZ O D , ft. lb ./In. 21 compositions over uncompounded "Teflon" tetrafluoroethylene resins is in resistance to wear. Stocks modified with silicates, chopped glass fibers, mhlybdenum powder, and graph ite show particularly good wear - resistance. Some typical values are given in Table 5. The linear coefficient of thermal expansion is lowered considerably by the addition of about 25-30% modifier (Figure 15h). Values approaching those of steel and copper are pos sible with very high modifier content. This property appears to be more dependent on the loading than on the particular additive used. The addition of modifiers increases the ther mal conductivity of "Teflon" tetrafluoroethyl ene resins to an appreciable degree. The mag nitude of this change depends on the nature of the additive, as well as the amount. The following are typical values: Thermal Additive %Additive Conductivity (by volume) B.T.U./hr./sq.ft./ F./in. n o n e ............ ................ 0 .. .................... 1.7 coke flour . . . ................ 66.7.. .................... 6.6 graphite . . . . ................50 .. .................... 9.5 graphite . . . . ................74 .. .................... 19.5 asbestos . . . . ................50 .. .................... 4.2 c o p p e r ..........................50 .. .................... 7.5 Excellent electrical properties are obtained at lower concentrations of additive. Typical data on power factor, dielectric constant, and volume resistivity are given in Tables 6 and 7. The water - absorption of compounded "Teflon" tetrafluoroethylene resins is negligi ble, depending on the nature of the additive. In many instances water-absorption is not de tected by standard tests, even after 24-hour immersion in boiling water. The density of compounded "Teflon" tetra fluoroethylene resins varies directly with the density of the additive. Inasmuch as porosity contributes to low density, a high density is a good measure of the quality of a molding. Annealing will, of course, increase density until the maximum value is attained. TA8LE 5--Wear rate of compounded "Teflon" tetrafluoroethylene resins ADDITIVE (1) . RATE OF WEAR, m g./h r. (2) none glass fibers plus pigment graphite copper molybdenum disulfide 0.74 0.0015 0.0015 0.032 0.038 (1) Commercial products containing 1 5 -2 5 % additive by weight. (2) White, H. S., National Bureau o f S tan d ard s Report No. 2 8 8 2 (O ctober 1953). Bearings Yt inch long x V* Inch I. D.; run on Type 3 0 3 stainless steel shafts, 0 .2 5 inch in diam eter, clearance of 0.0 0 2 Inch on diam eter; 2 ,0 0 0 lb ./sq . in.; room tem perature; 150 r.p.m. TABLE 6--Electrical properties of compounded "Teflon" tetrafluoroethylene resins ADDITIVE % ADDITIVE (by volume) POWER FACTOR, DIELECTRIC CONSTANT, 1000 cycles 1000 cycles none coke flour (1) 0 <0.0003 2.0 1 0.001 2.4 powdered glass quartz (1) iceberg clay (2) 50 0.0032 4.75 50 0.0008 3.65 50 0.05 talc (3) 50 0.0004 4.41 titanium dioxide (4) glass fiber 50 25 0.05 0.0019 (1) 1 0 0 -2 0 0 mesh; C. H. Chrystai Co., New York, N. Y. (2) Burgess Pigment Co., Paterson, N. J. (3) W hittaker, Clark, and Daniels, New York, N. Y. (4) "Tl-Pure" L, Pigments Departm ent, DuPont Co.,Wilmington, Del. TABLE 7--Volume resistivity of compounded "Teflon" tetrafluoroethylene resins ADDITIVE none graphite graphite coke flour asbestos copper glass fiber .......... % ADDITIVE (by volume) 0 50 75 66.7 50 50 25 VOLUME RESISTIVITY, ohm-cm. > 1 0 15 87 0 0 2 x 10'1 2x10* 2xio'> ; -j 1 J 22 i i Standard Products made o f "Teflon" tetrafluoroethylene resins A number of processors are equipped to manu facture stock or custom-made items from "Teflon" tetrafluoroethylene resins. Standard forms made from these resins and available commercially include molded parts, tape, sheets, rods, cylinders, tubes, film, coated fab rics, wire, enamels and finishes. Tape--"Teflon" tetrafluoroethylene resins are converted into tape by a variety of processes. Methods by which tape is made, thicknesses available, physical appearance, and form of the resin used in each case are listed in Ta ble 8, page 24. Colored tapes are made from a tetrafluoro ethylene resin for use where identification is necessary. A full range of colors satisfactory for JAN Specifications is available. Electrical properties of the colored tapes are the same as those for uncolored tape. Sheets, Rods, Cylinders -- In cases in which volume of production or other factors do not warrant molding, parts may be machined from stock shapes of "Teflon" molding powders, such as sheets, rods, and cylinders. These are available commercially in a variety of sizes and thicknesses. Coated Fabrics and Laminates--Class fabric coated with "Teflon" dispersion is supplied by the Fabrics Division of the Du Pont Company and other sources. This product is of particular importance in certain applications in the elec trical field, since it provides better mechanical strength and resistance to cut-through than unsupported tape. Sheets of glass fabric coated with "Teflon" dispersion are available in thick nesses of 3 to 10 mils. Laminates of glass fabric coated with "Teflon" dispersion are used where extra rigid ity and strength are needed in relatively thick sections. Finishes--Finishes made from a "Teflon" tetra fluoroethylene resin are supplied by the Fin ishes Division of the Du Pont Company. They have proved particularly successful in non- 5 23 i PROCESS T A B L E 8--Tape made from "Teflon" tetrafluoroethylene resins .4 FORM OF "TEFLON" , DESCRIPTION casting aqueous dispersion colorless, transparent skiving extrusion (compounded) calendering molding powder extrusion powder molding powder white, translucent to opaque bluish white, transparent to translucent bluish white, transparent 'to translucent coating of glass fabric aqueous dispersion tan, opaque THICKNESS, mils 0.25 to 4 1 to 125 4 to 40 2 to 20 3 to 14 j adhesive applications such as coatings on bread pans, cookie molds, rubber molds, and glue-dispensing equipment. The application of these finishes to metal and other surfaces requires a specialized technique, and custom finishing services are offered by a number of companies. Wire enamels are also supplied by the Finishes Division of the Du Pont Company. They are applied to wire by dip coating and sintering operations. Extremely thin coatings are obtainable in this manner. Coated Wire -- The method of applying a "Teflon" tetrafluoroethylene resin to wire de pends to a large extent on the thickness of in sulation desired. The full range of wall thick nesses required by the wire and cable industry can be obtained by a variety of methods, as listed in Table 9. In many applications, especially in the case of cable, the construction of the insulation in cludes glass braid, metal sheathing, or even a semi-conductive tape. The use of such ma terials in conjunction with "Teflon" molding and extrusion powders provides increased me chanical strength, resistance to cut-through, and shielding effects. ' METHOD OF ' APPLICATION dip coating FORM OF "TEFLON" USED enamel, made from aqueous dispersion extrusion (compounded) extrusion powder INSULATION THICKNESS, m ill up to 5 8 to 50 : calendering molding powder 15 tO 100 ; ram or screw extrusion molding powder 50 to 500 : tape wrapping tape, made by a variety of methods (Table 8) 4 and up . ._ TABLE 9--Wire and cable insulated with Teflpn" tetrattuoroethjrlene resins ' ] 24 ! I J , . Fabricating Techniques Machining--Articles made of "Teflon" tetrafluoroethylene resins can be readily machined to close tolerances, using standard equipment and techniques. Machining is particularly adaptable to standard shapes made of "Teflon" tetrafluoroethylene resins, such as rods, cylin ders, and sheets, available commercially. General Information. For best results, cut ting tools of high-speed steel, ground to pro duce minimum drag, should be used with "Teflon" tetrafluoroethylene resins. Because of the material's toughness and resiliency, it is most important that tools be kept sharp, and that yibration of machinery be avoided. The use of coolants such as water or soluble oils will permit higher cutting speeds, though the use of such coolants is generally not nec essary to produce work of good quality. The thermal expansion of "Teflon" tetrafluor oethylene resins is high (several times that of metals). Therefore, for close tolerances, all critical measurements should be made when the piece is at room temperature. Furthermore, since these resins undergo a crystalline transi tion at about 66-70F., their volume changes about 1.5% at this temperature. This fact must be considered in making measurements. It is recommended that measurements be made at a temperature above 70F. (e.g., 77F.). Sawing. Conventional equipment, including band saws, jig saws, and table saws, can be used without modification for sawing articles made of "Teflon" tetrafluoroethylene resins. Band saws and jig saws give high cutting speeds, but tend to leave rough surfaces. A conventional table saw equipped with hollowground metal-cutting blades or blades made especially for use with plastics will produce a smooth cut. The use of a coqlant is helpful in sawing articles of a "Teflon" tetrafluoroethylene resin. The production of webs or strings is evidence of overheating and indicates the need of a coolant. Drilling. Parts of "Teflon" tetrafluoroethyl ene resins can be drilled satisfactorily with conventional twist drills. Special drills, designed for use with plastics, are available from / , 25 drill manufacturers. These drills have deep flutes that are highly polished to facilitate re moval of chips. Too, some types have much longer flute leads than conventional drills. The use of these special drills for production work is recommended because of the higher drilling rate made possible. Of course, drilling equipment must be in good condition if accurate holes are to be obtained. Loose spindle bearings or bent or poorly sharpened drills will give inaccurate results with "Teflon" tetrafluoroethylene resins, as with any other material. The highest speed that will not cause burn ing or "gumming" should be used, with a slow, uniform feed, to produce a smooth hole of uni form diameter. Chips should be removed at frequent intervals by withdrawing the drill from the work to permit clearing of the hole. In deep holes, the application of cutting oil or other coolant will prevent sticking of the chips. Reaming. Articles made of "Teflon" tetra fluoroethylene resins can be reamed with con ventional types of reamers to produce holes with good finish and accurate dimension. Reamers of the expansion type are preferred. Because of the resiliency of "Teflon" tetra fluoroethylene resins, cuts made with a fixed reamer tend to be undersize. It is almost im possible to remove as little as 0.002-0.003 inch when reaming. Although the reamer will pass through the hole, no stock will be removed, and the hole will remain at the original dimen sion after the reamer is removed. At least 0.010 inch should be removed by the final reaming if a hole of correct size is to be produced. Threading and Tapping. Parts of "Teflon" tetrafluoroethylene resins can be threaded or tapped with conventional equipment. On auto matic or semi-automatic equipment self-open ing dies with high-speed chasers can be used. The use of a lubricant or coolant is desirable when threading or tapping articles made of "Teflon" tetrafluoroethylene resins, but is not always necessary. Threads may be cut in parts of "Teflon" tetrafluoroethylene resins using a lathe with conventional single-pointed tool. As with met als, several successive cuts of 0.005-0.010 inch should be made. The finish cut should not be le ss than 0.005 inch because of the resiliency of the material. When threading long lengths of rod stock, it is necessary to use a follow rest or other support to prevent the work from slipping away from the tool. In production tapping, it is frequently de sirable to use a tap 0.005 inch oversize unless a self-locking thread is desired. Turning. Articles of "Teflon" tetrafluoro ethylene resins can be turned quite easily on any standard metal-working lathe. No special precautions need be observed, although, as in other machining operations, tools should be very sharp. Bits should be ground as for yellow brass or bronze and should have minimum drag. Since "Teflon" tetrafluoroethylene resins tend to produce a continuous chip, which may cause trouble by wrapping around the work, it is helpful, when possible, to grind a chip breaker on the bit to overcome this. Otherwise, it is necessary to cut the chip loose at the end of each pass. High rotational speed with a fine feed will produce a smooth finish, if the tool is properly sharpened. Use of a coolant will permit higher speeds and feeds to be used without causing the surface of the work to soften. Blanking and Punching. Small flat parts such as washers, 1/16 inch or less in thickness, can often be produced more economically by punching or stamping from sheet stock than by injection molding. Conventional dies are used in either hand- or power-operated punch presses. With well - made dies, articles of "Teflon" tetrafluoroethylene resins may be blanked or punched cleanly at high speed. If cracking occurs, it can usually be overcome by preheating the strip or by soaking it in water. Forming--Tape and sheet stock made from "Teflon" tetrafluoroethylene resins can be formed by drawing between male and female dies. Cold forming will be adequate in many cases, though preheating will be helpful when extensive drawing is attempted. A draw of 26 depth equivalent to one-half the diameter of the original sheet can be obtained quite readily. Bonding--Articles of "Teflon" tetrafluoroethylene resins can be successfully bonded to them selves, or to other materials in a variety of ways. In the case of thin tapes or films (less than 20 mils thickness) heat-sealing is fre quently successful. This method involves a short heat cycle with mild contact pressure. For thicker sections (up to 120 mils) a bonding aid is also required. Two materials which have been found successful as a bond ing aid are (1) a film of unsintered tape made from a tetrafluoroethylene resin, and (2) a paste made from a tetrafluoroethylene resin and a fluorocarbon oil. In addition, "Teflon" tetrafluoroethylene res ins can be bonded with conventional adhesives after suitable surface treatment. Bonding with Unsintered Tape. Unsintered tape of "Teflon" tetrafluoroethylene resins with a thickness of 0.010 inch is very satisfactory for this technique. It should be placed between the pieces to be bonded and clamped. The area is then heated to 650F-720F. and al lowed to cool immediately with the clamps in place. Advantages of this tape method of bonding include cleanliness and precision. There is no extrudation accompanied by dripping or smok ing, as may occur with the paste flux method. Bonding with a Fluorocarbon Paste. The process of bonding articles made of "Teflon" tetrafluoroethylene resins to other articles made of "Teflon" tetrafluoroethylene resins is greatly accelerated by the presence of liquid fluorocarbon A suitable bonding aid is a paste consisting of 35 parts by weight "Teflon" mold ing or extrusion powder and 65 parts "Fluorolube"1 LG, a commercially available fluorinated hydrocarbon. In making a lap joint, a thin coating of the paste flux is applied to one surface, and the second piece is clamped securely into position. The area to be bonded is then heated to a temperature of 650F.-720F., and imme diately allowed to cool with clamps in place. It is essential to heat the bond area from both sides at the same time, and electrical strip heaters have been found satisfactory for this. Bonding With Conventional Adhesives--Vari ous processors have developed their own pat ented procedures for preparing articles of "Teflon" tetrafluoroethylene resins having spe cial surfaces to which conventional adhesives will bond. Conventional adhesives adhere to these treated surfaces. As a result, good bond ing strength can be achieved between "Teflon" tetrafluoroethylene resins and wood, glass, steel, aluminum, copper, ceramics, plastics-- and, in fact, any material that will bond with an adhesive. This development has opened up new applications where a material with anti stick qualities and excellent frictional proper ties is required at elevated temperatures and under severe corrosive conditions. Parts fabri cated of "Teflon" tetrafluoroethylene resins will withstand temperatures up to 500F. However, the adhesive maybe the limiting fac tor at elevated temperatures, and its maximum service temperature should be established be fore using under these conditions. R egistered tradem ark of Hooker Electrochem ical Co., N iagara Falls, N. Y. 27 J (.' Coloring "Teflon" tetrafluoroethylene resins Pigments can be incorporated into "Teflon" tetrafluoroethylene resins to give a variety of colors. Colored "Teflon" tetrafluoroethylene resin compositions are useful in wire and cable applications for distinguishing individual wires in multi-wire systems; in resistors and capac itors for indication of electrical rating; in other molded electrical and electronic parts for iden tification purposes; and in the chemical in dustry for the identification of various pipe and tubing systems. For all applications in which "Teflon" tetra fluoroethylene resins are sintered, the pigments must be capable of withstanding the sintering temperatures (720-740F.). Consequently, these applications usually require inorganic pigments. For the few applications in which "Teflon" tetrafluoroethylene resins are not sin tered, pigments of lower heat-resistance can be used. In many instances, it is important that the other properties of "Teflon" tetrafluoroethylene resins not be altered by the addition of pig ment. This can usually be accomplished with out difficulty, if the quantity of pigment added does not exceed 2% of the composition. The permissible concentration varies with the prop erties of the particular pigment. Specific in formation on the heat-stability, hiding power, and dielectric properties of individual pig ments can be obtained from pigment manu facturers. A list of suggested pigments is given in Table 10. Each of these can be incorporated into all forms of "Teflon" tetrafluoroethylene resin. ' In all cases, it is important to obtain a homo geneous mixture of the pigment and the "Teflon" tetrafluoroethylene resin. In the case of molding powder, this can best be done by grinding the two materials together in a "Mi- kropulverizor" (or similar equipment) or at liquid nitrogen temperatures. The latter meth od appears to give the best results. The extrusion powder can be colored by grinding the pigment to a particle size of about 0.2-0.5 microns; adding the pigment to the powder in a container; and rolling the mixture on standard jar rolls. The pigment can be j TABLE 10-- Pigments suitable for use with " Teflon'' tetrafluoroethylene resins. truded. When compositions including the PIGMENTS SUPPLIER extrusion aid are being blended, a sealed con ^'^"Cadmolith" Yellow No. 00 Glidden Company "Aqua-Black" Carbon,Black National Carbon Company ^ 'l ' - Cobalt Blue No. 1055B Du Pont Electrochemical} Dept. "Ti-Pure" Titanium Dioxide Du Pont Pigments Department "Monastral" Blue Du Pont Pigments Department "Monastral" Green Du Pont Pigments Department tainer must be used. Color can best be added to "Teflon" aqueous dispersion if the pigment is first dispersed separately in water containing "Triton"1 X-100 dispersing agent. The two dispersions are then . . . plus.the following colors made by the Ferro Corporation: F-5891 -- Maroon F-5892-- Dork red F-5893-- Red F-4869-- Dark pink F-5894--Orange red F-5895--Orange F-5896-- Light orange F-5897-- Orange yellow F-2967-- Buff F-8115-- Dork buff F-6112-- Red brown F-6113-- Dark yellow brown F-6114--Chocolate brown F-6111 --Medium brown F-6109-- Light yellow brown F-2969-- Yellow F-5512--Lemon yellow F-9658-- Green F-5688--Yellow green F-5274--Medium blue F-5272--Blue green F-5685--Turquoise F-5278--Light violet F-2302-- Black F-4708-- Black F-5073-- White poured together and blended by slow stirring. Either mechanical or hand stirring can be used, but care should be taken to prevent co agulation from excessive agitation. In some extrusion applications, the product may be of a solid color; in others a stripe or stripes are preferred. When a stripe is to be made, a wedge is cut from the preform of the natural-colored, compounded "Teflon" tetra fluoroethylene resin, and a wedge of the de sired color is inserted. The assembled preform is then placed in the extruder, and the tubing or wire-insulation made in the usual manner. Several stripes can be made in this way. If added before, at the same time, or after addi spirals are desired, a spiral groove is cut in the tion of the extrusion aid, in the case of applica preform, and a spiral wedge inserted. tions in which the fine powder is to be ex R e g is te re d tradem ark of Rohm & H aas Co. P h ilad e lp h ia , P a. i 29 Bibliography The chronological bibliography given below includes the more important items in the pub lished literature on "Teflon" tetrafluoroethyl- ene resins. 1. W. E. Hanford and R. M. Joyce, Polytetrafluoro, ethylene, J. A m . C h e m . Soc., 68, 2082 (1946). (This paper describes polymerization and chemical proper ties of "Teflon." ) 2. M. M. Renfrew and E. E. Lewis, Polytetrafluoroethylene, ln d . r Eng. C h e m ., 38, 870 (1946). (This paper lists detailed physical properties of "Teflon." ) 3. E. E. Lewis and M. A. Naylor, Pyrolysis of polytetrafluoroethylene, /. A m . C h e m . Soc., 69, 1968 (1947) . 4. P. W. Bridgman, Proc. A m . A c a d . A r ts S ci., 76, 55 (1948) . (This paper describes transitions in "Teflon" at high pressures.) ' 5. R. L. Scott, The solubility of fluorocarbons, ]. A m . C h e m . Soc., 78, 4090 (1948). 6. H. A. Rigby and C. W. Bunn, A room-temperature transition in polytetrafluoroethylene, N a tu re , 164, 583 (1949) . 7. H. W. Fox and VV. A. Zisman, The spreading of liquids on low energy surfaces (I)--polytetrafluoro ethylene, ]. C oll. S ci., 5, 514 (1950). 8. K. L. Berry and J. H. Peterson. Tracer studies of oxidation-reduction polymerization and molecular weight of "Teflon" tetrafluoroethylene resin, J. A m . C h e m . Soc., 73, 5195 (1951). 9. F. A. Quinn, Jr., D. E. Roberts, and R..N. Work, Volume-temperature relationships for the room tem perature transition in "Teflon." J. A p . P h ys., 22, 1085 (1951). 10. R. N. Haszeldine and A. G. Sharpe, Fluorine and its Compounds, JqfcmWiley and Sons, Inc., New York, New York (1951). 11. J. F. Lontz, W. B. Happoldt, Jr., "Teflon" tetra fluoroethylene resin dispersion--a new aqueous colloi dal dispersion of polytetrafluoroethylene, ln d . r E n g . C h e m ., 44, 1800 (1952). 12. J. F. Lontz, J. A. Jaffe, L. E. Robb and W. B. Happoldt, Jr., "Teflon" dispersion--extrusion properties of lubricated resin from coagulated dispersion, ln d . {? E n g . C h e m ., 44, 1805 (1952). 13. G. T. Furukawa, R. E. McCoskeg, and E. J. King, Calorimetric properties of polytetrafluoroethylene ( "Teflon" ) from 0 to 365K., J. R es. N a t. B u r. S ta n d ., 49, 273 (1952). (NBS Research Paper No. 2364.) 14. P. L. McGeer and H. C. Duus, Effect of pressure on the melting point of "Teflon" tetrafluoroethylene resin, /. C h e m . P h y s., 20, 1813 (1952). 15. H. W. Fox and W. A. Zisman, The spreading of liquids on low energy surfaces, J. C ol. Sci., 5, 514 (1950); K. V. Shooter and O. Taber, The frictional properties of plastics, Proc. P h y. S o c., 65B, 661-73 (1952). 16. K. V. Shooter, Frictional properties of plastics, P roc. R o y a l S o c., (A)212, 488 (1952). 17. K. V. Shooter and D. Tabor, Frictional properties of plastics, P roc. P h y. Soc. o f L o n d o n , 65B, 661 (1952) . 18. C. E. Weir, Transitions and phases of polytetra fluoroethylene ( "Teflon" ), J. R es. N a t. B ur. S ta n d ., 50, 95 (1953). (NBS Research Paper No. 2395.) 19. F. P. Bowden, Friction on snow and ice, Proc. R o y a l Soc., A217, 462 (1953). (This paper describes the use of "Teflon" on skis.) 20. E. E. Lewis, and C. M. Winchester, Rheology of lubricated polytetrafluoroethylene compositions--equip ment and operating variables, In d . 6 - E n g ., C h e m ., 45, 1123 (1953). 21. R. C. Bowers, W. C. Clinton and W. A. Zisman, Effect of halognation on frictional properties of plas tics, J. A p . P h y s., 24, 1066 (1953). 22. R. Carre and R. A. Paris, on the transformations of polytetrafluoroethylene--a note, C o m p t. re n d ., 236, 1559 (1953). (In French.) 23. J. B. Thompson and G. C. Nielsen, "Teflon" dis persion makes dope for pressure-tight pipe joints, C h e m . E n g ., November 1953, p. 196. 24. S. L. Madorsky, V. E. Hart, S. Straus and V. A. Sedlak, Thermal degradation of tetrafluoroethylene and hydrofluoroethylene polymers in a vacuum, J. R es. N a t. B u r. S ta n d ., 51, 327-333 (1953). (NBS Paper No. 2461.) 25. P. Erlich, Dielectric properties of "Teflon" from room temperature to 314C and from frequencies of 102 to 10 C/S, J. R es. N a t. B u r. S ta n d ., 51, 4, 185 (1953) . 26. S. L. Madorsky, V. E. Hart, S. Straus, and V. A. Sedlak, Thermal degradation of tetrafluoroethylene and hydrofluoroethylene polymers in a vacuum, J. R es. N a t. B u r. S ta n d ., 51, 6 , 327 (1953). 27. R. H. H. Pierce, Jr., W. M. D. Bryant, and J. F. Whitney, An X-ray study of the polymorphs of "Teflon" tetrafluoroethylene resins, presented at the Spring meeting of the American Chemical Society, Buffalo, New York, 1952; R. H. H. Pierce, Jr., W. M. D. Bryant, and J. F. Whitney, Crystalline phase transitions in "Teflon," presented at the Fall meeting of the Ameri can Chemical Society, Chicago, Illinois, 1953; C. W. Bunn and E. R. Howells, Structures of molecules and crystals of fluorocarbons, N a tu re , 174, 549 (1954). 28. B. S. Rabinovitch and J. F. Reed, Heat of forma tion of CF3 and some bond dissociation energies for fluorocarbons, J. C h e m . P h y., 22, 2092 (1954). 29. C -'A . Swenson, The mechanical properties of "Teflon" at low temperature, R eo . S c ie n . In st., 25, 834 (1954). 30. A. R. von Hippel, Dielectric materials and appli cations, T e c h . Pr. M .I.T . and John Wiley, New York (1954). 31. J. B. Thompson, G. C. Turrell, and B. W. Sandt, The coefficient of friction of steel on "Teflon" tetra fluoroethylene resin, Soc. Plas. E n g . J., 11, 4 (April 1955). 32. R. C. Bowers, W. C. Clinton, and W. A. Zisman, Frictional behavior of polyethylene, polytetrafluoro ethylene, and halogenated derivatives, N a v . R es. L a b ., Rep. 4167 (1955). 33. H. C. Duus, Thermochemical studies on fluoro carbons, In d . 6 - E n g . C h e m ., 47, 1445 (July 1955). 34. R. C. Doban, C. A. Sperati, and B. W. Sandt, The physical properties of "Teflon" polytetrafluoroethylene, Soc. Plas. E n g . J., 11, 9 fl'iov. 1955). 35. P. J. Wayne, W. M. Bruner, Heat bonding of "Teflon" tetrafluoroethylene resin, Soc. Plas. E n g . J., II, 10 (Dec. 1955). 36. V. G. Fitzsimmons and W. A. Zisman, Thin films of polytetrafluoroethylene resin ("Teflon" ) as lubri cants and preservative coatings for metals, N a v . R es. L a b ., Rep. 4753 (1956). 37. P. E. Thomas, J. F. Lontz, C. A. Sperati, J. L. McPherson, Properties of "Teflon" resins, Soc. Plas. E n g . }., 12, 6 (June 1956). / 31 TJIFLOM*For m ore in fo rm a tio n on tetrafluoroethylene resins The knowledge of an experienced group of Field Repre-/ '- sentatives is available to all users, or prospective users of "Teflon" tetrafluoroethylene resins. These men will gladly work with you or your supplier, or recommend sources from the excellent group of fabricators who proc ess tetrafluoroethylene resins. Also, an extensive library of literature is available describing the properties, uses and processing techniques for tetrafluoroethylene resins. Contact the nearest of our two District Offices listed on the back of this booklet for the additional information either our Field Representatives, or literature may supply. Our District Offices are at your service. Write or call as often as necessary. The Du Pont Company assumes no obligation or liability for any advice furnished by it, or results obtained with respect to these products. All such advice is given and accepted at the buy er's risk. Du Pont warrants that the materials themselves do not infringe the claims of any United States patent; but no license is implied nor is any further patent warranty made. o* z oHo S i u o V 4 3Oin s o Kz o a D istric t Offices: 350 Fifth Avenue, New York 1, New York LOngacre 3-6400 7250 N orth Cicero Avenue, Lincolnwood, Chicago 30, Illinois IN dependence 3-7250 * u .ft.M T .o rr BITTER THINGS FOR BETTER LIVING . . . THROUGH CH EM ISTR Y A-5T82 . AUGUST, 1997 PR IN T E D IN U .S .A .