EP0269850A1 - Copper coated fibers - Google Patents

Copper coated fibers Download PDF

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Publication number
EP0269850A1
EP0269850A1 EP87115698A EP87115698A EP0269850A1 EP 0269850 A1 EP0269850 A1 EP 0269850A1 EP 87115698 A EP87115698 A EP 87115698A EP 87115698 A EP87115698 A EP 87115698A EP 0269850 A1 EP0269850 A1 EP 0269850A1
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EP
European Patent Office
Prior art keywords
fibers
fiber
copper
tow
composition
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP87115698A
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German (de)
English (en)
French (fr)
Inventor
Franklyn Arthur Ballentine
Donna Anne Hutto
Ward Charles Stevens
Charles Kaufmann
Bruce Arthur Luxon
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Wyeth Holdings LLC
Original Assignee
American Cyanamid Co
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Filing date
Publication date
Priority claimed from US06/925,848 external-priority patent/US4808481A/en
Application filed by American Cyanamid Co filed Critical American Cyanamid Co
Publication of EP0269850A1 publication Critical patent/EP0269850A1/en
Withdrawn legal-status Critical Current

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    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M11/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F11/00—Chemical after-treatment of artificial filaments or the like during manufacture
    • D01F11/10—Chemical after-treatment of artificial filaments or the like during manufacture of carbon
    • D01F11/12—Chemical after-treatment of artificial filaments or the like during manufacture of carbon with inorganic substances ; Intercalation
    • D01F11/127—Metals
    • D—TEXTILES; PAPER
    • D02—YARNS; MECHANICAL FINISHING OF YARNS OR ROPES; WARPING OR BEAMING
    • D02G—CRIMPING OR CURLING FIBRES, FILAMENTS, THREADS, OR YARNS; YARNS OR THREADS
    • D02G3/00—Yarns or threads, e.g. fancy yarns; Processes or apparatus for the production thereof, not otherwise provided for
    • D02G3/44—Yarns or threads characterised by the purpose for which they are designed
    • D02G3/441—Yarns or threads with antistatic, conductive or radiation-shielding properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/14—Conductive material dispersed in non-conductive inorganic material
    • H01B1/16—Conductive material dispersed in non-conductive inorganic material the conductive material comprising metals or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys

Definitions

  • This invention relates to a tow or bundle of copper coated fibers, to a method for producing such tows, and to composites produced from such fiber tows.
  • the coated fibers of this invention may be used in a number of ways. Tows or fibers can be chopped and used as a radar obscuration chaff for example. Tows can also be incorporated into composites with various matrices. Composites using copper coated fibers can have the advantages of copper, such as high electrical and thermal conductivity, and can overcome some of the deficient properties of copper such as its high density and high coefficient of thermal expansion.
  • Such features are disadvantageous be­cause they give uneven or irregular properties to any material made from them.
  • a lack of uniformity of the coating thickness will result in an irregular distribution of the base fiber throughout the resulting copper matrix.
  • the presence of uncoated fibers and agglomerates of fibers leads to voids in the matrix in such a composite.
  • Such an uneven distribution of fibers and voids cause poor mechanical prop­erties as well as uneven thermal or electrical conductivity.
  • Agglomerations of fibers can also cause the tow of fibers to be difficult to spread and can thereby make difficult the production of thin composites.
  • the presence of agglomerations can make the tow of fibers less flexible and so make production of filament wound or woven materials difficult.
  • German (Federal Republic of Germany) patent 2,658,234 describes a process "for coating individual fibers of a bundle, in which the fiber bundle is exposed to a reaction solution from which, by a currentless chemical means, a substance is deposited onto the fiber.” In order to assure individualization of the fibers of the tow, "a portion of the fiber bundle is loosely suspended, and ... the reaction solution is fed along the fibers of this portion”. It is stated that "Because of the spreading of the fibers, the reaction solution can reach the surfaces of all the fibers.
  • the fibers can thus be uniformly coated over both their length and their cross section". In one sample embodiment, it is reported that "it is possible...to uniform­ly deposit a 1 micron copper layer on the individual fibers of the bundle". However, when repeated herein, unsuitable coatings were produced as will be shown in the comparative examples.
  • ion plating or vacuum deposition discloses the use of ion plating or vacuum deposition to form "an assembly...of a plurality of carbon fibers each coated with a matrix metal layer, the fibers having bonded points at the metal layers". This process does not form individualized fibers.
  • Japanese patent disclosure number 1982-SHOWA 57-57,851 discloses use of ion plating to coat fabrics of carbon fibers. However, the goal of this process is not to form individualized fibers as the present invention requires and forms.
  • 3,495,940 discloses a process "comprising the steps of (1) forming thin films of sensi­tizing and activating metals on the surface of an organic fiber, (2) electrolessly plating a thin layer of copper on the activated surface, (3) electrodepositing additional copper on top of said copper layer".
  • the process was used to form copper coatings comprising 10 to 50% by weight of said organic fiber. This is a coating thickness of only 0.048 to 0.24 microns for an organic fiber having a density of 1.25 g/cm2, too thin to provide the advantages of the relatively thick copper coatings required herein.
  • Kuz'min cited above, used a process of air oxidation or nitric acid etching, followed by electroless plating, and then electro­lytic plating. While the bath components are given, no specific bath formulation is given. In addition, no fiber handling techniques are noted. EPO 0-156-432 discloses the coating of single optical fibers with a combination of electroless followed by electrolytic plating.
  • the fiber In a favor­able embodiment...the fiber...is electroless plated continu­ously in a first step and is electroplated continuously with a metal layer in a second step....the fiber is passed successively through a number of deposition baths alternated by rinsing baths....In a particularly advantageous embodiment ...a layer of metal is provided continuously by electrodepo­sition on the electrically conductive layer in at least two successive steps, in which between the successive steps the current density is increased and the metal-coated fiber is electrically contacted". No plating of copper is actually exemplified.
  • composites that have a copper matrix reinforced with fibers, these having been formed by a number of techniques.
  • tows of reinforcing fibers can be impregnated with a slurry of copper powder and then consolidated under heat and pressure. Sometimes this process may involve sandwiching the fibers between copper foils.
  • Such methods have several disadvantages. Since copper does not spontaneously wet some fibers, especially carbon fibers, additives, for example, titanium, must be provided in the copper to permit wetting. However, such additives reduce the thermal and electrical conductivity of pure copper.
  • Such composites also have unevenly distributed reinforcing fibers.
  • An object of this invention is provide tows of fibers that are uniformly coated with copper which are use­ful as reinforcing fibers or as fillers in composites that require high thermal or electrical conductivity.
  • Such tows of fibers can be used as "free" fibers (as compared to fibers embedded in a matrix).
  • the fiber can be chopped and used as chaff, or it can be used as conductive brushes.
  • Another object of this invention is to provide a process by which fibers may be coated uniformly with copper.
  • a further object of this invention is provide copper matrix composite materials that are useful as mater­ials for low density radiators, low thermal expansion electrical conductors, and other applications.
  • yarns and tows comprising composite fibers, which have a core and at least one relatively thick, uniform and firmly adherent, electrically conductive layer comprising copper on said core.
  • such tows of composite fibers are produced by a process comprising (1) immersing at least a portion of the length of the fiber in a bath of an aqueous solution of a wetting agent, (2) sensitizing the fiber surface to the electroless deposition of a metal comprising copper by immersion in a bath of a colloidal suspension of palladium and tin chloride, (3) immersion in a bath capable of electrolessly plating the fibers with a metal comprising copper and depositing an electrical conductive layer of metal on said fibers, (4) immersion in a bath capable of electrolytically plating with a metal comprising copper, and (5) applying an external vol­tage between the fibers and the bath sufficient to deposit a metal comprising copper on the fibers, the voltage and resulting current to be applied for a time sufficient to produce a relatively thick, uniform and firmly adherent coating comprising copper on said core.
  • Such fiber can be used as "free" fiber or, accord­ing to still another aspect of the invention, it can be formed into composites comprising a continuous yarn or tow of composite fibers, the majority of which have a core and at least one relatively thick, uniform and firmly adherent electrically conductive layer comprising copper on said core, disposed in a matrix comprising a metal or an organic poly­ mer.
  • These matrices can be formed by incorporation, by direct consolidation by hot pressing or other methods. In the latter case, the composites obtained have a uniform distribution of fibers throughout.
  • an injection molding compound comprising elongated granules containing a bundle of elongated composite fibers
  • Said fibers have a core and at least one rela­tively thick, uniform and firmly adherent, electrically conductive layer comprising copper on said core, such fibers extending generally parallel to each other, lengthwise in the granule and uniformly dispersed throughout the granule in a thermally stable, film forming thermoplastic adhesive.
  • the fundamental improvement of the present invention over the prior art is to provide tows of fibers containing as many as 12,000 (12K) fibers that are coated with copper.
  • the present invention provides tows in which the copper coating is dis­tributed very uniformly over the fibers of the tow.
  • the fibers of this invention may have a coating thickness of between about 0.5 microns and about 3.0 microns of copper, preferably from about 0.6 microns to about 3.0 microns, especially preferably, greater than at least about 0.8 microns, and most preferably, greater than at least about 1.2 microns.
  • the coating thickness is uniform around the circum­ference of the fiber, having a standard deviation in thick­ness that is no more than 30% of the average thickness. It is also uniform from fiber to fiber, having a standard devia­tion in thicknesses that is less than 30% of the average thickness.
  • the fibers have a low degree of agglomeration. In the present invention, typically 80% of the fibers of the tow are present as individually coated fibers. As a result of the low agglomeration in the fiber tows of this invention, the tows are flexible and slidable. Furthermore, the copper coating of this invention can be very pure. This means that the highest thermal and electrical conductivities can be obtained.
  • the base fibers of this invention include carbon, graphite, polymeric, glass or ceramic fibers.
  • the choice of base fiber will depend on the nature of the application envisioned for the coated fiber.
  • Structural carbon fibers such as those produced from polyacrylonitrile (PAN), having moduli in the range of 30 to 50 x 106 pounds per square inch (psi), would be selected for applications where moderate strain to failure in the composite were needed.
  • Graphite fibers such as those produced from pitch that have moduli from 55 to 140 x 106 psi might be used where very high ther­mal or electrical conductivity or very low thermal expansion were required.
  • Ceramic fibers having a high diameter might be used in applications where compression strength were needed. Other criteria will be evident to those familiar with the design of composite materials.
  • the process of this invention has several novel and useful characteristics.
  • the process of this invention employs a conventional composition for the electroless bath, but includes preferred features to provide stability, speed of plating and uniformity of coating on the individual fibers throughout the tow.
  • the coating process provides a uniform product in either a batch or continuous process, with good rates of production and good stability of the component solutions.
  • the continuous version of the process uses features designed to give very little tension to the fiber tow and spread the tow. Damage to the fiber is reduced preferably by using a "straight through” design in which the fiber travels an essentially straight path through the plating line. This enables very low strain-to-failure fibers such as pitch based carbon fiber (e.g., Amoco Inc.'s P100 and P120 fibers) to survive the rigors of a continuous plating process.
  • pitch based carbon fiber e.g., Amoco Inc.'s P100 and P120 fibers
  • the copper coating process of the invention comprises the follow­ing steps taken in order:
  • Rinsing steps (ii), (iv), (vi) and (viii) are optional.
  • step (i) the need for an electroless copper solution with high deposition rates requires the use of a formaldehyde reduced bath. Although higher rates were ob­tained with this bath, the tows had poor through-plating resulting in uncoated inner filaments.
  • a wetting agent suitable for carbon surfaces should be used to allow for better penetration into the tow and adsorption of catalyst.
  • the suitable agents are Arquad® B-100, a surfactant made by Armak Chemicals (a division of Akzo Chemie America, Chicago, Illinois). It can be used at concentrations of 0.1 to 1.0% in water, although higher and lower concentra­tions are also possible.
  • the electroless solution can also contain other additives. For example, 1 ppm of mercaptobenzothiozole (MBT) can be included to provide stability to the bath.
  • the sensitizer solution (iii) can also be improved in stabil­ity by omitting urea which is commonly used.
  • step (vii) Although conventional acidic copper electroplat­ing solutions deposit copper onto the electroless copper layer in step (vii), the deposits can be dull, or rough or tend to oxidize soon after plating.
  • the acidic copper solution will be re­placed with a pyrophosphate copper plating solution, which results in brighter deposits that do not oxidize as rapidly as those from the more conventional acidic solutions.
  • Acidic copper plating solutions also have a drawback in the possible dissolution of the thin electroless copper layer on the fiber by the presence of strong acid in the plating solution. If the fiber is made cathodic before entering the solution, such difficulties are minimized.
  • a preferred wetting agent bath (Bath 1) is preferably 1 ml. of Arquad® B-100 surfactant per liter of deionized water.
  • Arquad® B-100 is a cationic, surface active, water soluble benzylalkyl­ammonium chloride. It is a 49% solution of alkyl dimethyl ammonium chloride with alkyl groups derived from fatty acids, with a typical molecular surfactant not only modifies the surface energy of the fiber so that it is easily wet by aqueous solutions, but it also enhances the adsorption of the tin and palladium used as sensitizers on the fiber surface.
  • a preferred sensitizing bath comprises: 1 g. PdCl2 dissolved in 500 ml. deionized H2O; 300 ml. HCl - 35% hydrochloric acid carefully added to palladium chloride solution while stirring; 1.5 g. SNCl4 dissolved in 100 ml. of 35% HCl acid then added to the above solution Heat to 80 deg. C then add 37.5 g. SnCl2 and Deionized water to 1 liter total volume then cool to room temperature and hold for 16 hours.
  • a suitable electroless copper bath (Bath 3) comprises: 19 g. CuSO4*5H2O dissolved in 750 ml. deionized H2O then add while stirring add the following: 31.6 g EDTA disodium salt, dihydrate (ethylene diamine tetraacetic acid) 2 ml. MBT (mercaptobenzothiozole) solution at 0.5g of MBT per liter methanol 16 g. NaOH dissolved in 100 ml. of deionized H2O heat copper solution to 45 deg C and immediately before use add 15 ml. formaldehyde Water to make one liter
  • Another suitable and especially preferred electro­less copper bath comprises: 10 g. CuSO4*5H2O dissolved in 750 ml. deionized H2O then, while stirring, add the following: 30 g. EDTA disodium salt , dihydrate (ethylene diamine tetraacetic acid) 0.5 ml. MBT (mercaptobenzothiozole) solution at 0.5 g of MBT per liter methanol 2 ml. of 2,2 ⁇ dipyridyl (DP) solution at 2g/100 ml methanol 10 g. NaOH dissolved in 100 ml. of deionized H2O Water to 0.990 liter Heat to 45 deg C and immediately before use add: 10 ml. formaldehyde Final pH should be 11.3
  • the copper sulfate is the source of the copper ions
  • EDTA salts act as a chelating agent
  • DP and MBT are stabilizers
  • sodium hydroxide is used to bring the solution a high pH, e.g., 11.3-12.2, formaldehyde will act as a reducing agent at a good rate.
  • a suitable electroplating bath (Bath 5) comprises: UNICHROME® Pyrophosphate Copper Plating Process; Technical Information Sheet No. P-C-10-Xb; and employs the following to make 10 gals. of solution (M&T Chemicals Inc., Rahway, NJ): To 5 gal. of deionized water, add in order the following while stirring: 0.35 gal. M&T Liquid C-11-Xb; 3.33 gal. M&T Liquid C-10-Xb copper pyrophosphate-­containing solution; and 0.05 gal. Ammonium hydroxide, C.P. Fill to total volume of 10 gal. with deionized water. Bath should be operated at 54.5°C and a pH of 8.3 ⁇ 0.2. A brightner M&T Addition Agent PY-61-H (0.9 ml/l) can be added if additional brightness is desired.
  • FIGURE 1 an apparatus for this pro­cess can be seen.
  • the tanks of the apparatus which hold the various solutions, are designed to allow the fiber to be treated with each solution without going over or under rollers which would increase the amount of tension on the fiber.
  • This method of plating is termed line-of-sight plat­ing.
  • FIGURE 2 shows such tanks which use a "weired" design, so called because a weir or overflow is created at the exits of the tank.
  • the fiber can be passed through a series of baths without having to go around a series of rollers or guides after the initial unspooling. It is possible to run several tows in parallel through the apparatus. For example, eight tows can be plated at a time, or even more.
  • spools of uncoated fiber can be supported on bearings which allow the fiber to be unspooled while creating very little tension.
  • the fiber tows are then threaded through eyelets (not shown) which guide the fiber into the first bath (FIG. 2).
  • the first bath contains a wetting agent, e.g., Arquad® B-100 in a 0.1 vol. % solution in the top tank, as shown in FIGURE 2. Filtration of the solution, which is performed by in-line filters, is very desirable to keep all solutions free of an accumulation of broken fibers.
  • a suitable rinse station consists of a table over which the fiber runs, and a water spray directed downward onto this table. The force of the water spray and subsequent run-off the edges of the "table" help to spread the fiber.
  • the second tank in the series contains a catalyst bath, such as an emulsion of palladous chloride and stannous chloride in a hydrochloric acid solution (Bath 2).
  • a catalyst bath such as an emulsion of palladous chloride and stannous chloride in a hydrochloric acid solution (Bath 2).
  • This solution serves to activate the surface of the fiber for the electroless deposition of copper.
  • the bath is circulated with a resevoir tank to maintain the concentration of the components.
  • the fiber is again optionally, but preferably, rinsed after leaving this tank. This rinse is very desirable because drag-out to the following electroless plating tank may severely limit the life and efficiency of the electroless plating solution.
  • the third bath is in a long tank, to provide a sufficient residence time for elec- for electroless plating.
  • the bath contains an electroless copper plating solution, such as given for Bath 3 or 4, above.
  • the bath temperature is maintained in a resevoir tank from which the solution is pumped, as shown in FIGURE 2.
  • the heated solution is then pumped into the inner tank of the weired plating tank arrangement.
  • the pH of the solution is maintained at 11.3, ⁇ 0.5.
  • stability of the bath is increased by aerating the bath by rapid pumping, stirring or sparging with a gas dispersion tube. Rapid solution flow also helps in replenishing solution near the fiber in order to increase the depostion rate of the copper.
  • the fiber optionally is again rinsed as before.
  • Electrolytic plating next is performed in a series of weired tanks all of which are of suitable length, e.g., 20 inches.
  • the plating line may have multiple tanks, e.g., 2, 3, 4, or more, and these many have different current densi­ties.
  • the initial electroplating tank can be run with a current of 8 amperes using 8 tows of 2K fiber.
  • Using a low current in the first tanks permits an initial deposition of an electrolytic layer of copper over the electroless copper.
  • the remaining tanks can be operated at currents of 20 to 30 amperes. This facilitates more rapid plating in any of the remaining tanks.
  • Spreading of the fiber in the electrolytic tanks in accordance with this invention can be carried out in many ways, for example, by use of ultrasonic vibration, agitation of the solution or by physically spreading the fiber.
  • a preferred method uses physically spreading the fibers.
  • beater bars to spread the fibers.
  • a suitable beater bar arrangement can be seen in FIGURE 3.
  • the "L"-shaped bar is oscillated vertically. This agitates the solution, forces fresh solution into the tow of fibers, and spreads the fibers of the tow.
  • the movement of fresh solution into the filaments of the tow increases the deposition rate and ensures uniformity of plating.
  • the stationary bars at either end of the tank help to keep the fiber under solution and also keep the fiber spread out when leaving the plating tank.
  • a 12K tow of IM-6 fiber can spread to almost 1 inch wide by the time it reaches the final plat­ing tank. This spreading keeps the fibers from plating together at neighboring filaments and increases the rate of plating by increasing the mass transfer of solution into the tow.
  • the fiber optionally but preferivelyably is rinsed as described above and then dried by means of an air knife, heat gun or rotary drum drier.
  • a heat gun is attached to a heating chamber (not shown).
  • the fiber is then spooled, either onto a spool with other tows or preferably individually onto separate spools by a fiber winder (e.g., graphite fiber winders made by Leesona Corp., South Carolina) (not shown).
  • a fiber winder e.g., graphite fiber winders made by Leesona Corp., South Carolina
  • Chaff according to the present invention is prepar­ed by chopping strands of copper coated composite fibers as described above into lengths designed to effectively reflect impinging radar waves.
  • the fibers are cut to a length roughly one-half the wavelength of the radar frequency the chaff is intended to be used against or, where very high radar frequencies are encountered, full wavelengths.
  • a radar operator may be monitoring several frequencies, currently in the 2-20 GHz range. In the future, radars may be developed using much higher frequencies.
  • An advantage of the chaff of the present invention is that it can be adapted to the present and contemplated radar frequen­cies. Therefore, while present strategic chaffs may contain different lengths of filament ranging from several centimeters and shorter (e.g.,0.01-10 cm), corresponding to the half wave­lengths (or full wavelengths) over an entire bandwidth, the range that may be achieved with the chaff of this invention is from 100 microns to hundreds of meters, depending on the specific use contemplated.
  • the chaff may be "tuned" by increasing the proportion of chaff dipoles reflecting that particular frequency, and many more dipoles per unit volume of chaff may be dispersed.
  • Chaff prepared in accordance with the present in­vention is highly efficient in comparison with previously known chaff materials because the coating is continuous and of high purity.
  • the chaff fibers are much stiffer than prior materials, which facili­tates dispersion. This ensures that the dipole length will remain tuned to the object radar frequency.
  • the dispersibility of the chaff may be assisted by further treatment of the fibers before chopping into strands to make them mutually repellant, or at least non-adhesive.
  • rinsing the coated fiber with a solution to change the surface qualities of the chaff dipoles is a typi­cal method.
  • sizing the coated fiber with a solution of oleamide in 1,1,1-trichloro­ethane e.g., about 10 g/l
  • the plated, sized tow of fibers is typically pulled through a series of rollers or rods ("breaker bars") to break apart fibers stuck together by the sizing. This also is a means of maintaining collimation of the fibers.
  • breaker bars rollers or rods
  • chaff dipoles When broad band reflection is desired a certain amount of contact between individual chaff dipoles may be advantageous. Because contact between two chaff dipoles according to the present invention creates an effective longer dipole, controlled contact provides larger dipoles that respond at different frequencies as the chaff disperses and the individual dipoles separate. This is another method of "tuning" the chaff to the radar, made possible by the present invention. Also, core fibers such as graphite fiber are available in various shapes, e.g., X or Y shapes, permit­ting multilobal radar reflection. A further advantage of the composite fiber chaff herein is its low bulk density.
  • the small comparative diameters of fibers contem­plated herein permit chopping to very short lengths, e.g., 100 microns, so as to be effective against super high fre­quency radars. Also, broad band reflection is within the scope of the present invention.
  • a variety of types of composites of the invention can be produced using the fibers having a copper coating thereon as described above. Methods for incorporating such fibers into polymeric and metallic matrices are contemplated. The methods include directly consolidating the copper coated fiber of this invention so that the coating becomes the matrix. Simply by hot pressing, for example, between 600°C and 900°C, most preferably between 725°C and 750°C, in a reducing atmosphere or a vacuum the fibers of this invention can be consolidated to form substantially void-free, uniform composites.
  • the fibers of this invention can be fabricated into composites by direct consolidation also by "laying up" the fibers. To do so, the fibers are aligned into single layer tow, which optionally may be held together by a fugitive binder or merely the capillary action of water. These layers are then stacked by either keeping the layers aligned in parallel or by changing the angle between adjacent layers to obtain a "cross-plied" laminate. Since the physical proper­ties of the composite and fiber are anisotropic, a range of properties can be achieved by changing the orientation of the various layers of the composite.
  • the coated fibers of this invention have few agglomerations, it is possible to spread the fiber into very thin plies, as low as 3 mils.
  • Thin plies are an advan­tage when large area structures are to be built, such as radiator structures.
  • the composite should be as thin as possible, yet to obtain sufficient stiffness in all directions, several layers, having several orientations, are required. Therefore, the thinner each ply is, the thinner the final, multi-layered composite can be. By making thinner structures, substantial weight savings can be effected which is crucial in any aerospace or transporta­tion application.
  • Composites produced by direct consolidation of the fibers of this invention have the advantage that the copper remains in intimate contact with the fibers during hot press­ing. This is possible because the carbon fibers are coated with copper by the plating process and are consolidated at relatively low temperatures (e.g, 750°C). This assures that dewetting does not occur during consolidation of the fibers into the composite.
  • the composites of this invention also have the advantage that they have a very uniform distribution of the base fiber throughout the thickness without undesir­able matrix-rich regions.
  • the void content of the composites is low because of the uniformity of coatings and low agglomeration rate of the starting coated fiber.
  • the purity of the copper matrix can be very high.
  • the very low agglomeration of the fibers of this invention makes possible thin copper matrix composites, filament wound com­posites, braided composites and woven composites.
  • the com­posites of this invention have good mechanical properties due to their uniformity, and good thermal and electrical proper­ties due to the purity of the copper component of the composite.
  • the organic polymeric materials for use as matrices in the composites of the invention are numerous and generally any known polymeric material may find application.
  • some of the known polymeric materials useful in the invention include: polyesters, polyethers, polycarbonates, epoxies, phenolics, epoxy-novolacs, epoxy-polyurethanes, urea-­type resins, phenol-formaldehyde resins, melamine resins, melamine thiourea resins, urea-aldehyde resins, alkyd resins, polysulfide resins, vinyl organic prepolymers, multifunctional vinyl ethers, cyclic ethers, cyclic esters, polycarbonate-co-­esters, polycarbonate-co-silicones, polyetheresters, poly­imides, bismalemides, polyamides, polyetherimides, polyamide­imides, polyetherimides, and polyvinyl chlorides.
  • the poly­meric material may be present alone or in combination with copolymers, and compatible polymeric blends may also be used.
  • any conventional polymeric material may be selected and the particular polymer chosen is generally not critical to the invention.
  • the polymeric material should, when combined with the composite fibers, be convertible by heat or light, alone or in combination with catalysts, accelerators, cross-linking agents, etc., to form the components of the invention.
  • the electrically conductive composite fibers used in the invention are shown in Fig. 6 in a cross-section of composite fibers in an epoxy resin matrix.
  • Each composite fiber comprises a core shown in black circles and at least one relatively thick, uniform and firmly adherent, electrically and/or thermally conductive layer of copper, shown in white rings.
  • the core may be made of carbon, graphite, a polymer, glass, a ceramic, or other fibers although carbon and graphite fibrils or filaments are commercially available from a number of sources.
  • Such composite fibers are well-suited for incorpor­ation with polymeric materials to provide electrically con­ductive components.
  • the composite fibers have a very high aspect ratio, i.e., length to diameter ratio, so that intimate contact between the fibers to provide conductive pathways through the polymer matrix is achieved at relatively low loading levels of fibers, and more particularly at much lower levels than the metal coated spheres and metal flakes utilized in prior art attempts to provide electrically con­ductive polymer compositions.
  • This ability to provide elec­trical, and/or thermal conductivity at low concentrations of fiber significantly reduces any undesirable degradation or modification of the physical properties of the polymer.
  • the copper coated fibers may be present in the com­posites as single strands, or bundles of fibers or yarn.
  • the fibers or bundles may be woven into fabrics or sheets.
  • the fibers, or bundles may be comminuted and dis­ persed within the polymeric material, may be made into non­woven mats and the like, all in accordance with conventional techniques well-known to those skilled in this art.
  • a com­posite is prepared by immersing and wetting a nonwoven mat of the composite fibers, such as into a polymeric resin solution, such as one formed by dissolving an epoxy resin or a phenolic resin in an alcohol solvent.
  • a polymeric resin solution such as one formed by dissolving an epoxy resin or a phenolic resin in an alcohol solvent.
  • Other forms such as unidirec­tional fibers, woven fabrics, braided fabrics and knitted fabrics can be used, too.
  • This composition may then be con­verted to an electrically conductive component in the form of a resin impregnated prepreg useful for forming electrically conductive laminates. More particularly, the polymer resin solution wetted mat may be heated to drive off the alcohol solvent.
  • a component comprising a layer of randomly oriented and over-lapping composite fibers or bundles of fibers having a polymeric resin layer, and in this case epoxy or phenolic resin layer, coating said fibers and filling any voids or interstices within the mat.
  • the resin impregnated prepreg so formed may be cut to standard dimensions, and several of the prepregs may be aligned one on top of the other, to form a conventional lay up.
  • the lay up is then heated under pressure in a conven­tional laminating machine which causes the polymer resin to flow and then cure, thereby fusing the layers of the lay up together to form a hardened, unified laminate.
  • the laminates prepared in accordance with the in­vention may be cut, molded, or otherwise shaped to form many useful articles.
  • the laminate could be made to form a structural base or housing for an electrical part or device, such as a motor, and because the housing is electric­ally conductive, effectively ground the device.
  • the composition of the invention comprises a thin, normally non-conductive polymer film or sheet and a woven, nonwoven unidirectional sheet, etc., formed of the composite fiber.
  • the polymeric film or sheet may be formed by conventional film forming methods such as by extruding the polymer into the nip formed between the heated rolls of a calender machine, or by dissolving the polymeric material in a suitable solvent, thereafter coating the polymer solution onto a release sheet, such as a release kraft paper with for example a "knife over roll” coater, and heating to remove the solvent.
  • the polymer film or sheet is then heated to between 100° and 200°F and laminated with the nonwoven mat of composite fibers by passing the two layers between the heated nip of a calender.
  • the resulting compon­ent in the form of a fused polymer film supported with a conductive mat is useful, for example as a surface ply for laminates.
  • Air foil structures made with such laminated com­posites provide an effective lightning strike dissipation system for aircraft.
  • the non-metallic parts would be subject to significant damage because of their non-conductive nature.
  • the resulting current will be conduc­ted and dissipated through the conductive fiber mat and conductive base laminate, thereby reducing the risk and occurrence of damage to the airfoil.
  • the composites are made from a molding composition wherein the polymeric material is, for example, a polyester, polycarbon­ate, polystyrene, nylon, etc., resin molding composition having the chopped or comminuted copper coated fibers, or woven mats, in contact therewith.
  • the copper coated fibers are dispersed in the resin by conventional means, and the composition is extruded to form pellets.
  • the pellets may then be injection molded in accordance with customary procedures to produce shaped electrically conductive molded articles.
  • the molded polyester resin articles exhibit good physical properties as well as conductivity.
  • the elongated granules of this invention each con­tain a bundle of elongated reinforcing copper coated fibers as defined above extending generally parallel to each other longitudinally of the granule and substantially uniformly dispersed throughout the granule in a thermally stable, film forming thermoplastic adhesive comprising
  • the injection molding compositions comprise:
  • the present invention con­templates, as an improvement in the process of injection mold­ing, the step of forcing into a mold an injection molding composition comprising a blend of:
  • each filament contained in the injection molding granule is surrounded by and the bundle is impregnated by the thermally stable, film-forming thermoplastic adhesive combin­ation.
  • the pellet itself may be of cylindrical or rectangular or any other cross-sectional configuration, but preferably is cylindrical.
  • the length of the granules can vary, but for most uses, 1/8 inch - 3/4 inch will be acceptable and 1/8 inch - 1/4 inch will be preferred.
  • the pellets of this invention have close-packed filaments and the thermoplastic adhesive jacket is substantially dispersed upon contact with hot molten thermoplastic in the present invention.
  • the prior art pellets will not readily separate into reinforcing filaments because of interference by the relatively thick jacket of thermoplastic resin.
  • the adhesive preferivelyably will be used also in an amount which is not substantial­ly in excess of that which maintains the fiber bundle integ­rity during chopping. This amount will vary depending on the nature of the fibers, the number of fibers in the bundle, the fiber surface area, and the efficiency of the adhesive, but generally will vary from 2.5 to 32.5% and preferably from 5 to 15% by volume of the granule.
  • a conventional surface active agent which facilitates wetting and bonding to numerous different substrates.
  • Anion­ ic, cationic and non-ionic surfactants are suitable for this purpose, the only requirement being that they be miscible with any solvent system used for impregnation and compatible with the thermoplastic film forming adhesive combination.
  • Pre­ferred surfactants, especially when graphite, or metal coated carbon fiber substrates are used comprise anionic surfactants especially sodium salts of alkyl sulfuric acids. Particularly useful is sodium hepadecyl sulfate, sold by Union Carbide Co., under the Trademark NIACET® No. 7.
  • thermoplastic adhesive combination Careful consideration should be given to selection of the film forming thermoplastic adhesive combination, sub­ject to the above-mentioned parameters. Some adhesives are more efficient than others, and some, which are suggested for use as fiber sizings in the prior art will not work.
  • poly(vinyl acetate) and poly(vinyl alcohol), the former being suggested by Bradt in U.S. 2,877,501, as a sizing do not work herein because, it is believed, thermo­setting or cross linking occurs and this operates to prevent rapid melting and complete dispersion in the injection mold­ing machine. While such materials are suitable for the resin rich compounded granules used in the Bradt patent, they are unsuitable herein.
  • poly(2-ethyl oxazoline) is thermoplastic, low viscosity, water-soluble adhesive. It can be used in the form of amber-colored and transparent pellets 3/16" long and 1/8" diameter.
  • Typical molecular weights are 50,000 (low); 200,000 (medium) and 500,000 (high). Being water soluble, it is environmentally acceptable for deposition from aqueous media. It also wets the fibers well because of low viscosity. It is thermally stable up to 380°C. (680°F.) in air at 500,000 molecular weight.
  • Poly(vinylpyrrolidone) is an item of commerce, being widely available from a number of sources, and varying in molecular weight, as desired. While the poly(oxazoline) appears to provide dispersibility to the elongated bundles the poly(vinylpyrrolidone) is useful for high temperature resistance.
  • poly(vinylpyrrolidone) works well in water based impregnation media.
  • Typical molecular weight ranges readily availabe can be used, for example 10,000; 24,000; 40,000; and 220,000.
  • the higher molecular weight material tends to provide bundles which are more difficult to disperse.
  • the lowest molec­ular weight causes some loss in heat resistance.
  • the adhesive combination on fiber bundles does not fracture appreciably during chopping to minimize free filaments from flying about, which can be a safety hazard.
  • the adhesive combination When blended with pellets of a thermoplastic resin system, the adhesive combination will melt readily allowing complete dispersion of the fibers throughout the resin melt while in a molding machine.
  • pellets bound with this thermoplastic adhesive combination are indefi­nitely stable with the resin pellets during blending, and don't break apart prematurely.
  • the fiber type can vary, any fiber being known to be useful as a filler or reinforcement in a resin system can be used.
  • Preferred fibers are carbon or graphite fibers, glass fibers, aramid fibers, ceramic, e.g., alumina or silica carbide, fibers, metal coated graphite fibers, or a mixture of any of the foregoing.
  • the preferred thermoplastic adhesive component (a) comprises poly(ethyloxazoline), having a molecular weight in the range of about 25,000 to about 1,000,000, preferably 50,000-500,000, most preferably about 50,000.
  • the preferred thermoplastic adhesive component (b) comprises polyI(vinylpyrrolidone), having a molecular weight in the range of from about 10,000 to about 220,000, preferively from about 24,000 to about 40,000 and most preferably about 24,000.
  • the adhesive be deposited onto the filaments from a solvent system which can comprise any polar organic solvent, e.g., methanol, or mixture of such solvents, or water, alone, or in admixture.
  • Acceptable bath concentrations for the thermoplastic adhesive can vary but is generally for component (a) it is in the range of 2.5-12% by weight, preferably 2.5-8%, and especially preferably 4-8% by weight and, for component (b), in the range of 1-8% by weight, preferably 1-6% by weight, and, especially preferivelyably, 1-4% by weight.
  • a surface active agent is used, this too can vary in type and amount, but generally if an anionic alkyl sulfate is used, such as sodium heptadecyl sulfate, bath concentrations can range from 0.0005-0.5% by weight, preferably from 0.0005 to 0.05%, and most preferably, 0.0005-0.005%, by weight.
  • the amount of non-filament material in the filament-­containing granules of the invention will vary, but, in gen­eral, will range from 2.5 to 32.5% by volume with any fiber, preferably from 5 to 15% by volume.
  • the amount of component (b) will be from about 7.5 to about 75% by weight based on the combined weights of (a) and (b) preferably from about 15% to about 50%.
  • the length of the elongated granule will generally range from 1/8 to 3/4 inch, preferably from 1/8 to 1/4 inch.
  • the diameters of each elongated granule can vary, depending primarily on the number of filaments and the thicknesses will vary from about one-forty eighth to about three-sixteenths inch in diameter. Preferably, the diameter will be in the range of from about one-thirty-second to about one-eighth inches.
  • thermoplastic resins can be employed with the elongated granules of the present invention.
  • any resin that can be injection molded and that can benefit from a uniform dispersion of fibers can by used.
  • polystyrene, styrene/acrylic acid copolymer, styrene/acrylo­nitrile copolymer, polycarbonate, poly (methyl methacrylate) poly(acrylonitrile/butadiene/styrene), polyphenylene ether, nylon, poly(1,4-butylene terephthalate), mixtures of any of the foregoing, and the like, can be used.
  • FIG. 5a A suitable apparatus is shown in FIG. 5a.
  • bundles of filaments such as graphite fiber tows or metal coated graphite fiber tows, 3,000 to 12,000 filaments per bundle, glass yarns, 240 filaments to a strand, or stainless steel tow, 1159 filaments per bundle, are drawn from storage roller 2 and passed through one or more baths 4, containing the thermally stable, film forming thermoplastic adhesive in a solvent medium, e.g., water, to impregnate the filaments, then through means such as die 6, to control pick up.
  • a solvent medium e.g., water
  • the impregnated filaments thereafter are passed into a heating zone, e.g., oven 8, to evaporate the solvent, e.g., water and then to flux the thermoplastic adhesive.
  • the treated fila­ments 10 are withdrawn from the heated zone, transported to chopper 12 and cut into fiber pellets illustratively varying beteen 1/8-1/4" according to the requirements of the particu­lar apparatus.
  • the pellets are then stored in a suitable container 14 for subsequent use. Any surfactant conveniently is included in a single bath with the adhesive. It will be observed that this procedure results in the orientation of the reinforcing fibers along one axis of the granule.
  • FIG. 5b a flow diagram in the general form illustrated in FIG. 5b is preferably employed.
  • Fiber pellets 16 are mixed with resin pellets 18 to produce a blended mixture 20. This is added to conventional hopper 22 on molding press 24. When passing through cylinder 26, prior to being forced into mold 28 a uniform dispersion of the fibers is accomplished. Re­moval of molded article 30 provides a fiber reinforced item produced according to this invention.
  • a batch process of this invention was used for the following examples. By first electrolessly depositing copper for predetermined times then electrodepositing for a variety of residence times, a variety of copper coating thicknesses could be produced on the fibers.
  • the carbon fiber used was Magnamite® IM-6, 12K, no size, no twist, supplied by Hercules, Inc., Magma, Utah.
  • the fibers were prepared for coating using above-described wetting Bath 1 and sensitizing Bath 2, and separate samples of fiber tows were immersed in the electroless plating Bath 3 for 0, 1, 3 or 5 minutes. These samples were then electroplated, using above-described Bath 5 for various times as given in the chart below. The thickness of a fiber's coating was measured and is included below.
  • Control sample A did not electroplate due to the lack of an electroless copper layer.
  • Coating thickness in Example 6 is anomously low, it may have been that an unrepresentative fiber was measured.
  • a batch process of this invention used Baths 1, 2, 4 and 5 described above to successively coat 12 K tows of IM-6 graphite fiber with copper. Both tows were held in Bath 4 for 5 minutes.
  • Example 9 was electroplated for 5 minutes at 2.5 amperes.
  • Example 10 was electroplated for 10 minutes at 2.5 amperes.
  • a photomicrograph of Example 9 appears herein as FIG. 6. SEM analysis of cross sections of the two tows showed the following:
  • Copper coated carbon fibers were prepared using the continuous process described in Example 8 using Baths 1, 2, 4 and 5. Two base fibers were used: 12K IM-6 graphite fiber (Hercules Co., Magma, Utah), and 2K P100 graphite fiber (Union Carbide Co., Danbury, CT). Coatings were applied in thicknesses sufficient to yield approximately 50% by volume of copper. The coated fiber tows were then aligned by hand into layers to form unidirectionally aligned samples 1 x 8 inches. Hot pressing was performed in a large hot press, FIG. 4, by heating to between 750° and 775°C under a pressure of 1000 psi. Composite panels were measured for electrical resistivity, thermal conductivity and coefficient of thermal expansion. Thermal expansion was measured using push rod dilatometry.
  • a composite is prepared by chopping the fibers of Example 8 into short lengths, 1/8" to 1/4", then thoroughly mixing with thermoplastic nylon polyamide in an extruder, and chopping the extrudate into molding pellets in accordance with conventional procedures.
  • the pellets are injection molded into plaques 4" x 8" x 1/8" in size.
  • the plaque is reinforced by the copper coated fibers. By virtue of the metal content, it also does not build up static charge, and it can act as an electrical shield in electronic assemblies.
  • Bundles of copper plated graphite fibers of about one inch in length prepared according to the procedure of Example 8 are mixed 1:9 with uncoated graphite fibers and laid up into a non woven mat, at 1 oz./1 sq. yard.
  • the mat has a metal content of about 10% by weight of copper and can be impregnated with thermosetting resin varnishes and consol­ided under heat and pressure into reinforced laminates having high strength and excellent electrical dissipation properties.
  • the following example illustrates the preparation of a comminuted copper coated graphite fiber filled epoxy resin film as a conductive surface ply for laminates.
  • a solution of catalyzed formulated epoxy resin system (American Cyanamid FM® 300) dissolved in 50/50 v/v mixture of ethyl­ene dichloride and methyl ethyl ketone at 78-80% solids is prepared in a 1 gallon capacity Ross Planetary mixture.
  • 30% by weight of copper plated graphite fiber prepared in accord­ance with Example 8 herein and chopped into 1/64 inch lengths is added to the mixer and the composition mixed until the copper fibers are uniformly dispersed throughout.
  • the com­position is degassed by stirring at a reduced pressure of 20 mm Hg for 15 minutes.
  • the epoxy resin-chopped fiber composi­tion is coated onto a sheet of silicone treated kraft paper with the "knife over roll" coater to a thickness of approx­imately 12 mils.
  • the coated kraft paper sheet is dried in an oven by gradually heating to about 190°F and the 190°F temp­erature was maintained for approximately 40 minutes.
  • a dry, filled polymer film according to this invention is produced.
  • the laminate is prepared with the polymer film prepared above as surface ply following standard procedures.
  • the lay-up contains 12 layers of a commercial prepreg which is bagged and cured in the cured in the autoclave at 350°F for 120 minutes at 20-50 psi.
  • the finished laminate has a uniform smooth surface suitable for final application without further finishing operations. When tested in accordance with ASTM 0257-78, the surface ply has a very low surface resistivity.
  • a polyester molding compound is prepared by charg­ing the following reactants to a sigma mixer: 10.5 parts styrenated, thermosettable polyester resin (USS Chemical MR 13017); 12.3 parts styrenated thermosettable polyester resin (USS Chemical MR 13018); 0.6 parts calcium stearate; 40.3 parts calcium carbonate; 0.5 parts t-butyl perbenzoate; and 0.06 parts inhibitor (35% hydroquinone in dibutyl­phthalate).
  • Chaff according to the present invention is pre­pared by chopping strands of composite fibers metal coated as described in Example 8 into lengths designed to effectively reflect impinging radar waves.
  • the fibers are cut to a length roughly one-half the wavelength of the radar frequency the chaff is intended to be used against or, where very high radar frequencies are encountered, full wave­lengths.
  • a radar operator may be monitoring several frequencies, typically in the 2-20 GHz range.
  • chaffs according to this invention are made to contain different lengths of filament ranging from several centimeters and shorter (e.g., 01-10 cm), corresponding to the halfwave lengths (or full wavelengths) over an entire bandwidth, the range that may be achieved with the chaff of this invention is from 100 microns to hundreds of meters, depending on the specific use contemplated.
  • a bath comprising the following is formulated:
  • a tow of continuous graphite fibers 2 (12,000 count) each of which has a copper coating thereon is led through bath 4.
  • the graphite filaments each average about 7 microns in diameter.
  • the copper-coating thereon is approximately 1.0 microns in thickness.
  • the copper coated graphite tows are prepared by continuous electroless plating followed by electroplating in accordance with the procedure described in Example 8. After passing through coating bath 4 the treated fibers are passed over grooved rollers 6 to remove excess adhesive then passed through oven 8 at about 300°F.
  • the impregnated filaments then are chopped to 1/4" lengths in chopper 12 and there are produced elongated granules of approximately 1/16" in diameter of cylindrical shape and form.
  • the non-filament material content is 9% by volume.
  • Example 20 The procedure of Example 20 is repeated substitut­ing for the thermoplastic resin pellets, pellets comprising poly(acrylonitrile/butadiene/styrene) (Borg Warner CYCOLAC® KJB) resin and plaques suitable for measuring SE effect are molded.
  • pellets comprising poly(acrylonitrile/butadiene/styrene) (Borg Warner CYCOLAC® KJB) resin and plaques suitable for measuring SE effect are molded.
  • Example 20 The procedure of Example 20 is repeated but poly­(2,6-dimethyl-1,4-phenylene ether)-high impact strength rubber modified polystyrene resin pellets (General Electric NORYL® N-190) are substituted, and plaques suitable for measuring SE are prepared.
  • FIG. 18 is a photomicrograph of the IM-6 coated with 50 volume percent copper that has been consolidated into a "cross-plied" laminate, that is, the fibers in the center layer are at approximately a 60 degree angle to the polish plane, while in the top and bottom layers, the fibers are perpendicular to the polish plane.
  • FIG. 17 is a higher mag­nification photo of P-55 coated with about 40% copper. In this laminate all the fibers shown are oriented perpendicular to the polish plane.
  • Direct electroplating of an untreated tow of graph­ite fibers was attempted using a commercially available copper electroplating bath.
  • the plating solution used was Bath 5, described above.
  • the graphite fiber used was P100 from Union Carbide (2,000 filament, no size, no twist). This graphite fiber was believed to have sufficient electrical conductivity to allow the electrodeposition of copper.
  • a 1 liter graduated cylinder was filled with 1 liter of Bath 5. The bath was heated to 45°C by means of a heating tape wrapped around the cylinder. The tape was plugged into a variable voltage controller and then monitored by a thermo­meter hung on the inside of the cylinder. Two long rectangles of OFHC grade copper sheet stock (high purity copper) were hung in the bath by bending one end of the sheet over the side of the cylinder.
  • the sheets were connected to a power supply to serve as cathodes.
  • the P100 fiber was wrapped around a piece of copper bar stock which rested on the top of the graduated cylinder. The fiber was then clamped to the bar and connected to the power supply as the anode. Using a current of 1 ampere, plating was carried out for five minutes. The fiber was then rinsed with deionized water and dried in a vacuum oven for 15 min. at 120°F at a vacuum of 25 mm of Hg. Visual inspection of the fiber showed plating to be sporadic and uneven. The material was considered to be unsuitable for hot pressing.
  • the thicknesses ranged from 0.3 microns for the 1 min. residence time to 3.0 microns for the 30 min. residence time. It was noted that the coating began to have nodular growths after 10 min. in the plating solution. At 10 minutes the coating thickness was 1.8 microns.
  • German Pat. No. 2,658,234 is said to guarantee the uniform coating of individual very thin fibers with a metallic coating, such as copper.
  • the patent diagrams an apparatus which is comprised of a funnel through which a tow of graphite fiber is suspended. Various solutions are then pumped into the funnel and flow down the tow and causing it to be spread.
  • the principal requirements of the apparatus are: a pump, capable of attaining a flow of 1 liter/min., and a funnel having an inner diameter of be­tween 3 and 12 times the outer diameter of the tow to be coated.
  • the height of the liquid in the funnel must be 2 cm or more.
  • the pump's flow was restricted by an adjustable hose clamp. Flow was adjusted to 1 liter per minute.
  • the i.d. of the bottom opening of the funnel was 0.5 cm. With a pumping rate of 1 liter/min., and this funnel, it was possible to maintain a solution level height of 5 cm in the funnel when a tow of fibers was suspended through the funnel opening.
  • One meter of carbon fiber (12,000 filament tow of IM-6 fiber from Hercules, no size, no twist) was hung from the top of a ring stand.
  • the fiber used by Schmidt had five twists per meter. Therefore, five twists were made in the fiber tow.
  • the bottom of the tow was run through a 5 cm. long glass tube.
  • the glass tube did not create tension in the tow, but gently rested on the bottom of the catch basin to keep the fiber from untwisting. All of the water used was deionized water, including the water which was used to rinse the fiber.
  • the treatment of the fiber was as follows: 10 min. using Shipley Conditioner 1160B; 5 min. rinse with deionized water; 1.5 min. with 25 vol. % HCl in deionized water; 3.5 min. with Shipley Catalyst 9F; 5 min. rinse with deionized water; 5 min. with Shipley Accelerator 19; 5 min. rinse with deionized water; 12 min. using a Shipley electroless copper plating solution which was prepared by combining 79 vol. % deionized water, 11 vol. % Shipley CP-78M, 4.5 vol. % Shipley CP-78R, heating to 115°F then adding 5.5 vol. % Shipley CP-78B; and 5 min. rinse with deionized water.
  • This area corresponded to the section which was believed to contain a "wrapper".
  • the tow appeared very bright and copper colored and felt soft to the touch, although the fiber did not seem completely free. This could indicate some evidence of "overplating” or the plating together of neighboring fibers (agglomeration).
  • SEM Scanning Electron Microscopy
  • FIG. 10 Thickness variations were also seen from fiber to fiber in the tow. Near the outside of the tow fibers were coated to a thickness of 2.5 microns while in the center of the tow coatings as thin as 0.2 microns were seen.
  • the tows were also highly agglomerated having only 43% of the fibers in a cross section individualized.
  • the agglomeration was charac­terized by counting the number of agglomerates containing 1, 2, 3, 4, 5, 6, or greater than 6 fibers. The percentage of all fiber contained in agglomerates of each size was then calculated. The results are shown below:
  • the Lowenheim solution also included 17 g/L of Versene-T (EDTA + triethanolamine), however, since this com­pound was not indicated by Sakovich it was not used in the preparation of the electroless plating bath of this example.
  • the exact compositions and concentrations for the stannous and palladous chloride baths were not given so commercially available solutions for the chemical deposition of copper were used. These solutions are commonly used in the printed circuit board industry.
  • a tow of graphite fibers (12,000 filament IM-6 from Hercules, no size, no twist) was used to perform the experi­ment.
  • Four 1 liter graduated cylinders were obtained to hold the reaction solutions. Water was heated to boiling in an Erlenmeyer flask on a hot plate. The water was then poured into the first graduated cylinder. This cylinder was warmed by means of a heating tape wrapped around the cylinder.
  • the fiber was immersed in the hot water for five minutes. In this time period the water temperature fell to 92°C.
  • the fiber was then transferred to the second cylinder containing a stannous chloride solution (Shipley Accelerator 19) for 5 min.
  • the fiber was then rinsed with deionized water for 2 min.
  • the fiber was placed in a palladous chloride solution (Shipley Catalyst 9F) for 5 min.
  • the fiber was again rinsed for 2 min. with deionized water. At the end of the two min. rinse, the run-off from the fiber appeared colorless and free of catalyst.
  • the fiber was then placed in the cylinder containing the electroless plating solution.
  • This solution was made in the following manner (as outlined in Lowenheim): 35 g of copper sulfate pentahydrate (CuSO4*5H2O) was dissolved in 600 mls. of dionized H2O; 170 g of potassium sodium tartrate was added while stirring; 50 g of sodium carbonate was added to the above solution while stirring; 50 g of sodium hydroxide pellets were dissolved in 100 mls. of water and this solution was then slowly added to the stirred copper solution; Deionized water was then added to bring the total volume of solution to 810 mls; and Immediately before plating, 191 mls. of 37% formal­ dehyde was added to the solution.
  • the solution was at room temperature and the pH was measured to be 12.2. Immediately after placing the fiber and frame into solution, evidence of gas evolution was seen. Bubbling continued during the entire reaction time which was 33 min. This time period was indicated to be long enough to produce a copper coating of 1 micron in thickness. A color change in the solution was apparent after approximately 15 min. The solution changed from a clear blue to a cloudy, dark blue green. At the end of the reaction time, the fiber was rinsed and dried in a vacuum oven at 120°C for 15 min. at a vacuum of 25 ml of Hg. The fibers were inspected visually and then a section was provided for SEM analysis. Three one and one-half inch sections were cut from the tow of fibers for consolidation into a composite.
  • the visual inspection of the fibers showed an excess of copper agglomerated on the tow.
  • the color of the metallic plating was dark reddish brown.
  • the inside of the tow was not easy to see since the outside of the bundle was covered in a dark powdery copper.
  • the coating thickness was relatively uniform around the fiber circumference, however, the thick­ness varied from fiber to fiber. A typical view is shown in FIG. 11. The minimum thickness seen was 0.32 microns, and the maximum was 1.54 microns. The average thickness was 0.98 microns with a standard deviation of 0.43 microns. Only 43% of the fibers were individualized.
  • the agglomeration was characterized as in Example 3A; the results are given below:
  • the electroless copper plating solution which is described in both the paper and the patent, is an alkaline solution containing copper sulfate, formaldehyde solution, sodium hydroxide, potassium-sodium tartrate, and sodium di­ethyldithiocarbonate.
  • Two commercial sources did not carry any chemical named sodium diethyldithiocarbonate, but sodium diethyldithiocarbamate is listed and is known to be used as a chelating agent. Thus the use of carbonate was taken to be a typographical error.
  • Neither the patent nor the journal article give concentrations for the components of the plating bath. However, comparison to the text by Lowenheim, above­mentioned, does suggest a possible bath make-up.
  • the coating thickness is given as between 0.1 to 0.4 microns for a resid­ence time between 3 to 6 minutes.
  • the electrolytic deposition of copper onto the graphite fibers is more fully described.
  • the solution to be used is made from combining 260 g/L copper sulfate pentahydrate and 60 ml/L sulfuric acid and plating at a current density of 2-5 A/100 cm2 and a pH of 1-2 in four hours. They report that consolidation into a composite is performed in a vacuum for 30 minutes at a temperature of 940°C under pressure of 50 kg/cm2. This method should pro­duce a composite with a 5% weight fraction of fibers. The paper explains that in some of the composites scanning microscopy showed some defects in the composite, including "clusters of fibers, pores in the matrix".
  • a frame made from a glass rod bent into a rectangular shape, was used to hold the fiber.
  • the fiber used was a 40 in. long segment of 12,000 filament IM-6 graphite fiber (Hercules, 7 micron fiber), which was attached to the frame and ten twists were introduced into the fiber, then the second end was taped to the top of the frame.
  • the fiber and frame were submersed into 65% nitric acid for 5 minutes then thoroughly rinsed with deionized water.
  • the fiber was then held in a commercially available palladous chloride solution (Shipley Catalyst 9F) for 5 min. and care­fully rinsed with deionized water.
  • a solution for the electroless deposition of copper was made by the following method: 13 g of copper sulfate pentahydrate (CuSO4.5H2O) were dissolved in 800 ml of deionized water; 66 g of potassium sodium tartrate was added to this solution while stirring; 0.018 g of sodium diethylydithiocarbamate was added to the above solution while stirring; 19.3 g of sodium hydroxide was dissolved in 100 mls of deionized water and this solution was slowly added to the stirred copper solution; Deionized water was added to this solution to bring the volume to 960 ml total volume; and Immediately before plating, 38 mls of 37% formalde­hyde was added to the solution.
  • CuSO4.5H2O copper sulfate pentahydrate
  • 66 g of potassium sodium tartrate was added to this solution while stirring
  • 0.018 g of sodium diethylydithiocarbamate was added to the above solution while stirring
  • the solution was at room temperature for the treat­ment of the fibers.
  • the fiber and frame was immersed in the plating solution for a total of five minutes.
  • the fiber sur­face showed evidence of gas evolution upon immersion in the solution.
  • An electroplating solution was prepared by dissolving 1040 g of CuSO4.5H2O in 3.5 liters of deionized water while stirring.
  • the solution was heated slightly in order to dissolve all the copper sulfate into this volume of water.
  • the solution was then allowed to cool to room temperature. After cooling, 240 ml of sulfuric acid was carefully added to this solution. Deionized water was then added to bring the total volume of solution to 4 liters.
  • Electroplating was performed in a tank (FIG. 8) which con­tained an OFHC grade copper bar stock anode.
  • the cathodes were two sections of copper tubing which were both supplied with current. Each end of the fiber was wrapped around a cathode roller. A section of fiber approximately 125 cm in length was held below the surface of the solution by two bent glass rods. The power supply was turned on and current con­trolled. The current was slowly increased to 5 Amps. The cathodes and the section of fiber between the cathode and solution surface was kept cool by spraying this section with water from a plastic rinse bottle. After approximately 20 min. the fiber began to spark near the intersection of the fiber and the solution interface. At this point the experi­ment was discontinued.
  • the fiber was removed from the bath, rinsed and then dried in a vacuum drying oven for 15 min. at a vacuum of 25 mm of Hg.
  • a small section of fiber was cut out of the tow and provided for scanning electron microscopy. Visual inspection of the tow showed some areas of incomplete coverage. The fibers did not spread easily, suggesting that neighboring fibers were plated together. Three small sections of fiber were removed and used to prepare a composite sample. Visual inspection had further shown that coverage of the fiber was incomplete. This was documented by the SEM analysis. Cross sections of the fiber tows showed relatively good evenness of coating thickness around the circumference of the fibers, but very large variations from fiber to fiber in the tow.
  • Japanese Patent No. 70-17095 (1985) by Yashioka et al. teaches that electroplating graphite fibers in copper electroplating baths without a brightener creates a non-­bright coating with poor slidability during knitting into a cloth due to the roughness of the coating.
  • the patent states that its objective is to produce copper coated carbon fibers with an improved discoloration resistance and slidability.
  • a number of copper electroplating baths are discussed and the availability of suitable brighteners is assured.
  • UBAC-1 (trade name OMI Corp.) is used for a copper sulfate bath
  • copper ryumu (trade name MKT Co.) is used for a cyanide bath.
  • Example 1 a bundle of carbon fibers consisting of 3,000 single fibers having an average diameter of about 7 (microns) was pretreated by calcining at ca. 500°C and plated in a copper sulfate plating bath con­taining a brightener (composition: copper sulfate 100 g/l, sulfuric acid 100 g/l, brightener UBAC-1 10 ml/l,Cl- 10 ppm) at an average current density of 6 A/dm 2, yielding a ca 2­(micron) thick bright copper-plated layer. This was compared to a sample which did not contain a brightener as to the brightness and slidability.
  • a brightener composition: copper sulfate 100 g/l, sulfuric acid 100 g/l, brightener UBAC-1 10 ml/l,Cl- 10 ppm
  • Electroplating was performed in a tank (FIG. 8) which contained an OFHC grade copper bar stock anode.
  • the cathodes were two sections of copper tubing which were both supplied with current. Each end of the fiber was wrapped around a cathode roller. A section of fiber approximately 20 inches in length was held below the surface of the solution by two bent glass rods. The power supply was turned on and current controlled. The current was slowly increased to 5 Amps. The cathodes and the section of fiber between the cathode and solution surface was kept cool by spraying this section with water from a plastic rinse bottle. After approximately 20 minutes the fiber began to spark near the intersection of the fiber and the solution interface. At this point the experiment was discontinued.
  • the fiber was removed from the bath, rinsed and then dried in a vacuum drying oven for 15 minutes at a vacuum of 25 mm of Hg.
  • a small section of fiber was cut out of the tow and submitted for evaluation by scanning electron microscopy. Visual in­spection of the tow showed some areas of incomplete coverage. The quality was not suitable for hot-pressing. A typical view is shown in FIG. 13. The fibers did not spread apart easily, suggesting some evidence of plating together of neighboring fibers.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Dispersion Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Mechanical Engineering (AREA)
  • Chemically Coating (AREA)
  • Woven Fabrics (AREA)
  • Laminated Bodies (AREA)
  • Chemical Or Physical Treatment Of Fibers (AREA)
EP87115698A 1986-10-31 1987-10-26 Copper coated fibers Withdrawn EP0269850A1 (en)

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
US92584286A 1986-10-31 1986-10-31
US92585186A 1986-10-31 1986-10-31
US92584186A 1986-10-31 1986-10-31
US925841 1986-10-31
US925842 1986-10-31
US925848 1986-10-31
US06/925,848 US4808481A (en) 1986-10-31 1986-10-31 Injection molding granules comprising copper coated fibers
US925851 1997-09-09

Publications (1)

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EP0269850A1 true EP0269850A1 (en) 1988-06-08

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EP (1) EP0269850A1 (ko)
KR (1) KR880005317A (ko)
AU (1) AU609425B2 (ko)
BR (1) BR8705811A (ko)
DK (1) DK568787A (ko)
FI (1) FI874781A (ko)
IL (1) IL84284A (ko)
NO (1) NO874527L (ko)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2239263A (en) * 1989-12-22 1991-06-26 Gen Electric Silicon carbide fibre-reinforced titanium base composites and coated silicon carbide fibres
WO1997023916A2 (de) * 1995-12-22 1997-07-03 Hoechst Research & Technology Deutschland Gmbh & Co. Kg Materialverbunde und ihre kontinuierliche herstellung
EP0859373A1 (en) * 1997-02-14 1998-08-19 Riken Vinyl Industry Co., Ltd. Conductive resin composition
US8137752B2 (en) 2003-12-08 2012-03-20 Syscom Advanced Materials, Inc. Method and apparatus for the treatment of individual filaments of a multifilament yarn
ITTO20110531A1 (it) * 2011-06-16 2012-12-17 Telerie D Arte S R L Sistema per la fabbricazione di fili tessili rivestiti con uno strato di un metallo prezioso, in particolare oro
WO2013043813A1 (en) * 2011-09-21 2013-03-28 Applied Nanotech Holdings, Inc. Carbon-metal thermal management substrates
WO2015057780A1 (en) * 2013-10-17 2015-04-23 Rudinger Richard F Post-extruded polymeric man-made synthetic fiber with copper
US20150219577A1 (en) * 2014-02-06 2015-08-06 The Boeing Company Determination of anisotropic conduction characteristics
US9828701B2 (en) 2013-10-17 2017-11-28 Richard F. Rudinger Post-extruded polymeric man-made synthetic fiber with polytetrafluoroethylene (PTFE)
US10314215B2 (en) 2007-07-16 2019-06-04 Micrometal Technologies, Inc. Electrical shielding material composed of metallized stainless steel monofilament yarn

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KR100434443B1 (ko) * 2001-05-21 2004-06-04 (주)메디텍스 섬유원단에 금속을 차등 도금하는 방법
CN113372063B (zh) * 2021-06-23 2022-06-07 北京民佳混凝土有限公司 一种耐热混凝土及其制备方法

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US3676916A (en) * 1970-01-02 1972-07-18 Monsanto Co Method for preparing metal molding compositions
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DE2739179A1 (de) * 1977-08-31 1979-04-12 Bayer Ag Metallisiertes fasermaterial
DE2820502A1 (de) * 1978-05-11 1979-11-15 Bayer Ag Metallisierte aramidfasern
DE2820525A1 (de) * 1978-05-11 1979-11-15 Bayer Ag Metallisierte polycarbonatfasern
DE2937874A1 (de) * 1979-09-19 1981-04-02 Bayer Ag, 5090 Leverkusen Vergoldete, metallisierte, textile flaechengebilde, garne und fasern, verfahren zu ihrer herstellung und verwendung des textilgutes bei der absorption und reflexion von mikrowellen
GB2062364A (en) * 1979-10-31 1981-05-20 Siemens Ag Electrical brush
DE3106506A1 (de) * 1981-02-21 1982-10-07 Bayer Ag, 5090 Leverkusen Metallisierte kohlenstoffasern und verbundwerkstoffe, die diese fasern enthalten
EP0088884A1 (en) * 1982-03-16 1983-09-21 Electro Metalloid Corporation Yarns and tows comprising high strength metal coated fibers, process for their production, and uses thereof
US4443726A (en) * 1981-05-09 1984-04-17 Toho Beslon Co., Ltd. Brushes and method for the production thereof
EP0111139A2 (de) * 1982-11-10 1984-06-20 Bayer Ag Getemperte Rovings, textile Flächengebilde und Monofilamente aus vernickelten Kohlenstoffasern
DE3301669A1 (de) * 1983-01-20 1984-07-26 Bayer Ag, 5090 Leverkusen Blitzschutzverbundmaterial

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US2877501A (en) * 1952-12-24 1959-03-17 Fiberfil Corp Glass-reinforced thermoplastic injection molding compound and injection-molding process employing it
US2979424A (en) * 1953-09-17 1961-04-11 Owens Corning Fiberglass Corp Metal coated glass fibers and method of making them
US2814162A (en) * 1954-06-25 1957-11-26 Ohio Commw Eng Co Apparatus for production of metallized and bonded blown glass fibers
US3083550A (en) * 1961-02-23 1963-04-02 Alloyd Corp Process of coating vitreous filaments
GB1215002A (en) * 1967-02-02 1970-12-09 Courtaulds Ltd Coating carbon with metal
US3495940A (en) * 1967-09-28 1970-02-17 Celanese Corp Production of high temperature resistant continuous filaments
DE1944361A1 (de) * 1968-09-25 1970-04-02 Cellophane Sa Verfahren zur kontinuierlichen Herstellung von Garnen aus vollstaendig oder teilweise metallisierten Fasern
GB1325434A (en) * 1969-08-14 1973-08-01 Int Research & Dev Co Ltd Current transfer brush
US3676916A (en) * 1970-01-02 1972-07-18 Monsanto Co Method for preparing metal molding compositions
DE2166599A1 (de) * 1971-12-18 1974-12-05 Maschf Augsburg Nuernberg Ag Verfahren zur herstellung eines faserverbundwerkstoffs
DE2739179A1 (de) * 1977-08-31 1979-04-12 Bayer Ag Metallisiertes fasermaterial
DE2820502A1 (de) * 1978-05-11 1979-11-15 Bayer Ag Metallisierte aramidfasern
DE2820525A1 (de) * 1978-05-11 1979-11-15 Bayer Ag Metallisierte polycarbonatfasern
DE2937874A1 (de) * 1979-09-19 1981-04-02 Bayer Ag, 5090 Leverkusen Vergoldete, metallisierte, textile flaechengebilde, garne und fasern, verfahren zu ihrer herstellung und verwendung des textilgutes bei der absorption und reflexion von mikrowellen
GB2062364A (en) * 1979-10-31 1981-05-20 Siemens Ag Electrical brush
DE3106506A1 (de) * 1981-02-21 1982-10-07 Bayer Ag, 5090 Leverkusen Metallisierte kohlenstoffasern und verbundwerkstoffe, die diese fasern enthalten
US4443726A (en) * 1981-05-09 1984-04-17 Toho Beslon Co., Ltd. Brushes and method for the production thereof
EP0088884A1 (en) * 1982-03-16 1983-09-21 Electro Metalloid Corporation Yarns and tows comprising high strength metal coated fibers, process for their production, and uses thereof
EP0111139A2 (de) * 1982-11-10 1984-06-20 Bayer Ag Getemperte Rovings, textile Flächengebilde und Monofilamente aus vernickelten Kohlenstoffasern
DE3301669A1 (de) * 1983-01-20 1984-07-26 Bayer Ag, 5090 Leverkusen Blitzschutzverbundmaterial

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2239263B (en) * 1989-12-22 1993-10-06 Gen Electric Silicon carbide fiber-reinforced titanium base composites having improved interface properties
GB2239263A (en) * 1989-12-22 1991-06-26 Gen Electric Silicon carbide fibre-reinforced titanium base composites and coated silicon carbide fibres
WO1997023916A2 (de) * 1995-12-22 1997-07-03 Hoechst Research & Technology Deutschland Gmbh & Co. Kg Materialverbunde und ihre kontinuierliche herstellung
WO1997023916A3 (de) * 1995-12-22 1998-03-19 Hoechst Ag Materialverbunde und ihre kontinuierliche Herstellung
EP0859373A1 (en) * 1997-02-14 1998-08-19 Riken Vinyl Industry Co., Ltd. Conductive resin composition
US8137752B2 (en) 2003-12-08 2012-03-20 Syscom Advanced Materials, Inc. Method and apparatus for the treatment of individual filaments of a multifilament yarn
US10314215B2 (en) 2007-07-16 2019-06-04 Micrometal Technologies, Inc. Electrical shielding material composed of metallized stainless steel monofilament yarn
ITTO20110531A1 (it) * 2011-06-16 2012-12-17 Telerie D Arte S R L Sistema per la fabbricazione di fili tessili rivestiti con uno strato di un metallo prezioso, in particolare oro
WO2012172514A1 (en) 2011-06-16 2012-12-20 Telerie D'arte S.R.L. Equipment for the manufacture of textile threads coated with a layer of a precious metal, in particular gold
WO2013043813A1 (en) * 2011-09-21 2013-03-28 Applied Nanotech Holdings, Inc. Carbon-metal thermal management substrates
US9469923B2 (en) 2013-10-17 2016-10-18 Richard F. Rudinger Post-extruded polymeric man-made synthetic fiber with copper
US9828701B2 (en) 2013-10-17 2017-11-28 Richard F. Rudinger Post-extruded polymeric man-made synthetic fiber with polytetrafluoroethylene (PTFE)
WO2015057780A1 (en) * 2013-10-17 2015-04-23 Rudinger Richard F Post-extruded polymeric man-made synthetic fiber with copper
US20150219577A1 (en) * 2014-02-06 2015-08-06 The Boeing Company Determination of anisotropic conduction characteristics
CN104833870A (zh) * 2014-02-06 2015-08-12 波音公司 各向异性导电特性的测定
EP2905610A1 (en) * 2014-02-06 2015-08-12 The Boeing Company Determination of anisotropic conduction characteristics
JP2015148608A (ja) * 2014-02-06 2015-08-20 ザ・ボーイング・カンパニーＴｈｅＢｏｅｉｎｇ Ｃｏｍｐａｎｙ 異方導電特性の決定
US9488609B2 (en) * 2014-02-06 2016-11-08 The Boeing Company Determination of anisotropic conduction characteristics
CN104833870B (zh) * 2014-02-06 2019-05-28 波音公司 各向异性导电特性的测定

Also Published As

Publication number Publication date
IL84284A (en) 1992-01-15
AU8053787A (en) 1988-05-05
KR880005317A (ko) 1988-06-28
BR8705811A (pt) 1988-05-31
DK568787A (da) 1988-05-01
IL84284A0 (en) 1988-03-31
DK568787D0 (da) 1987-10-30
AU609425B2 (en) 1991-05-02
NO874527L (no) 1988-05-02
NO874527D0 (no) 1987-10-30
FI874781A (fi) 1988-05-01
FI874781A0 (fi) 1987-10-30

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