FI75876B - AV HAOLLFASTA METALLBEKLAEDDA FIBER PICTURES TRAODAR OCH LINOR, FOERFARANDE FOER DERAS FRAMSTAELLNING OCH ANVAENDNING. - Google Patents

Description

1 75876

This invention relates to continuous yarns and ropes consisting of strong bundles of composite fibers consisting of thin adhesive metal layers coated with conductive semi-metal cores, and to processes for their production. the use of wires and ropes.

Bundles of strong non-metallic and semi-metallic fibers, such as carbon, boron, silicon carbide, and the like, in the form of strands, mats, fabrics, and staple fibers, are known to be useful in reinforcing metals and organic polymeric materials. Products made of such fiber-reinforced metals or plastics are widely used to replace heavier parts made of less strong conventional materials such as aluminum, steel, titanium, vinyl polymers, nylons, polyesters, etc. in airplanes, automobiles, office machines, areas.

A common problem with these fibers, as well as with glass, asbestos, and other fibers, is the apparent lack of ability to transfer the properties of the strong fibers to the material to which these fibers are to be permanently and intimately incorporated.

This problem manifests itself in many ways; for example, if a piece of strong carbon fiber wire is closed longitudinally in the center of a molten and then solidified lead rod and the rod is stretched to the breaking point, the tensile strength is less than would be expected under the alloy rule and greater than 35 of the lead thanks to. The lack of reinforcement is due entirely to the weak strength transfer between carbon fibers and lead. The same happens if an unsuitable strong fiber is mixed with a plastic material.

5 If certain types of carbon, boron, silicon carbide, etc. fibers in the form of strips, chopped strips, nonwovens, felts, papers, etc., or woven fabrics are mixed with organic polymeric materials such as phenols, styrenes, epoxy resins, polycarbonates, and the like, or fused metals such as lead, titanium, etc., they only fill these without any reinforcing effect, and often cause even a deterioration of the physical properties.

15 All these problems have now, after years of research, been recognized as a result of the need to ensure adequate bonding between the strong fiber and the so-called matrix material, the metal or plastic to be reinforced. It is also known that binding can be promoted by carefully paying attention to the surface layer of each micro- or macrofiber or fibril in the material selected for use. For example, the glass fibers are cleaned with a flame and then treated with a plastic-compatible organosilane to produce reinforcements that are particularly well suited to plastics.

Such methods do not work well with other fibrous materials and, for obvious reasons, are not suitable for carbon fibers that do not have a final surface finish of 30 and have different boundary layers.

High-strength carbon fibers are prepared by heating a polymeric fiber, for example, acrylonitrile polymers or copolymers, in two steps; first to remove volatiles and effect carbonization 35 and then to convert the amorphous carbon to crystalline.

3 75876 During such an event, the carbon is known to change from amorphous to monocrystalline and then to orient into fibrils. If the fibers are stretched during the formation of graphite, very strong fibers are formed. This is crucial for the formation of the interface, because as the crystals grow, high surface energies are formed, manifested by incomplete bonds, edge-to-edge stresses, morphological differences, etc. It is also known that new carbon fibers in this form can absorb oxygen from the air, and even organic matter, non-carbon surface layers are formed that are tightly and chemically bonded to the fiber, although some can be removed by solvent treatment, and some cavities and voids are formed at the interfaces. Like impurities in unrefined, unfinished glass fibers, these carbon-fiber interfaces are the main reason for failure to reinforce plastics and metals.

Numerous failed attempts have been made to manufacture such fibers, especially carbon fibers, in a form well suited for reinforcing metals and plastics. Most often, metals, especially nickel and copper, have been deposited as thin surface layers on the strands. Such a composite fiber was then intended to be used in a plastic or metal matrix. In known methods, metals have been precipitated by the vacuum method, using electricity and electrolytically, but the composite products obtained have not been suitable.

Vacuum precipitation (e.g. nickel, U.S. Pat. No. 4,132,828) gave a seemingly uniform coating, which, however, is not really the case because the vacuum precipitated metal first contacts the fibrils through the openings in the interface, then grows outwards like a sponge, joins 35 together outside the surface, was observed under a scanning electron microscope as the formation of nodular nuclei. If the fiber is bent, such a coating 75876 4 falls off. The low-density, non-crystalline layer limits use.

Non-electrically operated nickel baths have also been used to coat such fibers, but again face the same problem; nickel or other non-electrically charged metal first forms only small dots at the openings in the boundary layer, then the new metal grows like a sponge and coalesces to look like a uniform coating, but it also falls off when the fiber 10 is bent. The cores of the metal compound occur only very locally and this also limits the use.

In the case of both vacuum deposition and electroless deposition, the bond strength between the metal and the core is always significantly less than one tenth of the tensile strength of the metal layer itself.

Electrolytic coating with nickel and other metals has also been mentioned in the described attempts to produce carbon fibers with a metal layer that would be compatible with metals and plastics, for example R.V. Sara, U.S. Patent 3,622,283. Short carbon fibers were attached to a coil pole screw, immersed in an electrolyte, and electroplated with nickel. When the coated fibers were placed in a tin-stable matrix, the fibers did not transfer their strength to the mat-25 rice to the extent that would have been expected under the alloy rule. When the fibers thus produced are bent at an acute angle, a number of transverse fractures appear on the compression side of the fold, and on the stretching side, the metal breaks and detaches as flakes.

30 If the metal coating is removed mechanically and the underside is examined under a powerful microscope, it does not show any patterns left by the fibril or is at most incomplete; a scanning electron microscope with a resolution of 35 40 A was used in the assay. The last two observations strongly suggest that the failure to strengthen the tin matrix was due to a weak bond between the carbon and the nickel coating. In these cases, the strength of the bond between the metal and the core is at most half of the tensile strength 5 in at most 10% of the fibers and well below one-tenth in the remaining 90%.

It has now been found that if an electrolytic coating is used, and if the external voltage is very high, much higher than could be achieved by known methods, uniform, continuously adhered, thin coatings can be produced for reinforcing fibers, especially carbon fibers. The voltage should be high enough to generate enough energy to push the metal ions through the boundary layer, thereby causing uniform formation of nuclei directly on the surface of the fibrils.

The composite fiber yarns or ropes according to the invention are characterized in that the majority of the fibers have an electrically conductive carbon, boron or silicon carbide core and at least one thin, uniform, tightly bonded, electrically conductive layer of at least one electrically precipitated metal with said core, said wire or rope is made by a) forming a continuous web of a plurality of electrically conductive carbon, boron or silicon carbide core fibers, 25 b) continuously immersing at least a portion of said web in a bath capable of electrolytically precipitating at least one metal, and c) connecting the fibers and an external voltage of at least 10 volts between the bath to dissociate the metal very deeply into the fibers and to uniformly nucleate the dissociated metal through any barrier layer on the surface of said fibers, and maintaining said voltage for a sufficiently long period of time. to form a tightly bonded, electrically conductive electrolyte-deposited metal layer on said core.

6 75876

Combinations of yarns or ropes, a woven fabric, yarns and the like according to the invention formed of a thin metal coating on fibers can be knitted and bent without detaching the metal. The combinations differ from all known products in that they can be bent at an acute angle without the fibrils slipping inside the metal tube, as was found in electrically and vacuum-coated combinations, and their sharp bending, especially in the case of nickel, does not cause transverse fractures or compression cracks. fracture and peeling when the elongation of the metal is exceeded on the stretch side of the fold. In other words, the combinations according to the invention differ from the known ones because (i) they are continuous; (ii) most of the composite fibers are uniformly coated with metal; and (iii) the bond strength (metal / core) in most of the fibers is at least about 10% of the tensile strength of the metal layer, preferably not significantly less than about 25%, particularly preferably not significantly less than 50%. In the most preferred embodiments, the bond strength between the metal and the core is not substantially less than 90% of the tensile strength of the metal layer. The best properties are achieved with wires or ropes made of composite fibers with a bond strength between the metal and the core of almost 25 to 90% of the tensile strength of the metal, which are specifically mentioned here.

Products made by adding the yarns or ropes of the invention to the matrix-forming material are also known in the art to be strongly reinforced. In addition, the articles have other advantages, for example, they conduct away electrical charges, and if certain non-hazardous metals, such as gold and platinum, are used in the coatings, there is no rejection when placed at the desired target.

35 The invention will be more readily understood from the accompanying drawings, in which: 7 75876

Figure 1 is a cross-sectional view of a metal-coated fiber according to the invention.

Figure 1a is a longitudinal sectional view of a metal coated fiber according to the invention.

Figures 2 and 2a are cross-sectional views of "multi-core" and "cracking" fibers, respectively, coated with metal in accordance with the invention.

Figure 3 shows a longitudinal section of a strongly bent metal-coated fiber according to the invention; Figure 3a shows a longitudinal section of a strongly bent metal-coated assembly made by a known method.

Figure 4 is a fragmentary sectional view of a metal coated composite fiber reinforced polymer made in accordance with the invention.

Figure 5 shows an apparatus for carrying out the method according to the invention.

All drawings show examples of the products described.

The bond strength between said electrodeposited layer and said core is not significantly less than about 10% of the tensile strength of the metal.

The bond strength in each fiber is at least such that when the fiber is strongly bent so that the coating breaks on the stretch side due to exceeding its elastic limit, the coating remains attached to the core on the compression side of the fold and does not break circumferentially:

In particularly preferred forms, the core consists of carbon fiber.

Most preferred yarns made of composite fibers are those in which, when the coating is mechanically removed, a depression pattern left by the fiber or fibril is visible on its inner surface when examined with a scanning electron microscope having a resolution of 40 Å or better.

The various forms of the invention include interlocking ropes and yarns made from new composite fibers, fabrics woven from such yarns, fibreboards, mats and papers made from such fibers, chopped strips made from such fibers, and products containing such fibers uniformly and with metal. or a matrix formed by an organic polymeric material. In preferred embodiments, the coating metals are nickel, silver, zinc, copper, lead, arsenic, cadmium, tin, cobalt, gold, indium, iridium, iron, palladium, platinum, tellurium, tungsten, or mixtures of any of the foregoing, without limitation, preferably in crystalline form.

The invention also relates to a process for the production of continuous yarns or ropes of high-strength composite fibers, which process comprises a) forming a continuous web of a plurality of electrically conductive carbon, boron or silicon carbide core fibers, b) continuously immersing at least a part of said fibers in a bath capable of electrolytically precipitating at least one metal, 20 c) an external voltage is connected between the fibers and the bath.

The method is characterized by using an external voltage of at least 10 volts to dissociate the metal very deep into the fibers and uniformly nucleate the dissociated metal through any barrier layer on the surface of said fibers, and to maintain the above voltage for a sufficiently long, uniform, tightly bonded, electrically bonded to form a conductive layer of electrolytically precipitated metal on said core.

In the resulting product, the bond strength between said electrically deposited layer and said core is not substantially less than about 10% of the tensile strength of the metal.

9 75876

In particularly preferred forms, the process uses core fibers formed from carbon fibrils.

In a preferred embodiment, the plurality of core fibers form a carbon fiber rope, resulting in a composite fiber rope that can be formed without removing the metal layer or portions thereof from the core fibers.

In other preferred embodiments, yarns made by the process are woven from fabric, made into fibreboards, or cut into short pieces.

In other preferred embodiments, the method is performed in an electrolysis bath that is recycled into contact with the fibers immediately prior to immersion in the bath to provide improved current carrying capacity to the fibers and to replenish the electrolyte feed to the surface of the fibers.

The continuous yarns and ropes shown in Figures 1 and 1a, which are suitable for use in the core 2 according to the invention, are commercially available from numerous manufacturers. Suitable carbon fiber yarns are sold, for example, by Hercules Company, Hitco, Great Lakes Carbon Company, AVCO Company, and other similar manufacturers in the United States and elsewhere. All are generally prepared by the method described in U.S. Patent No. 3,677,705. The fibers can be long and continuous or short, for example 25 1-15 cm long. As mentioned above, all such carbon fibers contain a thin, imperfect boundary layer (not shown) consisting of chemically bound oxygen and chemically or mechanically bound other materials such as organic materials.

The metal layer 4 can be any electrolytically precipitable metal and is electrically continuous. Two or even more layers of metal can be used, and the metals can be either the same or different metals, as shown in the examples. In any case, the inner layer is so tightly attached to the core 10 75876 2 that bending at an acute angle (Figure 3) causes the metal to flatten and adhere to the fiber core and to break on the tensile side of the bend when its elastic limit is exceeded. This is done so that the metal-5 li does not come off when it breaks (Fig. 3a), which is a problem in fibers coated with metals by known methods. Another difference from the known methods is that the metal layer according to the invention fills the pores and "cracks" of the fibers completely and uniformly, as can be seen from Figures 2 and 2a.

The high-strength metal-coated fibers according to the invention can be used by conventional methods for composite preparations such as in Figure 5, where the matrix 6 is a plastic, e.g. epoxy resin, or metal-15, e.g. lead, the matrix being reinforced by the presence of high strength fiber cores 2.

The formation of the metal coating by the electrolytic deposition method according to the invention can be realized in many ways. For example, a set of 20 core fibers can be immersed in an electrolyte bath and the required high external voltage can be connected by means of suitable electrical connections. In one embodiment of the method, a high voltage is used for a short time. For example, a pulse generator sends an overvoltage wave through the electrolyte strong enough to push or force the metal ion through the boundary layer into contact with carbon or other cathode fiber. The short duration of the pulse prevents heat from accumulating in the fiber and the fiber from burning. Because the fibers are so small, e.g., 5-10 microns in diameter, and because the innermost fibers are usually surrounded by hundreds or even thousands of other fibers (although only 0.5-2.6 volts are needed to dissociate the electrolyte metal, e.g., nickel, gold , silver or copper ions), depending on the salt used, high external voltages of the order of 5 times the dissociation voltages are required to pass the ions uniformly through the fiber bundle to the innermost fiber and then through the boundary layer. The previous external voltage is at least 10-50 V or even higher.

Although the pulse method described above is suitable for small-scale applications, for example for metallizing woven fabric pieces, and short carbon fiber yarns and ropes, it is preferable to implement the method for a continuously moving fibrous rope. For example, in order to prevent the fibers from burning due to high voltages, the fibers 10 can be separated and water poured on them to keep them sufficiently cool outside the bath, but it is preferable to use the device schematically shown in Figure 5. The electrolyte bath solution 8 is in the tank 10. The device also includes anode baskets 12 and spacers 14 near the bottom 15 of the tank 10. Above the tank there are two electrical contact wheels 16. The rope 24 is pulled from the feed roller 26 over the first contact wheel 16 by a device (not shown). over the second contact wheel 16 and receive the take-up reel 28. In this example, the length of the rope in the bath is about 1.8 m. Possibly, but very preferably, a simple circuit consisting of a pump 18, a tube 20 and a feed end 22 is used. At a rate of -25 ur., For example 7-11 1 / min, and pump it onto the contact wheels 16. When the solution is pumped just above the wheels, the rope 24 entering and leaving the bath is completely wetted and thus cooled. With the large amounts of current carried by the rope, the heat generated in some cases could destroy the rope before it reaches the bath or when it leaves the bath without such cooling. Electrolyte flow overcomes anisotropy. Of course, more than one coating bath in series can be used, and the fibers can be rinsed clean of the electrolyte solution, treated with other conventional materials, and dried, broken, woven into fabric, etc. by conventional methods.

12 75876

The following examples illustrate, but do not limit, the invention.

Example 1

The continuous electrolytic coating system uses a bath with the following composition:

Ingredient "......

- Content of nickel sulphate (NiSO2 .61 ^ 0) 300 g / l nickel chloride (NiCl2-6H2O) 90 - 150 g / l 10 boric acid (H3BC> 3) 37 - 60 g / l

Wetting agent (WA-129,

State Chemical) 2% v / v brightener (Starlite 915,

State Chemical) 2 vol% 15%

The bath temperature is 60-71 ° C and the pH is 3.8-4.2.

The anode baskets are kept filled with electrolyte-nickel pellets, and 4 ropes (bundles of fibers) each consisting of 12,000 carbon fibers (7 μm thick) are continuously drawn through the bath at an external voltage of 30 V and a current adjusted to a total current of 600 As / 1000 fiber. At the same time, the electrolyte solution is circulated in the circuit so that it comes into contact with the incoming and outgoing parts of the rope. Next, the rope is continuously passed through a similar bath at a speed of 1.5 m / min with a current of 180 A in each bath. The final product is a rope formed by the high-strength composite fibers according to the invention, each of which consists of 7 μm-30 and crystalline electrolytically precipitated nickel (about 50% by weight of the combination) which is tightly bound to the core.

If the piece of fiber is bent at an acute angle and then examined, no circumferential cracking has occurred in the metal coating on the stretch side of the bending point. The rope can be twisted and knotted without peeling off the coating in the form of flakes or powder. If part of the 75876 13 coating is mechanically removed from the fibrils, a complete pattern left by the fibrils can be seen on its inner surface.

Example 2 When the procedure of Example 1 is repeated, but using a series of two baths having the following compositions and silver in anode baskets, the silver-coated graphite fibers of the invention are obtained. Ingredient First bath Second bath 10 silver cyanide 0.75 ^ 2.2 g / l 52 - 82 g / l calcium cyanide 90 - 150 g / l 90 g / l potassium hydroxide --- 7.5 - 15 g / l The operating voltage in the first bath is 12 to 36 V and temperature room temperature; in the second bath ice-15 volume is 6 to 18 V and the temperature is room temperature.

Example 3

The procedure of Example 2 can be modified by using nickel-coated graphite fibers prepared in accordance with Example 1 as a feed and reducing the voltage of the first bath to about 18 volts. Thus, very strong composite fibers according to the invention are obtained, in which the silver coating surrounds the nickel coating around the graphite fiber core.

Example 4 The procedure of Example 1 can be modified by replacing a nickel bath with a bath having the following composition using zinc in anode baskets to give the zinc coated graphite fibers of the invention: Ingredient Amount Zinc sulphate 60 g / l ammonium base 22-30 g / l potassium hydroxide 120 g / 1 potassium cyanide 22 g / 1 35 The driving temperature is 38 ° C and the external voltage is 18 V.

14 7 5 8 7 6

Example 5

The procedure of Example 1 can be modified by replacing the nickel bath with the following bath, using copper in anode baskets, to obtain copper-coated graphite fibers according to the invention:

Ingredient Amount of copper cyanide 26 g / l sodium cyanide 34 g / l sodium carbonate 30 g / l 10 sodium hydroxide 3.7 g / l

Rochelle salt 45 g / l

The bath temperature is 60 ° C and the external voltage is 18 V. Copper-coated fibers should be washed with sodium dichromate solution immediately to prevent fading after coating. If the procedure of Example 3 is repeated, but the copper bath of this example is used instead of the silver bath, very strong composite fibers of the invention are obtained in which the copper coating surrounds the nickel-20 coating on top of the graphite fibers.

Example 6

The procedure of Example 1 can be modified by replacing the nickel bath with two baths having the following composition and using conventional 80% Cu / 20% Zn-25 anodes to give the brass-coated graphite fibers of the invention.

Ingredient Amount of copper cyanide 30 g / l 30 zinc cyanide 9.4 g / l sodium cyanide 56 g / l sodium carbonate 4 g / l

The operating temperature of both baths is 43-49 ° C.

Since one third of the brass precipitates in the first bath at 24 V, and two thirds in the second at 15 V, the current is distributed accordingly. After rinsing with water, the brass-coated fibers are washed with sodium dichromate solution to prevent tarnishing 5 and then rinsed twice with water.

Example 7

The procedure of Example 1 can be modified by replacing the nickel bath with a bath having the following composition and using solid lead rods in anode-10 baskets to give the lead-coated graphite fibers of the invention.

Ingredient Amount of lead fluoroborate, Pb (BF4) 2,105 g / Pb / 1 15 fluoroboric acid, HBF ^ 97 g / l

Optionally, about 2 g / 1/3-naphthol and gelatin are added, the pH is below 1, the operating temperature is 27 ° C and the external voltage is 12 V. If the thickness of the coating exceeds 0.5 μm, lead tends to form bridges between the fibers.

Example 8

According to Example 1, but by replacing the nickel bath with a conventional gold bath, and using a sufficient external voltage, very strong fibers consisting of a graphite core and a gold coating can be produced.

Example 9

The silicon carbide fibers and boron fibers are coated with nickel by placing them as cathodes in a nickel coating bath according to Example 1 and using an external voltage of 30 V.

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Example 10

The composite preparation is made by cutting the composite fibers of Example 1 into small pieces 3.2 to 2.5 mm long, then thoroughly mixing them with the thermoplastic polyamide in an extruder, and breaking the extrudate into cast pellets by conventional methods. The pellets are injection molded into tiles measuring 10 x 20 x 0.32 cm. The tile is reinforced with composite fibers. Due to its metal content, it is also not statically charged 10 and can be used to protect electrical equipment.

Example 11

The bundles of nickel-plated graphite fibers 15 about 25 mm long prepared according to Example 1 are mixed 1: 9 with uncoated graphite fibers, and the mixture is made into a nonwoven mat having a basis weight of 34 g / m 2. The mat has a metal content of about 0.5% by weight of nickel and can be impregnated with thermosetting resin varnishes and bonded to heat and pressure reinforced laminates which are very strong and have excellent electrical conductivity properties.

Example 12

The long, nickel-plated graphite yarns made by the general method of Example 1 are pressed at high speed with molten lead in a device which emits a 3.2 mm thick solid rod with nickel-plated graphite fiber in the middle. Lead alloys to nickel 30 without causing complete dissolution of the nickel, and the nickel remains well attached to the graphite fibrils. This results in a good transfer of the physical strength of the graphite fibers through the nickel layer, the nickel / lead interlayer and the lead matrix. The rod is stretched in 17 75876 devices to measure the breaking strength. Compared to an equally thick lead rod, the tensile strength of the graphite fibers of the nickel coatings according to the invention is much higher.

5 The above patents and other publications are incorporated herein by reference. Many variations of this invention are possible to those skilled in the art in light of the detailed description above. For example, aluminum can be precipitated from ether solutions. Metals, for example tungsten, can be precipitated from brine melt solutions, for example sodium tungstate solutions. The rope can be treated to partially remove the metal, and thus segment structures are obtained which can be used, for example, as electrical resistors. All such modifications are within the scope of the invention as defined by the appended claims.

Claims (6)

1. A continuous yarn or rope consisting of composite fibers of very high shelf strength, characterized in that most of the fibers have an electrically conductive core of koi, boron or silicon carbide and at least one thin, uniform, tightly seated an electrically conductive layer consisting of at least one electrically precipitated metal, in said core, wherein said yarn 10 or rope is made a) by forming a continuous web of a plurality of electrically conductive koi, boron or silicon carbide core fibers; b) by continuously lowering at least part of the web consisting of said fibers in a bath which is capable of electrolytically precipitating at least one metal, and c) by coupling between the fibers and the bath an outer spin of at least 10 volts for dissociation of the metal very deeply among the fibers, and for nuclear attachment of the dissociated metal uniformly through which as a barrier layer on the surface of said fibers, and by maintaining said a spinning long enough to replace a thin, uniform, tightly seated, electrically conductive layer of an electrolytically precipitated metal 25 in said core. A method of producing continuous yarns or ropes consisting of composite fibers of very high shelf strength, according to method (a) forming a continuous web of a plurality of electrically conductive koi, boron or silicon core fibers, (b) at least a portion of the web being consisting of said fibers is continuously lowered in a bath capable of electrolytically precipitating at least one metal,