MXPA01007246A - Injection moldable conductive aromatic thermoplastic liquid crystalline polymeric compositions - Google Patents

Abstract

A method for making a shaped article or a shaped article having a volume resistivity of less than 10-2 ohm-cm with a desired combination of properties and processibility in an injection moldable composition. In particular the shaped articles formed include injection molded bipolar plates as current collectors in fuel cell applications.

Description

CRYSTALLINE POLYMERIC COMPOSITIONS CRYSTALLINE LIQUID COMPOSITIONS AROMATIC CONDUCTOR, MOLDABLE BY INJECTION Field of the Invention The present invention relates to an electrically conductive, injection-moldable composition comprising crystalline polymers. 1 aromatic thermoplastic liquids (LCP) electrically conductive articles made from them, and the process of injection molding to make them. The compositions of the invention are useful in a wide variety of applications including ect rochemical devices such as battery and current collectors, high interference shields! Efficiency for radio / electromagnetic frequency,? , and packaging that dissipates electrostatic and equipment ojamientos. The present invention is particularly useful in energy cells. BACKGROUND OF THE INVENTION In the current state of the art, a typical energetic cell comprises the elements shown in Figure 1. A membrane / electrode assembly MEA), 10, comprises a membrane separator] 11, and coatings Ref: 129577 catalysts, 12, in arabos laaos thereof, and two (2) diffusion gas control sheet, 20, are sealed by ethic joints, between the two (2) electrically conductive graphite plates, 40. The plates are often They have a multiple role as current collectors that carry electrons to the external load by means of electrical connections not shown, as mechanical supports for other energy cell components, and as gas and water distribution networks by means of a pattern of flow fields inscribed on the surfaces of the same, 50. The inlets and the outlets of gas and water are generally integrated with the graphite plate, but are not shown, graphite plates usually serve as an interface between the adjacent cells in a pile. The plates are known variously with current collectors, flow fields,} bipolar (or onpolar) plates For additional information, see, for example, Ullmann's In Cyclopedia of Industrial Chemistry, 5th edition, Vol. 12a, page 55 onwards, VCH, New York, 1989. Due to its role - Multiple, the bipolar plate has a number of strengths to collect. The plate must have good electrical conductivity, good mechanical or structural properties and high. Chemical stability in the chemically reactive energetic cell environment. In addition, due to its gas distribution role, it must be a gas-impermeable material and d < ibera be formed with complex gas release channels through its surface. In the current practice of the technique, graphite is the material of choice for bipolar plates due to its high electrical conductivity, high resistance and immunity to corrosion. However, this is brittle, expensive, and requires expensive machining to occur. The fragility of the graph needs to use plates 6 millimeters thick in ca. that add either weight and volume to the energy cell, thus reducing its power density (kW / 1 or kW / kg) during use. Thermoplastic polymers filled with carbon / graphite have been identified as a promising alternative to graphite in bipolar plates. In a principle, reinforced, conductive thermoplastic polymer compositions, they can be molded directly into intricate, complex shape components, using low-cost, high-speed molding processes. In addition, these more ductile materials allow the development of new stacking designs due to the fact that moldable plastics have a much greater flexibility to the formula of the energy cell components. Unfortunately, this potential has not been realized in the art despite the fact that numerous attempts have been made of electrically conductive thermoplastic polymer compositions that provide a specific resistance volume of 10"3-10" 2 ohm-cm. they are known in the art, and are of particular interest in the production of energetic cell current collectors US-A 3, 954, 844 for Nickols discloses polymeric / hrietal compounds. Copolymers of polysulfone, sulfide, polyphenylene, polyphenylene oxide, acrylonitrile, and styrene are combined in a variety of forms with stainless steel, silver, gold, and nickel. The amount of either metal powder, fillers or both, in the polimer / metal compound varies from 50 to 80: in weigh. Specific resistance levels as low as 10"J ohm-cm are reported, US-A-, 098, 967 for Biddick et al., Providing a bipolar tortoise formed from thermoplastic resin. filling with 40-80% by volume of finely-divided v. -carbon plastics EmpJr-adfs plastics in the compositions include polyvinylidene fluoride and polyphenylene oxide.The plates are formed by dry-blended compositions molded by compression and possess a specific resistance in the order of 0.002 ohmj-cm Bipolar plates molded by compression of mixtures in graphite powder solution and polyvinylidene fluoride are described in the S-3, 801, 374 for Dews et al. ? formed in this manner has a density of 2.0 g / cc and a specific resistance volume ds 4xl0 ~ 3 ohm-cm US-A-4, 214, 969 for Lawrance describes a bipolar plate manufactured by die-casting a dry mix of particulates of carbon or graphite and a resin of f luor opol imero. The graphite carbon is presented in a ratio by weight to the polymer of between 2.5: 1 and 16: 1 For polymer concentrations in the range of 6-28% by weight, the volume The specific resistance is in the range of 1.2-3.5x10 ~ 3 ohm- in. In US-A-4, 3 39, 322 to Balko et al., The physical strength of the compound molded by compression. of US-A-4, 21, 969 is improved by replacing the carbon fibers or other fibrous carbon structures with some of the graphite powder. The typical composition includes 20% (by weight) of polyvinylidene fluoride (PVDF), 16% by weight) of carbon fiber, and graphite powder. The dry mix is mixed, and then molded by pressure on the plates, the specific strength volume is in the range of 1.9x10 ~ 3 to 3.9x10 ~ 3 ohm-in at binder / resin loading levels of 7-25 % in weigh. US-A-4, 554, 06 3-85 for Braun et al. Describes a process for making cathode current collectors. The current collector consists of high purity graphite (synthetic) powder, which has particle sizes in the range from 10 (microna) to 200 (micron) and carbon fibers that are unevenly distributed in it, and have lengths from 1 mm to 30 mm, the ratio graphite powder / mass of carbon fiber is in the range from 10: 1 up to 30: 1 The agglutinante / res ina used is polyvinylidene fluoride. To produce the current collector, the binder is dissolved in, for example, dimethylformamide. The graphite powder and the carbon fibers are then added and the mass similar to the resulting lubricating grease is brought to the desired thickness by spreading on a glass plate and drying for about an hour around 50 ° C. The plates are also formed by wrapping, extension and extrusion. US-A-5, 582, 622 for Lafollette discloses bipolar plates that burn a long carbon fiber composition, a carbon particle filler and a fluoroel tornero. It is also known in the art to use crushed graphite fibers coated with metal, particularly nickel coated, to form conductive polymer compositions. In order to reduce the tracing of fibers by the component, the prior art describes the use of a thermoplastic resin impregnated in a packet of graphite fibers coated with nickel, which are directly injection mouldable with a thermoplastic matrix resin with only one step. preliminary dry mixing. See for example, Kiesche, "Conductive Conjuncts Find Their Niche", Plastics Technology, foviembre 1985, P. 1 1 f f; Murthy et al, "Metal Coated Graphite Fiber Structural Foam Composites," Fourteenth Annual Structural Annual Structural Foam Conference and Parts Competition, The Society of the Plastics Industry, Inc., April 1986, pages 86 and onwards. The use of wider gates and flow channels in the molding machines that process graphite fibers is described, for example in the inter- national Encyclopedia of Composites, S. Lee, ed Pages 474 onwards, VCH publicists, 1990. It is also described in this the increase in conductivity made by the orientation of conductive fibers of high aspect ratio in the matrix of the polymer during the molding process. Methods for forming graphite fibers impregnated with resin which also apply to metal coated graphite are known in the art. Some of these methods are described in 'Graphite Fiber Composites (Elect rochemical Processing by Iroh in Polymeric Materials Encyclopedia, J, C, Room one, ed., Pages 2861 onwards, CRC Press 1996 The earlier mentioned technique is directed to replace components of pure metal or graphite that require extensive machining to be formed into final articles with moldable compositions. based on thermoplastic polymer resins that require less machining after molding to form the thermofix article. The problem of realizing the advantages of molded thermoplastic polymer parts has been related in an inverse relationship between the concentration of conductive fillers on the one hand and the process and mechanical properties on the other. In practice, as shown in the aforementioned technique, the amounts of conductive filler required to realize the specific resistance goal of 10 2 ohm-cm in energetic cells results in products that limit their practical utility. This is particularly true with respect to the formation of current collectors in energy cell applications. It is desired to achieve a combination of properties and processability in an injection moldable composition without the limitation in the injection in the form of the characteristic particles by means of a particle size of less than 1500 micrometers with graphite filler to form a mixture at a temperature below the melting point of the thermoplastic liquid crystalline polymer resin, the graphite coating being present in a concentration of about 5% up to about 80% by weight of the total mixture; feeding the mixture to an injection molding machine wherein the liquid crystalline polymer resin aromatic rmoplastic melts and feeds in a molten state to a mold; cool the mold to a temperature at which the resin in the mixture does not flow; and, removing said molded mixture from the container (mold). Brief Description of the Figures Other features of the present invention will be apparent from the following description of the method and during reference to the figures, in which: Figure 1 is a schematic illustration of a tactic power cell, and Figure 2 is a schematic illustration of a molded bipolar plate with fluid distribution channels. Detailed Description of the Invention The compositions of the present invention provide a novel balamee between conductivity, processability, and structural properties. Surprisingly, it has been found in the practice of the invention that injection molding plates having excellent strength and rigidity can be produced with a specific electrical resistance volume in the range of 10"3-10" ohm c. The plates thus formed are suitable for use as current collectors in energetic cells at a thickness in the range of about 0.2 to about 10 mm, with a preferred thickness of 1-3 mm. The combination of properties made by these plates compares favorably with the machined graphite plates representing the current state of the art in the development of energy cells. However, the present invention provides the advantage of a significant reduction in cost, in the process of forming the molded articles.

In a preferred embodiment of the present invention, the necessary balance of properties to allow direct injection molding of complex shaped articles with structural properties exceeds: is, processability, and specific resistance volume of 10"ohm-cm or less is realized. In spite of the teachings of the prior art, and the obvious economic incentive to develop injection molding current collectors that replace the current expensive method, current molding current collectors have been produced prior to the present invention. Injection is unsatisfactory It is well known in the art that the processability and structural properties deteriorate when the amount of filler incorporated in the polymer matrix is increased In the technique as referred to above, in order to perform the specific resistance volume of 10"2 ohm-cm or less required for practical application to energy cells, the required or loaded amount of conductive fibers and other fillers in the selected polymer matrices results in a viscosity of fusion go u and high to allow injection molding, and such properties poor structural ales such as ductility, flexural strength, and impact resistance that only excessively thick plates can be used without exhibiting a structural failure in use. The term "thermoplastic" as used herein refers to a thermoplastic liquid crystalline polymer resin suitable for the practice of the present invention which may be processed by fusion of conformity with conventional methods known: in the art for plastics that can be processed by melting such as rotary extrusion and extrusion molding, In the present invention, the ease of molding thermoplastic liquid crystalline polymers allows the formation of conductive shaped articles of complex shape and thin walls and sufficiently loaded with conductive fillers that provide excellent conductivity. The excellent chemical resistance of the molded aromatic thermoplastic liquid crystalline polymers combined with the complex forms as molded make the process of the present invention particularly suitable for the manufacture of bipolar plates useful in energy cells.

Additionally, one embodiment of the present invention provides an injection moldable composition comprising a thermoplastic polymer-thermoplastic polymer crystalline resin crystallized to an injection moldable thermoplastic aromatic liquid, and a conductive graphite filler, which is fed to a molding machine by injection wherein the crystalline polymer-thermoplastic polymer thermoplastic liquid crystal or aromatic thermoplastic liquid is melted, the graphite filler is dispersed within the molten polymer to be formed during the advance of the rotary molding injection, and the molten resin composition is it feeds the mold where it solidifies and then it is taken out as a solid shaped article. In a preferred embodiment of the present invention, the ingredients of the composition are mixed dry before feeding. Dry mixing can be carried out by any convenient means such as cleaning parts by stirring in a drum. Preferably, the composition also comprises a dispersing agent, and such other additives as desirable or required to improve the processing capacity or end-use properties. Aromatic thermoplastic liquid crystalline polymers suitable for the practice of the present invention include those described in US Pat. No. 3,991,013 3, 991, 014 4,011,199; 4, 048, 148, 4, 075, 262 4, 083, 829, 4,118,372; 4, 122, 070 4, 130, 545 4, 153, 779, 4159, 365; 4, 161, 470 4, 169, 933 4, 184, 996, 4,189,549; 4, 219, 461 4, 232, 143 4, 232, 144, 4,245, 082; 4, 256, 624 4, 269, 964 4, 272, 625, 4,370,466; 4, 383, 105 4, 47, 592, 4, 522, 974, 4,617,369; 4, 664, 972 4, 684, 712 4, 727, 129, 4,727,131; 4, 728, 714, 4,749, 769, 4,762, 907, 4,778,927; 4, 816, 555, 4,849,499, 4,851,496, 4,851,497; 4, 857, 626 4, 864, 013 4, 868, 278, 4,882,410; 4, 923, 947 4, 999, 416 5, 015, 721, 5,015, 722; 5, 0254, 082 5, 086, 158 5, 102, 935, 5,110,896; 5, 143, 956. Useful aromatic thermoplastic liquid crystalline polymers include polyesters, pol i (ester-amides), poly (ester imides), and polyazomethines. Especially useful are the aromatic thermoplastic liquid crystalline polymers which are polyesters or Included within the present definition of an aromatic thermoplastic liquid crystalline polymer, is a mixture of 2 or more liquid crystalline aromatic thermoplastic polymers, or a mixture of an aromatic thermoplastic liquid crystalline polymer with one or more non-thermoplastic liquid crystalline polymers. aromatics, where the aromatic thermoplastic liquid crystalline polymer; s the continuous phase. In one embodiment of the present invention, an aromatic thermoplastic liquid crystalline polymer resin is combined with a conductive graphite fiber coated with metal, preferably coated with nickel, formed in pellets by the adhesive action of a binder of a thermoplastic resin. In the process of the invention, the aromatic thermoplastic liquid crystalline resin is preferably dry blended, such as for drumming, with the metal-coated graphite-coated chippers to form a coarse homogenous mixture. The mixture is fed to the neck of the feeder of an injection molding machine and the fused resins as the resin mixture are carried along the flights of the turn while the action The spinner causes the fibers to disperse within the melt of aromatic thermoplastic liquid crystalline resin. The molten dispersion is fed to the mold in which the melt hardens to form an articulate} , formed that is then removed from the mold. In a preferred embodiment of the present invention, the formed article that is formed in accordance with the process of the invention, is a bipolar plate having flow channels molded on the surface thereof, being suitable for use in hydrogen or methanol energy cells direct with little or no final back molding required. Suitable conductive fibers are graphite fibers, preferably graphite fibers re coated with metal, more preferably graphite fibers coated with nickel. The length of the graphite fibers is less than ca, 1", preferably 0.125-0.5", and the diameter is in the range of about 5 to about 40 microns, preferably about 5 to about 15 microns. . Although any degree of metal coating is an improvement over uncoated graphite fibers, a level of metal coating of The following discussion is provided for the purpose of illustrating a preferred embodiment of the invention and not to limit it due to the limitations both in residence time and rotating design in the injection molding machines, it is considered that there is a considerable beneficial increase when the time available for the dispersion of the graphite-coated metal fiber in the fused resin matrix is maximized. Confound this point, it is preferable that the thermoplastic binder resin become fluid at a lower temperature than that which melted the aromatic thermoplastic liquid crystalline resin, in this way, ensuring that the dispersion of the fiber will be good even when the crystalline resin aromatic thermoplastic liquid is founded. The thermoplastic binder resin may or may not be useful as a dispersing agent. Alternatively, it is desired to add a dispersing agent to the composition. The thermoplastic resin binder can be deposited on the fibers of the invention by means known in the art including melt impregnation, impregnation by solution, polymerization? in situ of the dispersed monomer, and electrodeposition. No other means, known in the art, is preferred over another. The aromatic thermoplastic liquid crystalline polymers are manufactured and commercially available as pellets from ca. 0.125"in diameter It has surprisingly been found in the practice of the present invention that the conductivity is improved when the aromatherapy crystalline pellets are subjected to attrition or wear of size to form particles having an average particle size of less of 1500 μm, preferably less than 1000 μm, before combining with a conductive graphite filler. In a further embodiment of the present invention, an aromatic thermoplastic liquid crystalline resin having an average particle size d less than 1500 μm, preferably less than 1000 μm, is combined with a conductive graphite filler. In the process of the present invention the liquid thermoplastic liquid crystalline resin is preferably mixed dry, such as by reaction, with the graphite filler to form a thick homogenous mixture. The mixture is fed to the feed neck of an injection molding machine and the aromatic thermoplastic liquid crystalline polymer melts as it is carried along the turns flights, and the spin action causes the filling to disperse within the molten aromatic thermoplastic liquid crystalline resin. The molten dispersion is fed into a mold in which the melt hardness to form a formed article which is then removed from the mold The conductive graphite filler is presented in the composition of the invention at concentrations in the range of air from 5% up to 80%, preferably about 30 to 70% by weight, more preferably 30 to 50% by weight. Suitable graphite fillers include powdered graphite, such as Conoco, Inc.'s Thermocarb® graphite powder, more preferably a graphite fiber, such as resin-based graphite fibers, available from Conoco Inc., even more preferably, a Graphite fiber coated metal, more preferably a graphite fiber nickel coated such as that described above. The particle size wear of aromatic thermoplastic liquid crystalline resin pellets can be carried out in accordance with the following process. A rotary cutter or lino, such as an ABBE cutter (model number: 00 D Laboratory Rotary Cutter Serial No. 49491, Abbe Enginneering Company, Brooklyn, NY 11211), is equipped with a metal screen that has holes of 0.060 inches (0.15 cm) in diameter. A precipitation cuvette is filled with pellets of liquid thermoplastic to crystalline crystalline resin and immersed in liquid nitrogen to maintain it by ca. two minutes after the boiling of the liquid has stopped. After immersion in the liquid nitrogen, the pelletizing pellet of the pellets is removed and the pellets are fed to the moving knives of the cutter. The clarity of frequency of the cutter is necessary because only the ac. 50% of the resin pellets are currently cut effectively, 1 raising contaminants to the cutter with increased pellets.

The remaining pellets can be recycled to be cut after further immersion in liquid nitrogen. It has been found in the practice of the invention that when the nickel-coated graphite pellets d 3.2 mm in size and length are combined they are the thermoplastic liquid crystal resin of less than 1.5 mm in size, and particularly less than 1.0 mm in size. in size, some separation of the components occurs during feeding to the injection molding machine. Some loss of homogeneity may occur in and around the resulting molding parts. Therefore, it is desirable to take additional measures to ensure that the above components are thoroughly mixed on a microscopic scale within the feeder. This can be done by using nickel-coated graphite fibers which have a small aspect ratio so that the pellets formed therefrom can have smaller dimensions. Another method is to adapt a known boxer technology for their feed extruders to feed machines of the same type. injection molding. Still another method is to keep the Uniform mixing when the material is fed into the rotator of the injection molding machine.

This, and other methods known in the art may be employed alone or in combination, to maintain homogeneity in the embodiments of the invention in which a mismatch of considerable size occurs in the materials that are fed. To improve the hompgeneity of the dispersion of the conductive filler in the aromatic thermoplastic liquid crystalline polymer, it is desired to incorporate in the arrangements, formed according to the process of the present invention, a dispensing aid. The dispersion aid can be of any type known in the art to be effective in increasing the dispersibility of metal or graphite fibers in polymer fusions. The dispersion aid may be crys- taline or non-crystalline, and may be normally liquid at room temperature. In the present invention, the dispersion aid is required to be immobilized in the composition at room temperature. For a liquid dispersion aid the liquid must be immobilized by absorption or absorption in the fiber. Suitable dispersion aids include low molecular weight species such as fatty acids, silanes, difunctional oligomers and so forth. The dispersion aids may be polymeric in nature, such as the thermoplastic resin binder incorporated in the nickel-coated graphite fiber pellets that are preferred for use in the present invention. The choice of the dispersion aid is also governed by the compatability with the polymer matrix. Compatibility is widely an empirical determinationThe compatible dispersion aid is one that can cause the fiber to be dispersed within the polymer matrix, while an unsupportive dispersion aid does not cause dispersion but instead causes isolated fiber clumps to form in the fiber. The composition of the present invention may contain as many other additives as may be required to improve its processability or its properties. In particular, in the practice of the present invention, the addition of ca. 5-20% by weight of carbon black to the composition provides a desirable improvement in the fusion, and they lead to the mold followed by cooling and removal. The injection moldable composition of this invention is suitable for use in any injection molding machine that provides the limited melting shear stress necessary for dispersion of the fibers in the matrix of | molten polymer. Although a wide range of molding and running geometries can be employed, it is advantageous to reduce the degree of stress to which the fusion is subjected by using large diameter and running ports. For the purposes of the present invention, the dry or non-melt premixing of the ingredients at low shear includes simply feeding separate ingredients directly into the feed hopper of the mold machine. by injection, using a controlled ratio of low weight feeders where mixing is done in situ inside the feed neck of the injection molding machine. This invention permits the production of slimming (for example, all the molding samples in the following examples section are from The nickel-coated graphite fibers are supplied in the form of 12,000 fiber pellets containing 5-15% by weight of a low melting polyamide binder with a melting point of 32 ° C. The fibers also consist of 60% by weight of nickel and 25-35% by weight of graphite. The fibers are provided in lengths of 1/4"and 1/2. The drying conditions applicable to the materials cited in the examples are listed below as shown in Table 2.

TABLE 2 Drying conditions Material Temperature Drying time Others D temperature (° C) (hours) Zenite® HX8000 105 = 12 Drying hopper under N2 Fibers of 220 = 4 Drying furnace graphite under N2 coated with nickel Thermocarb © Used as CF300 receives Used Fibers as graphite receives mesoresin In all the examples, the injection molding was carried out using a 180 ton injection molding machine (N Lssei Manufacturing, Nagano Japan) . The formed parts were flat plates of 3 '' xß '' xO .125 '' and 4 '' Y? '' xO .125 ''. All the specific resistance volume measurement was given in flat molding plates using a four-point probe (reference: "Electrical Resistivity Measurements of Polymer Materials" by A.R. Bly the in Polymer Testing 4 (1984) 195-200). Six (6) measurements were made on each of the sides of the sample and the average of the measurements was reported as the volume conductivity number in the following samples. EXAMPLE 1 2730 g of HX8000 (dropped at 105 ° C for 12 hours) was mixed dry by: amboreation with 910 g of each of the 1/4"and 1/2 nickel-coated graphite fiber pellets. " of length. The mixture was injection molded under the following conditions. Fusing temperature: 320 ° C Molding temperature: 30-70 ° C Injection pressure 703 kg / cm2 Molding speed 2.5-5 cm / sec Rotation speed: 50-75 RPM Co-injection time (max): 14 seconds Cure time set (max) seconds Start time of the cycle set (max): 1 second Previous pressure 0 kg / cm 'The volume of the specific gingiva was found to be around 2.0x10 ohm-cm Se now refers to Figure 2, which shows a molded bipolar plate of Example 1 with fluid distribution channels, 100, molded therein. Example 2 3185 g of HX8000 were dry mixed with 682 g of each of the 1/4"long, 1/2" long nylon-coated graphite fiber pellets. The mixture is injection molded in the following: it is conditions. Fusing temperature: 320 ° C Molding temperature: 80-87 ° C Injection pressure 492 kg / cm2 Injection speed 2.5-5 cm / seconds (variable in cycle) Rotation speed: 50-75 RPM Injection time placed ( max) 14 seconds Cured time set (max): 18 seconds Start time of the maximum placed cycle: 1 second Previous pressure: 0 kg / cm2 Size of the head to: 54% The specific scratch volume was found to be around l.OxlO "2 ohm-cm Comparative Example 2730 g of HX 8000 and 6370 g of graphite powder Thermocarb CF300 were melted in compound under vacuum in a 20 mm rotary counter Twisting Extruder We. [lding Engineers (King of Prussia, PA). the first zone while the graphite was fed downstream after the polymer had melted.The speed of rotation was 125-150 rpm, and the total yield was ca. 4550-6800 g.The temperature of the die was approx. 290-300 ° C. The extruded filaments were ground in pellets of ca 0.125 'around 1360 g of the formulation in this composite manner a dry one was first mixed with 910 g of additional HX8000 and then mixed dry with 455 g of each one of the n graphite fiber pellets 1/2"long and 1/4" nickel long. The mixture was moved by injection under the following conditions. Fusing temperature: 320 ° C Mold temperature or 80-87 ° C Injection pressure: 984 kg / cm2 Injection speed: 2.5-5 cm / seconds (variable in cycle) Rotation speed: 50-75 RPM Injection time set (max) 14 seconds Set-up time (max): 18 seconds Start time of the maximum set time: 1 second Previous pressure: 0 kg / cm2 The volume of Specific assistance was found to be around 2.5x10"2 ohm-cm Comparative Example 2730 g HX8000 dry-mixed with 1820 g of copper-coated graphite fiber pellets (or nickel coated) (about 45% by weight) metal in the base fiber.) Each of the pellets contained 12,000 fibers held together with a proprietary nylon base binder (5-15% by weight of base fiber). The mixture was molded by injection under the following conditions. holes in the bottom filled with wire handles with resin pellets of ca. 1/8"(3.2 mm) followed by immersion of the filled precipitation bucket in a large bath of liquid nitrogen contained in a Dewar flask.The precipitation bucket is kept in the liquid nitrogen for a period of two minutes after which The boiling activity of liquid nitrogen ceases.A ABBE rotary cutter provided with a metal amiz that has 0.060"(1.5mm) holes starts with the closed cutting hopper, using a face shield and thermally insulating gloves, the precipitation tank filled with the resin is removed from the liquid nitrogen and its contents are discharged into the cutter feed hopper The sliding lid opens and the pellets fall on the knives. In any given run, only about 50% of 1 fed DS pellets are milled. Therefore it is necessary to stop every third fourth run to completely clean the pelletized waste now warmed and recycle it through the process. The determination of: sizes is given using the laser diffraction method using a Malver Matersizer X manufactured by Malvern Instruments Ltd, Malvern UK If required in powder or pelletized form, Zenite 8000 thermoplastic liquid crystalline resin (available in 3.2mm pellets from DuPont, Wilmington, DE) is dried for 12- hours at 105 ° C under nitrogen. In all cases, a 180-ton injection molding machine (Nissei Mftg., Nagano, Japan) is used to form plates with dimensions of 3''x6''x0.125"or 4" x4"xO. 125 '' The results are tabulated in Table 3 Example 3 700 grams of the thermoplastic liquid crystalline powder resin are mixed in a drum with 1300 grams of graphite powder Thermocard® CF300, the mixture is then immediately fed to the molding machine by injection and is molded under the following conditions of injection molding. Fusing temperature: 320 ° C Mold temperature 150 ° C Injection pressure 1125 kg / cm2 Injection speed 5 cm / seconds variable in cycle) Rotational speed: 125-140 RPM Co-injection time (max): 30.0 seconds Cure time set (max 60.0 seconds Start time of the placed cycle (max): 1 second Previous pressure: 0 kg / cm2 Size of -la Example 4 The materials and co-additions of Example 3 were repeated except that 600 grams of thermoplastic crystalline resin powder were combined with 1400 grams of Thermocarb® CF300 Example 5 1050 grams of liquid crystalline resin powder thermoplastics were drum blended with 1290 grams of Thermocarb® CF300 graphite powder, 660 grams of graphite fibers based on ream month fasa The combination was immediately fed to the injection molding machine, and injection molded under the following injection molding conditions. Melting temperature: 320 ° C Mold temperature: o: 150 ° C Injection pressure. : 1335 kg / cm2 Injection speed: 2.5-5 cm / seconds (variable in cycle) Rotation speed 100-125 RPM Injection time set (max) 25.0 seconds Curing time set (max 45.0 seconds) Start time of the placed cycle (max): 1 second Previous pressure: 0 kg / cm2 Size of the discharge: -40-60%. Example 6 The materials and processes of Example 5 were employed, except that 990 grams of the graphite fiber was used. Comparative Example 700 grams of Zenite 8000 pellets were dry mixed by drumming with 1300 grams of Thermocarb CF300 graphite powder. The mixture is injection molded directly in accordance with the following injection molding conditions Melting temperature: 320 ° C Molding temperature 150 ° C Injection pressure: 1195 kg / cm2 Injection speed 2.5-5 cm / seconds (variable in cycle) Rotation speed 100-125 RPM Co-injected injection time (max): 20.0 seconds Curing time set (max 30.0 seconds) Start time of the placed cycle (max): 1 second Previous pressure: 0 kg / cm2 Size of the discharge: -40-60%. Comparative Example The materials and procedures of Example 3 were employed, except that 600 grams of dry Zenite 8000 pellets were combined with 1400 grams of Thermocarb CF300 1050 grams of dry Zenite 8000 pellets were dry mixed by drumming with 1290 grams of Thermocarb CF300 graphite powder, and 660 grams of resin-based graphite fibers. The mixture was molded by injection under the following molding conditions by injection: Fusing temperature 320 ° C Mold temperature or: 150 ° C Injection pressure 1195 kg / cm2 Injection speed 2.5-5 cm / seconds (variable in cycle) Rotation speed: 1 0 0 - 12 5 R PM Injection time placed (max): 20. 0 sec. S Cured curing time (max): 30. 0 second Start time of the placed cycle (max): 1 second Previous pressure: 0 kg / cm2 Size of the head to: -40-60%. Comparative Example 6 The materials and procedures of comparative example 5 were repeated except that 1050 grams of Zenite were combined with 990 grams of Thermocarb CF300 and 990 resin-based graphite fibers. TABLE 3 Volume of Specific Resistance in Examples 4-8 and Comparative Examples 4-8 Example Specific Resistance Volume (4 pt per probe) ohm-cm Example 3 0.18 E j us 0.21 Comparative 3 Example 4 0.12 E j us 0.15 comparative 4 Example 5 0.18 E j usable 0.27 comparative 5 It is noted that in relation to this date, the best method known or by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention

Claims (1)

1. Claims Having described the invention as above, it is claimed as property what is contained in the following re-mediations. A process for manufacturing a shaped article having a specific strength volume of less than 10 ~ 2 ohm-cm, the process characterized in that it comprises combining a moldable aromatic thermoplastic liquid crystalline polymer resin and a composition comprising graphite fibers nickel-coated impregnated with a crystalline non-liquid thermoplastic binder resin, to form a mixture at a temperature below the melting point of the thermoplastic liquid crystalline polymer resin, the graphite fibers being of a length of less than 2 cm and comprising about 5 to about 50% by weight of the mixture, and the binder resin comprising about 0.1 to about 20% by weight of the graphite; feed the mixed to an injection molding machine in where. • the thermoplastic liquid crystalline polymer resin melts fed into the molten state into a mold; cool the mold to a temperature at which the thermoplastic liquid crystalline polymer in the mixture does not flow; and removing the mixture from the mold 2. The process according to claim 1, characterized in that the graphite-nickel-coated fibers comprise about 10 up to a. about 40% by weight of the total composition. 3. The process according to claim 1, characterized in that the graphite fibers coated with nickel have a diameter in the range of about 5 to about 15 microns. The process according to claim 1, char. bristled because the nickel-coated graphite fibers have a nickel coating representing about 45% up to about 60% or a total weight of the graphite fibers re covered with nickel, 5. The process according to claim 1, characterized in that the liquid crystalline polymer thermoplastic aromatic is a polyester or a poly (ethylamide). 6. The process according to claim 5, characterized in that at least 50% of the ester bonds or amide groups are carbon atoms qup are part of aromatic rings. 7. The process according to claim 6, characterized in that at least the 75% of the ester bonds or amide groups are carbon atoms that are part of aromatic rings. 8. The process according to claim 1, characterized in that the binder resin comprises about 5 to about 15% by weight of graphite. 9. A shaped article having a specific resistance volume of less than 10 ~ 2 ohm-cm, characterized in that it comprises about 50 to about 95? by weight of an aromatic thermoplastic liquid crystalline polymer about 5% up to [About 50% by weight of a nickel-coated graphite fiber of a length of less than 2 cm, and a non-liquid crystalline thermoplastic resin at a concentration of about 0.1% up to about 20% by weight with respect to the weight of the graphite. The article formed according to claim 9, characterized in that the formed article comprises about 10% up to about 40% by weight of the graphite fiber coated with nickel. 11. The shaped article according to claim 9, characterized in that the nickel-coated graphite fiber is of a diameter in the range of about 5 to about 15 micrometers 12. The article formed in accordance with claim 9, c. : Characterized because the nickel coating represents around 45 to about 60% or the total weight of the coated graphite fiber of nickel. 13. The article for: according to claim 9, characterized in that the aromatic thermoplastic liquid crystalline polymer is a polyester or a polyester (ether-amide). 14. The article formed according to claim 13, characterized in that at least 50% of the ester bonds or amide groups are carbon atoms that are part of aromatic rings. 15. The forged article according to claim 14, characterized in that at least 75% of the ester bonds or amide groups are carbon atoms that are part of aromatic rings. 16. The article fo rmed in accordance with claim 9, characterized in that the binder resin comprises from about 5% to about 15% by weight of the graphite. 17. The article formed in accordance with claim 9, end face because it comprises a shape of a bipolar plate. 18. The article formed in accordance with claim 17, face etherized because the bipolar plate has a thickness in the range of about 0.1 to about or 10 mm. 19. The article formed according to claim 18, characterized in that the thickness of the bipolar plate is in the range of about 1 to about 3 m. 20. The article fo rmed in accordance with claim 17, the etherized face because it further comprises fluid distribution channels inscribed on the surface thereof. of nickel-coated graphite are of a diameter in the range of 5 to 1 5 micrometers 29 The process according to claim 26, characterized in that the nickel coating represents about 45% up to about 60% of the total weight of the nickel-coated graphite. the graphite fiber coated with nickel. 30. The process according to claim 21, characterized in that the aromatic thermoplastic liquid crystalline polymer is a polyester: r or a poly (ether er-amide). 31. The process according to claim 30, characterized in that at least 50% of the bonds to 1 ester or amide groups are carbon atoms that are part of aromatic rings. 32. The process according to claim 31, characterized in that at least 75% of the bonds to 1 ester or amide groups are carbon atoms that are part of aromatic rings. 33. The process according to claim 26, characterized in that the nickel-coated graphite fiber further comprises a non-liquid crystalline tjermoplastic binder resin 34. The process according to claim 33, characterized in that the binder resin comprises about 0.1% to 20% by weight of the graphite. 35. The process d. according to claim 34, characterized in that the binder resin comprises about 5% to about 15% by weight of the graphite. 36. An article formed in accordance with the process of claim 1. 37. An article formed in accordance with the process of claim 21. 38. The article formed in accordance with claim 36, etherized because it comprises a form of a bipolar plate. 39. The article formed in accordance with claim 37, the end face because it comprises a shape of a bipolar plate. 40. The article formed in accordance with claim 36, characterized in that it also comprises fluid distribution channels inscribed on the surface thereof. 41. The article formed in accordance with claim 37, characterized in that it also comprises fluid distribution channels inscribed on the surface thereof. ? - - Summary of the Invention A method for making a formed article or a shaped article having a specific resistance volume of less than 10 -. 10 -2 ohm-cm with a desired combination of properties and its processability in an injection moldable composition. In particular, the shaped articles that are formed include bipolar plates molded by injection as current collectors in energy cell applications.