CA1070939A - Electrodeposition of non-conductive surfaces - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A composition of matter specifically adapted to be employed in a process of electrodeposition comprising a polymer from the group of poly-ethylene, polypropylene and mixtures and copolymers thereof and, in percent by weight of the total composition, about 15% to about 60% of carbon black and a material from the group of sulfur and sulfur donors in an amount equivalent in sulfur content to about 1% to about 10% of dipentamethylenethi-uram hexasulfide, said carbon black being in an amount sufficient to provide in said composition of matter in massive form an electrical volume resis-tivity of less than about 1000 ohm-centimeters.

Description

93g The present applica-tion is a clivisional o f Canadian application Serial No. 203,8~3, filed J~lly ~, 1974, and is concerned with polymer-con-taining cathodes used in a process of electrodeposition of Group VIII metal.
More particularly, the present invention provides a composition of matter speci~ically adapted to be employed in a process of electrodeposition comprising a polymer from the group of polyethylene, polypropylene and mix-tures and copolymers thereof and, in percent by weigh~ of the total composi-tion, about 15% to about 60% of carbon black and a material from the group of sulfur and sulfur donors in an amount equivalent in sulfur content to about 1% to about 10% of dipentamethylenethiuram hexasulfide, said carbon black being in an amount sufficient to provide in said composition of matter in massive form an electrical volume resistivity of less than about 1000 ohm-centimeters.
BACKGROUND OF THE INVENTION
Since the start of electroplating, a large number of proposals have been made with respect to electroplating on non-electrically-conductive sub-strates ranging in size and shape across the gamut of l~aves, flowers, baby shoes, plastic knobs, bottle tops, molded plastic parts for automotive usage and uncounted other practical and decorative structures. Basically, two processes have been used. The first process involves the coating of the non-conductive object with an electrically conductive lacquer ollowed by electroplating. The second process involves sensitizing the non-conductive object, chemically depositing a metal on the sensitized surface and there-ater electroplating the thus metallized surface.
The two generally available processes as practiced in the prior art have certain disadvantages. Because of high loadings of conductive pig-ments such as graphite or metal, prior art conductive lacquers are generally very weak and thus constitute a weak link in the ultimate electroplated structure. A variation of the lacquer process which involves coating the tacky lacquer surface with graphite again produces very weak bonds between electrodeposited metal and the lacquer much like the ephemeral bond pro-.

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duced between graphitized wax and electrodeposited metal in the electro-typing process. If lower pigment loadings are used in a conductive lacquer to give greater strength in the lacquerJ the rate of inltial metal coverage of - la ' ..

~7~g~39 the article during electroplating is radi~ally decr~ased necessitating the use of multiple electrical contact points on the object to be plated or allowance of a long time for metal covera~e and consequent uneven plating thlcknesses.
The second process as ~enerall~ practiced b~ the prior art, can achieve good results but onl~ at a cost of employin~ a large number of individual processin~ operations carried out with very great care by skilled personnel.
Furthermore, because the underlying chemically deposited metal can be different from metal subsequently electrochem-ically deposited, there is a good chance of forming an elec-trochemical couple between the two even when, nominally the metals are the same. Thus the possibility of accelerated, locali~ed corrosion exists wherever and whenever the outer electrodeposited layer is not continuous.
Recently, U.S. Patents No. 3,523,875 to Minklei and No. 3,682,786 to Brown et al have issued. ~hese recently issued patents aré worthy of discussion because, superficially they might appear to resemble the process of the present in-vention. Minklei proposed to treat a plastic s~lrface with an aqueous solution of alkali metal sulfide followed by contact-ing the treated surface with a metal salt prior to electro-plating. Brown et al proposed contacting a plastic surface with a solution or dispersion of sulfur in an organic medium and contacting the treated surface with an aqueous solution of cuprous salt prior to plating. In both instances, the proposals involve the formation of a metal sulfide on the plastic surface and not the type of metal-polymer bond, which,

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will become apparen~ from the subsequent description.
It ~ould be advantageous to have a process for electrodepositing metal on non-electrically-conductive substrates and in particular on sub-strates which are not amenable to ordinary electrodeposition techniques.
It would also be advantageous to have polymer-containing cathodes which could be used in a process o~ electrodeposition.
The following description is to be taken in conjunction with the drawing in which Figure 1 depicts electrodeposit growth obtained in accor-dance with the present invention and; Figure 2 depicts undesirable electro-deposit growth obtained when an essential requirement of the process as described herein is omitted.
Generally speaking the present invention contemplates a process wherein at least part of a substrate for electrodeposition comprises or is coated with an adherent layer of a mixture of an organic polymer and an ?
electrically conductive carbon black of such proportion so as to have an electrical resistivity of less than about 1000 ohm-centimeter; at least the exposed surface of the layer is caused to contain an effective amount of sulfur, and the thus coated object is then introduced into a nickel, cobalt, or iron plating bath as the cathode to cause rapid deposition of metal across the coated surface. Thereafter the metal coated object can be subjected to further electrodeposition in ways well known to those skilled in the art.
The polymer used along with conductive carbon black in the coating layer (and which may also constitute the substrate) is, advantageous-ly a member of the group of organic polymers which readily react with molecular sulfur or a sulfur donor of the type described herein. Advanta-geous polymers For use in the process include hydrocarbonaceous and substituted hydrocarbonaceous elastomers such as natural rubber, poly-chloroprene, butyl rubber, chlorinated butyl rubber, polybutadiene rubber, 30 ~ acrylonitrile-butadiene rubber, s~yrene-butadiene rubber, etc. These , ~7~93~
elastomers are ~ms~turated ancl reaclily combine with molecular sulfur through either ~msaturatecl linkages in the carbon skeletal structure oE
the polymer or through activated sites on the polymer structure associated with unsaturated linkages or pendant substituent atoms. Another advantageous type of polymer for use in the process is an ethylene-propylene terpolymer comprising a saturated poly-ethylene-propylene main chain having unsaturated groups derived from non-conjugated dienes, e.g., hexadiene, dicyclopentadiene etc., pendant from the main chain. Such a terpolymer is readily vulcanized with sulfur. Other polymers useful in the process include essentially saturated polymers such as polystyrene, polyvinyl chloride, palyurethane etc., which apparently possess active sites for reaction with sulfur. While polyethylene (and similar polymers of limited solubility) are not readily suited or use in coating formulations, it has been found that milled and molded polyethylene compositions containing carbon black and a sulfur donor can advantageously be employed in the process. Undoubtedly some organic polymers, for example, perhaps, polytetrafluoroethylene are too inert to react with sulfur and these polymers are excluded from the ambit of the process. However, the great bulk of normally used organic polymeric materials appears to be useable in the process.
Of those polymers which react with sulfur, those having elastomeric characteristics, e.g., rubbers, elastomeric polyurethane etc., are considered to be advantageous when used as a coating covering a rigid base and overlied by the deposited metal because an elastomer has the ability to dampen stress concentrations which can result in failure of the deposited coating upon exposure to applied stress or thermal cycling.
In addition, with most elastomers, the carbon black included for the purpose of providing a proper degree of electrical conductivity acts as a reinforcement agent to improve the physical characteristics of the elastomer. Further factors which make elastomers most advantageous include rapidity of metal coverage low cost of materials. Among the elastomers, ~r~ ~ ' ~ 4' ~

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~71)~3139 the unsaturated elastomers are deemed to be the most advantageous.
Those skilled in the art will appreciate that in the foregoing description of polymers operable in the process the examples given are mere-ly illustrative and that many other polymeric and copolymeric materials and mixtures can be used in place of the specifically mentioned substances. For example, very often in rubber formulations amounts of compatible non-elastomeric resins are included for various purposes. Polymers other than rubber can, and often are compounded with plasticizers in order to obtain a product having flexibility. Such compounded materials as well as co-polymers and mi~ed polymers are operable for purposes of the present invention.
When as is always advantageous the exposed surface of the polymer-conductive carbon black composition is caused to contain sulfur it is possible that the sulfur initially attacks the polymer chain at activated positions, to provide activated sites for bonding of nickel to the polymer.
Regardless of the theoretical explanation howeverJ applicant's experiments have shown that when nickel deposits are made in accordance with the teachings of the present inventivn very strong, highly useful metal to organic bonds are formed very rapidly on polymer-carbon black surfaces. It is important to avoid overcuring of a polymer with sulfur (or other curative) prior to plating. It appears that a polymer-sulfur-metal bond can occur with most polymers as long as activated sites on the polymer chain exist.
Heavy curing, especially in sulfur monochloride will remove these sites ~ 1 from an unsaturated elastomer causing poor plating both as to sp~eed of coverage and as to adherence of the metal.
The exposed surface of the polymer-carbon black plating substrate can contain sulfur by inclusion of sulfur in the whole mass of the plat m g substrate or by enriching the exposed surface with sulfur. -Normally, a plating substrate containing an unsaburated polymeric elastomer will contain about 0.5% to about 5% of sulfur based upon weight ~`1 ~70939 of elastomer in order to permit curing of the elastomer. When agents other than sulfur or sulfur compounds are used for curing the exposed surface of ~he elastomer can be enriched in sulfur by contacting the surface with a solution containing elemental sulfur or by exposing the surfaces to a sulfur-containing vapor e.g., the vapor of sul~ur monochloride ~S2Cl2).
The plating substrate will normally contain ingredients other than sulfur, elastomer and conductive carbon black such are normally included in rubber compositions. Such other ingredients include vulcanization accelerators and modifiers, anti-oxidants and similar types of materials which have been found to be useful in rubber technology. For best results, particularly with respect to adhesion of electrodeposited metal all ingredients should be limited in amount to amounts which will be permanently soluble in the cured elastomer at normal temperatures i.e., about 25C.
Plating substrates which can be used usually contain carbon black and polymer in weight ratios of about 0.2 to about 1.5 ~conductive carbon black to polymer) although somewhat higher or lower weight ratios can be used. It is usually more advantageous to employ weight ratios of conductive carbon black to polymer in the range of about 0.5 to 1Ø
It has been noted with coating, on non-electrically conductive substrate, that speed of coverage of polymer-carbon black surfaces becomes very low at very high loadings of carbon black indicating that a minimum surface concentration of polymer is necessary not only for attaining mechanical streng~hbut also for purposes of facilitating the metal spreading mechanism of the invention. Because carbon blacks vary greatly depending upon sources and methods of manufacture, it is not practical to specify with more precision the relative amounts of polymer and carbon black required. In addition to variations involved in different types of carbon black difference in dispersion conditions when co~pounding with polymer can also introduce variations in the polymer-carbon black mixtures. For example, 3Q if an acetylene black sold by Shawinigan Products Corp. of ~nglewood Cliffs, ~

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New Jersey, is millecl with an elastomer in a Banbury-type mill, it is likely that at least part of the chain-like structures of the acetylene black will be broken. On the other hand using less agressive mixing tech-niques, the chain structures will be retained. Consequently, the composition milled in the Banbury mixer will exhibit a higher vol~mle resistivity than will a composition milled in solution form in a blender even thou~h the loading of the carbon black is the same. Thus, the criterion of operability of a particular polymer-carbon black mixture is the electrical volume resistivity. As stated hereinbefore, the volume ;~
resistivity must be less than about 1000 ohm-centimeters and more advan-tageously is less than about 10 ohm-centimeters.

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Ordinarily, it is neither possible nor desirable to obtain polymer-carbon black mixtures having volume resistivities less than about 1 ohm-centimeter. At such low resistivities, the strength oE the polymer-carbon black mixture is low.
Optimum results have been obtained using conductive carbon blacks made from acetylene such as sold by Shawingan Products Corporation under the trade designation Acetylene Carbon Black.
Another commercially available conductive carbon black which possesses relatively hi~h resistance to mechanical breakdown during milling with a polymer is sold by Cabot Corporation under the trade designation of Vulcan* XC72. I~ desired, mix-tures of conductive and non-conductive carbon blacks can be usecl provided that final polymer-carbon black product has a volume resistivity in the range set forth hereinbefore. In some instances the proper volume resistivity can be achieved in polymer-carbon black compositions which are made entirely with non-conductive carbon blacks for example, furnace blacks.
Such compositions ordinarily do not have adequate electrical characteristics when used as coatings and dried on a substrate.
However, these compositions may have adequate characteristics for use as molded, extruded or like-formed shapes which can be treated electrochemically in accordance with the present invention without a separate preliminary coating step.
The rate of coverage of nickel cobalt or iron on a cathode having a surface of polymer-carbon black mixture * Trademark ~07~939 e.Ytending from a point of contact with an electronic conductor (e.g., a metal) is depenclent at least Ipon the resistivity of the mixture, the sulfur content at the mixture surface, the applied voltage flcross the anode-electrolyte-cathode circuit; and the nature of the polymer. Generally speak-ing the minimum rate at which nickel spreads across the cathode surface at a voltage of 3.0 volts is about 0~5 centimeter per minute (cm/min.). A series of polymer-acetylene black compositions were made containing 100 parts by weight of polymer and 50 parts by weight of the carbon black. The composi-tions devoid of sulfur were coated on an ABS panel having a metal contact point at one end. In a first series of tests the panels were immersed in a Watts' type nickel plating bath as cathodes at a voltage of 3Ø The rate of nickel coverage was measured. In a second series of tests the panels were dipped in a solution of 1% (by weight) of sulfur in cyclohexane, removed and the cyclohexane allowed to evaporate prior to electrolyte treat-ment in exactly the same manner as was the first series. The results of these tests are set forth in Table I.
TABLE I
!
Polymer Ni coverage rate (cm/min) Series I Series II

Polystyrene 0.251.19 Polyvinyl chloride 0.150.99 Chlorinated Rubber (Parlon)* 0.310.89 Nitrile Rubber (Paracril* BJLT) 0.31 2.24 Natural Rubber (Smoked Sheet) 0.31 0.89 Neoprene Rubber (Neoprene* AD) 0.58 1.78 ~` , ' .
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~ able I shows that a very small amount of sulEur incorporated in the exposed surface of the polymer increases nickel coverage rates by a factor of at least about 2.5.
When sulfur is included in the polymer-carbon black composi-tions and not merely in the very surface layer as in the mate-rials of Series ~I Table I, rates of nickel coverage can be much higher. For example, with a composition containing 100 - parts by weight nitrile rubber, 50 parts by weight acetylene black and 4 parts by weight sulfur, nickel coverage rates at

3.0 volts of over 6 cm/min. can be obtained. The rate of nickel coverage increases linearly with increases in voltage. Using a composition containing a weight ratio of 2 to 1 of nitrile rubber to acetylene black and 2.5~ by weight of sulfur based upon the weight of rubber, a nickel coverage rate of about 9.5 cm/min. was obtained at a voltage of 3.0 and a rate of about 14.7 cm/min. at a voltage of 4.5. It is important that the sulfur present in the polymer-carbon black compositions be in the form of non-ionic sulfur, i.e., that it not be tied up as a metal sulfide or in a stable ion such as the sulfate ion.
Ordinarily, elemental sulfur is used but, if desired, sulfur in the form of a sulfur donor such as sulfur chloride, 2-mercapto-benzothiazole, N-cyclo-hexyl-2-benzothiazole sulfonomide, dibutyl xanthogen disulfide and tetramethyl thiuram disulfide or combinations of these and sulfur can -~
also be employed. Those skilled in the art will recognize that these sulfur donors are the materials which have been used or have been proposed for use as vulcanzing agents or accele-rators.

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The advantage obtained when sulEur is included in the polymer-carbon black surface is dramatically depicted in the drawing. Referxing now thereto both Figures 1 and 2 depict identical acrylonitrile-butadiene-styrene plaques 11 coated with polymer-carbon black coating 12 containing 20 parts by weight of neoprene and 10 parts by weight of acetylene black and having a wire contact 13.
The coating 12 of Figure 1 initially contained a small amount of thiuram and was treated with a 1~ by weight solution of sulfur in cyclohexane prior to plating so as to incorporate a small effective amount of sulfur in the coating.
Coating 12 of Figure 2 was made with a neoprene free of :
thiuram, was not exposed to a sulfur solution and therefore contained no sulfur. Both plaques were made cathodic under identical voltage conditions (3 volts closed circuit cell potential) in the same nickel plating bath. After 1 1/2 minutes the area 15 above line 14 in Figure 1 was uniformly coated with a highly adherent nickel deposit. At this time the plaque was removed from the plating bath. If it were not removed from the bath, the plating front, as depicted by line 14, would continue downwardly across plague 11 of Figure 1 until, at the end of about 5 minutes the whole plaque would be coated with a firm, adherent, even deposit of nickel. In contrast, the pla~ue of Figure 2, after 20 minutes in the plating bath, had a loosely adherent fern-like deposit on the area external of closed, irregular curves 16 and 17 lea~ing sulfur-free coating 12 exposed internally of closed irregular curves 16 and 170 A compari-16~7~939 son of Figures 1 and 2 of the clrawing clearly shows that plating practice in accordance with the process described herein is highly advantageous.
The cathodic electrolytic treatment to induce nickel coverage across the expanse of polymer-carbon blà~k mixture surface is carried out in an electrolytic bath from which nickel can be deposited and which, ordinarily is aqueous and contains about 70 to abou~ 120 grams per liter (gpl) of nickel ion, complementing anion from the group of sulfate, chloride, sulfamate, fluoborate and mixtures thereof and exhibits of p~l of about 2.8 to about 4.5 stabilized by inclusion o a buffer such as boric acid in the bath. An ordinary Watts bath is quite satisfactory for use both as the initial bath for nickel coverage and for subsequent plating. IE desired, after nickel coverage has been established, one can plate in a nickel bath containing any kind of additive, e.g., levelling agents or brightening agents, etc., known to the art. Further after nickel coverage is esta-blished one can plate not only with nickel but also with any other electro-depositable metal compatible with nickel, e.g., chromium, copper, zinc, tin, silver, gold, platinum, pa~lladium, cadmium, etc.
The cathodic treatments to induce the growth of iron or cobalt across the polymer carbon-black surface can be carried out in any elec-troplating bath from which these metals can be deposited. For example, the process of the convention has been carried out using an aqueous ferrous chloride bath to deposit iron and an aqueous cobal~ chloride-cobalt sulfate bath to deposit cobalt. Details of operation for these and other iron, cobalt and nickel baths can be obtained from any text on electroplating, for example, Electroplating Engineering ~landbook, Edited by A. Kenneth Graham, Reinhold Publishing Corporation,lCopyright 1955. Those skilled in the art will appreciate that for partlcular purposes, it may be advantageous to deposit alloys of nickel, cobalt and iron such as iron-nickel alloys, nickel-cobalt alloys, etc.
In addition to iron, nickel and cobalt, other metals of G~oup ,:

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VIII ot` the Periodic rable ot` E`lements can be depositecl in the m.mner as depicted in Figure I o~ the drawing, that is initially behind a deposition front moving across the polymer-carbon black surface. In particular palladium has been found to spread across a polymer-carbon black surface at ' a rate rougllly equivalent to the rate at which iron spreads, which rate is somewhat slower ~han the spreading rate of nickel and cobalt all other conditions being equal. ;
While the process is especially concerned with electrodeposition of metal on a wide variety of plastic and other non-conductors (and on other -materials which are not generally amenable to ordinary electroplating ~
:
techniques) using a coating ~echnique involving an essentially solid polymer carbon-black-sulfur-containing coating adhered directly or through an intermediate layer onto a base, the process is also applicable to bases having the requisite carbon black-polymer-sulfur composition. As an example, a sample of EPDM synthetic rubber having a volume resistivity of about 235 ohm-centimeters md containing reinforcing type, .~ , ' ' :' ' :, , : . .

~7~936~

furnace carbon black and sulfur is directly plat~able in a Watts-type nickel bath to provide a highly adherent, rapidly formed overall deposit of nickel. The spreading o the deposit from a point of metallic conduction differs somewhat in the case of a solid base of pol~mer-carbon black-surface from the spreading depicted in Figure 1 of the drawing which is typical of metal spreading usi~g coatings. With a solid polymer-carbon black~sulfur base the electrodeposited metals tends to rapidly film over the entire surface of the object blurring to a certain extent the metal deposition front depicted in Figure 1 of the drawing.
In order to give those skilled in the art a better understanding and appreciation of the invention, the follow~
ing examples are given;
EXAMPLE I
A coating formulation was made up as ~ollows:

MaterialParts-by-weight Natural R~bber (Smoked Sheet) 100 Nitrile R~bber (Pæacril BJLT)l 100 Asetylene Carbon Black2100 Sulfur 4 Irichloroethylene 10,000 (1) Product of Uniroyal Chemical, Naugatuck, Conn.
(2) Product of Shawinigan Products Cbrp., Engléw3od Cliffs, N.J.
The aforedescribed coating formulation was sprayed on an acrylonitrile-butadiene-styrene (ABS) surface to pro~ide a dried coating about 0.0025 cm thick. The coated and dried ABS surface was then exposed for 40 seconds to the vapor above ~4 -,~- ~

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sulfur monochloride held at room temperature (about 25C).
The surface having a single metal contact was then placed in a Watts-type nickel plating bath as a cathode with a driviny voltage of about 3 volts in opposition to a nickel anode.
The nickel deposit grew rapidly across the coated ABS surface and deposition was continued until the deposited nickel had a substantially uniform thickness of about 0.0025 cm. The electrodeposit showed a 90 peel strength of about 1.88 kilo-gram per centimeter (kg/cm) width (10.5 lb/in width) when pulled at 2.54 cm/minute.
EXAMPLE II
The following coating formulations were prepared:
oating A
Material Parts-by-Weight Nitrile Rubber (Paracril BJLT) 9.87 ; Stearic Acid 0.099 '~

Zinc Oxide 0-493 Dibutyl Xanthogen Disul~ide (C-P-B)l 0.394 Zinc diethyl dithiocarbamate (Ethazate*)l 0.025 Dibenzylamine (D-B-A) 0.394 Sulfur 0.394 Methyl Ethyl Ketone (MEK) 11.3 Xylene 77.5 ;;

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10 7G~939 ~ t.i.~ 13 ~laLcLial l'arLs-~)y-~lc.igllL
~cetylene Car~on ~lack ~.39 Nitrile Rub~er (Paracril ~JL'r) 8.78 Stearic Acid 0.088 Zinc Oxide 0.044 Butyl Rubber 0-044 Dibutyl Xanthogen Disulfide tC-P-B)l 0.351 Zinc diethyl dithiocarbamate (~thazate)l 0.022 Dibenzylamine (D-~-A)l 0.351 Sulfur 0.351 Trichloroethylene 32.9 Xylene 52.6 lProducts of ~niroyal Chemical, Naugatuck, Conn.
Coating A was applie~ ~y brushiny onto a poly-(vinyl chloride) (PVC) pla~ue, and then coating ~ was applied in simi.lar fashion over the dried coating A. ~fter curing in an air oven for 3 hours at 90C. ~he plaque was dipped into a 1 w/o solution of sulfur in cyclo-hexane, then plated to a thickness of about .001 inch with Watts nickel. Initially the nickel deposit grew xapidly across the surface of the plaque from a single metal contact. A 90 degree peel strength of 2.5 kg/cm (12 lb/in) was achieved for the electrodeposit.

~IIL07~39 EXAMPLE III

The following coating formulations were prepared:
Coating C
Material Parts-by-Weight ::
Neoprene* AFl 50 Neozone* Dl 1 ~:~
Magnesia 2 Zinc Oxide 2.5 Alkyl Phenolic Resin (SP-136*) 20 Ethyl Acetate 80 Hexane 82 Toluene 81 Water 0.
Coating B
Material Parts-by-Weight Acetylene Carbon Black 15 Natural Rubber (Smoked Sheet) 7.5 Styrene Butediene Rubber (Naugapel* 1503)3 7.5 Sulfur o.9 ~ :~
Heptane 240 -Turpentine 70 Trichloroethylene 75 Products of E. I. Dupont de Nemours and Co. ~ .
2Product of Schenectady Chemical Inc., Schenectady, NY
3Product of Uniroyal Chemical, Naugatuck, CN
An ABS panel was dipped in coating C, air dried, then dipped :~
into coating D, and again air dried. It was then directly electroplated in a Watts bath and the resulting nickel electro-* Trademark .

deposi-t had a 90 degree peel strength of :L.79 ]cg/cm of width ~10 lb/in.).
EX~MP~E IV
Coatings A and B Erom Example II were modified so that the concentration of curatives (C-P-B, Ethazate, D-B-A and sulfur) was doubled. In addition, MEK was added to coating A such that its final weight equaled that of the xylene (ie, from 11.3 to 77.5). An ABS panel was successively dipped in modified coating A, then into modified coating B.
The panel was cured at 85C for 1-1/2 hours, during which time a noticeable sulfur bloom appeared on the surface. The panel was then directly electroplated with Watts nickel with a rapid initial rate of coverage. The resulting metal deposit exhibited a 90 degree peel adhesion of about 3.58 kg/cm of width (20 lb/inl.
EXAMPLE V
An ABS panel (Cycolàc* standard test plaque) was coated by successively dipping in first coating A, then coating B of Example II. After curing 15 hours in air at 85C, the panel was dipped into a 1 w/o solution of sulfur in cyclo-hexane. It was then plated with a Watts flash, 0.0009 inch of semibright (Perflow*) nickel, 0.0003 inch of bright (Udylite) nickel and 15 ~ in conventional chromium. The plated panel was given a thermal cycle of 90C for 2 hours, room temperature for 1 hour, -40C for 2 hours, and then given a 16-hour exposure to CASS testing. No detectable failure resulted on the panel from this treatment.
Those skilled in the art will appreciate that although in most of the foregoing examples ABS plastic plaques were f ~ * Trademark .~ ~ _ ,~f _ !P

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93g used, the process is equally as well adapted to the elec~roplating of utilitarian and decorative objects made of other plastics such as poly-styrene, phenolformaldehyde resins, urea-formaldehyde resins, polyacrylates and methacrylates, polyurethane, silicons, vinyls, vinylidenes J epoxys, polyolefins and similar thermoplastic and thermosetting resinous materials.
In addition, the process can also be used to plate metals which are coated with non-metallic, non-electrically conductive coatings,e.g., varnished aluminum and the like. Those skilled in the art, in considering the scope of utility of the process will re~ognize that with some base materials it will be necessary to include an adhesive layer between the polymer carbon black plating substrate and the par~icular base material.
While the form and character of the base material is not of significance to the operability of the process particular base materials can provide qualities of utility not ordinarily contemplated. ~or example, a loosely matted paper was coated with a polymer-carbon black-sulfur mixture to provide after metal deposition a novel useful electrode skeleton for a battery plaque, fuel cell electrode or the like. In this regard ~;
special attention is directed to the deposition of precious metals from Group VIII. While economic factors make it unlikely that platinum, ;~
- palladium- rhodium, iridium, ruthenium and osmium would find much use in the decorative plating of plastics, these metals can be usefully deposited in the form of electrodes, catalysts,etc., where their particular chemical and electrochemical characteristics can be utilized.
EX~MPLE VI
A sample plastic treated and coated as in Example III was immersed as a cathode in an aqueous plating bath containing 300 gpl of ferrous chloride, 150 gpl of calcium chloride adjusted to a pH of 1.2 to 1.8 and held at a temperature of about 87C. Upon passage of current through the bath at avoltage of 6 volts, the surface of the sample became covered with a smooth adherent coating of iron.

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EXAMPLE VII
The sample of ExampLe VI was immersed as a cathode in an aqueous cobalt plating bath contai.ning about 335 gpl of cobalt sulfate, about 74 gpl of cobalt chloride. about ~6.5 gpl of boric acid and about 1.2 gpl of sodium fluoborate. Upon passage of current through the bath, the sample rapidly filmed over with cobalt.
EXAMPLE VIII
One hundred parts by weight of a low-density, general purpose polyethylene were milled in a Banbury type mixer at a temperature of about 178C along with 50 parts by weight of Vulcan XC72 carbon black (supplied by Cabot Corporation) and Tetrone* A brand dipentamethylenethiuram hexa-sulfide. The milled composition was then molded and the molding thus produced was inserted as a cathode in a nickel plating bath. Nickel rapidly spread over the surface from a metallic point of contact and plating was continued to provide a firm, adherent nickel electrodeposit having a 90 peel strength of about 1.8 kg/cm of width.
Although the present invention has been described in conjunc-tion with the electrodeposition process those skilled in the art will appreciate that the molding composition upon which nickel was deposited in Example VIII is illustrative of a broader range of polyethylene, polypropylene and mixtures and copolymers thereof having blended therein about 15% to about 60% by weight (of the total composition) of carbon black, to give a volume resis~ivity of less than about 1000 ohm-centimeters, along with sulfur or a sulfur donorj for example, of the dipentamethylenethiuram hexasulfide type in an amount equivalent in sulfur content to about 1% to about 10% by weight (of the total com-position) of dipentamethylenethiuram hexasulfide. In plating massive polymer bodies as in Example VIII an interesting phenomenon has been noted, that is, the bond strength of nickel electrodeposited on the polymer surEace improves with aging at room temperature. Thus the 90 ~7(~3~3 peel strength set forth in Example VIII is the peel streng-th observed immediately after plating. After a few days aging the observed bond strength is o-ften double (or more) of that streng~h as set forth in Example VIII. Such compositional and processing modifications and variations are considered to be within the purview ~md scope of the invention and appended claims.

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Claims (2)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A composition of matter specifically adapted to be employed in a process of electrodeposition comprising a polymer from the group of poly-ethylene, polypropylene and mixtures and copolymers thereof and, in percent by weight of the total composition, about 15% to about 60% of carbon black and a material from the group of sulfur and sulfur donors in an amount equivalent in sulfur content to about 1% to about 10% of dipentamethylenethi-uram hexasulfide, said carbon black being in an amount sufficient to provide in said composition of matter in massive form an electrical volume resis-tivity of less than about 1000 ohm-centimeters.

2. A composition of matter as in claim 1 containing polyethylene and dipentamethylenethiuram hexasulfide.