CA1128740A

CA1128740A - Composite strands of resin, carbon and glass and product formed from said strands

Info

Publication number: CA1128740A
Application number: CA329,281A
Authority: CA
Inventors: Richard H. Ackley
Original assignee: PPG Industries Inc
Current assignee: PPG Industries Inc
Priority date: 1979-02-02
Filing date: 1979-06-07
Publication date: 1982-08-03
Also published as: JPS6359862B2; FR2447806B1; FR2447806A1; BE876837A; GB2042010B; JPS646019B2; IT7968292A0; JPS621527A; DE2924602A1; IT1118749B; CH640572A5; GB2042010A; JPS55103927A; DE2924602C2; NL7904769A

Abstract

Abstract of the Disclosure Composite strands of resin, carbon and glass and resin sheets reinforced by glass and carbon strands are described. In the process of forming the composite strands and sheets glass strands are passed through a die as they emerge from the bath to control their resin content and wound on a mandrel. The carbon strands are passed directly into the die and are wetted by the resin in the die and on the mandrel. The composite strands of resin and glass and carbon strands are laid on the mandrel with resin to provide a fiber reinforced resin sheet.

Description

-~L~2~374a3 Background of the Invention In recent years the need for structural plastic parts has increased rapidly. Thus directionally reinforced resin sheets which can be molded into~structural automotive parts such as transmission supports, door beams and the like have been produced. These directionally reinforced sheets contain glass strands which have been helically wound on a mandrel in a crisscross pattern and in amounts ranging between 60 to 80 percent by weight glass. While moldable glass reinforced sheets of a high glass content produce parts having excellent structural strength ; 10 when molded, it is often desired to provide better modulus characteristics than are normally realized. Carbon fibers in molded parts are known to impart good modulus characteristics to resin parts in wbich they are employed. Blends oE glass and carbon fibers in resins have thus been used to utllize the qualitles oE strength and modulus that each provides to a resin matrix~ In attempting to wind carbon fibers with glass fibers in the preparation of resin reinforced sheeting, considerable difficulty has been encountered processing the carbon strands. Thus, frequently the carbon fibers which- are in strand form break in the resin bath or the die. This appears to be caused by the viscous drag on the strand going through the bath which causeF the strand of carbon to fllamentize, i.e., separate into I

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the filaments forming it, and ultimately break out. In accordance with the instant invention, a methad has been developecl to wet ttle carbon st~and with resin and combine it with the glass str~nds to provide a useul composite strand for forming resin sheet reinEorced with both carbon and - glass strand.
, .

The Present Invention In accordance with a process of the instant invention, novel carbon and glass strands are wound on a mandrel to prepare resin sheets.

In the sheet preparation process the glass strands are fed from a glass supply into a resin bath where they are thoroughly wetted. The strands of glass are then passed through a die metering means which regulates the quantity of resin which is to be included with the glass strands. The carbon strand o the composite to be made is fed directly to Lhe back ot the die used to control the resin content of the glass strand and is contacted with the resin at the point where the resin backwashes from the die. Feeding the carbon strand at this point in the process eliminates the fiberizing of that strand, provides good wet out to the strand and permits it to be wound on the mandrel with the glass without the attendant breaks encountered when the carbon strand is fed through a resin bath. The composite strand of the invention is formed of resin, a plurality of glass strands and at least one carbon strand.

Detailed Description of the Invention In the preparation of glass-carbon resin reinforced sheet having structural characteristics and containing 55 to ~0 percent glass and carbon with 20 to 45 percent resin by weight, the strands of carbon ~lZ~37~0 and glass are first coated w;th a resin and then are wound on a rocating mandrel. In the discussion of the process, reference ~ill be ~lade to the accompanying drawing in which:
~ IGURE 1 is a flow sheet in perspective of the equipment used to manufacture the resin-glass-carbon sheets of the instant invention;
FIGURE 2 is an enlarged view in perspective of the resin applica-tion section of the process depicted in FIGURE l; and FIGURE 3 is a section view looking into the resin application pan 9 to show the die 13 and point of entry of the carbon strand.
In the preparation of the resin-glass-carbon composites of the instant invention a plurality o glass strands are used. ~s shown in FIGURE I for illustrative purposes, only six glass fiber forming packages Z are employed. These packages 2 are mounted on a stand or cree~, not shown, and the glass strand ends I from each of the packages are threaded through eyelets 4 and 5 mounted on the wall member 3, typically a sheet metal plate. In the illustration of FIGURE I the upper row of glass forming packages have their strands ends 1 passed through eyelet 5 and the lower row strands ends l are passed through eyelet 4. The physically combined strands form two glass ribbons 1' which are passed under the retaining bars ll and 15 of the resin tank 9. These strands 1' and 1 are then fed through the dies 12 and 13 and located at the forward end of the pan 9. Mounted on the top of the wall 3 are two packages 18 and 18' which contain carbon strands 8 and 8', respectively. The carbon strands 8' and 8 are introduced into the dies 12 and 13, respectively~ by passing them through the resin backwash 14 a~cumulating as the dies wipe resin from the surface of the glass strands l' and 1. The consolidated glass-carbon strands 19 and 19', which e~it the dies 13 and 12, are then consolidated .

1~2~4~) into a band 17 in guide eyelet 22 located on a traveling guide 21 an~ this ribbon is wound on a rotating mandrel 15 to the desired thickness. ~Eter the composite reaches its desired thickness, the mandrel 15 is stopped and the resulting sheet is cut from its surface and the process i9 repeated.
The p~ocess generalLy depicted in the drawing is obviously subject to many variables. Thus, while only a one strand ribbon 17 is shown in the drawing as being wound on the mandrel 15, this is solely for illustrative purposes. The mandrel may have a band or ribbon of many - collimated parallel composite strands wound at the same time on its surface.
Similarly the number of glass ends used to form the strands at 1' can be varied. Thus one end can be used as the strand 1' or any multiple of ends can be used to`form the strand l'. Typically the number of ends employed to form the strands 1' has ranged from 1 to 10 or more. The width of the band 17 desired in the final produce determines the number and diameter of strands,that will be used to Eorm the band. By width of band is meant the width measured perpendicular to the band direction.
In the process shown in the drawing the mandrel l5 is rotating in a clockwise direction on a shaft, not shown, which is driven by a suitable motor. The guide plate 21 reciprocates in a horizontal plane and lays the composite strand 17 do~ on the surface of the mandrel 15.
The sCrand 17 is normally laid on the mandrel 15 at a predetermined helix angle to provide directional reinforcement properties to the finished sheet. The helix angle is the included acute angle created by the inter-section of the band 17 on the body of the mandrel 15 with a line on the body of the mandrel parallel to the longitudinal axis of the mandrel. This angle for the structural sheets produced by this process is generally in the range of 60 to ~9 degrees. The wind angle of the mandrel in relation ~2874~

to the strand 17 is the included acute angle created by the intersectio~ o the band 17 on the body of the mandrel 15 with a Line on the body of the mandrel perpendicular to the longitudinal axis of the mandrel. In a -~ typical use of the process this angle is between 30 to I degrees.
- In the normal operation the mandrel 15 rotates continuously during the process and the guide 21 reciprocates in a horizontal plane causing the ribbon or band 17 co be laid down on the mandrel 15 in a crisscross fashion to form layers of composite on the surface of the mandrel. For purposes of this disclosure a layer is Eormed when the band 17 has covered the mandrel in both traversing directions. The finished sheet containing the glass and carbond serands will contain the number of layers desired to produce a produce of the desired density in pounds per square foot.
The resin pan g during the operation is constantly supplied with resin 10 to insure that sufficient resin is maintained in the pan 9 to thoroughly wet the glass strands 1 and 1' whic~ are passed through it under the bars 11 and 15. This can be done continuously by providing an automatic feed inlet and overflow system or the resin can be added manually as required. The pan Y, depending on the width of the mandrel 15 can remain stationary or it can be reciprocated in a horizontal plane coordinated with the movement of the plate 21.
The strand and article of the invention may be formed using any suitable resin. Typical of suitable thermoplastic resins are thermo-plastic resins such as polyethylene, polypropylene and polystyrenes.
- The thermosetting resin employed in the syscem may include many types and typically resins such as vinyl esters, quick curing epoxy resins and general~purposes polyester resins have been employed. Isophthalic polyester 74~

resins have been found to be particularly eEEective in making the compos ites of this invention and are preferred. Resins s~lch as B-sta~e c~lring epoxy resins and thickened polyesters are desirable as they may be stored after remova} from the mandrel and then cut and molded to cure at a later date.
- Typically polyesters which may be employed in the invention are the class of resins shown and described in U.S. Patent No. 3,840,618.

An important consideracion in preparing composites is the regulation of the resin content of the Einal product. In this process this is accomplished by regulating the size of the orifice in the dies 12 and 13. In general i~ has been found desirable to maintain these orifices in the range of 0.014 to 0.078 inch.
The graphite strands fed to the system may be pulled directly from the wall member 3 as shown or can be drawn from a creel placed closer to the front end of the pan 9. The point of entry of the carbon strand in the resin pan is an important consideration in achieving success in forming the composite ribbons or bands 19 and 19' however. The residence time and drag on the carbon strand must be minimized to prevent damage or degradation to the strand. Thus, it is important that the carbon strand be introduced into the process at or close to the entrance to the dies and preferably in the central area of the resin backwash of that die. This prevents the carbon strand from receiving any excussive strain of being pulled through the resin and allows the strand of carbon to enter the system with little or no viscous drag applied to it.
The sheet composites and composite strands produced by this process on a volume basis generally contain 50 to 5 percent carbon strand and 5 to 50 percent glass strand. ~owever, it is within the invention , ~

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to have on a volume basis between about 20 percent and 95 percent glass and between about 80 percent carbon and about 5 percent carbon st~nd.
This corresponds to between about 35 and about 98 percent by weight glas~s strand and about 65 percent to 2 percent by weigh~ carbon. The strands of carbon and glass are fed to the system and the composite strand wound on the mandrel at speeds ranging between 50 and 500 Eeet per minute.
The resins used are supplied to the composite strands and typically the sheets formed are placed between two layers of clear sheet such as polyethylene. Thus in practice the surface of the mandrel is covered with a polyethylene sheet prior to winding the resin containing composite strand. ~hen the requsite number of layers have been applied to the mandrel, the mandrel is stopped and the composite sheet is covered with another layer of polyethylene sheet and then cut Erom the mandrel. By sandwiching the composite sheet between the polyethylene layers, the resin composite can be readily handled and stored until a molded part is to be made from it. Heat applied to the composite sheet during molding converts the sheet product into a thermoset, hardened part.
Carbon strands are produced by treating organic fibers by pyrolysis to produce strands of carbon Eibers. Thus, carbon filaments have been produced by pyrolyzing rayon precursor yarns, polyacrylonitriles and the like. Several of these strands are available in industry today and have been described in the literature. (Modern Plastics Encyclopedia, 54, lOA, page 172, Oct-. 1977; Advanced Materials, C.Z. Carroll-Porczynski, Chemical Publishing Co., N.Y. 1962; Industrial Chemistry, 7th Ed., pg. 342, Van Nostrand Reinhold Co., N.Y., 1974.) A particularly useful ~strand for use in the instant process is a carbon fiber called CELION~ manufactured by Celanese Corporation.

~Z~40 In a typical application of the presellt process a resin-glass-carbon sheet was made by Eilling the resin pan with a resin mix~ure containing 90 parts of an isophthalic polye.ster resin, 10 parts o ~tyrene monomer, 0.5 part o zinc stearate, 1 par~ ~ertiary butylperbenzoate ancl 3.5 parts of magnesium oxide thickener.
Twelve glass Eiber forming packages were mounted on a creel, each of the packages containing K-37 glass strands. These strands have 400 glass filaments, each filament having a diameter of 0.0005 inch. Three glass ribbons were prepared by pulling strands from four packages and combining them prior to introducing them into the resin pan. A total of three glass ribbons were passed through the resin pan continuously at a rate of 100-200 feet per minute. The resin pan containing the resin mixture referred to above w~s maintained constantly supplied with res;n during the run. The three gldss strands passing through the resin pan were withdrawn through three precisiQn dies, each having a diameter of 0.045 inch. Three carbon strands were fed into the system by passing one of each into a die through which each of the three glass ribbons was being féd and on the resin pan side of the die so that the carbon strand entered the die near the center portion in the backwash of resin that was generated by the die in wiping exce~ss resin from the surface of th`e glass ribbon being ~ed thereto. In passing through the die, the carbon strand becomes wetted with the resin contained in the die and the backwash and is physically combined with the glass ribbon passing through the die to thereby form three con-solidated glass-carbon bands or ribbons. These three consolidated ribbons were passed through three guide eyes positioned on a reciprocating guide de~ice positioned above a rotating mandrel. 1'he strands were wound on the surface of the mandrel in side by side relationship at a helix angle o ~12i3740 85.4 degrees and a wind angle of 4.6 degrees. Ttle reciprocating guide was passed back and forth above the surface oE hte mandrel and the consolidated strands were wound until three layers were la,i~l on the mandrel, surEace.
The mandrel was then stopped and the composite strand-resin sheet was removed. The Einished sheet was cut to a blank si%e for molding flat panels. Panels were molded from these blanks on a press and formed satis-factory structural panels.
While the invention has been described with winding of the strands onto a mandrel it is also possible to use the composite strand of resin, carbon and glass in other ways. ~le strand would be wound onto spools for later use. The spools could be unwound for use in winding at remo~e locations. The spools also could be used irl weaving woven rein-forcement or used in only certain portions of articles where extra rein-forcement was desirable. The strands could also be wound together to form cables. Further the strands could be fed directly from the bath onto a belt in swirls and then into a laminator.
While the invention has been described with reference to certain specific embodiments, it is not intended to be limited thereby except insofar as appears in the accompanying claims.

Claims

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

1. A composite strand comprising resin, a plurality of glass fiber strands and at least one carbon fiber strand.

2. The composite strand of Claim 1 wherein said resin comprises a heat curable polyester.

3. The composite strand of Claim 1 wherein the carbon and glass fiber strands in said composite are between about 35 and about 98 percent by weight glass and between 65 and 2 percent by weight carbon.

4. The composite strand of Claim 3 wherein said resin content is between about 20 and about 45 percent by weight of said composite.

5. The composite strand of Claim 1 wherein said resin is selected from the group consisting of polyethylene, polypropylene, polyamides, polyurethanes, polyesters, epoxies and mixtures thereof.

6. The composite strand of Claim 1 wherein said strand is impregnated with a resin comprising thickened uncured polyester.

7. The composite strand of Claim 1 impregnated with a B-stage cured resin.

8. The strand of Claim 1 wherein the strand is wound on spools.

9. The strand of Claim 1 wherein the carbon and glass fiber strands in said composite comprise on a volume basis between about 50 and about 5 percent carbon and between about 5 and about 50 percent glass.

10. A fiber resin composite article comprising compressed helically wound strands of resin wherein said strands comprise composite strands comprising resin, a plurality of glass fiber strands and at least one carbon fiber strand.

11. The composite of Claim 10 wherein said composite was wound at a helix angle of about 85.4 degrees.

12. The composite of Claim 10 wherein there are three layers of helically wound strands.

13. The composite article of Claim 10 wherein said resin comprises a heat curable polyester.

14. The composite article of Claim 10 wherein the carbon and glass fiber strands in said composite strands are between about 35 and about 98 percent by weight continuous glass fibers and between 65 and 2 percent by weight continuous carbon fibers.

15. The composite article of Claim 10 wherein said strands are impregnated with a resin comprising thickened uncured polyester.

16. The composite article of Claim 10 mpregnated with a B-stage cured resin.

17. The strand of Claim 10 wherein the strand is wound on spools.

18. The strand of Claim 10 wherein the carbon and glass fiber strands in said composite strands comprise on a volume basis between about 50 and about 5 percent carbon and between about 5 and about 50 percent glass.

19. The composite article of Claim 14 wherein said resin content is between about 20 and about 45 percent by weight of said composite.

20. The composite article of Claim 1 wherein said resin is selected from the group consisting of polyethylene, polypropylene, polyamides, polyurethanes, polyesters, epoxies and mixtures thereof.

21. A method of forming a sheet of resin reinforced with glass and carbon strands comprising coating glass strands with a heat curable polyester resin, passing the coated glass strands through a metering means to remove excess resin and regulate the glass-resin content on a weight basis, introducing carbon strand directly into the metering means to minimize fiberizing of said carbon strand, wetting the carbon strand with resin as it passes through the metering means and consolidating the carbon strand with the glass strand, removing the consolidated glass and carbon strand from the metering means and directing it onto the surface of a rotating surface, reciprocating the consolidated strand across the rotating surface to apply said consolidated strand onto said surface and re-moving the resin consolidated strand from said surface in an uncured state.

22. A method of forming a composite sheet of resin-glass strand and carbon strand comprising introducing glass strand into a body of curable resin, passing the glass strand through the body of curable resin to coat the glass strand with resin, passing the strand after coating through a die to remove ex-cess resin and regulate the resin content of the glass on a weight basis, in-troducing carbon strands directly into the die to minimize fiberizing of said carbon strand and physically combining it with the glass strand in the die while applying to the carbon strand resin contained on the die, passing the consolidated glass-carbon strand emerging from the die through a guide, and winding the con-solidated strand onto a rotating surface by reciprocating consolidated strand across the surface until the surface is covered with resin-glass strand and carbon strand and removing the resin consolidated strand from said surface in an uncured state.

23. The method of claim 22 wherein the resin content of the carbon and glass strands is controlled to between 45 and 20 percent by weight.

24. The method of claim 21 wherein the rotating surface is a mandrel surface and the consolidated glass and carbon strand is removed from the metering means and reciprocated onto the rotating surface so that it is applied in success-ive layers thereon, and cutting the resulting layered composite resin consolidated strand product from the surface.

25. The method of claim 22 wherein the consolidated strand is wound by reciprocation across the surface in a horizontal plane until the surface is covered to a desired depth with a sheet of resin-glass strand and carbon strand and removing the sheet from said surface in an uncured state.

26. The method of claim 21 wherein the said consolidated strand is applied to said surface at a helix angle of between 60 and 89 degrees.

27. The method of claim 21 wherein the resin content of the layered composite is between 20 to 45 percent by weight and the glass-graphite content is between 55 and 80 percent by weight.