GB2042010A

GB2042010A - Method for preparing composite strands of resin, carbon and glass and product formed from said strands

Info

Publication number: GB2042010A
Application number: GB7919524A
Authority: GB
Original assignee: PPG Industries Inc
Current assignee: PPG Industries Inc
Priority date: 1979-02-02
Filing date: 1979-06-05
Publication date: 1980-09-17
Also published as: JPS6359862B2; JPS646019B2; DE2924602C2; JPS621527A; BE876837A; NL7904769A; CA1128740A; DE2924602A1; FR2447806B1; GB2042010B; FR2447806A1; JPS55103927A; CH640572A5; IT1118749B; IT7968292A0

Abstract

This invention relates to improved composite strands comprising resin, a plurality of glass fiber strands and at least one carbon fiber strand. This invention also relates to composite articles formed from the composite strand and to a method of forming the composite strands and composite articles. In the process of this invention, glass stands (1') are passed through a die (12, 13) as they emerge from a resin bath (9) to control their resin content and are wound on a rotating surface (15). Carbon strands are passed directly into the die and are wetted by the resin in the die and on the rotating surface. The composite strands of resin, glass strands and carbon strands are laid on the rotating surface to provide a fiber reinforced resin sheet which may be kept in uncured form for moulding at a later time. <IMAGE>

Description

SPECIFICATION Method for. preparing composite strands of resin, carbon and glass and product formed from said strands The present invention relates to composite strands of resin, carbon and glass and to products formed from said strands.

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 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 which they are employed. Blends of glass and carbon fibers in resins have thus been used to utilize the qualities of 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 causes the strand of carbon to filamentize, i.e., separate into the filaments forming it, and ultimate break out.

In accordance with the present invention, a method has been developed to wet the carbon strand with resin and combine it with the glass strands to provide a useful composite strand for forming resin sheet reinforced with both carbon and glass strand.

In accordance with a process of the present 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 of the composite to be made is fed directly to the back of 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.

In the preparation of glass-carbon resin reinforced sheet having structural characteristics and containing 55 to 80 percent glass and carbon with 20 to 45 percent resin by weight, the strands of carbon and glass are first coated with a resin and then are wound on a rotating mandrel.

The present invention will now be further described with reference to the accompanying drawings, in which: Figure 1 is a flow sheet in perspective of the equipment used to manufacture the resinglass-carbon sheets of the present invention; Figure 2 is an enlarged view in perspective of the resin application section of the process depicted in Fig. 1; and Figure 3 is a section view looking into the resin application pan 9 to show the die 1 3 and point of entry of the carbon strand.

In the preparation of the resin-glass-carbon composites of the present invention a plurality of glass strands are used. As shown in Fig. 1 for illustrative purposes, only six glass fiber forming packages 2 are employed. These packages 2 are mounted on a stand or creel, not shown, and the glass strand ends 1 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 Fig. 1 the upper row of glass forming packages have their strands ends 1 passed through eyelet 5 and the lower row strands ends 1 are passed through eyelet 4. The physically combined strands form two glass ribbons 1' which are passed under the retaining bars 11 and 1 5 of the resin tank 9.These strands 1' are then fed through the dies 1 2 and 1 3 and located at the forward end of the pan 9. Mounted on the top of the wall 3 are two packages 1 8 and 18' which contain carbon strands 8 and 8', respectively. The carbon strands 8 and 8' are introduced into the dies 1 2 and 13, respectively, by passing them through the resin backwash 14 accumulating as the dies wipe resin from the surface of the glass strands 1'. The consolidated glass-carbon strands 1 9 and 19', which exit the dies 1 2 and 13, are then consolidated into a band 1 7 in guide eyelet 22 located on a traveling guide 21 and this ribbon is wound on a rotating mandrel 1 5 to the desired thickness.

After the composite reaches its desired thickness, the mandrel 1 5 is stopped and the resulting sheet is cut from its surface and the process is repeated.

The process generally depicted in the drawing is obviously subject to many variables.

Thus, while only a one strand ribbon 1 7 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 1'. Typically the number of ends employed to form the strands 1' has ranged from 1 to 10 or more. The width of the band 1 7 desired in the final product determines the number and diameter of strands that will be used to form the band. By width of band is meant the width measured perpendicular to the band direction.

In the process shown in the drawings the mandrel 15 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 1 7 down on the surface of the mandrel 15. The strand 1 7 is normally laid on the mandrel 1 5 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 intersection of the band 1 7 on the body of the mandrel 1 5 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 89 degrees.The wind angle of the mandrel in relation to the strand 1 7 is the included acute angle created by the intersection of the band 1 7 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 1 degrees.

In the normal operation the mandrel 1 5 rotates continuously during the process and the guide 21 reciprocates in a horizontal plane causing the ribbon or band 1 7 to be laid down on the mandrel 1 5 in a crisscross fashion to form layers of composite on the surface of the mandrel. For purposes of this disclosure a layer is formed when the band 1 7 has covered the mandrel in both traversing directions. The finished sheet containing the glass and carbon strands will contain the number of layers desired to producle a product of the desired density in pounds per square foot.

The resin pan 9 during the operation is constantly supplied with resin 10 to ensure that sufficient resin is maintained in the pan 9 to thoroughly wet the glass strands which are passed through it under the bars 11 and 1 5.

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 9, 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 resin are thermoplastic resins such as polyethylene, polypropylene and polystyrenes. The thermosetting resin which may be employed in the system 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 resins have been found to be particularly effective in making the composites of this invention and are preferred. Resins such as B-stage curing epoxy resins and thickened polyesters are desirable as they may be stored after removal 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, incorporated herein by reference.

An important consideration in preparing composites is the regulation of the resin content of the final product. In this process this is accomplished by regulating the size of the orifice in the dies 1 2 and 1 3. In general it 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 1 9 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 excessive 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.

However, it is within the invention 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 strand. This corresponds to between about 35 and about 98 percent by weight glass strand and about 65 percent to 2 percent by weight 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 feet per minute.

The resins used are supplied to the compos ite 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. When 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 from 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 fibers. 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, 1 or, page 172, Oct. 1977; Advanced Materials, C.Z., Carroll-Porczynski, Chemical Publishing Co., N.Y. 1962; Industry Chemistry, 7th Ed., pg.

342, Van Nostrand Reinhold Co., N.Y., 1974.) A particularly useful strand for use in the present process is a carbon fiber called CELION(E) manufactured by Celanese Corporation.

The present invention will now be further illustrated by way of the following Example: EXAMPLE In a typical application of the present process a resin-glass-carbon sheet was made by filling the resin pan with a resin mixture containing 90 parts of an isophthalic polyester resin, 10 parts of styrene monomer, 0.5 part of zinc stearate, 1 part tertiary butylperbenzoate and 3.5 parts of magnesium oxide thickener.

Twelve glass fiber 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 was maintained constantly supplied with resin during the run. The three glass strands passing through the resin pan were withdrawn through three precision 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 fed 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 excess resin from the surface of the glass ribbon being fed 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 consolidated glass-carbon bands or ribbons. These three consolidated ribbons were passed through three guide eyes positioned on a reciprocating guide device positioned above a rotating mandrel. The strands were wound on the surface of the mandrel in side by side relationship at a helix angle of 85.4 degrees and a wind angle of 4.6 degrees. The reciprocating guide was passed back and forth above the surface of the mandrel and the consolidated strands were wound until three layers were laid on the mandrel surface. The mandrel was then stopped and the composite strand-resin sheet was removed. The finished sheet was cut to a blank size for molding flat panels. Panels were molded from these blanks on a press and formed satisfactory 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. The strand could be wound onto spools for later use. The spools could be unwound for use in winding at remote locations. The spools also could be used in weaving woven reinforcement or used in only certain portions of articles where extra reinforcement 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.

Claims

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

2. A composite strand as claimed in claim 1, wherein said resin comprises a heat curable polyester.

3. A composite strand as claimed in claim 1, wherein said resin is selected from polyethylene, polypropylene, polyamides, polyurethanes, polyesters, epoxies and mixtures thereof.

4. A composite strand as claimed in claim 1, wherein said strand is impregnated with a resin comprising thickened uncured polyester.

5. A composite strand as claimed in claim 1, wherein said strand is impregnated with a B-stage cured resin.

6. A composite strand as claimed in any of claims 1 to 5, wherein the carbon and glass fiber strands in said composite are from 35 to 98 percent by weight glass and from 65 to 2 percent by weight carbon.

7. A composite as claimed in any of claims 1 to 5, wherein the carbon and glass fiber strands in said composite comprise, on a volume basis, from 50 to 5 percent carbon and from 5 to 50 percent glass.

8. A composite as claimed in any of claims 1 to 7 wherein said resin content is from 20 to 45 percent by weight of said composite.

9. A composite strand as claimed in any of claims 1 to 8, wherein the strand is wound on spools.

10. A fiber resin composite article, which comprises 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. A composite article as claimed in claim 10, wherein said resin comprises a heat curable polyester.

1 2. A composite article as claimed in claim 10, wherein said strands are impregnated with a resin comprising thickened uncured polyester.

1 3. A composite article as claimed in claim 10, wherein said strands are impregnated with a B-stage cured resin.

14. A composite article as claimed in claim 10, wherein said resin is selected from polyethylene, polypropylene, polyamides, polyurethanes, polyesters, epoxies and mixtures thereof.

1 5. A composite article as claimed in any of claims 10 to 14, wherein said composite is wound at a helix angle of about 85.4 degrees.

16. A composite article as claimed in any of claims 10 to 15, wherein there are three layers of helically wound strands.

1 7. A composite article as claimed in any of claims 10 to 16, wherein the carbon and glass fiber strands in said composite strands are from 35 to 98 percent by weight continuous glass fibers and from 65 to 2 percent by weight continuous carbon fibers.

1 8. A composite article as claimed in any of claims 10 to 16, wherein the carbon and glass fiber strands in said composite strands comprise, on a volume basis, from 50 to 5 percent carbon and from 5 to 50 percent glass.

1 9. A composite article as claimed in any of claims 10 to 18, wherein said resin content is from 20 to 45 percent by weight of said composite.

20. A composite article as claimed in any of claims 10 to 19, wherein the strand is wound on spools.

21. A method of forming a composite sheet of resin-glass strand and carbon strand, which comprises 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 excess resin and regulate the resin content of the glass, introducing 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 consolidated strand on a rotating surface by reciprocating consolidated strand 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.

22. A method as claimed in claim 21, wherein the resin content of the carbon and glass strands is controlled to from 45 to 20 percent by weight.

23. A method of forming a sheet of resin reinforced with glass and carbon strands, which comprises 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 mandrel, reciprocating the consolidated strand across a rotating surface to apply said consolidated strand on said surface in successive layers and cutting the resulting layered composite resin consolidated strand product from the surface.

24. A method as claimed in claim 23, wherein said consolidated strand is applied to said surface at a helix angle of from 60 to 89 degrees.

25. A method as claimed in claim 23 or 24, wherein the resin content of the layered composite is from 20 to 45 percent by weight and the glass-graphite content is from 55 to 80 percent by weight.

26. A composite strand as claimed in claim 1 and substantially as hereinbefore described with reference to the Example.

27. A composite strand as claimed in claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.

28. A composite article as claimed in claim 10 and substantially as hereinbefore described with reference to the Example.

29. A composite article as claimed in claim 10 and substantially as hereinbefore described with reference to the accompanying drawings.

30. A method as claimed in claim 21 and substantially as hereinbefore described with reference to the Example.

31. A method as claimed in claim 21 and substantially as hereinbefore described with reference to the accompanying drawings.