CA2419345A1 - Fibre-reinforced thermoplastics - Google Patents
Fibre-reinforced thermoplastics Download PDFInfo
- Publication number
- CA2419345A1 CA2419345A1 CA002419345A CA2419345A CA2419345A1 CA 2419345 A1 CA2419345 A1 CA 2419345A1 CA 002419345 A CA002419345 A CA 002419345A CA 2419345 A CA2419345 A CA 2419345A CA 2419345 A1 CA2419345 A1 CA 2419345A1
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- Prior art keywords
- prepregs
- fibre
- composite
- polymer
- thermoset
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B15/00—Pretreatment of the material to be shaped, not covered by groups B29B7/00 - B29B13/00
- B29B15/08—Pretreatment of the material to be shaped, not covered by groups B29B7/00 - B29B13/00 of reinforcements or fillers
- B29B15/10—Coating or impregnating independently of the moulding or shaping step
- B29B15/12—Coating or impregnating independently of the moulding or shaping step of reinforcements of indefinite length
- B29B15/122—Coating or impregnating independently of the moulding or shaping step of reinforcements of indefinite length with a matrix in liquid form, e.g. as melt, solution or latex
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/24—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs
- C08J5/248—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs using pre-treated fibres
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
- B29C70/06—Fibrous reinforcements only
- B29C70/08—Fibrous reinforcements only comprising combinations of different forms of fibrous reinforcements incorporated in matrix material, forming one or more layers, and with or without non-reinforced layers
- B29C70/086—Fibrous reinforcements only comprising combinations of different forms of fibrous reinforcements incorporated in matrix material, forming one or more layers, and with or without non-reinforced layers and with one or more layers of pure plastics material, e.g. foam layers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
- B29C70/06—Fibrous reinforcements only
- B29C70/10—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres
- B29C70/16—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of substantial or continuous length
- B29C70/22—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of substantial or continuous length oriented in at least two directions forming a two dimensional structure
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
- B29C70/28—Shaping operations therefor
- B29C70/40—Shaping or impregnating by compression not applied
- B29C70/50—Shaping or impregnating by compression not applied for producing articles of indefinite length, e.g. prepregs, sheet moulding compounds [SMC] or cross moulding compounds [XMC]
- B29C70/52—Pultrusion, i.e. forming and compressing by continuously pulling through a die
- B29C70/525—Component parts, details or accessories; Auxiliary operations
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2101/00—Use of unspecified macromolecular compounds as moulding material
- B29K2101/10—Thermosetting resins
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2101/00—Use of unspecified macromolecular compounds as moulding material
- B29K2101/12—Thermoplastic materials
Abstract
This invention relates to a fibre-reinforced prepreg that is made of a plurality of fibres impregnated with a thermoset polymer, about which is disposed a thermoplastic coating.
The prepregs can be consolidated into composites, for example by pultrusion or by forming laminates. The composites formed thereby can be shaped and reshaped when the thermoplastic polymer is in a molten state.
The prepregs can be consolidated into composites, for example by pultrusion or by forming laminates. The composites formed thereby can be shaped and reshaped when the thermoplastic polymer is in a molten state.
Description
Patent Applicati~n FIBRE-REINFORCED THERMOPLASTICS
FIELD OF THE INVENTION
The present invention relates to the field of thermoplastic pultrusion.
BACKGROUND OF THE INVENTION
Polymers can be reinforced by fibrous materials, such as .fiberglass, to provide them with additional strength. One common method of making fibre-reinforced polymer is pultrusion, which is a process of producing continuous lengths of constant cross-section components using long continuous fibres held together with polymeric resin. In the pultrusion process a fibre reinforcing material is pulled through a resin impregnation bath and into a shaping die where the resin is subsequently cured. Traditionally the resin has been a thermosetting polymer, because these polymers have a low viscosity and are able to better penetrate between the fibres than a higher-viscosity thermoplastic polymer.
However, these pultrusions are straight, and of constant cross section, and because pultrusions made with thermosetting polymers cannot be reformed once shaped, the attachment of such pultrusions to one another is limited to bolting, gluing, and the like. In fibre-reinforced laminates, sheets or lamiae of polymeric material and fibrous material are stacked together, usually in a mold, and pressed at an elevated temperature under pressure to consolidate the material. As thermosetting polymers are often used to penetrate the fibrous material, these laminates suffer many of the same limitations as do pultrusions.
The substitution of a thermoplastic binder would allow reshaping of a pultrusion or laminate after it is formed, greatly increasing its utility in. product development. It would also significantly increase the impact strength of the composite material.
The major problem with thermoplastic pultrusion and lamination is the impregnation of the tightly bundled fibres with the viscous thermoplastic resin. Results to date have generated composites that have a high void content and are poorly consolidated. In an attempt to make the thermoplastic pultrusion and laminating commercially viable, several types of processes have been deveioped, including: co-mingling, pre-impregnation, resin injection, powder coating and solvent baths. To achieve consolidation with existing DMSLegal\030319\0028311419392v3 technology, very slow pulling speeds, or long pressing times, are required.
This not only defeats the potential economic advantage of the process, but introduces potential severe material degradation problems resulting from keeping the thermoplastic polymer above its melting point for extended periods of time. At this point, only very thin cross-sections can be produced in a satisfactory manner.
SUMMARY OF THE INVENTION
Disclosed herein is a prepreg formed by impregnating a small bundle of reinforcing fibres with a thermosetting polymer to generate a thermoset fibre bundle, and coating the thermoses fibre bundle with a thermoplastic polymer. The diameter of the thermoset fibre bundle is determined by bending considerations. 'The prepregs may then be consolidated into a composite, as by pultrusion through a consolidation die, or by lamination. The composite can be reshaped, by heating it to a temperature that is above the melting point of the thermoplastic polymer.
Accordingly, in one aspect, this invention is fibre-reinforced prepreg comprising:
(a) a plurality of fibres impregnated with a thermoset polymer, and (b) a thermoplastic coating disposed about said fibres and thermoset polymer.
In another aspect, this invention is a fibre-reinforced composite formed by consolidation of the prepregs of this invention. In one embodiment, the composite is formed by assembling the prepregs in a consolidation die, for example by pultrusion, while the thermoplastic polymer is in a molten state. In yet another embodiment, the composite is formed by weaving the prepregs together into a woven layer, stacking the woven layers together and consolidating the layers.
In another aspect, this invention is a laminate formed by consolidation of the prepregs of this invention.
In yet another aspect, this invention is a method of making a fibre-reinforced prepreg comprising:
(a) impregnating a plurality of fibres with a thermoset polymer, to generate a thermoset fibre bundle, and DMSLegal\030319\00283\1419392v3 (b) coating the thermoset fibre bundle with a layer of thermoplastic polymer.
In one embodiment of this method, pultrusion is used to impregnate the plurality of fibres with a thermoset polymer.
In yet another aspect, this invention is a method of making a fibre reinforced composite, comprising:
(a) pulling a plurality of prepregs of claim 11 through a consolidation die, and (b) consolidating the plurality of prepregs.
In yet another aspect, this invention is a method of making a fibre reinforced composite, comprising:
(a) weaving a plurality of prepregs of claim 11 together to make a woven layer of prepregs, (b) stacking a plurality of woven layers together; and (c) consolidating the plurality of woven layers.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a cross section of an embodiment of a prepreg of this invention.
Figure 2A and B show cross sections of two different embodiments of a consolidation of prepregs.
Figure 3A shows one embodiment of a woven layer of prepregs and Figure 3B
shows one embodiment of a laminate formed by consolidating several layers.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
As shown in Figure 1, the prepreg 10 of this invention includes a plurality of fibres 12 impregnated with a thermosetting polymer 14, the fibres 12 and polymer 14 forming a thermoset fibre bundle 18 that has disposed thereabout a thermoplastic polymer coating 16. A plurality of prepregs 10 can be consolidated into a variety of different composites, shown in Figures 2 and 3.
DMSLega110303I9\00283\1419392v3 "Consolidation" as used herein means a process that compresses fibre and thermosetting polymer together, or ~. process that compresses prepregs, or prepregs and thermoplastic polymer together, all processes designed to reduce voids, to achieve a desired density, and to achieve a desired shape. The process involves the application of pressure, and the application of sufficient heat to keep the thermosetting or thermoplastic polymer in a molten state until the desired density and/or shape is achieved.
"Composite" as used herein means a construction or manufacture that is formed by consolidation of prepregs 10 alone, or in combination with other polymeric materials.
"Polymer" as used herein includes a matrix or a resin.
"Prepreg" as used herein means a thermoset fibre bundle that is coated with a thermoplastic coating.
"Jet-out" as used herein refers to the impregnation of fibres with molten thermosetting polymer, such that substantially all voids between the fibres are filled with polymer, and to the impregnation of the thermoset fibre bundles with molten thermoplastic polymer, such that substantially all voids between the thermoset fibre bundles are filled with polymer.
The diameter of the thermoset fibre bundle 18 is fundamental to the utility of this invention and is determined by bending considerations. If one considers a thin rod or strip of material, the bend radius, meaning the radius of curvature that such a rod or strip can bend before material failure, is dependent upon the strip thickness, as the strain imposed by bending is roughly equal to the strip diameter divided by twice the radius of curvature of the bend. Typical glass fibres used in composite materials are 0.013 mm in diameter.
If a layer or strip 0.013 mm thick is subjected to 1% strain without damage, the minimum bend radius that can be obtained is 0.65 mm. If several layers are stacked together and bent, the inside bend radius of such a stack could conceivably be as little at 0.65 mm, irrespective of the thickness of the stack. If larger bend radii can be tolerated, thicker layers can be used.
In normal composite design and fabrication, a bend radius of 3 mm is sufficient for most purposes. If the material of construction is, for example, epoxy coated glass fibers that are DVISi,egal\030319\00283V419392v3 able to withstand a strain of about 2.5%, then the rod or strip thickness required to prevent material failure is about 0.15 mm, or about ten times the thickness of a single glass fibre.
In this invention, a very small diameter bundle of individual fibres 12 is impregnated with thermosetting polymer 14 to form thermoset fibre bundle 18. Impregnation of the fibres 5 with thermosetting resin can be accomplished in a variety of ways known to those skilled in the art, however pultrusion is particularly preferred. The thermoset fibre bundle is then covered with thermoplastic polymer coating 16 to generate prepreg 10, a plurality of which are consolidated into larger bundles or laminates, as described below.
Although the thermoset fibre bundles are formed with a thermoset polymer, they are capable of bending, within the limits disclosed above and they can be used to form composites of a variety of shapes other than, but including, straight shapes.
This invention is a means for using the benefits of both thermosetting and thermoplastic polymers, in pultrusion technology. A low viscosity thermosetting polymer is used initially to achieve penetration of polymer into the fibre bundle, thereby avoiding the main problem associated with using thermoplastic polymers in pultrusion - poor penetration in to fibres. However, because the diameter of the fibre bundle is kept small, the thermoset fibre bundles are still capable of bending and therefore the thermoset fibre bundles can be bent to some extent.
A thermoplastic polymer is used for consolidation of the prepregs 10 into a composite, thereby adding to the workability and impact strength of the composite as compared to a fibre-reinforced composite made with a thermosetting polymer. Composites can be formed by consolidation of a plurality of prepregs. Consolidation can be achieved, for example, by pultrusion or by forming a laminate. With regard to pultrusion, the prepregs are drawn through a die and the thermoset fibre bundles 18 will be embedded in the thermoplastic as the coating becomes molten and melds together. As the thermoset fibre bundles are larger in diameter than the fibres themselves, the penetration of the thermoplastic polymer between the thermoset fibre bundles is improved over straight application of thermoplastic polymer directly onto a fibre bundle.
Accordingly, this invention essentially provides a fibre-reinforced composite that is made by pultrusion with a thermoplastic polymer and yet is well penetrated by the polymer. The composite can be shaped and reshaped unlike composites of the same size made with a thermosetting DMSL.egal\030319\00283\1419392v3 polymer alone. Likewise, this invention essentially provides a fibre-reinforced Laminate which is well penetrated by a thermoplastic polymer and which can be shaped and reshaped.
The fibres 12 can be made of any of a number of suitable materials, including graphite, carbon and polymerics, but particularly preferred is glass fibre. The fibres 12 can be assembled loosely together, as in a roving, or they can be woven, braided, or twisted together, as in a yarn. Fibres that are substantially continuous along the length of the thermoset fibre bundles 18 are preferred, however there is no limitation as to fibre length.
Thermosetting polymers useful in the invention disclosed herein include thermosetting urethane and vinyl esters, polyesters, phenolics and epoxies. However, other thermosetting polymers can be used to make the thermoset fibre bundle 18 disclosed herein, provided that the polymer can be suitably bonded, as outlined below, to an appropriate thermoplastic polymer. This invention is intended to include all such thermosetting polymers that are now known or which hereafter become known and which meet at least these two requirements.
One method of manufacturing the thermoset fibre bundles 18 is to pull strands of continuous fibres arranged in bundles of diameter 1/2 rnm to 2 mm, but not restricted to these dimensions, through a bath containing the thermosetting resin of choice.
'These wetted bundles are then pulled through a shaping die that may or may not be heated. The removes the excess resin and any entrapped air from the bundle. Pulling speed is not important but it has been found that 1 m/sec through several 10's of m/sec.
works adequately. Care must be taken to ensure that the fibers are not bent unduly during this process so that they do not break.
The thermoset fibre bundles 18 can be any shape in cross section and are coated with a layer of thermoplastic polymer, to make prepreg 10. The prepreg may, or may not be, circular in cross-section, and can vary in shape from the shape of the thermoset fibre bundle used to produce it.
Thermoplastic polymers useful in the invention disclosed herein include thermoplastic urethane, polystyrene and acetonitrile/butadiene/styrene (Al3S). Other thermoplastic polymers can be used to make the prepreg 10 disclosed herein, provided that the polymer DMSLega11030319\0028311419392x3 selected can be bonded, as outlined below, to an appropriate thermosetting polymer. This invention is intended to include all such thermoplastic polymers that are now known or which hereafter become known and which meet at least this requirement.
The specific thermoplastic and thermosetting polymer combinations are chosen such that the two types of polymers will bond integrally to one another to provide a composite with adequate structural integrity for the purposes for which the composite will be used.
Additionally, the melt temperature of the thermoplastic polymer should not result in significant degradation of the thermosetting polymer. As examples, the inventors have achieved suitable bonding between the following pairs of polymers:
thermosetting urethane/thermoplastic urethane, vinyl ester/polystyrene and vinyl ester/ABS.
Sometimes it is useful to treat the polymers or thermoset fibre bundles, to facilitate bonding between the thermoset and thermoplastic polymer. Bonding between the layers of polymer may also be achieved, for example, by applying an adhesive layer to the thermoset fibre bundle, or by roughening the surface of the thermoset fibre bundle to aid in mechanical keying of the thermoplastic polymer. V6~hen styrene-based thermoplastic/thermosetting polymer pairs are used, bonding between the two polymer types may be strengthened by dissolving some of the thermoplastic polymer in the thermosetting polymer, before the thermosetting polymer is used in the pultrusion (Balazek and Griffiths, In situ Integration of Thermoplastic Extrusions into the Therwcoset Pultrusion Process, 47'h Annual Conference, Composites Institute, The Society of the Plastics Industry Inc., Feb., 1992, s.10-C; pp.l-3; Balazek, et al.
PultrusioyclExtrusion Method, U.S. Patent #4,938,823) After wet-out of the fibres 12 with the thermosetting polymer 14 and the thermosetting polymer, the thermoplastic coating 16 can be applied immediately, for example by using a coating die. The thermoplastic polymer coating 16 can be applied before or after the thermosetting polymer is cured. Particularly preferred is application of coating 16 after the thermosetting polymer has gelled, and before it is cured, as a better bonding between the two polymer types is achieved if this approach is used.
After the thermoplastic polymer coating 16 is applied to thermoset fibre bundle 18, the coating can be allowed to cool to below its melt point. If this is done, the prepregs 10 can be spooled and coiled for storage and possibly transport to another location.
DMSLegal\030319\00283\1419392v3 Alternatively, after the thermoset fibre bundle is coated with thermoplastic polymer coating 16, the resultant prepreg 10 can immediately be consolidated with other prepregs to form composites.
One way of consolidating the prepregs is to pass the prepregs 10 through a consolidation die by pultrusion. The prepregs 10 can be assembled loosely together, as in a roving, or they can be woven, braided, or twisted together, as in a yarn. If the thermoplastic coating is still in it's molten state, the prepregs can immediately be consolidated by the application of pressure and optionally, additional heat. If the thermoplastic coating has been permitted to cool to a temperature below its molten state, the thermoplastic coating must first be heated until it melts, before the prepregs 10 can be consolidated by the application of pressure and optionally, additional heat. As in apparent, additional thermoplastic polymer may be used during this process. The thermoset fibre bundles 18 can be bent, according to the bending limitations outlined above, in order to mold the final composite into a selected shape. The whole structure is then cooled to below the thermoplastic melt temperature, to form a consolidated part.
Various embodiments of a composite made by pultrusion of thermoset fibre bundles 18, are shown Figure 2. Figure ZA shows a plurality of prepregs 10 that are consolidated, as indicated by arrow (a), into a composite 20 that is approximately circular in cross-section, and which is comprised of a plurality of thermoset fibre bundles 18 that are arranged randomly in the composite and that are of varying diameters. Figure 2B shows a composite 200 that is approximately rectangular is cross section and which is comprised of a plurality of thermoset fibre bundles 18 that are arranged in a regular pattern and that are of two consistent diameters.
Another means of consolidating the prepregs 10 is shown in Figure 3. Figure 3A
shows a plurality of prepregs 10 that are woven into a layer 30. A plurality of layers 30 are then stacked together as shown in Figure 3B and consolidated into a laminate 40, as represented by arrow (a) in Figure 3B. The prepregs in layer 30 may additionally be consolidated before stacking the layers 30 together. The thermoset fibre bundles 18 can be bent, according to the bending limitations outlined above, in order to mold the laminate into a selected shape.
DMSLegal\030319\00283\1419392v3 Alternatively, or in addition, layers 30 can be stacked together with layers of another polymeric material, for example additional thermoplastic polymer, which is capable of bonding to layers 30. The entire stack of layers is then consolidated, as by the application of pressure and optionally, heat, to form a laminate.
After the composite has been formed, whether by pultrusion ox by making a laminate, the composite can be reshaped by heating the composite to a temperature above the melting temperature of the thermoplastic, molding it and cooling it to below the melting temperature of the thermoplastic.
While the invention has been described in conjunction with the disclosed embodiments, it will be understood that the invention is not intended to be limited to these embodiments.
On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
The following examples are intended only to illustrate and describe the invention rather than limit the claims that follow.
EXAMPLE
Profile Pultrusion A standard shape, such as a rod was pultruded using the vinyl ester and glass fibres to make the thermoset fibre bundle. An injection head to fit on a standard die will was fabricated. The method of feeding molten thermoplastic polymer to the injection head was a small laboratory extruder. Thermoset fibre bundles were made with a diameter of typically lmm. These were pulled through a cross-feed injection head held at a temperature of about 250°C. Pulling speeds were approximate 1 m/sec.
The injection rate of the thermoplastic polymer, polystyrene, was the minimum allowed by the extruder.
The prepregs were consolidated in a cylindrical die about 5 mm in diameter.
After cooling in a water spray, the consolidated prepregs were easily bent over a pipe heated to about 200°C.
Scanning electron micrographs (SEM) of pultruded glass fiber roving-reinforced polystyrene composites (at a resolution is 100 Vim) demonstrate that there is a very thin DMSLegal\030319\00283\1419392x3 vinyl ester layer in the interface between the glass fiber and the polystyrene matrix. This interface is dim, indicating that that vinyl ester has a good bonding with polystyrene. The SEM's also show that the glass fiber roving is well impregnated with thermoset resin, as no void is found among the glass fibers.
DMSLegal\030319100283\1419392v3
FIELD OF THE INVENTION
The present invention relates to the field of thermoplastic pultrusion.
BACKGROUND OF THE INVENTION
Polymers can be reinforced by fibrous materials, such as .fiberglass, to provide them with additional strength. One common method of making fibre-reinforced polymer is pultrusion, which is a process of producing continuous lengths of constant cross-section components using long continuous fibres held together with polymeric resin. In the pultrusion process a fibre reinforcing material is pulled through a resin impregnation bath and into a shaping die where the resin is subsequently cured. Traditionally the resin has been a thermosetting polymer, because these polymers have a low viscosity and are able to better penetrate between the fibres than a higher-viscosity thermoplastic polymer.
However, these pultrusions are straight, and of constant cross section, and because pultrusions made with thermosetting polymers cannot be reformed once shaped, the attachment of such pultrusions to one another is limited to bolting, gluing, and the like. In fibre-reinforced laminates, sheets or lamiae of polymeric material and fibrous material are stacked together, usually in a mold, and pressed at an elevated temperature under pressure to consolidate the material. As thermosetting polymers are often used to penetrate the fibrous material, these laminates suffer many of the same limitations as do pultrusions.
The substitution of a thermoplastic binder would allow reshaping of a pultrusion or laminate after it is formed, greatly increasing its utility in. product development. It would also significantly increase the impact strength of the composite material.
The major problem with thermoplastic pultrusion and lamination is the impregnation of the tightly bundled fibres with the viscous thermoplastic resin. Results to date have generated composites that have a high void content and are poorly consolidated. In an attempt to make the thermoplastic pultrusion and laminating commercially viable, several types of processes have been deveioped, including: co-mingling, pre-impregnation, resin injection, powder coating and solvent baths. To achieve consolidation with existing DMSLegal\030319\0028311419392v3 technology, very slow pulling speeds, or long pressing times, are required.
This not only defeats the potential economic advantage of the process, but introduces potential severe material degradation problems resulting from keeping the thermoplastic polymer above its melting point for extended periods of time. At this point, only very thin cross-sections can be produced in a satisfactory manner.
SUMMARY OF THE INVENTION
Disclosed herein is a prepreg formed by impregnating a small bundle of reinforcing fibres with a thermosetting polymer to generate a thermoset fibre bundle, and coating the thermoses fibre bundle with a thermoplastic polymer. The diameter of the thermoset fibre bundle is determined by bending considerations. 'The prepregs may then be consolidated into a composite, as by pultrusion through a consolidation die, or by lamination. The composite can be reshaped, by heating it to a temperature that is above the melting point of the thermoplastic polymer.
Accordingly, in one aspect, this invention is fibre-reinforced prepreg comprising:
(a) a plurality of fibres impregnated with a thermoset polymer, and (b) a thermoplastic coating disposed about said fibres and thermoset polymer.
In another aspect, this invention is a fibre-reinforced composite formed by consolidation of the prepregs of this invention. In one embodiment, the composite is formed by assembling the prepregs in a consolidation die, for example by pultrusion, while the thermoplastic polymer is in a molten state. In yet another embodiment, the composite is formed by weaving the prepregs together into a woven layer, stacking the woven layers together and consolidating the layers.
In another aspect, this invention is a laminate formed by consolidation of the prepregs of this invention.
In yet another aspect, this invention is a method of making a fibre-reinforced prepreg comprising:
(a) impregnating a plurality of fibres with a thermoset polymer, to generate a thermoset fibre bundle, and DMSLegal\030319\00283\1419392v3 (b) coating the thermoset fibre bundle with a layer of thermoplastic polymer.
In one embodiment of this method, pultrusion is used to impregnate the plurality of fibres with a thermoset polymer.
In yet another aspect, this invention is a method of making a fibre reinforced composite, comprising:
(a) pulling a plurality of prepregs of claim 11 through a consolidation die, and (b) consolidating the plurality of prepregs.
In yet another aspect, this invention is a method of making a fibre reinforced composite, comprising:
(a) weaving a plurality of prepregs of claim 11 together to make a woven layer of prepregs, (b) stacking a plurality of woven layers together; and (c) consolidating the plurality of woven layers.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a cross section of an embodiment of a prepreg of this invention.
Figure 2A and B show cross sections of two different embodiments of a consolidation of prepregs.
Figure 3A shows one embodiment of a woven layer of prepregs and Figure 3B
shows one embodiment of a laminate formed by consolidating several layers.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
As shown in Figure 1, the prepreg 10 of this invention includes a plurality of fibres 12 impregnated with a thermosetting polymer 14, the fibres 12 and polymer 14 forming a thermoset fibre bundle 18 that has disposed thereabout a thermoplastic polymer coating 16. A plurality of prepregs 10 can be consolidated into a variety of different composites, shown in Figures 2 and 3.
DMSLega110303I9\00283\1419392v3 "Consolidation" as used herein means a process that compresses fibre and thermosetting polymer together, or ~. process that compresses prepregs, or prepregs and thermoplastic polymer together, all processes designed to reduce voids, to achieve a desired density, and to achieve a desired shape. The process involves the application of pressure, and the application of sufficient heat to keep the thermosetting or thermoplastic polymer in a molten state until the desired density and/or shape is achieved.
"Composite" as used herein means a construction or manufacture that is formed by consolidation of prepregs 10 alone, or in combination with other polymeric materials.
"Polymer" as used herein includes a matrix or a resin.
"Prepreg" as used herein means a thermoset fibre bundle that is coated with a thermoplastic coating.
"Jet-out" as used herein refers to the impregnation of fibres with molten thermosetting polymer, such that substantially all voids between the fibres are filled with polymer, and to the impregnation of the thermoset fibre bundles with molten thermoplastic polymer, such that substantially all voids between the thermoset fibre bundles are filled with polymer.
The diameter of the thermoset fibre bundle 18 is fundamental to the utility of this invention and is determined by bending considerations. If one considers a thin rod or strip of material, the bend radius, meaning the radius of curvature that such a rod or strip can bend before material failure, is dependent upon the strip thickness, as the strain imposed by bending is roughly equal to the strip diameter divided by twice the radius of curvature of the bend. Typical glass fibres used in composite materials are 0.013 mm in diameter.
If a layer or strip 0.013 mm thick is subjected to 1% strain without damage, the minimum bend radius that can be obtained is 0.65 mm. If several layers are stacked together and bent, the inside bend radius of such a stack could conceivably be as little at 0.65 mm, irrespective of the thickness of the stack. If larger bend radii can be tolerated, thicker layers can be used.
In normal composite design and fabrication, a bend radius of 3 mm is sufficient for most purposes. If the material of construction is, for example, epoxy coated glass fibers that are DVISi,egal\030319\00283V419392v3 able to withstand a strain of about 2.5%, then the rod or strip thickness required to prevent material failure is about 0.15 mm, or about ten times the thickness of a single glass fibre.
In this invention, a very small diameter bundle of individual fibres 12 is impregnated with thermosetting polymer 14 to form thermoset fibre bundle 18. Impregnation of the fibres 5 with thermosetting resin can be accomplished in a variety of ways known to those skilled in the art, however pultrusion is particularly preferred. The thermoset fibre bundle is then covered with thermoplastic polymer coating 16 to generate prepreg 10, a plurality of which are consolidated into larger bundles or laminates, as described below.
Although the thermoset fibre bundles are formed with a thermoset polymer, they are capable of bending, within the limits disclosed above and they can be used to form composites of a variety of shapes other than, but including, straight shapes.
This invention is a means for using the benefits of both thermosetting and thermoplastic polymers, in pultrusion technology. A low viscosity thermosetting polymer is used initially to achieve penetration of polymer into the fibre bundle, thereby avoiding the main problem associated with using thermoplastic polymers in pultrusion - poor penetration in to fibres. However, because the diameter of the fibre bundle is kept small, the thermoset fibre bundles are still capable of bending and therefore the thermoset fibre bundles can be bent to some extent.
A thermoplastic polymer is used for consolidation of the prepregs 10 into a composite, thereby adding to the workability and impact strength of the composite as compared to a fibre-reinforced composite made with a thermosetting polymer. Composites can be formed by consolidation of a plurality of prepregs. Consolidation can be achieved, for example, by pultrusion or by forming a laminate. With regard to pultrusion, the prepregs are drawn through a die and the thermoset fibre bundles 18 will be embedded in the thermoplastic as the coating becomes molten and melds together. As the thermoset fibre bundles are larger in diameter than the fibres themselves, the penetration of the thermoplastic polymer between the thermoset fibre bundles is improved over straight application of thermoplastic polymer directly onto a fibre bundle.
Accordingly, this invention essentially provides a fibre-reinforced composite that is made by pultrusion with a thermoplastic polymer and yet is well penetrated by the polymer. The composite can be shaped and reshaped unlike composites of the same size made with a thermosetting DMSL.egal\030319\00283\1419392v3 polymer alone. Likewise, this invention essentially provides a fibre-reinforced Laminate which is well penetrated by a thermoplastic polymer and which can be shaped and reshaped.
The fibres 12 can be made of any of a number of suitable materials, including graphite, carbon and polymerics, but particularly preferred is glass fibre. The fibres 12 can be assembled loosely together, as in a roving, or they can be woven, braided, or twisted together, as in a yarn. Fibres that are substantially continuous along the length of the thermoset fibre bundles 18 are preferred, however there is no limitation as to fibre length.
Thermosetting polymers useful in the invention disclosed herein include thermosetting urethane and vinyl esters, polyesters, phenolics and epoxies. However, other thermosetting polymers can be used to make the thermoset fibre bundle 18 disclosed herein, provided that the polymer can be suitably bonded, as outlined below, to an appropriate thermoplastic polymer. This invention is intended to include all such thermosetting polymers that are now known or which hereafter become known and which meet at least these two requirements.
One method of manufacturing the thermoset fibre bundles 18 is to pull strands of continuous fibres arranged in bundles of diameter 1/2 rnm to 2 mm, but not restricted to these dimensions, through a bath containing the thermosetting resin of choice.
'These wetted bundles are then pulled through a shaping die that may or may not be heated. The removes the excess resin and any entrapped air from the bundle. Pulling speed is not important but it has been found that 1 m/sec through several 10's of m/sec.
works adequately. Care must be taken to ensure that the fibers are not bent unduly during this process so that they do not break.
The thermoset fibre bundles 18 can be any shape in cross section and are coated with a layer of thermoplastic polymer, to make prepreg 10. The prepreg may, or may not be, circular in cross-section, and can vary in shape from the shape of the thermoset fibre bundle used to produce it.
Thermoplastic polymers useful in the invention disclosed herein include thermoplastic urethane, polystyrene and acetonitrile/butadiene/styrene (Al3S). Other thermoplastic polymers can be used to make the prepreg 10 disclosed herein, provided that the polymer DMSLega11030319\0028311419392x3 selected can be bonded, as outlined below, to an appropriate thermosetting polymer. This invention is intended to include all such thermoplastic polymers that are now known or which hereafter become known and which meet at least this requirement.
The specific thermoplastic and thermosetting polymer combinations are chosen such that the two types of polymers will bond integrally to one another to provide a composite with adequate structural integrity for the purposes for which the composite will be used.
Additionally, the melt temperature of the thermoplastic polymer should not result in significant degradation of the thermosetting polymer. As examples, the inventors have achieved suitable bonding between the following pairs of polymers:
thermosetting urethane/thermoplastic urethane, vinyl ester/polystyrene and vinyl ester/ABS.
Sometimes it is useful to treat the polymers or thermoset fibre bundles, to facilitate bonding between the thermoset and thermoplastic polymer. Bonding between the layers of polymer may also be achieved, for example, by applying an adhesive layer to the thermoset fibre bundle, or by roughening the surface of the thermoset fibre bundle to aid in mechanical keying of the thermoplastic polymer. V6~hen styrene-based thermoplastic/thermosetting polymer pairs are used, bonding between the two polymer types may be strengthened by dissolving some of the thermoplastic polymer in the thermosetting polymer, before the thermosetting polymer is used in the pultrusion (Balazek and Griffiths, In situ Integration of Thermoplastic Extrusions into the Therwcoset Pultrusion Process, 47'h Annual Conference, Composites Institute, The Society of the Plastics Industry Inc., Feb., 1992, s.10-C; pp.l-3; Balazek, et al.
PultrusioyclExtrusion Method, U.S. Patent #4,938,823) After wet-out of the fibres 12 with the thermosetting polymer 14 and the thermosetting polymer, the thermoplastic coating 16 can be applied immediately, for example by using a coating die. The thermoplastic polymer coating 16 can be applied before or after the thermosetting polymer is cured. Particularly preferred is application of coating 16 after the thermosetting polymer has gelled, and before it is cured, as a better bonding between the two polymer types is achieved if this approach is used.
After the thermoplastic polymer coating 16 is applied to thermoset fibre bundle 18, the coating can be allowed to cool to below its melt point. If this is done, the prepregs 10 can be spooled and coiled for storage and possibly transport to another location.
DMSLegal\030319\00283\1419392v3 Alternatively, after the thermoset fibre bundle is coated with thermoplastic polymer coating 16, the resultant prepreg 10 can immediately be consolidated with other prepregs to form composites.
One way of consolidating the prepregs is to pass the prepregs 10 through a consolidation die by pultrusion. The prepregs 10 can be assembled loosely together, as in a roving, or they can be woven, braided, or twisted together, as in a yarn. If the thermoplastic coating is still in it's molten state, the prepregs can immediately be consolidated by the application of pressure and optionally, additional heat. If the thermoplastic coating has been permitted to cool to a temperature below its molten state, the thermoplastic coating must first be heated until it melts, before the prepregs 10 can be consolidated by the application of pressure and optionally, additional heat. As in apparent, additional thermoplastic polymer may be used during this process. The thermoset fibre bundles 18 can be bent, according to the bending limitations outlined above, in order to mold the final composite into a selected shape. The whole structure is then cooled to below the thermoplastic melt temperature, to form a consolidated part.
Various embodiments of a composite made by pultrusion of thermoset fibre bundles 18, are shown Figure 2. Figure ZA shows a plurality of prepregs 10 that are consolidated, as indicated by arrow (a), into a composite 20 that is approximately circular in cross-section, and which is comprised of a plurality of thermoset fibre bundles 18 that are arranged randomly in the composite and that are of varying diameters. Figure 2B shows a composite 200 that is approximately rectangular is cross section and which is comprised of a plurality of thermoset fibre bundles 18 that are arranged in a regular pattern and that are of two consistent diameters.
Another means of consolidating the prepregs 10 is shown in Figure 3. Figure 3A
shows a plurality of prepregs 10 that are woven into a layer 30. A plurality of layers 30 are then stacked together as shown in Figure 3B and consolidated into a laminate 40, as represented by arrow (a) in Figure 3B. The prepregs in layer 30 may additionally be consolidated before stacking the layers 30 together. The thermoset fibre bundles 18 can be bent, according to the bending limitations outlined above, in order to mold the laminate into a selected shape.
DMSLegal\030319\00283\1419392v3 Alternatively, or in addition, layers 30 can be stacked together with layers of another polymeric material, for example additional thermoplastic polymer, which is capable of bonding to layers 30. The entire stack of layers is then consolidated, as by the application of pressure and optionally, heat, to form a laminate.
After the composite has been formed, whether by pultrusion ox by making a laminate, the composite can be reshaped by heating the composite to a temperature above the melting temperature of the thermoplastic, molding it and cooling it to below the melting temperature of the thermoplastic.
While the invention has been described in conjunction with the disclosed embodiments, it will be understood that the invention is not intended to be limited to these embodiments.
On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
The following examples are intended only to illustrate and describe the invention rather than limit the claims that follow.
EXAMPLE
Profile Pultrusion A standard shape, such as a rod was pultruded using the vinyl ester and glass fibres to make the thermoset fibre bundle. An injection head to fit on a standard die will was fabricated. The method of feeding molten thermoplastic polymer to the injection head was a small laboratory extruder. Thermoset fibre bundles were made with a diameter of typically lmm. These were pulled through a cross-feed injection head held at a temperature of about 250°C. Pulling speeds were approximate 1 m/sec.
The injection rate of the thermoplastic polymer, polystyrene, was the minimum allowed by the extruder.
The prepregs were consolidated in a cylindrical die about 5 mm in diameter.
After cooling in a water spray, the consolidated prepregs were easily bent over a pipe heated to about 200°C.
Scanning electron micrographs (SEM) of pultruded glass fiber roving-reinforced polystyrene composites (at a resolution is 100 Vim) demonstrate that there is a very thin DMSLegal\030319\00283\1419392x3 vinyl ester layer in the interface between the glass fiber and the polystyrene matrix. This interface is dim, indicating that that vinyl ester has a good bonding with polystyrene. The SEM's also show that the glass fiber roving is well impregnated with thermoset resin, as no void is found among the glass fibers.
DMSLegal\030319100283\1419392v3
Claims (15)
1. A fibre-reinforced prepreg comprising:
(a) a plurality of fibres impregnated with a thermoset polymer, and (b) a thermoplastic coating disposed about said fibres and thermoset polymer.
(a) a plurality of fibres impregnated with a thermoset polymer, and (b) a thermoplastic coating disposed about said fibres and thermoset polymer.
2. A fibre-reinforced composite formed by consolidation of a plurality of prepregs of claim 1.
3. The composite of claim 2 formed by:
(a) assembling the plurality of prepregs in a consolidation die, and (b) consolidating the plurality of prepregs.
(a) assembling the plurality of prepregs in a consolidation die, and (b) consolidating the plurality of prepregs.
4. The composite of claim 3 wherein the plurality of prepregs are woven together before they are assembled in the consolidation die.
5. The composite of claim 2 formed by:
(a) weaving the plurality of prepregs together to make a woven layer of prepregs, (b) stacking a plurality of woven layers together; and (c) consolidating the plurality of woven layers.
(a) weaving the plurality of prepregs together to make a woven layer of prepregs, (b) stacking a plurality of woven layers together; and (c) consolidating the plurality of woven layers.
6. The composite of claim 5 wherein a layer of another polymeric material that is able to bond with the woven layer upon consolidation, is inserted between one or more pairs of woven layers, before consolidation of the plurality of woven layers.
7. A fibre-reinforced composite formed by repeating the composite of claim 2, 3, 4, 5 or 6, to a temperature at which the thermoplastic polymer is molten, reshaping the composite, and cooling the composite to a temperature at which the thermoplastic polymer is no longer molten.
8. A fibre-reinforced laminate formed by:
(a) weaving a plurality of prepregs of claim 1 together into a woven layer, (b) stacking a plurality of woven layers together; and (c) consolidating the plurality of woven layers.
(a) weaving a plurality of prepregs of claim 1 together into a woven layer, (b) stacking a plurality of woven layers together; and (c) consolidating the plurality of woven layers.
9. The laminate of claim 8 wherein a layer of another polymeric material that is able to bond with the woven layer upon consolidation, is placed between one or more pairs of the woven layers.
10. A fibre-reinforced laminate formed by repeating laminate of claim 8 or 9 to a temperature at which the thermoplastic polymer is molten, reshaping the laminate, and cooling the composite to a temperature at which the thermoplastic polymer is no longer molten.
11. A method of making a fibre-reinforced prepreg comprising:
(a) impregnating a plurality of fibres with a thermoset polymer, to generate a thermoset fibre bundle, and (b) coating the thermoset fibre bundle with a layer of thermoplastic polymer.
(a) impregnating a plurality of fibres with a thermoset polymer, to generate a thermoset fibre bundle, and (b) coating the thermoset fibre bundle with a layer of thermoplastic polymer.
12. The method of claim 11, wherein pultrusion is used to impregnate the plurality of fibres with a thermoset polymer.
13. A method of making a fibre reinforced composite, comprising:
(a) assembling a plurality of prepregs of claim 1 in a consolidation die, and (b) consolidating the plurality of prepregs.
(a) assembling a plurality of prepregs of claim 1 in a consolidation die, and (b) consolidating the plurality of prepregs.
14. The method of claim 13, wherein pultrusion is used to assemble the plurality of fibres in the consolidation die.
15. A method of making a fibre reinforced composite, comprising:
(a) weaving a plurality of prepregs of claim 11 together to make a woven layer of prepregs, (b) stacking a plurality of woven layers together; a.nd (c) consolidating the plurality of woven layers.
(a) weaving a plurality of prepregs of claim 11 together to make a woven layer of prepregs, (b) stacking a plurality of woven layers together; a.nd (c) consolidating the plurality of woven layers.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002419345A CA2419345A1 (en) | 2003-02-20 | 2003-02-20 | Fibre-reinforced thermoplastics |
| PCT/CA2004/000233 WO2004073948A2 (en) | 2003-02-20 | 2004-02-19 | Fibre-reinforced thermoplastics |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002419345A CA2419345A1 (en) | 2003-02-20 | 2003-02-20 | Fibre-reinforced thermoplastics |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2419345A1 true CA2419345A1 (en) | 2004-08-20 |
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ID=32855068
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002419345A Abandoned CA2419345A1 (en) | 2003-02-20 | 2003-02-20 | Fibre-reinforced thermoplastics |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2419345A1 (en) |
| WO (1) | WO2004073948A2 (en) |
Families Citing this family (3)
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|---|---|---|---|---|
| KR101449204B1 (en) | 2012-12-27 | 2014-10-13 | 주식회사 포스코 | Method of Preparing Continuous Carbon Fiber-reinforced Thermoplastic Prepreg |
| DE102013219820A1 (en) * | 2013-09-30 | 2015-04-02 | Bayerische Motoren Werke Aktiengesellschaft | Fiber composite component, method for producing a fiber composite component and use of fiber bundles and bracing means for producing a fiber composite component |
| CN115431564A (en) * | 2017-05-04 | 2022-12-06 | 泽菲罗斯有限公司 | Pultruded impregnated fibers and uses thereof |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5143501B2 (en) * | 1973-01-27 | 1976-11-22 | ||
| US4743413A (en) * | 1986-07-23 | 1988-05-10 | Galichon Jean P | Method of manufacturing thermostable pieces made from composite materials and the pieces thus obtained |
| GB9101691D0 (en) * | 1991-01-25 | 1991-03-06 | British Petroleum Co Plc | Toughened resins and composites |
| CN1228050A (en) * | 1996-08-12 | 1999-09-08 | 欧文斯－科尔宁格公司 | Chemical treatments for fibers and wire-coated composite strands for molding fiber-reinforced thermoplastic composite articles |
-
2003
- 2003-02-20 CA CA002419345A patent/CA2419345A1/en not_active Abandoned
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2004
- 2004-02-19 WO PCT/CA2004/000233 patent/WO2004073948A2/en active Search and Examination
Also Published As
| Publication number | Publication date |
|---|---|
| WO2004073948A2 (en) | 2004-09-02 |
| WO2004073948A3 (en) | 2004-10-28 |
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