Fibre matrix and a method of making a fibre matrix

Abstract

A method of forming a three dimensional fiber structure is disclosed which comprises the steps of a) providing a starting material which comprises liquid carrier, fibers and binder; b) passing the starting material over a substrate so as to deposit fibers onto the substrate; c) forming a three dimensional fiber matrix; and d) curing the binder. The flow of material onto the substrate may be controlled such that the flow of a starting material over the substrate is chaotic and fibers are laid down in a three dimensional structure containing a high proportion of voids. The preform may be pressurized while moist and is cured under pressure. The fibers may comprise carbon fibers; recycled carbon fiber has been found to be particularly useful. The resulting preform may be stochastic and is suitable for use in ablative and braking applications.

Claims

1. A stochastic fibre preform, comprising a non woven substrate of fibres having a stochastic three dimensional matrix, wherein the preform has fibres arranged in the x, y and z directions, and these fibres are randomly oriented, and wherein the fibres are held together in the matrix formation by a cured binder and wherein the fibres comprise carbon fibres, and wherein the preform has a fibre volume fraction of 20% or higher.

2. A fibre preform according to claim 1 wherein 10 wt % or more of the fibres are carbon fibre.

3. A fibre preform according to claim 1 wherein the fibre preform is a fibre matrix obtainable by a method comprising the steps of: a) providing a starting material which comprises liquid carrier, fibres and binder; b) passing the starting material over a substrate so as to deposit fibres onto the substrate; c) forming a three dimensional fibre matrix; and d) curing the binder.

4. A fibre preform according to claim 3 wherein step d) comprises curing the binder by the application of heat whilst applying a pressure of 5 kPa or more.

5. A fibre preform according to claim 4 wherein step d) comprises curing the binder by the application of heat whilst applying a pressure of 50 kPa to 50000 kPa or more.

6. A fibre preform according to claim 5 wherein step d) comprises curing the binder by the application of heat whilst applying a pressure of such as from 100 kPa to 25000 kPa or more.

7. A fibre preform according to claim 4 wherein in step d) the pressure is applied to the fibrous matrix while the matrix contains moisture.

8. A fibre preform according to claim 1 in which the fibres are arranged in x, y and z directions and from 5 to 30 wt % of the fibres are arranged substantially in the z direction.

9. A fibre preform according to claim 1 wherein the preform is a monolithic structure.

10. A fibre preform according to claim 1 wherein the percentage of binder in the product is from 5% to 60% of the weight of the dried fibrous matrix.

11. A fibre preform according to claim 10 wherein the percentage of binder in the product is from 5% to 30% of the weight of the dried fibrous matrix.

12. A fibre preform according to claim 11 wherein the percentage of binder in the product is from 5% to 20% of the weight of the dried fibrous matrix.

13. A fibre preform according to claim 1 wherein the binder is selected from the group consisting of: epoxy novolac binders, urethanes, acrylics, methacrylates, styrenes, polyurethane co polymers, phenols, poly vinyl imides, poly vinyl alcohols, vinyl acetate/vinyl chloride copolymers, polyamides, PVC, PVDC, polyvinyl sulphones, PEEK (poly ether ketone) materials, polyesters, polyhydroxyether and epoxy materials, castor based hydroxy functional polyols, organic binders, silane binders, acrylic latex binders, highly carbonisable imide binders, and polyvinylpyrrilidone binders.

14. A fibre preform according to claim 13 wherein the binder is selected from the group consisting of: epoxy novolac binders, phenols, poly vinyl imides, poly vinyl alcohols, vinyl acetate/vinyl chloride copolymers, PEEK (poly ether ether ketone) materials, polyhydroxyether and epoxy materials, castor based hydroxy functional polyols, acrylic latex binders, highly carbonisable imide binders, and polyvinylpyrrilidone binders.

15. A fibre preform according to claim 1 in which the preform contains 20% or more of voids by volume.

16. A fibre preform according to claim 15 in which the preform contains 20% to 75% of voids by volume.

17. A fibre preform according to claim 1 wherein the preform has a fibre volume fraction of from 20% to 40%.

18. A carbon-composite product that comprises a fibre preform as defined in claim 1.

19. A laminated fibre preform which comprises at least one layer of a fibre preform as defined in claim 1 and one or more layers of aramid fibres.

20. An article for use in high temperature applications comprising a preform as defined in claim 1.

21. The article of claim 20, which is an article for use in brakes or rocket motor housings.

22. The article of claim 21, wherein the article is a brake shoe lining.

23. A method of producing an article for use in high temperature applications, the method comprising the steps of: (i) providing a preform as defined in claim 1; and (ii) carrying out a CVD or CVI process on the preform.

24. A method of making a fibre matrix, comprising the steps of: a) providing a starting material which comprises liquid carrier, fibres and binder; b) passing the starting material over a substrate so as to deposit fibres onto the substrate; c) forming a three dimensional fibre matrix as defined in claim 1; and d) curing the binder.

Description

(1) The invention will now be further described by way of example only with reference to the following examples and drawings in which:

(2) FIG. 1 is a sketch of a laboratory test system;

(3) FIG. 2 is an illustration of a production system,

(4) FIG. 3 is an illustration of an alternative production system utilising a multiple vacuum manifold, and

(5) FIG. 4 is an illustration of an alternative production system having a chaotic flow over the substrate.

(6) In FIG. 1 a starting material comprising slurry 1 formed of a liquid carrier, binder and carbon fibres is poured and dropped from a container 2 onto a substrate comprising a mesh 4 located at a base of a mould 6. A mould wall 8 surrounds the mesh 4 and chaotic flow of the starting material occurs in the mould 6. Liquid carrier material drains through the mesh 4 and into the drain 10. A vacuum force is applied to the drain 10.

(7) FIG. 2 illustrates a production system in which the starting material is prepared in a holding container 12 having a shear mixer 14 which agitates the starting material. The starting material flows out of the holding container by means of outlet 16 through a pipe 18 and into a manifold 20. The starting material is dispersed in the manifold and drained from manifold outlets 22 into a mould 24. In this embodiment the manifold is provided with eight manifold outlets and the starting material drains into the mould 24 under gravity. The manifold is positioned approximately at least 100 cms above a mesh substrate 26 located in a base of the mould 24. The starting material flows into the mould 24 from the eight manifold outlets 22, and counter currents and cross flows are set up within the starting material in the mould creating a chaotic flow therein and forming a three dimensional stochastic matrix.

(8) Liquid carrier is drained from the mould through a drainage channel 28. A vacuum force is applied by a vacuum 30. The mesh substrate 26 is removed from the mould 24 and moved by means of a conveyor 30 to a press where the preform can be placed under pressure and heated to cure the preform.

(9) FIG. 3 illustrates an alternative production system utilising a multiple vacuum manifold 40 drawing liquid carrier from the substrate. The system is largely the same as the production system described with reference to FIG. 2. The system comprises a holding container 42 containing dispersed fibre. The starting material may be heated prior to being held in the holding container or the contained may be heated. The starting material is removed from the holding container by means of a pipe 44 and a pump 46 controls removal of the starting immaterial. The starting material flows into a mould 48 and drops onto a substrate 50 located at a base of the mould 48. It will be understood that the pump 46 may pump the starting material into the mould 48 under pressure. A draw manifold 40 is located below the substrate 50 and has multiple draw points 52 which lead to a central drain 54. The provision of multiple draw points 52 in the vacuum manifold 40 creates a number of flows of liquid carrier through the matrix deposited on the substrate and forms a three dimensional fibre matrix structure.

(10) FIG. 4 illustrates and alternative embodiment of a production system in which a manifold 60 is fed from a holding container by means of a gravity feed or a pump. The manifold 60 has a number of outlets 62. Of these eight outlets 62 are arranged to deliver starting material vertically to the substrate 64 located at the base of a mould 66. Additional outlets from the manifold 60 are connected to sides 68 of the mould 66.

EXAMPLES

(11) All of the examples were prepared using the process of the invention, with the starting material comprising the stated liquid carrier, fibres and binder being passed over a substrate so as to deposit fibres onto the substrate, a three dimensional fibre matrix being formed and the binder being cured.

Example 1

(12) A 0.0968 m.sup.2 sample was prepared using the process of the invention.

(13) A starting material was prepared using: 480 g of a fibre blend (50 wt % 25 mm carbon fibre and 50 wt % 50 mm carbon fibre) 12 kg of water 120 g of binder (acrylic based binder system)

(14) This starting material was dropped over a mesh substrate so as to deposit fibres onto the substrate, and then subjected to a vacuum force of approximately 550 torr before then being heated to a temperature of 170 C. under a compression force of 70 N/cm.sup.2.

(15) A sheet of 10.2 mm thick, with a fibre volume of 23% and basis weight of 4000 gm.sup.2, was produced. A void content of approximately 69% was present in the product of this example.

Example 2

(16) A further sample was prepared using the same methods and materials as in Example 1. However, 30 wt % of colloidal silica was added to the starting material.

(17) The final fibre volume fraction in this case was 26%, with a thickness of 8.2 mm and basis weight of 3650 gm.sup.2. A void content of approximately 60% was present in the product of this example.

Examples 3-8

(18) In all these examples, a 10 kg, 20 kg or 30 kg batch of the end product was made.

Example 3

(19) A starting material was prepared using: PAN virgin fibre blend (40 wt % 3 mm long; 30 wt % 6 mm long; 25 wt % 12 mm long; 5 wt % 25 mm long) polyvinyl (PVOH) binder water

(20) No filler was added.

(21) A pump feed was used to pressurise the starting material, to give a Reynolds number for this feed in excess of 4000. This starting material was passed over a mesh substrate, so as to deposit fibres onto the substrate, and then subjected to a vacuum force of approximately 600 torr, before then being heated to a temperature of 180 C. under a compression force of approximately 120 N/cm.sup.2.

(22) The fibre matrix produced comprised: carbon fibre 80 wt % PVOH binder 20 wt %.

(23) A preform was prepared having a size of 650 mm650 mm and a thickness from 16 mm to 32 mm. The basis weight was from 12200 gm.sup.2 to 13200 gm.sup.2.

(24) The fibre volume fraction for 32 mm thickness product was from 23% to 24%. A void content of approximately 70% was present in this product.

(25) The fibre volume fraction for 16 mm thickness product was 49%. A void content of approximately 37.5% was present in this product.

Example 4

(26) A starting material was prepared using: PAN virgin fibre blend (40 wt % 3 mm long; 30 wt % 6 mm, 25 wt % 12 mm long; 5 wt % 25 mm long) polyvinyl (PVOH) binder water

(27) No filler was added.

(28) A pump feed was used to pressurise the starting material, to give a Reynolds number for this feed in excess of 4000. This starting material was passed over a mesh substrate, so as to deposit fibres onto the substrate, and then subjected to a vacuum force of approximately 600 torr before then being heated to a temperature of 180 C. under a compression force of 120 N/cm.sup.2.

(29) The fibre matrix produced comprised: carbon fibre 85 wt % PVOH binder 15 wt %.

(30) A preform was prepared having a size of 500 mm500 mm and a thickness from 16 mm to 32 mm. The basis weight was from 12200 gm.sup.2 to 13200 gm.sup.2.

(31) The fibre volume fraction for 32 mm thickness product was from 23% to 24%. A void content of approximately 71.5% was present in this product.

(32) The fibre volume fraction for 16 mm thickness product was 49%. A void content of approximately 39% was present in this product.

Example 5

(33) A starting material was prepared using: 100% recycled carbon (random blend of fibre lengths between 3 and 12 mm) polyvinyl (PVOH) binder water a filler of milled carbon, having a maximum particle diameter size 50 m, provided as a dispersion in a liquid carrier with a PVP binder.

(34) A pump feed was used to pressurise the starting material, to give a Reynolds number for this feed in excess of 4000. This starting material was passed over a mesh substrate, so as to deposit fibres onto the substrate, and then subjected to a vacuum force of approximately 700 torr, before then being heated to a temperature of 180 C. under a compression force of 140 N/cm.sup.2.

(35) The fibre matrix produced comprised carbon fibre 70 wt % PVOH binder 10 wt % milled carbon 15 wt % PVP binder 5 wt %.

(36) A preform was prepared having a size of 500 mm500 mm and a thickness of 32 mm. The fibre volume fraction was from 23% to 24% and the basis weight was from 12200 gm.sup.2 to 13200 gm.sup.2. A void content of approximately 69% was present in this product.

Example 6

(37) A starting material was prepared using: PAN virgin fibre blend (25 wt % 3 mm long; 25 wt % 6 mm long; 35 wt % 12 mm long; 15 wt % 25 mm long) polyvinyl (PVOH) binder water a filler of milled carbon, having a maximum particle diameter size 50 m, provided as a dispersion in a liquid carrier with a PVP binder.

(38) A pump feed was used to pressurise the starting material, to give a Reynolds number for this feed in excess of 4000. This starting material was passed over a mesh substrate, so as to deposit fibres onto the substrate, and then subjected to a vacuum force of approximately 700 torr, before then being heated to a temperature of 180 C. under a compression force of 140 N/cm.sup.2.

(39) The fibre matrix produced comprised carbon fibre 70 wt % PVOH binder 10 wt % milled carbon 15 wt % PVP binder 5 wt %.

(40) A preform was prepared having a size of 500 mm500 mm and a thickness of 32 mm. The fibre volume fraction was from 23% to 24% and the basis weight was from 12200 gm.sup.2 to 13200 gm.sup.2. A void content of approximately 69% was present in this product.

Example 7

(41) A preform was prepared having a size of 500 mm500 mm and a thickness of 6 mm.

(42) Variant A

(43) A starting material was prepared using: PAN virgin fibre blend (40 wt % 3 mm long; 30 wt % 6 mm long; 25 wt % 12 mm long; 5 wt % 25 mm long) polyvinyl (PVOH) binder water

(44) A pump feed was used to pressurise the starting material, to give a Reynolds number for this feed in excess of 4000. This starting material was passed over a mesh substrate, so as to deposit fibres onto the substrate, and then subjected to a vacuum force of approximately 600 torr, before then being heated to a temperature of 170 C. under a compression force of 260 N/cm.sup.2.

(45) The fibre volume fraction was about 30% and the basis weight was from 2550 gm.sup.2 to 3100 gm.sup.2. A void content of approximately 65% was present in this product.

(46) Variant B

(47) A starting material was prepared using: PAN virgin fibre blend (40 wt % of 3 mm fibre, 30 wt % of 6 mm fibre, 25 wt % of 12 mm fibre, 5 wt % of 25 mm fibre) plus milled carbon particulate; polyvinyl (PVOH) binder water a filler of milled carbon, having a maximum particle diameter size 50 m, provided as a dispersion in a liquid carrier with a PVP binder

(48) A pump feed was used to pressurise the starting material, to give a Reynolds number for this feed in excess of 4000. This starting material was passed over a mesh substrate, so as to deposit fibres onto the substrate, and then subjected to a vacuum force of approximately 700 torr, before then being heated to a temperature of 180 C. under a compression force of 240 N/cm.sup.2.

(49) The fibre volume fraction was about 30% and the basis weight was from 2550 gm.sup.2 to 3100 gm.sup.2. A void content of approximately 60% was present in this product.

(50) The fibre matrix produced comprised: carbon fibre 70 wt % PVOH binder 10 wt % milled carbon 15 wt % PVP binder 5 wt %.

Example 8

(51) A preform was prepared having a size of 500 mm500 mm and a thickness of 35 mm or 17.5 mm.

(52) Variant A

(53) A starting material was prepared using: 100% recycled carbon fibre (random blend of fibre lengths between 3 and 12 mm) polyvinyl (PVOH) binder water

(54) No filler was used.

(55) A pump feed was used to pressurise the starting material, to give a Reynolds number for this feed in excess of 4000. This starting material was passed over a mesh substrate, so as to deposit fibres onto the substrate, and then subjected to a vacuum force of approximately 700 torr, before then being heated to a temperature of 180 C. under a compression force of 260 N/cm.sup.2.

(56) The fibre matrix produced comprised: carbon fibre 85 wt % PVOH binder 15 wt %

(57) The fibre volume fraction was about 30% and the basis weight was from 14,900 gm.sup.2 to 17,900 gm.sup.2. A void content of approximately 65% was present in the 35 mm thickness product.

(58) Variant B

(59) A starting material was prepared using: recycled carbon fibre blend (random blend of fibre lengths between 3 and 12 mm) polyvinyl (PVOH) binder water a filler material comprising milled carbon having a maximum particle diameter size 50 m, provided as a dispersion in a liquid carrier with a PVP binder

(60) A pump feed was used to pressurise the starting material, to give a Reynolds number for this feed in excess of 4000. This starting material was passed over a mesh substrate, so as to deposit fibres onto the substrate, and then subjected to a vacuum force of approximately 600 torr, before then being heated to a temperature of 170 C. under a compression force of 240 N/cm.sup.2.

(61) The fibre matrix produced comprised carbon fibre 60 wt % PVOH binder 10 wt % milled carbon filler 25 wt % PVP binder 5 wt %.

(62) The fibre volume fraction was about 30% and the basis weight was from 14,900 gm.sup.2 to 17,900 gm.sup.2. A void content of approximately 57.5% was present in the 35 mm thickness product.

Example 9

(63) A preform was prepared having a size of 500 mm700 mm and a thickness of 3 mm or 17 mm.

(64) A starting material was prepared using: 100% recycled carbon fibre (random blend of fibre lengths between 3 and 100 mm) vinyl acetate/vinyl chloride copolymer binder (Mowlith VC600) water

(65) No filler was used.

(66) This starting material was dropped from a height onto a mesh substrate, so as to deposit fibres onto the substrate, and then subjected to a vacuum force of approximately 700 torr, before then being heated to a temperature of 180 C. under a compression force of 260 N/cm.sup.2.

(67) The fibre matrix produced comprised carbon fibre 70 wt % binder 30 wt %

(68) The first product made had a basis weight of 16000 gsm and a thickness of 17 mm. The fibre volume fraction was 52% and the void fraction was 23%.

(69) The second product made had a basis weight of 2000 gsm and a thickness of 3 mm. The fibre volume fraction was 36% and the void fraction 40%.

Example 10

(70) A laminated material was produced using a fibre matrix formed in accordance with the invention. A substrate having an overall fibre basis weight of 3000 gsm was formed of three layers. An upper and a lower portion of the laminate was 1000 gsm formed from 6 mm chopped aramid fibres (Kevlar). A core of the laminate was formed of 1000 gsm substrate formed from recycled carbon fibre of fibre lengths between 3 mm and 12 mm. The core was formed in accordance with the method set out above (in Example 9). The layers were stacked and pressed using a vinyl acetate/vinyl chloride copolymer (Mowlith VC600) at 10% addition at a temperature of 170 C. The layers comprising Kevlar fibres were also formed in accordance with the invention. The laminate had a final fibre volume fraction of around 30% and a void fraction of around 68%.

Example 11

(71) An alternative version of a laminated material was formed by using a substrate of 1000 gsm overall fibre basis weight formed using recycled carbon of lengths between 3 mm and 23 mm and made in accordance with the method set out above (in Example 9), as an upper layer and a lower layer. A core layer formed of 6 mm chopped aramid fibres (Kevlar) was used. The core layer had an overall fibre basis weight of 1000 gsm. The laminated material was formed by stacking and pressing using a vinyl acetate/vinyl chloride copolymer (Mowlith VC600) at 10% addition and was cured at 170 C. The laminated material had an overall fibre basis weight of 3000 gsm and a fibre volume fraction of about 30% and a void fraction of around 68%.

Example 12

(72) A fibre matrix was formed using a blend of fibres. In this example 6 mm Kevlar chopped fibres and recycled carbon fibre having a chopped length from 3 mm to 12 mm were blended in a ratio of 1:1 (weight ratio) of recycled carbon fibres and Kevlar fibres. The method of Example 9 was used. The fibre matrix was pressed and cured with 10% Mowlith VC600 vinyl acetate/vinyl chloride binder to give a fibre volume fraction of around 30% and a void fraction of around 68%.

(73) It is believed that aramid fibre blend variants, as shown in Examples 10-12, may be particularly useful for friction and ballistic applications.

Example 13

(74) A fibre matrix was formed using virgin carbon fibre. The material that was combined with water to provide the starting material was: 3 mm fibre30 wt % 6 mm fibre20 wt % 12 mm fibre15 wt % 25 mm fibre5 wt % vinyl acetate/vinyl chloride copolymer binder (Mowlith VC600)30 wt %

(75) The starting material was passed to a mesh substrate, located in a mould, via a manifold having a single entry and eight exits. The starting material drops into the manifold via its single entry and drains from the eight manifold outlets into the mould. The manifold is positioned above the mesh substrate so that the slurry drops from a height onto the mesh substrate.

(76) The starting material passed over the mesh substrate, so as to deposit fibres onto the substrate, and was subjected to a vacuum force of approximately 700 torr, before then being heated to a temperature of 180 C. under a compression force of 260 N/cm.sup.2.

(77) A 16000 gsm sheet was pressed to a thickness of 13.5 mm to give a fibre volume fraction of approximately 66% and a void fraction of approximately 30%.

Example 14

(78) A fibre matrix was formed using recycled carbon fibre. The material that was combined with water to provide the starting material was: chopped random recycled carbon (lengths between 3 mm-12 mm)70 wt % vinyl acetate/vinyl chloride copolymer binder (Mowlith VC600)30 wt %

(79) The starting material was passed to a mesh substrate, located in a mould, via a manifold having a single entry and eight exits. The starting material drops into the manifold via its single entry and drains from the eight manifold outlets into the mould. The manifold is positioned above the mesh substrate so that the slurry drops onto the mesh substrate.

(80) This starting material was passed over the mesh substrate, and was subjected to a vacuum force of approximately 700 torr, before then being heated to a temperature of 180 C. under a compression force of 260 N/cm.sup.2.

(81) A 16000 gsm sheet was pressed to a thickness of 13.5 mm to give a fibre volume fraction of approximately 66% and a void fraction of approximately 30%.

(82) Binder Tests

(83) A number of different binders have been experimented with and their usefulness compared. A table setting out a summary of the results follows. In the table FBW is the fibre basis weight in grams per square meter and VF is the fibre volume fraction.

(84) TABLE-US-00001 % Binder Binder VF Chemical FBW Percol % % Pos- Type Binder Type Recipe Made Used INPUT OUTPUT sible Comments Carboxylated Rohm and Haas Addition 180 C. Press 1000 0 20 0 0 acrylic Aquaset 150 Carboxylated Rohm and Haas Addition 180 C. Press 1000 0 40 0 0 acrylic Aquaset 150 Carboxylated Rohm and Haas Addition + flocced with 1000 300 50 0 0 acrylic Aquaset 150 Percol 180 C. Press Carboxylated Rohm and Haas Addition + flocced with 1000 100 50 0 0 acrylic Aquaset 150 Al sol 180 C. Press Vinyl acetate/ Celanese Mowlith Addition 180 C. Press 1000 0 20 0 0 vinyl chloride VC600 Vinyl acetate/ Celanese Mowlith Addition 180 C. Press 1000 0 40 0 0 vinyl chloride VC600 Vinyl acetate/ Celanese Mowlith Addition + flocced with 1000 300 20 15 27 No relaxation or softening vinyl chloride VC600 Percol 180 C. Press after 24 hours submerged in water - suitable storm shielding Vinyl acetate/ Celanese Mowlith Addition + flocced with 1000 300 40 35 30 No relaxation to 430 C., vinyl chloride VC600 Percol 180 C. Press 450 C. totally relaxed - suitable for CVI process Vinyl acetate/ Celanese Mowlith Addition + flocced with 6000 300 25 15 31-35 Made 10-11 mm thick = vinyl chloride VC600 Percol 180 C. Press 31-35% VF Styrene Celanese Addition + flocced with 1000 300 20 18 30+ relaxed at 400 C. - not acrylic Vinacryl 7179 Percol 180 C. Press suitable for CVI process Styrene Celanese Addition + flocced with 1000 300 40 35 30+ No relaxation or softening acrylic Vinacryl 7179 Percol 180 C. Press after 24 hours submerged in water - suitable storm shielding Styrene Celanese Addition + flocced with 6000 300 25 20 30+ acrylic Vinacryl 7179 Percol 180 C. Press Carboxylated Rohm and Haas Addition + flocced with 1000 1000 100 0 0 Not possible need Ca ion acrylic Aquaset 150 Percol 1000% 180 C. Press Bismaleimide Evonik Added powder pre mixed with 1000 0 30 0 0 Not possible with water Compimide P500 water 180 C. Press drawn process Epoxy/Novolac Phenodur Added before fibre and then 1000 200 30 7.5 16 Percol worked well but 200% VPW1946 added fibre and then Percol not enough - 7.5% binder 180 C. Press produced medium VF Epoxy/Novolac Phenodur Added before fibre and then 1000 300 30 15 18 VPW1946 added fibre and then Percol 180 C. Press Epoxy/Novolac Phenodur Added before fibre and then 1000 400 30 15 20 VPW1946 added fibre and then Percol 180 C. Press Epoxy/Novolac Phenodur Added before fibre and then 1000 600 30 22.5 23 VPW1946 added fibre and then Percol 180 C. Press Epoxy/Novolac Phenodur Added before fibre and then 1000 1000 35 35 32+ 200 C. Press started to make VPW1946 added fibre and then Percol material brown indicating 200 C. Press binder starting to decompose Epoxy/Novolac Phenodur Added before fibre and then 1000 800 35 18 17 200 C. Press worked fine - VPW1942 added fibre and then Percol could go to 230 C. 200 C. Press Epoxy/Novolac Phenodur Added before fibre and then 1000 900 35 20 21 200 C. Press worked fine - VPW1942 added fibre and then Percol could go to 230 C. 200 C. Press Epoxy/Novolac Phenodur Added before fibre and then 1000 1000 35 17 21 200 C. Press worked fine - VPW1942 added fibre and then Percol could go to 230 C. 200 C. Press Epoxy/Novolac Phenodur Added before fibre and then 1000 1200 35 22.5 23 200 C. Press worked fine - VPW1942 added fibre and then Percol could go to 230 C. 200 C. Press Polyether/ Impranil Addition + flocced with 1000 1000 30 0 0 Not possible need Polyurethane Percol 1000% 180 C. Press different floc? Polyester/ Baybond Addition + flocced with 1000 1000 30 22 12 Soft and like rubber Urethane Percol 1000% 180 C. Press Acrylic Fulatex PD2163 Addition + flocced with 1000 1000 30 30 22 Percol 1000% 180 C. Press Acrylic Fulatex PD2163 Addition + flocced with 1000 500 30 27 18 Percol 500% 180 C. Press Acrylic Fulatex PD2163 Addition + flocced with 1000 250 30 22 15 Percol 250% 180 C. Press Acrylic Fulatex PD2163 Addition + flocced with 1000 125 30 10 10 Percol 125% 180 C. Press Acrylic Fulatex PD2163 Addition + flocced with 6000 700 30 30 32 Excellent Hard Binder - Percol 700% 180 C. Press easy to use and floc HIGH VF Possible Polyether Baybond PU405 Addition + flocced with 1000 200 30 30 23 Soft Binder Urethane Percol 200% 180 C. Press Polyurethane Baybond XP2596 Addition + flocced with 1000 200 30 30 25 Harder than PU but still Percol 200% 180 C. Press soft Epoxy/Novolac Phenodur To pulper 5 g acid 1.7 pH 95 g 1000 1000 25 20 32+ 200 C. Press started to make VPW1946 water and carbon fibre, then material brown indicating added 25% solids, long mix binder starting to decompose Epoxy/Novolac Phenodur To pulper 3 g acid 1.7 pH 95 g 1000 1000 25 22 32+ 200 C. Press started to make VPW1946 water and carbon fibre, then material brown indicating added 25% solids, long mix binder starting to decompose

(85) From the above results it can be seen that carboxylated acrylic with Percol did not in this trial form a suitable matrix for high fibre volume fractions. However, it is believed that an alternative destabilising agent would form a suitable gel in the starting material and improve the results achieved for applications requiring a high fibre volume fraction. Improved results have been achieved with the use of calcium sulphate as a destabilising additive, causing gelling and improving polymer pick up on the substrate.

(86) It can be seen that acrylic binder in the form of Fulatex provided excellent results with a high fibre volume fraction achievable.

(87) As discussed earlier, the binder is chosen to be stable to a temperature greater than the curing temperature. In the examples using Phenodur 1946 and heating to 200 C. the tests indicate that the binder material is beginning to decompose at this temperature. However, curing at 180 C. is satisfactory and does not decompose the binder material.

(88) It can be seen that the binder selected can contribute to the characteristics of the final product and thus selection of the binder enables the characteristics of the product to be tailored in terms of handling and stiffness.

(89) It can be seen from the examples that, inter alia, particularly good results can be obtained for products where any one of the following embodiments are used: dropping the starting material a distance onto the substrate plus applying a vacuum force to the fibres on the substrate; passing the starting material over the substrate from a plurality of outlet points plus applying a vacuum force to the fibres on the substrate; supplying the starting material to the substrate at a pressure plus applying a vacuum force to the fibres on the substrate.