GB2106484A - Carbon fibres - Google Patents

Abstract

Carbon fibre material, for example carbon filaments or sheets tape, roving and such woven or spun from such carbon filaments, is treated with an electrical corona discharge, for example to so modify its surface structure as to improve its wetability and adhesion properties with respect to curable resin or plastics material.

Description

SPECIFICATION Treating carbon fibre This invention relates to the treatment of carbon fibre, in filamentary, woven or spun form or in the form of say tape pre-impregnated with resin, particularly but not exclusively to improve or control the adhesion to the fibre of resin or curable plastics material with which the fibre is used to make fibre reinforced plastics items.

In the invention the fibre is treated by subjecting it to the action of a corona discharge.

For a better understanding of the invention reference will now be made by way of example, to the accompanying drawings, in which: figure 1 is a simplified electrical diagram of single-stage treatment apparatus, figure 2 is a simplified electrical diagram of two-stage treatment apparatus, and figures 3 and 4 are diagrammatic views of the single and two-stage apparatus respectively.

In figure 1, a mains supply is fed via switch 1, fuses 2, a current transformer 3 connected to an ammeter 4, and a controller 5 for example a Variac (trade Name), to the "240,440,550" Volt primary winding of a transformer 1 6, of which transformer, the 1 5KV secondary winding is connected between the shaft of a roller 6 made of insulating material or having an insulating surface and a light-alloy shoe 7 adjustably mounted on high voltage insulators (not shown).

As shown in figure 3, carbon fibre 8 from reel 9 is led via guide 10 and spreader/tension rollers 11 to the roller 6 where a corona discharge is applied via shoe 7, and thence via further spreader/tension rollers 12 to a take-up reel 13.

As shown by figures 2 and 4, there may be two rollers 6 and shoes 7 supplied by the same or different high voltage source(s) and operable to apply corona to the fibre material successively so that both sides of the material are treated.

The shaft(s) of roller(s) 6 may be earthed or isolated from earth.

As may be seen, the corona is produced by a supply which incorporates direct voltage variation of an Alternating Current which will result in the variable condition of the Carbon Fibres surface atomic structure, the supply further incorporating a low frequency high voltage single or multi-phase power source.

As a result of the variable control the Corona atmosphere will vary so as to change the atomic form of the fibre to suit varying requirements.

The process as described will change the surface molecules to a varying degree to suit the adhesion required for the specific task.

The apparatus illustrated provides for the treatment of surfaces of Carbon Fibres to allow variable and better adhesion of synthetic Resins.

This is done by exposing the fibres to an electrical corona in either a single or double process. The treatment will change the molecular structure of the material surface.

The varying voltage levels will afford varying levels of treatment, thus making a controllable grading system for the many different uses of Carbon Fibre.

The single process system will treat up to 50% of the material surface.

The double process system will treat up to 100% of the material surface.

1. A method of treating carbon fibre material in which the material is subjected to the action of an electrical corona discharge.

2. A method according to claim 1, wherein said material is guided past a high-voltage corona discharge generator.

3. A method according to claim 2, wherein said material is guided past first one and then at least one more high-voltage corona-discharge generators.

4. A method according to claim 2 or 3, wherein said material is guided past the or each generator by being entrained over a respective roller comprising insulating material at least at its surface and positioned adjacent the associated generator.

5. A method according to claim 2, 3 or 4 wherein the spacing between said generator and means for guiding the material therepast is adjustable.

6. A method according to any preceding claim, wherein said electrical corona discharge is produced by high-voltage corona discharge generating means driven by voltage controllable electrical supply means, for example supply means comprising a variable-transformer.

7. A method of treating carbon fibre substantially as hereinbefore described with reference to the accompanying drawings.

8. Carbon fibre material which has been treated by the method of any preceding claim.

9. A carbon fibre reinforced plastics material article which has been made using the carbon fibre material of claim 8.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Treating carbon fibre This invention relates to the treatment of carbon fibre, in filamentary, woven or spun form or in the form of say tape pre-impregnated with resin, particularly but not exclusively to improve or control the adhesion to the fibre of resin or curable plastics material with which the fibre is used to make fibre reinforced plastics items. In the invention the fibre is treated by subjecting it to the action of a corona discharge. For a better understanding of the invention reference will now be made by way of example, to the accompanying drawings, in which: figure 1 is a simplified electrical diagram of single-stage treatment apparatus, figure 2 is a simplified electrical diagram of two-stage treatment apparatus, and figures 3 and 4 are diagrammatic views of the single and two-stage apparatus respectively. In figure 1, a mains supply is fed via switch 1, fuses 2, a current transformer 3 connected to an ammeter 4, and a controller 5 for example a Variac (trade Name), to the "240,440,550" Volt primary winding of a transformer 1 6, of which transformer, the 1 5KV secondary winding is connected between the shaft of a roller 6 made of insulating material or having an insulating surface and a light-alloy shoe 7 adjustably mounted on high voltage insulators (not shown). As shown in figure 3, carbon fibre 8 from reel 9 is led via guide 10 and spreader/tension rollers 11 to the roller 6 where a corona discharge is applied via shoe 7, and thence via further spreader/tension rollers 12 to a take-up reel 13. As shown by figures 2 and 4, there may be two rollers 6 and shoes 7 supplied by the same or different high voltage source(s) and operable to apply corona to the fibre material successively so that both sides of the material are treated. The shaft(s) of roller(s) 6 may be earthed or isolated from earth. As may be seen, the corona is produced by a supply which incorporates direct voltage variation of an Alternating Current which will result in the variable condition of the Carbon Fibres surface atomic structure, the supply further incorporating a low frequency high voltage single or multi-phase power source. As a result of the variable control the Corona atmosphere will vary so as to change the atomic form of the fibre to suit varying requirements. The process as described will change the surface molecules to a varying degree to suit the adhesion required for the specific task. The apparatus illustrated provides for the treatment of surfaces of Carbon Fibres to allow variable and better adhesion of synthetic Resins. This is done by exposing the fibres to an electrical corona in either a single or double process. The treatment will change the molecular structure of the material surface. The varying voltage levels will afford varying levels of treatment, thus making a controllable grading system for the many different uses of Carbon Fibre. The single process system will treat up to 50% of the material surface. The double process system will treat up to 100% of the material surface. CLAIMS

1. A method of treating carbon fibre material in which the material is subjected to the action of an electrical corona discharge.

2. A method according to claim 1, wherein said material is guided past a high-voltage corona discharge generator.

3. A method according to claim 2, wherein said material is guided past first one and then at least one more high-voltage corona-discharge generators.

4. A method according to claim 2 or 3, wherein said material is guided past the or each generator by being entrained over a respective roller comprising insulating material at least at its surface and positioned adjacent the associated generator.

5. A method according to claim 2, 3 or 4 wherein the spacing between said generator and means for guiding the material therepast is adjustable.

6. A method according to any preceding claim, wherein said electrical corona discharge is produced by high-voltage corona discharge generating means driven by voltage controllable electrical supply means, for example supply means comprising a variable-transformer.

7. A method of treating carbon fibre substantially as hereinbefore described with reference to the accompanying drawings.

8. Carbon fibre material which has been treated by the method of any preceding claim.

9. A carbon fibre reinforced plastics material article which has been made using the carbon fibre material of claim 8.