DE2147418A1 - Process for the production of endless * carbon fiber cables - Google Patents

Description

DR. ING. A. VAN DERWERTH DR. FRANZ LEDERER

21 HAMBURG 90 8 MUNICH 8O

WITSTORFER »TR. S3 · TtL. 10 «III 77 0β 61 lUCILi-OBAHN-.TR. 33 · TEL. 10.111 44 Οβ 40

Munich, September 22, 1971 PP / 2628

UNITED KINGDOM ATOMIC ENERGY AUTHORITY 11 Charles II Street, London, S.W.L England

"Process for the production of endless carbon fiber cables"

The invention relates to the continuous manufacture of carbon fiber tow. It is known that carbon fibers of organic polymeric fibers, in particular polyacrylonitrile (PAN) or a copolymer which is built up mainly from acrylonitrile, can be prepared by heating the fibers to about 100O ⁰ O. This carbonization step may be preceded by a stage of oxidation, in which the PAN-Faeern be exposed to an oxidizing atmosphere at temperatures of the order of 200 to 30O ⁰ C. Other handlers can also switch to the carbonization stage.

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Lungs follow, including a graphitization, in which temperatures in the order of 2000 to 2600 ⁰ G are applied, and a final surface oxidation treatment.

Such a method is described in GB-PS 1 110 791. This invention is characterized in that the ultimate This increases the tensile strength of the individual carbon fibers can be that one pasers during the period the conversion of the polymer into the end product is exposed to the combined influence of heat and tension (tensile stress).

Carbon fibers are often sold to consumers in the form of cables, and it is desirable that the cable have a high tensile strength over substantial lengths and that the individual fibers of the cable are well aligned with one another. The present invention relates to the improvement of the properties of carbon fiber cables with regard to the tear strength and the alignment of the individual fibers to one another; it does not concern the improvement of the properties of the individual carbon fibers. In this connection it should be pointed out that the tensile strength of a carbon fiber cable is not directly dependent on the tensile strengths of the individual (essentially inextensible) fibers that make up the cable. The reason for this is that some of the lines are different in length than the remaining lines of the cable. These passers take the load first. They tear before the cable is taut and

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incidentally lead to the formation of slack cables that are not let it roll up well.

The invention relates to a method for the production of endless carbon fiber cables, which consists in that one endless cable made of carbonizable, organic, polymeric fibers under tension during carbonization in an oven, the tension being exerted on the cable over a length which is considerably larger than the length of the carbonization furnace is.

The invention particularly relates to application to pas cable made of polyacrylonitrile or a copolymer, the greater part of which is composed of acrylonitrile, with the fiber cable can be used as such or in an oxidized state.

In the previous implementation of the method according to the invention, cables of 10,000 individual threads are preferably used PAN worked from 3 denier. For these cables, tensions of at least 100 g up to 3500 g or more are suitable, with Tensions of 300 g are preferred. For cables with larger or smaller diameters, the voltages are preferred proportionally larger or smaller.

It is important »that the tension is applied evenly across the cable. This sets an upper limit for The size of the processable cables is set, since the carbon fibers are slippery and only those fibers are full of the Subject to tension in essentially direct contact

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with the tension-transmitting devices, e.g. tension pulleys, stand. The method can be applied to cables with a greater number of monofilaments if the cable is in front the passing of the tensioning rollers is spread to form a band of the appropriate width; This allows cables with up to can be easily processed into 1,000,000 filaments or more by this method.

The length over which the tension is applied to the cable is preferably at least 3 times, in particular at least 5 times as large as the length of the carbonization zone in the furnace. It has been shown that when using the Voltage on a cable length of 4.57 m, which is 10 times the 45.7 cm long garbonization zone of a special Furnace, gets good results.

The tension can be created with the help of driven rollers at the lower end and braked rollers at the upper end of the system. Since the carbon fibers are slippery, | a pair of simple holding rollers at the lower end may not be sufficient to grip the cable. If so, an arrangement in which the cable is wrapped around one or both of the rollers is a simple remedy. In the previous process of the invention, the cable is preferably wound onto a driven, _slow-speed> large-caliber barrel.

In that section of the cable that is under tension, during the conversion of the polymeric fiber

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Other treatment stages were also carried out in addition to the carbon fiber will. If the output fiber is in a non-oxidized state, the oxidation can be carried out under tension although this causes some stretching of the cable. The graphitization and surface treatments can also be done on the live carbon cable.

When the method according to the invention was carried out under tension, a carbon fiber with a tensile strength of 63 _f 50 kg, based on a length of 10 cm, was obtained in an experiment, while a comparable cable produced without application of tension only had a tensile strength of 31.75 kg was established. Similar improvements were found over larger sections of the cable.

In carrying out the method of the invention, the stress also causes better equalization of already cracked ones Pasern to the rest of the cable. This effect can be improved if there are narrow glass diffusers at the entrance and exit of the furnace be used. This makes it easier to manufacture tightly packed cables with no slack ends.

The appearance and alignment of the individual fibers in the cable is compromised as a result of being guided around a pair of tensioning rollers or being wound on a drum, even if the cable is large in diameter. Therefore, the appearance and orientation of the cables are preferably fixed by applying a resin to the cable while it is still under tension. The resin can be sprayed on or on

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distributed to the cable, e.g. by applying felt. at In a preferred embodiment, the cable is immersed in a bath containing the resin, with the greatest possible avoidance A small angle of immersion is preferably maintained in the event of fiber breakage.

The resin can be used in the form of a solution, preferably in a rapidly evaporating solvent such as acetone or ether. In this V / else finds a rapid cooperation W stick the cable instead.

The nature of the resin is not particularly important and can be selected with regard to the matrix used by the Carbon fiber is to be reinforced. Examples of suitable resins are epoxy resins, polyvinyl alcohol, based resins of polyvinyl acetate, polyester or polyamides.

The resin is used, for example, in a small amount, for example 1% by weight, based on the cable, used to achieve an easy fixation of the fiber. For pre-impregnation of the cable before use In further treatment steps, the resin is applied in a relatively large amount, for example 30% by weight, based on the cable.

The resin treatment according to DT-PA 21 37 604-5 is good , Get results.

Claims

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Claims (1)

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Patent application 1. Method of making continuous carbon fiber tow using tension on a continuous tow of carbonizable, organic, polymeric fibers during carbonization in an oven, characterized in that the voltage is applied to the cable uses a length that is significantly greater than the length of the carbonation oven. 2. The method according to claim 1 ,, characterized in that one uses fibers made of polyacrylonitrile or of a copolymer, the greater part of which is made up of acrylonitrile. 3. The method according to claim 1 or 2, characterized in that that one has a tension of 100 to 3500 g and for a cable made of 10,000 polyacrylonitrile single filaments of 3 denier Larger or smaller diameter cable applies proportionally larger or smaller voltages. 4. The method according to any one of claims 1 to 3, characterized in that that one uses cables with up to 1,000,000 pasers. 5. The method according to any one of claims 1 to 4, characterized in that the voltage is applied over a cable length which is at least 3 times as long as the carbonization zone of the furnace. 2098U / 1012 ο. Method according to claim 5, characterized in that the voltage is applied over a length of cable that is at least 5 times as long as the oven's boning zone. 7. The method according to any one of claims 1 to 6, characterized in that that the cable tension by pulling the cable from a braked drum and winding it up on a slow speed driven drum with large Diameter generated. 8. The method according to any one of claims 1 to 7, characterized in that that the tensioned cable at the entrances and exits of the carbonization furnace through narrow glass ducts runs. 9. The method according to any one of claims 1 to 8, characterized in that that a resin is applied to the carbonized fibers that are still under tension. 10. Endless carbon fiber cables manufactured according to one of Claims 1 to 9 2098U / 1M?