DE3401195A1 - Composite materials made from polyether-imide and reinforcing fibres - Google Patents

Abstract

A process for the production of thermoplastically mouldable, synthetic resin-bound continuous fibre strands (prepreg rovings) in which continuous fibre strands are passed through a bath where they are impregnated with a solution of a polyether-imide in a solvent, preferably dichloromethane. The dried prepreg rovings can be used for the production of pipes by the winding method or, in the form of tapes or sheets of a plurality of rovings lying one on top of the other, as a sheet-like semifinished product.

Description

composite materials made of polyetherimide and. Reinforcement fibers

The invention relates to a method for producing thermoplastic deformable, synthetic resin-bound continuous fiber strands (prepreg rovings) »at the continuous fiber strands are impregnated with polyetherimide.

For the production of deformable prepreg rovings are usually Continuous fiber strands (rovings) 'impregnated with a plastic. The prepreg rovings can e.g. be wound on a core and become rotationally symmetrical skills, e.g. '. Pipes, can be further processed, or they can be laid parallel and formed into plate-shaped Semi-finished products are connected. This procedure has so far been practically exclusive carried out with highly crosslinked thermosets, but the disadvantage is that the ultimately manufactured finished parts must be subjected to a curing process.

Polyetherimides are amorphous thermoplastics that have recurring structures of the formula I: They have good heat resistance. This gave rise to the task of providing composite material based on polyetherimides and reinforcing fibers.

The invention therefore relates to a method for production of thermoplastically formable, synthetic resin-bound continuous fiber strands (prepreg rovings), in which one leads endless strands of fibers through a bathroom, where they are connected to a £ Osung a polyetherimide are soaked, and then the solvent is evaporated.

It is preferable to work with solutions of polyetherimide in dichloromethane, which have a solids content of 10 to 20, in particular 15 to 25% by weight and one Viscosity when soaking below 1000 mPas, preferably between 100 and 800 have mPas.

Usual continuous razor strands, e.g. made of glass or carbon, are used or aromatic polyamides (aramid fibers). The rovings can be used individually or in Tape form can be pulled through the solvent bath lying next to each other. The rovings should be spread as well as possible, i.e. pulled apart flatly, what through known devices can be effected.

The polyetherimide used have average molecular weights (Mn) from 20,000 to 40,000, preferably between 25,000 and 35,000. The fiber content of the soaked roving should preferably be 30 to 85, in particular 45 to 65% by volume be. The fiber content can be determined by the concentration of the impregnation solution and the residence time in the bath, as well as by a pair of nip rollers arranged after the impregnation bath will. Subsequent to the impregnation bar, the impregnated rovings pass through a drying section, where the solvents, preferably at temperatures above 700C, in particular between 80 and 1500C can be evaporated.

The impregnated, synthetic resin-bonded prepreg rovings can - in In the form of single threads or 0.5 to 2 cm wide tapes - non-sticky on spools to be wrapped. They represent a storage-stable semi-finished product that is thermoplastic can be further processed. You can e.g. - if necessary also directly after the Impregnation and drying - after thorough run a preheating section Wind up on cores, connect there by heating to temperatures above 340 ° C and in this way to produce rotationally symmetrical prefabricated parts, e.g. pipes, which no longer have to be post-hardened.

Furthermore, the impregnated roving can be placed directly on a winding core position and only then remove the solvent.

Flat prepregs can be made by having a variety of of rovings in parallel through the impregnation bath and the resulting, preferably 2 to 150 cm wide impregnated, synthetic resin-bonded roving tape after drying cuts into plate-shaped 'pieces' or winds endlessly on spools.

These preferably 0.1 to 0.5 mm thick, unidirectionally fiber-reinforced Prepregs can be stacked in layers, with the individual prepregs can be placed at any angle to each other. The stacks can then go through Compression to give finished parts at temperatures above the melting range of the polyetherimide are processed. The stack is heated outside the press and then placed then in the press, which is at a temperature below the glass transition point of the polyetherimide is held.

The semi-finished and finished parts made with polyetherimide as a matrix have a high heat resistance. For example, the interlaminar shear strength decreases at 1500 C only by 38% of the value at room temperature, the flexural strength is at 1500C and 72 7o of the value at room temperature and the tensile strength at 800C is still 94% of the value at room temperature.

The parts and percentages given in the examples relate to - unless otherwise noted - by weight.

Examples 1) A 1'5%, a 20% and a 25% solution of PEI (Ultem 1000 from General Electric) with an average molecular weight (Mn) from 25,000 - 35,000 were produced at 20 0C by adding pre-dried PEI in granulate form were stirred into dichloromethane until the desired concentration. The viscosity was determined immediately after dissolution and then again after 24 hours at 200 ° C. in each case.

The following values were found: 15% 20% 25% fresh 190 mPas 900 mPas 4,900 mPas 24 hours 190 mPas | 900 mPas - These stable solutions were used to soak glass, carbon and aramid fibers.

2) A glass fiber roving with 1200 tex from Gevetex was made by a Coil boom coming through a soaking bath at a speed of 150 m / h a 20% solution (according to Example 1) drawn. The thermoplastic part was with With the help of the thread tension and a pair of squeegee rollers, it is regulated to 40% by volume. To In the drinking bath, the soaked roving runs through a drying zone, with the solvent was completely withdrawn at 1200C. The dry prepreg roving with a fiber content of 60 vol is wound on a drum and is as long as you like until further processing storage stable.

5) An aramid fiber roving with 7900 tex was soaked as in Example 2 and dried. After being wound onto a storage drum, it had some fiber content of 55% by volume.

4) Aramid fiber rovings with 7900 tex each were made as in Example 3 PEI solution impregnated by running the rovings in parallel is obtained after the drying zone a "prepreg tape" with a width of 12 mm. The fiber content in the dry tape was 50 % By volume. The tape was stored on reels as in the previous examples.

5) A 300 mm wide roving tape made from 170 parallel carbon fiber rovings with 6000 filaments each was through an impregnation bath with a 20% PEI solution (according to Example 1) out, the order regulated with the help of nip rollers, then the solvent was drawn off when passing through a rotary oven and that now dry, unidirectionally reinforced semi-finished product was finished with a sheeter cut into stackable blanks 0.25 mm thick. The fiber content in the t 'repreg plate "was 55% by volume.

6.) A 300 mm wide roving tape made of 94 parallel glass fiber rovings with 1200 tex / rovings was soaked, dried and cut as in Example 5. The unidirectionally reinforced semifinished product obtained had a fiber content of 60% by volume with a nominal thickness of 0.25 mm.

7) A 370 mm wide roving tape made of 100 parallel aramid fibers with 7900 tex / roving was soaked, dried and cut to size as in Example 5. The unidirectionally reinforced semi-finished product obtained had a fiber content of 60 Vol.

%) A prepreg roving produced according to Example 2 with 60 volume p Glass fiber content was processed as follows: 'The prepreg roving was from the coil come through a preheating section, where it is heated to 2500C became.

Then he was on a cylindrical mandrel with 40 mm Diameter and 1 m length. The mandrel was on a winding machine stretched, which made it possible to use the prepreg roving at an angle of 45 ° to To put down the mandrel axis. The winding mandrel itself was largely covered with a reflective apron enclosed.

The temperature required to fuse the deposited prepreg rovings of 3900C is achieved by means of bright radiators. By moving the thread support back and forth could produce a villagiges pipe with + 450C fiber arrangement and 3 mm wall thickness will. After cooling and demolding, the tube had a glass fiber content of 60 % By volume.

9) A prepreg roving produced according to Example 3 was as in Example 8 processed. The resulting tube had a fiber content of 55 vol-2, 10) A carbon fiber prepreg with 40 volume S PEI was made on a winding machine with light emitters and reflection apron processed into pipes for high torsional loads as in Example 8. The mandrel diameter was 50 mm and the length 440 mm. The thread tray in relation on the longitudinal axis took place in the 900 / +450 / 450/900 pattern. After merging was cooled and removed from the mold.

11) The one according to Example 2 was used on a winding machine Prepreg roving with 60 volume S glass fiber a pressure vessel with a cylindrical Wrapped middle part and hemispherical mandrel caps. The diameter was 150 nmi, the length 400 mm. The temperature necessary for the intimate fusion of the prepreg rovings from over 350 ° C was again by means of bright radiators and a reflective apron scored the thorn. At the end of the winding process, it is cooled down and removed from the mold. The wall thickness of the container was 2 mm, the glass content was 60% by volume 12) The semi-finished product from Example 6 was further processed as follows: Eight of these semi-finished panels were unidirectional Fiber orientation placed one on top of the other in a pressing tool and at .3800C for 2 minutes at a pressure of 100 bar to a unidirectionally reinforced 2 mm thick test plate pressed.

13) The semi-finished product from example 6 was processed further as follows: Eight unidirectionally reinforced prepreg sheets were made with the following layer structure layered on top of each other in a pressing tool (angle in relation to the later, test direction) 0 ° / + 45 ° / -45 ° / 0 ° / 0 ° / -45 ° / + 45 ° / 0 ° The pressing conditions were the same as indicated in Example 12, The finished test plate had a tensile strength of 750 N / mm2 in the 0 ° direction, a tensile modulus of elasticity of 25,000 N / mm2 and a shear module of 6000 N / mm2.

The prepreg sheets obtained according to Example 5 with 55 volume SC fiber were further processed as follows. Eight semi-finished panels became more intimate with one Fiber orientation placed one on top of the other in a press tool and at 3800C for 2 minutes long at 100 bar to a unidirectionally reinforced test plate 2 mm thick pressed.

The mechanical test parallel to the fiber direction showed a tensile strength of 1900 NImm2, a tensile modulus of elasticity of 120,000 Nm2, a flexural strength of 1300 N / mm2 and a flexural modulus of 100,000 N / mm2 (values at 23 ° C).

15) The prepreg sheets obtained according to Example 7 with 60% by volume of aramid fibers were processed as follows: Eight semi-finished panels were made with one intimate fiber orientation placed one on top of the other in a pressing tool and at 380 ° C. for 2 minutes with one pressure from 100 bar TO a unidirectionally reinforced test plate with a thickness of 2 mm. The fiber content of the test plate was also 60% by volume.

The mechanical test parallel to the fiber direction showed a tensile strength this material of 1700 N / mm2, a modulus of elasticity of 7600 N / mm2, a flexural strength of 1300 N / mm2.

16) Eight semi-finished panels with unidirectional aramid fiber reinforcement and a fiber content of 50% by volume are placed one above the other in a press tool placed so that the fibers or layers face the planned direction of loading (0 ° direction) include the following angles 0 ° / + 45 ° / -45 ° / 0 ° / 0 ° / -45 ° / + 45 ° / 0 ° As in Example 15, the layer package became a composite with 50% by volume Compressed aramid fiber.

The mechanical test in the 0 ° direction showed a tensile strength of 1000 N / mm2 and a tensile modulus of elasticity of 44,000 N / mm2.

Claims (6)

gatentansprffche 1. Process for the production of thermoplastic deformable, synthetic resin-bound endless fiber strands (prepreg rovings), thereby marked that one leads continuous fiber strands through a bath, where they are treated with a Solution of a polyetherimide are soaked, and then the solvent evaporated. 2. The method according to claim 1, characterized in that one 15 to 25% strength by weight solution of the polyetherimide in dichloromethane is used. 3. The method according to claim 1, characterized in that the Wraps prepreg rovings on a core. 4. Prepreg rovings, produced according to claim 1, characterized in that that they have a fiber content of 3C to 70 vol. 5. A method for the production of flat prepregs, characterized in that that according to claim 1, a plurality of continuous fiber strands through a parallel Soaking bath leads, and the resulting tape is cut into pieces after drying or winds endlessly on bobbins. 6. Flat prenregs, produced according to claim 4, characterized in that that they have a width of 2 to 150 cm.