RU2793890C1 - Method for obtaining finished carbon fibre and polyether ether ketone composite based on it - Google Patents

Abstract

FIELD: carbon fibres.

SUBSTANCE: products manufactured using additive techniques. The method for obtaining dressed carbon fibres includes applying a dressing composition from a solution followed by drying. The sizing composition contains an oligomeric ether ether ketone based on diphenylolpropane, difluorobenzophenone and isophthaloylamide. A polyether ether ketone composite is also proposed.

EFFECT: group of inventions makes it possible to improve the physical-mechanical and rheological properties of a polyester ether ketone composite material containing finished carbon fibre.

2 cl, 1 tbl, 6 ex

Description

The invention relates to a method for obtaining finished carbon fibers and polyetheretherketone composites based on them, and can be used as structural polymeric materials for the production of special-purpose products in additive technologies.

One of the ways to improve the performance of carbon fiber polyether ether ketone composites is to coat the carbon fiber surface with coupling agents, which makes it possible to modify the structure of the interfacial layer and increase intermolecular adhesive interactions at the polymer-filler interface.

Known polymer composite materials containing polyetherketones.

Patent EP0224236A2 is devoted to the creation of polymer compositions with improved chemical resistance and stable molding for injection molding, which contain polyether ketone (PEK), (not polyether ether ketone (PEEK)) aromatic polysulfone, and fillers, including carbon fiber.

EP0316681A2 also describes fibrous composites of polyethersulfone, polyetherketone (not polyetherketone) and carbon fiber. Both patents provide composites obtained from a mixture of two polymers - polyethersulfone, polytherketone, filled with fibers. They do not provide information on the finishing of carbon fibers to obtain PCM with enhanced mechanical properties.

In the patent RU 2278126, publ. 06/20/2006, bull. No. 17 shows the compositions used for crosslinking chains. This paper proposes to use a blend of amino-terminated polyetherketone (not PEEK) and anhydride-terminated polyethersulfone (PES) and copolyetherethersulfone (PEES) copolymers. The mixture is dissolved in a high-boiling solvent, N-methylpyrrolidone, and carbon fibers are treated with it. The disadvantage of the solution is the use of a solvent with a high boiling point (203 ^° C), which is difficult to remove from the composition, and its residues at high operating temperatures of the products will lead to the appearance of bubbles in the castings, and as a result, to a decrease in operational properties.

From the prior art, various types of sizing additives are known that are used in the creation of polymer composite materials. So, in the patent for invention RU 2057767, a polymer composite material is given, which includes a polysulfone polymer and carbon fibers. Carbon fibers contain on the surface as a sizing layer a copolymer consisting of units of methacrylic acid, diethylene glycol and benzosulfonic acid in a molar ratio of 49.5:49.5:1 to 49:49:2 in an amount of 0.52-5.0% of fiber mass in the following ratio of components, wt. %: carbon reinforcing fibers containing a copolymer, 25-75; polysulfone matrix rest. According to the inventors, the use of said copolymer as a sizing layer makes it possible to increase the interlaminar shear strength of polysulfone carbon plastics by a factor of 1.8-2.2. The main disadvantage of the proposed solution is the use of an aqueous medium for applying a mixture of monomers to a carbon tape. Since carbon fibers and tapes are hydrophobic, it is difficult to achieve a uniform distribution of an aqueous solution of a mixture of monomers. As a result of polymerization, incomplete conversion of monomers is also possible, which can lead to the formation and release of water at other stages of obtaining a polymer composite, which will lead to the formation of pores and a decrease in strength characteristics. The presence of benzenesulfonic acid in an aqueous medium will contribute to the accumulation of ions, which will worsen the dielectric properties of materials.

According to the patent of the Russian Federation No. 2201423, polymer compositions were obtained from a polymer binder (sizing) and fiberglass or carbon filler. First, a binder is obtained - an oligomer by the reaction of aromatic tetracarboxylic acid tetranitrile and aromatic bis-o-cyanamine at temperatures of 170-180 ° C. The binder is obtained in the form of a powder. The main disadvantage of this solution is the complexity of the process of obtaining a binder. With incomplete conversion of monomers during synthesis, low molecular weight by-products of the reaction may be released during the combination of the binder with the filler at an elevated temperature, resulting in the formation of voids in the composite material. This will lead to a deterioration in the strength characteristics of the material. In addition, powdered finishes may not cover the surface of the filler evenly enough.

Polyetheretherketone composites are known according to US patent No. 4049613. To increase the wettability of carbon fiber by a polymer matrix, the authors propose to keep the filler in hot nitric acid for three days, which is technologically and economically disadvantageous.

The next patent provides a method for sizing carbon fiber according to RF patent No. 2054015 "Method for sizing carbon fiber for the production of polysulfone carbon fiber." According to the proposed method, the block copolymer is mixed with a solvent. A block copolymer consisting of units of bismethacryloyloxydiethylene glycol phthalate and bismethacryloyloxy triethylene glycol phthalate is used to impregnate the carbon filler, followed by drying to remove the solvent and polymerize the sizing film on the fiber, characterized in that the mixing is carried out in water with simultaneous exposure to ultrasonic radiation at a frequency of 15 to 44 kHz and duration exposure from 5 to 14 minutes. The disadvantages of this method are the use of aqueous solutions of block copolymers for wetting hydrophobic surfaces of carbon fiber and the need for further polymerization on the surface of the filler. The result may be uneven wetting of the filler, and, consequently, a decrease in the properties of the resulting carbon fiber.

The closest analogue is the patent of the Russian Federation No. 2752625, "Polyester composite material based on polyetheretherketone and carbon fiber and a method for its production." The disadvantages of the patent include not too high values of the given physical and mechanical parameters of composite materials and the duration of the process of obtaining finished fibers.

The objective of the present invention is to develop a method for obtaining sized carbon fibers and polyether ether ketone composites based on them with higher values of physical, mechanical and rheological parameters, based on a polyether ether ketone (PEEK) matrix polymer filled with sized carbon fiber (CF).

The task is achieved by the fact that polyetheretherketone composites filled with carbon fibers are obtained by pre-treatment of carbon fiber with a sizing composition, which is a mixture of oligomeric etheretherketone (OG-79) based on diphenylolpropane and difluorobenzophenone with a degree of polycondensation n = 7÷9 and isophthaloylamide (ELISA).

Matrix polyetheretherketone is an industrial polymer PEEK 450, which is a polycondensation product of 1,4-dioxybenzene and 4,4'-difluorodiphenylketone of the formula:

In this case, the following ratios (wt. %) of the components in the filler are taken:

carbon fiber 95.5 OG-79 1.0÷3.5 ELISA 3.5÷1.0

The amount of finished carbon fiber in the composite material corresponds to 10 wt. %. Such treatment with a sizing composition increases the wettability of the filler with a sizing composition, makes it possible to repeatedly heat treat the resulting product, if necessary, without changing the properties of the sizing agent.

The carbon filler is coated with a sizing composition by processing in a by-product of the production of ethyl alcohol - the head fraction (ESHF).

Composite materials of the present invention are obtained by pre-mixing the polymer matrix and sized carbon fiber using a high-speed homogenizer Multi function disintegrator VLM-40B. Then the polymer mixture is extruded using a laboratory twin-screw extruder with three heating zones at processing temperatures of 200 °C, 315 °C, 355 °C. RK-306 grade carbon fiber (IFI Technical Production) and PEEK 450 grade industrial polyether ether ketone grade with a reduced viscosity of 0.36 dl/g, measured from a 1% solution in concentrated sulfuric acid, were used.

Below are examples illustrating the method of obtaining finished carbon fibers, the sizing composition is applied from a solution with a mass concentration of 0.7 mass. % in an organic volatile solvent.

Example 1. Obtaining finished CF with 1.0 wt. % OG-79 and 3.5 wt. % ELISA.

23.875 g (95.5 wt.%) of HC with a fiber length of 0.2 mm is placed in a three-necked reaction flask equipped with a stirrer, nitrogen gas supply and a direct condenser, and the solution obtained by dissolving 0.25 g (1.0 wt. %) OG-79 and 0.875 g (3.5 wt. %) ELISA in 172.5 ml of ESHF (0.7 wt. % solution). The flask is placed in a water bath, the stirrer is turned on, the nitrogen supply is turned on, and the flask is kept at 25 °C for 10 minutes. Then, the contents of the flask are heated and the ESHF is distilled off according to the regime: 35 ° C - 15 minutes; 55 °С - 15 min.; 65 °С - 10 min.; 85 °С - 15 min.

The dressed fiber is dried in a vacuum oven at 88-90 ^° C for 2 hours.

Example 2. Obtaining finished CF with 1.5 wt. % OG-79 and 3.0 wt. % ELISA.

23.875 g (95.5 wt.%) of HC with a fiber length of 0.2 mm is placed in a three-necked reaction flask equipped with a stirrer, a supply of gaseous nitrogen and a direct condenser and a solution obtained by dissolving 0.375 g (1.5 wt.%) OG-79 and 0.75 g (3.0 wt. %) of ELISA in 172.5 ml of ESHF (0.7 wt. % solution). The flask is placed in a water bath, the stirrer is turned on, the nitrogen supply is turned on, and the flask is kept at 25 °C for 10 minutes. Then, the contents of the flask are heated and the ESHF is distilled off according to the regime: 35 ° C - 15 minutes; 55 °С - 15 min.; 65 °С - 10 min.; 85 °С - 15 min.

The dressed fiber is dried in a vacuum oven at 88-90 ^° C for 2 hours.

Example 3. Obtaining finished CF with 2.0 wt. % OG-79 and 2.5 wt. % ELISA.

23.875 g (95.5 wt.%) of HC with a fiber length of 0.2 mm is placed in a three-necked reaction flask equipped with a stirrer, nitrogen gas supply and a direct condenser, and the solution obtained by dissolving 0.5 g (2.0 wt. %) OG-79 and 0.625 g (2.5 wt. %) ELISA in 172.5 ml of ESHF (0.7 wt. % solution). The flask is placed in a water bath, the stirrer is turned on, the nitrogen supply is turned on, and the flask is kept at 25 °C for 10 minutes. Then, the contents of the flask are heated and the ESHF is distilled off according to the regime: 35 ° C - 15 minutes; 55 °С - 15 min.; 65 °С - 10 min.; 85 °С - 15 min.

The dressed fiber is dried in a vacuum oven at 88-90 ^° C for 2 hours.

Example 4. Obtaining finished HC with 2.5 wt. % OG-79 and 2.0 wt. % ELISA.

23.875 g (95.5 wt. %) of HC with a fiber length of 0.2 mm is placed in a three-necked reaction flask equipped with a stirrer, a supply of gaseous nitrogen and a direct condenser and a solution obtained by dissolving 0.625 g (2.5 wt. %) OG-79 and 0.5 g (2.0 wt. %) ELISA in 172.5 ml ESHF (0.7 wt. % solution). The flask is placed in a water bath, the stirrer is turned on, the nitrogen supply is turned on, and the flask is kept at 25 °C for 10 minutes. Then, the contents of the flask are heated and the ESHF is distilled off according to the regime: 35 ° C - 15 minutes; 55 °С - 15 min.; 65 °С - 10 min.; 85 °С - 15 min.

The dressed fiber is dried in a vacuum oven at 88-90 ^° C for 2 hours.

Example 5. Obtaining finished CF with 3.0 wt. % OG-79 and 1.5 wt. % ELISA.

23.875 g (95.5 wt.%) of HC with a fiber length of 0.2 mm is placed in a three-necked reaction flask equipped with a stirrer, nitrogen gas supply and a direct condenser, and the solution obtained by dissolving 0.75 g (3.0 wt. %) OG-79 and 0.375 g (1.5 wt. %) ELISA in 172.5 ml of ESHF (0.7 wt. % solution). The flask is placed in a water bath, the stirrer is turned on, the nitrogen supply is turned on, and the flask is kept at 25 °C for 10 minutes. Then, the contents of the flask are heated and the ESHF is distilled off according to the regime: 35 ° C - 15 minutes; 55 °С - 15 min.; 65 °С - 10 min.; 85 °С - 15 min.

The dressed fiber is dried in a vacuum oven at 88-90 ^° C for 2 hours.

Example 6. Obtaining finished CF with 3.5 wt. % OG-79 and 1.0 wt. % ELISA.

23.875 g (95.5 wt.%) of HC with a fiber length of 0.2 mm is placed in a three-necked reaction flask equipped with a stirrer, a supply of gaseous nitrogen and a direct condenser, and a solution obtained by dissolving 0.875 g (3.5 wt.%) OG-79 and 0.25 g (1.0 wt. %) ELISA in 172.5 ml of ESHF (0.7 wt. % solution). The flask is placed in a water bath, the stirrer is turned on, the nitrogen supply is turned on, and the flask is kept at 25 °C for 10 minutes. Then, the contents of the flask are heated and the ESHF is distilled off according to the regime: 35 ° C - 15 minutes; 55 °С - 15 min.; 65 °С - 10 min.; 85 °С - 15 min.

The dressed fiber is dried in an oven under vacuum at 88-90°C for 2 hours.

Composite materials containing 10 wt. % of carbon fibers finished with a mixture of OG-79 and ELISA.

Table 1 shows the compositions and physical and mechanical properties of composite materials containing various amounts of sizing composition according to examples 1-6.

Table 1

Compound PTR,
g/10 min А _r , kJ/m²
11 J
s/n E _izg ,
MPa E _growth , GPa σ _grow,
MPa σ _current,
MPa PEEK 450 + 10% UV 0.2 mm raw 4.46 8.65 5.9 4.74 105 110.3 According to example 1 5.82 9.45 5.91 4.97 110.2 112.7 According to example 2 5.93 10.9 5.91 5.13 113.6 113.8 According to example 3 6.25 11.8 5.94 5.21 115.4 114.3 According to example 4 6.29 12.1 5.94 5.22 115.7 114.3 According to example 5 6.33 12.5 5.96 5.27 116.8 115.8 According to example 6 6.36 12.3 5.98 5.26 116.5 116.1

where, MFR is the melt flow index, A _p is notched impact strength, E izg is the modulus of elasticity in bending, σ _rast and E _rast are the breaking stress and tensile modulus of elasticity; σ _tech - tensile yield strength.

As can be seen from the above results, polyetheretherketone composites containing sized CFs (nos. 1-6) exhibit higher physical, mechanical and rheological properties compared to a composite containing untreated carbon fiber.

The technical result of the invention is to reduce the time of the process of obtaining finished fibers, and improve the physico-mechanical and rheological properties of the created polyester ether ketone composites by introducing a sizing composition - an oligomeric ether ether ketone based on diphenylolpropane and difluorobenzophenone with a degree of polycondensation n = 7÷9 and isophthaloylamide, which increases wettability of the carbon fiber, and increases the interface interactions between the filler and the polyether ether ketone matrix. In addition, the ethyl alcohol of the head fraction, which is a by-product in the production of ethanol, is utilized.

Claims (4)

1. A method for producing finished carbon fibers intended for structural products in additive technologies, based on finishing carbon fiber by applying a sizing composition from a solution, followed by drying in an oven under vacuum at 88-90 ° C, characterized in that the sizing composition is oligomeric etheretherketone based on diphenylolpropane and difluorobenzophenone with a degree of polycondensation n=7-9 (OG-79) and isophthaloylamide (ELISA) is applied from a solution with a mass concentration of 0.7 wt. % in an organic volatile solvent - ethyl alcohol of the head fraction and carry out a stepwise rise in temperature with simultaneous distillation of the solvent according to the regime: 25 ° C - 10 min; 35°С - 15 min; 55°C - 15 min; 65°C - 10 min; 85°C - 15 min, and the quantitative ratio of the components corresponds, wt. %: carbon fiber 95.5 OG-79 1.0-3.5 ELISA 3.5-1.0 2. Polyetheretherketone composite intended as structural polymeric materials for the production of products in additive technologies, based on polyetheretherketone and carbon fiber treated with a sizing composition, characterized in that the sized carbon fiber obtained by the method according to claim 1 is used, moreover, the quantitative ratio of components in polyetheretherketone composite corresponds, wt. %: polyetheretherketone 90 finished carbon fiber 10