RU2798166C1 - Method for obtaining treated carbon fibres and polyether ether ketone compositions based on them - Google Patents

Abstract

FIELD: production of structural products using additive techniques.

SUBSTANCE: claimed method for producing sized carbon fibre consists of applying a sizing, which is a mixture of bis(4-chlorophenyl)methanone 0.4-3.6 wt.% and bis(4-aminophenyl)methanone 3.6-0.4 wt.%, on carbon fibre from a solution with a mass concentration of 0.54% in a mixture of ethyl alcohol 75 vol.% and methylene chloride 25 vol.%, followed by heating to 85°C and simultaneous distillation of solvents. Finished carbon fibre obtained by the proposed method, and polyether ether ketone composition, which contains 80 wt.% of a polymer matrix based on polyether ether ketone and 20 wt.% of the proposed finished carbon fibre are also claimed.

EFFECT: improvement of the physical, mechanical and rheological properties of the created polyether ether ketone composition due to introduction of a sizing composition, which increases the wettability of the filler and increases the boundary interactions between the filler and the polyether ether ketone matrix.

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Description

The invention relates to a method for obtaining sized carbon fibers and polyetheretherketone compositions 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 compositions 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 tetranitrile aromatic tetracarboxylic acid 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 coupling agents may not evenly cover the surface of the filler.

Polyetheretherketone composites are known under US Pat. No. 4,049,613. In order to increase the wettability of carbon fiber by a polymer matrix, the authors propose keeping the filler in hot nitric acid for three days, which is technologically and economically disadvantageous.

A known method of finishing carbon fiber according to the patent of the Russian Federation No. 2054015 "Method of finishing 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 method of finishing carbon fiber according to RF patent No. 2744893. "Polymeric carbon fiber composition and method for its production". The patent proposes to use hydroquinone as a sizing component of carbon fiber (carbon fiber, CF). The disadvantages of the proposed solution is the low stability of the coupling agent at elevated temperatures, which will lead to a decrease in the performance characteristics of the compositions.

The objective of the present invention is to develop a method for obtaining sized carbon fibers and polyether ether ketone compositions 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).

This task is achieved by the fact that polyetheretherketone compositions filled with carbon fibers are obtained by pre-treatment of carbon fiber with a sizing composition, which is a mixture of bis(4-aminophenyl)methanone (4-AFM) and bis(4-chlorophenyl)methanone (4-CFM).

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 96.0 4-HFM 0.4÷3.6 4-AFM 3.6÷0.4

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.

The carbon filler is coated with a sizing composition by processing in a mixture of a by-product of the production of ethyl alcohol - the head fraction (ESHF), 75 vol.%, and methylene chloride (MC), 25 vol. %.

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. Used carbon fiber brand RK-306 (IFI Technical Production) and industrial polyetheretherketone brand PEEK 450 with a reduced viscosity of 0.35 dl/g, measured for 1 wt. % solution in concentrated sulfuric acid.

Below are examples illustrating the method of obtaining finished carbon fibers.

Example 1. Obtaining finished CF with 0.4 wt. % 4-CFM and 3.6 wt. % 4-APM.

24.0 g (96.0 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 0.1 g (0.4 wt.%) 4-CPM and 0.9 g (3.6 wt.%) 4-APM in a mixture of 135 ml of ESHF and 45 ml of MQ (0.54% solution). The flask is placed in a water bath, the stirrer is turned on, nitrogen is supplied, and it is kept at 25°C for 12 minutes. 55°С - 10 min.; 65°С - 12 min.; 85°C - 12 min.

The dressed fiber is dried in an oven under vacuum at 91-92°C for 2 hours.

Example 2. Obtaining finished CF with 1.2 wt. % 4-CFM and 2.8 wt. % 4-APM.

24.0 g (96.0 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 0.3 g (1.2 wt.%) 4-CPM and 0.7 g (2.8 wt.%) 4-APM in a mixture of 135 ml of ESHF and 45 ml of MQ (0.54% solution). The flask is placed in a water bath, include a stirrer, nitrogen supply, and incubated at 25°C for 12 minutes. Then, the contents of the flask are heated and ESHF and MX are distilled off according to the regime: 30°C - 12 min.; 55°С - 10 min.; 65°С - 12 min.; 85°C - 12 min.

The dressed fiber is dried in an oven under vacuum at 91-92°C for 2 hours.

Example 3. Obtaining finished CF with 2.0 wt. % 4-CFM and 2.0 wt. % 4-APM.

24.0 g (96.0 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.%) 4-CFM and 0.5 g (2.0 wt.%) 4-APM in a mixture of 135 ml of ESHF and 45 ml of MQ (0.54% solution). The flask is placed in a water bath, include a stirrer, nitrogen supply, and incubated at 25°C for 12 minutes. Then, the contents of the flask are heated and ESHF and MX are distilled off according to the regime: 30°C - 12 min.; 55°С - 10 min.; 65°С - 12 min.; 85°C - 12 min.

The dressed fiber is dried in an oven under vacuum at 91-92°C for 2 hours.

Example 4. Obtaining e finished HC with 2.8 wt. % 4-CFM and 1.2 wt. % 4-APM.

24.0 g (96.0 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 0.7 g (2.8 wt.%) 4-CFM and 0.3 g (1.2 wt.%) 4-APM in a mixture of 135 ml of ESHF and 45 ml of MQ (0.54% solution). The flask is placed in a water bath, include a stirrer, nitrogen supply, and incubated at 25°C for 12 minutes. Then, the contents of the flask are heated and ESHF and MX are distilled off according to the regime: 30°C - 12 min.; 55°С - 10 min.; 65°С - 12 min.; 85°C - 12 min.

The dressed fiber is dried in an oven under vacuum at 91-92°C for 2 hours.

Example 5. Obtaining finished CF with 3.6 wt. % 4-CFM and 0.4 wt. % 4-APM.

24.0 g (96.0 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 0.9 g (3.6 wt.%) 4-CPM and 0.1 g (0.4 wt.%) 4-APM in a mixture of 135 ml of ESHF and 45 ml of MQ (0.54% solution). The flask is placed in a water bath, include a stirrer, nitrogen supply, and incubated at 25°C for 12 minutes. Then, the contents of the flask are heated and ESHF and MX are distilled off according to the regime: 30°C - 12 min.; 55°С - 10 min.; 65°С - 12 min.; 85°C - 12 min.

The dressed fiber is dried in an oven under vacuum at 91-92°C for 2 hours.

Polyether ether ketone compositions containing 20 wt. % finished with a mixture of 4-CFM and 4-AFM carbon fibers.

Table 1 presents the compositions, as well as the rheological and physico-mechanical properties with sizing carbon fibers of polyether ether ketone compositions according to examples 1-5, treated with various amounts of sizing composition.

Table 1 Compound А _r , kJ/m²
11 J, s/n _σgrowth ,
MPa ε, % PEEK 450+20% UV 0.2 mm unseamed 7.0 132.2 3.7 According to example 1 7.37 138.4 3.95 According to example 2 7.78 140.1 4.45 According to example 3 7.79 142.9 4.62 According to example 4 7.86 143.7 4.74 According to example 5 7.87 143.6 4.60

where, And _p - notched impact strength, σ _rast - tensile strength; ε, % - relative elongation in tension after sample failure.

As can be seen from the above results, polyetheretherketone compositions containing sized CFs (Nos. 1-5) exhibit higher physical, mechanical and rheological properties compared to a composition containing untreated carbon fiber.

The technical result of the invention is to improve the physico-mechanical and rheological properties of the created polyether ether ketone compositions by introducing a sizing composition - bis (4-aminophenyl) methanone and bis (4-chlorophenyl) methanone, which increases the wettability of carbon fiber, and increases the boundary interactions between filler and polyetheretherketone matrix. In addition, the head fraction of the production of ethyl alcohol, which is a by-product in the production of ethanol, is utilized.

Claims (5)

1. A method for producing sized carbon fibers intended for structural polymeric materials in additive technologies based on sizing carbon fiber by applying a sizing composition from a solution followed by drying in an oven under vacuum at 90-92 ° C, characterized in that the sizing composition, which is a mixture of bis (4-aminophenyl) methanone (4-AFM) and bis (4-chlorophenyl) methanone (4-CFM), is applied from a solution with a mass concentration of 0.54% in a mixture of solvents - ethyl alcohol of the head fraction 75 vol .% and methylene chloride 25 vol.% and heating is carried out with the distillation of solvents according to the regime: 25 ° C - 12 min; 30°C - 12 min; 55°C - 10 min; 65°C - 12 min; 85°C - 12 min, and the quantitative ratio of the components corresponds in wt.%: carbon fiber 96.0 4-HFM 0.4 - 3.6 4-AFM 3.6 - 0.4 2. Finished carbon fiber for structural products in additive technologies, obtained by the method according to claim 1. 3. Polyetheretherketone composition intended as a structural polymeric material used for the production of products in additive technologies, containing a polymer matrix based on polyetheretherketone and finished carbon fiber, characterized in that the finished carbon fiber according to claim 2 is used, moreover, the quantitative ratio of components in polyetheretherketone composition corresponds in wt.%: Polyetheretherketone 80 Finished carbon fiber 20