RU2802447C1 - Method for obtaining finished carbon fibres and composites based on them - Google Patents

Abstract

FIELD: carbon fibre production.

SUBSTANCE: invention is related to a method for producing finished carbon fibres and polyether ether ketone composites based on them. A method for obtaining finished carbon fibres intended for structural polymeric materials in additive technologies is described, based on finishing of carbon fibre by applying a finishing component from a solution, followed by drying, in an oven under vacuum at 85-86°C, characterized in that the sizing component is applied as solutions with a mass concentration of 0.23÷0.46% obtained by dissolving epoxypolyether (EPPE) based on epichlorohydrin and 1,3-dioxibenzene with a degree of polycondensation n=115-120 in an organic solvent in trichloromethane and a stepwise increase in temperature is carried out with simultaneous distillation of the solvent in the following way: 20°C - 11 min; 35°C - 11 min; 45°C - 11 min; 60°C - 10 min; 65°C - 20 min, and the quantitative ratio of the components corresponds to the following wt.%: carbon fibre 96-98; EPPE 4-2. A carbon fibre polyester ether ketone composite is also described, intended as a structural polymer material used for production of special-purpose products in additive technologies, containing a polymer matrix based on polyether ether ketone and finished carbon fibre, characterized in that it uses a finished carbon fibre obtained by the above method, and the ratio of components in polyetheretherketone composite corresponds to the following wt.%.: Polyetheretherketone 80, finished carbon fibre 20.

EFFECT: improving physical and mechanical properties of the created polyetheretherketone composite due to introduction of a sizing component that increases wettability of the filler and increases intermolecular interactions between carbon fibre and the polyetheretherketone matrix.

2 cl, 1 tbl, 5 ex

Description

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

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

Beginning of the form

Polymer composite materials containing polyether ketones are known.

Patent EP0224236A2 focuses on the creation of polymer compositions with improved chemical resistance and stable molding for injection molding that contain polyetheretherketone (PEK), (not polyetheretherketone (PEEK)), aromatic polysulfone, and fillers, including carbon fiber.

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

In patent RU 2278126, publ. 06/20/2006, bulletin. No. 17 shows compositions used for stitching chains. This work proposes the use of a mixture of amine-terminated polyetheretherketone (non-PEEK) and anhydride-terminated copolymers of polyethersulfone (PES) and copolyetherethersulfone (PEES). 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 ^o 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 performance properties.

Various types of sizing additives used in the creation of polymer composite materials are known from the prior art. Thus, the patent for invention RU 2057767 describes a polymer composite material, 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 from 49.5:49.5:1 to 49:49:2 in an amount of 0.52-5.0% of fiber mass with the following ratio of components, mass. %: carbon reinforcing fibers containing copolymer, 25-75; polysulfone matrix the rest. According to the authors of the invention, the use of the specified copolymer as a sizing layer makes it possible to increase the interlayer shear strength of polysulfone carbon plastics by 1.8-2.2 times. The main disadvantage of the proposed solution is the use of an aqueous medium to apply a mixture of monomers to the carbon tape. Since carbon fibers and tapes are hydrophobic, it is difficult to achieve uniform distribution of the aqueous solution of the monomer mixture. 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 environment will contribute to the accumulation of ions, which will worsen the dielectric properties of materials.

According to RF patent No. 2201423, polymer compositions were obtained from a polymer binder (sizing agent) 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 powder form. The main disadvantage of this solution is the complexity of the process of obtaining the binder. With incomplete conversion of monomers during synthesis, the release of by-products of low molecular weight reaction may occur during the combination of the binder with the filler at elevated temperatures, 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 sizing agents 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 the polymer matrix, the authors propose keeping the filler in hot nitric acid for three days, which is technologically and economically unprofitable.

There is a known method for sizing carbon fiber according to RF patent No. 2054015 “Method for sizing carbon fiber for the production of polysulfone carbon fiber plastic.” According to the proposed method, the block copolymer is mixed with a solvent. A block copolymer consisting of bismethacryloyloxydiethylene glycol phthalate and bismethacryloyloxy-triethylene glycol phthalate units 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 mixing is carried out in water with simultaneous exposure to ultrasonic radiation at a frequency of 15 to 44 kHz and duration ness exposure from 5 to 14 minutes. The disadvantages of this method are the use of aqueous solutions of block copolymers to wet the hydrophobic surfaces of carbon fiber and the need for further polymerization on the surface of the filler. The consequence may be uneven wetting of the filler, and, consequently, a decrease in the properties of the resulting carbon fiber reinforced plastic.

The closest analogue is the method of finishing carbon fiber according to RF patent No. 2744893. “Polymer carbon fiber composition and method for its production.” The patent proposes using hydroquinone as a sizing component for carbon fiber (carbon fiber, CF). The disadvantages of the proposed solution are the low stability of the sizing 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 producing finished carbon fibers and polyetheretherketone composites based on them with higher values of physical and mechanical properties, based on a polyetheretherketone (PEEK) matrix polymer filled with dressed carbon fiber.

This task is achieved by the fact that polyetheretherketone composites filled with carbon fibers are obtained by pre-treating the carbon fiber with a sizing component, which is epoxy polyester (EPPE) based on epichlorohydrin and 1,3-dioxybenzene with a degree of polymerization n = 115÷120:

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

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

Carbon fiber 96 ÷ 98 EPPE 4 ÷ 2

The amount of finished carbon fiber in the composite material corresponds to 20 wt. %. Such treatment with a sizing composition increases the wettability of the filler with the sizing composition and makes it possible to repeatedly heat treat the resulting product, if necessary, without changing the properties of the sizing composition.

The carbon filler is coated with a sizing composition by treatment with trichloromethane, followed by drying to constant weight.

The composites of the present invention are prepared by pre-mixing the polymer matrix and finished carbon fiber using a high-speed Multi function disintegrator VLM-40B homogenizer. Then the polymer mixture is extruded using a laboratory twin-screw extruder with three heating zones at processing temperatures of 200 ^o C, 315 ^o C, 355 ^o C. Carbon fiber grade RK-306 (IFI Technical Production) and industrial polyetheretherketone grade PEEK 450 with the given viscosity 0.37 dl/g, measured for a 1% solution in concentrated sulfuric acid.

Below are examples illustrating the method of producing sintered carbon fibers.

Example 1

In a three-neck round-bottomed flask equipped with a direct refrigerator, a device for supplying nitrogen gas, a heater and a mechanical stirrer, place 24.5 g (98 wt.%) of discrete hydrocarbons with a fiber length of 0.2 mm and add the solution obtained by dissolving 0.5 g (2 wt.%) EPPE in 145 ml of trichloromethane (0.23% solution). Turn on the stirrer, nitrogen supply and stir for 11 minutes at 20 °C. Next, the contents of the flask are heated and trichloromethane is distilled off according to the following regime: 35 °C - 11 minutes; 45 °C - 11 min.; 60 °C - 10 min.; 65 °C - 20 min.

The dressed fiber is dried in a drying oven under vacuum at 85-86 ^o C for 2 hours.

Example 2

In a three-neck round-bottomed flask equipped with a direct refrigerator, a device for supplying nitrogen gas, a heater and a mechanical stirrer, place 24.375 g (97.5 wt%) of discrete hydrocarbons with a fiber length of 0.2 mm and add the solution obtained by dissolving 0.625 g (2 .5 wt.%) EPPE in 145 ml of trichloromethane (0.29% solution). Turn on the stirrer, nitrogen supply and stir for 11 minutes at 20 °C. Next, the contents of the flask are heated and trichloromethane is distilled off according to the following regime: 35 °C - 11 minutes; 45 °C - 11 min.; 60 °C - 10 min.; 65 °C - 20 min.

The dressed fiber is dried in a drying oven under vacuum at 85-86 ^o C for 2 hours.

Example 3

In a three-neck round-bottomed flask equipped with a direct refrigerator, a device for supplying nitrogen gas, a heater and a mechanical stirrer, place 24.25 g (97.0 wt%) of discrete hydrocarbons with a fiber length of 0.2 mm and add the solution obtained by dissolving 0. 75 g (3 wt.%) EPPE in 145 ml of trichloromethane (0.35% solution). Turn on the stirrer, nitrogen supply and stir for 11 minutes at 20 °C. Next, the contents of the flask are heated and trichloromethane is distilled off according to the following regime: 35 °C - 11 minutes; 45 °C - 11 min.; 60 °C - 10 min.; 65 °C - 20 min.

The dressed fiber is dried in a drying oven under vacuum at 85-86 ^o C for 2 hours.

Example 4

In a three-neck round-bottomed flask equipped with a direct refrigerator, a device for supplying nitrogen gas, a heater and a mechanical stirrer, place 24.125 g (96.5 wt%) of discrete hydrocarbons with a fiber length of 0.2 mm and add the solution obtained by dissolving 0.875 g (3 .5 wt.%) EPPE in 145 ml of trichloromethane (0.41% solution). Turn on the stirrer, nitrogen supply and stir for 11 minutes at 20 °C. Next, the contents of the flask are heated and trichloromethane is distilled off according to the following regime: 35 °C - 11 minutes; 45 °C - 11 min.; 60 °C - 10 min.; 65 °C - 20 min.

The dressed fiber is dried in a drying oven under vacuum at 85-86 ^o C for 2 hours.

Example 5

In a three-neck round-bottomed flask equipped with a direct refrigerator, a device for supplying nitrogen gas, a heater and a mechanical stirrer, place 24.0 g (96 wt.%) of discrete hydrocarbons with a fiber length of 0.2 mm and add the solution obtained by dissolving 1.0 g (4 wt.%) EPPE in 145 ml of trichloromethane (0.46% solution). Turn on the stirrer, nitrogen supply and stir for 11 minutes at 20 °C. Next, the contents of the flask are heated and trichloromethane is distilled off according to the following regime: 35 °C - 11 minutes; 45 °C - 11 min.; 60 °C - 10 min.; 65 °C - 20 min.

The dressed fiber is dried in a drying oven under vacuum at 85-86 ^o C for 2 hours.

Polymer composites containing 20 wt.% were obtained from finished CF and PEEK. % HC (Table 1).

Table 1

Properties of carbon fiber polyetheretherketone composites

Compound E _izg ,
MPa σ _izg,
MPa E _rise, GPa σ _rise,
MPa ε, % PEEK 450 + 20% HC 0.2 mm 13.6 240.6 8.75 132.2 3.7 Following example1 13.84 244.9 9.24 139.6 3.72 According to example 2 14.06 248.7 9.61 145.2 3.76 According to example 3 14.17 250.6 9.75 147.3 4.25 According to example 4 14.27 252.4 9.84 148.7 4.53 According to example 5 14.23 251.8 9.82 148.3 4.48

where, σ _bend and E _bend are the breaking stress and elastic modulus in bending; σ _grow and E _grow - breaking stress and tensile modulus of elasticity, ε, % - relative tensile elongation

The data presented in the table show that composite materials containing coated carbon fibers (examples No. 1-5) have higher values of physical and mechanical properties compared to the unfinished sample (first row).

The technical result of the present invention is to improve the physical and mechanical properties of the created carbon fiber polyetheretherketone composites due to the introduction of epoxy polyester based on epichlorohydrin and 1,3-dioxybenzene with a degree of polymerization n = 115÷120, which increases the wettability of carbon fiber and increases intermolecular interactions between the filler and polyetheretherketone matrix.

Claims (4)

1. A method for producing sizing carbon fibers intended for structural polymer materials in additive technologies, based on sizing carbon fiber by applying a sizing component from a solution followed by drying in a drying oven under vacuum at 85-86°C, characterized in that the sizing component applied from solutions with a mass concentration of 0.23÷0.46%, obtained by dissolving epoxy polyether (EPPE) based on epichlorohydrin and 1,3-dioxybenzene with a degree of polycondensation n = 115-120 in an organic solvent in trichloromethane and carry out a stepwise increase in temperature with simultaneous distillation of the solvent according to the following mode: 20°C - 11 min; 35°C - 11 min; 45°C - 11 min; 60°C - 10 min; 65°C - 20 min, and the quantitative ratio of the components corresponds to wt. %: Carbon fiber 96 ÷ 98 EPPE 4 ÷ 2 2. Carbon fiber polyetheretherketone composite, intended as a structural polymer material used for the production of special-purpose products in additive technologies, containing a polymer matrix based on polyetheretherketone and coated carbon fiber, characterized in that coated carbon fiber is used, obtained by the method according to claim 1, wherein the quantitative ratio of the components in the polyetheretherketone composite corresponds to wt. %: Polyetheretherketone 80 Finished carbon fiber 20