RU2811395C1 - Method for obtaining finished carbon fiber and polyetheretherketone composite material - Google Patents

Abstract

FIELD: carbon fiber.

SUBSTANCE: method for producing finished carbon fibers and polyetheretherketone composites based on them. To obtain a modified material, a finished composition is applied to the fiber, followed by drying at 50-51°C. The finished composition is 0.7 wt.% solution of a mixture of copolyepoxyether based on diane, phenolphthalein and epichlorohydrin (CPEEDP) with 2,4-toluylenediamine (2,4-TDA) in acetone and methylene chloride. The resulting composition is kept at 20°C for 4 minutes and a stepwise increase in temperature with distillation of solvents is carried out according to the following regime: 27° C – 5 min; 33° C – 5 min; 53° C – 4 min; 63° C – 13 min. The content of components in the resulting composition is (wt.%): carbon fiber 95.5; copolyepoxyether based on diane, phenolphthalein and epichlorohydrin (CPEEDF) 1.0÷3.5; 2,4-toluylenediamine (2,4-TDA) 3.5÷1.0.

EFFECT: reducing the duration of the carbon fiber sizing process and improving the physical, mechanical and rheological properties of the created polyetheretherketone composite material by introducing a finished composition that increases the wettability of the filler and increasing the intermolecular interactions between the carbon fiber and the polyetheretherketone matrix.

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Description

The invention relates to a method for producing finished carbon fibers and polyetheretherketone composite materials, 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 composite materials 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.

Polymer composite materials containing polyether ketones are known.

Patent EP 0224236 A2 is devoted to the creation of polymer compositions with improved chemical resistance and stable molding for injection molding, which contain polyetheretherketone (PEK), (not polyetheretherketone (PEEK)), aromatic polysulfone, and fillers, including carbon fiber.

EP 0316681 A2 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°C), which is difficult to remove from the composition, and its residues at high operating temperatures of 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 - an oligomer - is obtained 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 a polymer matrix, the authors propose keeping the filler in hot nitric acid for three days, which is technologically and economically unprofitable.

The following patent describes a method for sizing carbon fiber according to RF patent No. 2054015 “Method for sizing carbon fiber for the production of polysulfone carbon fiber reinforced 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 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 RF patent No. 2752625, “Polymer composite material based on polyetheretherketone and carbon fiber and a method for its production.” The disadvantages of the patent include the not too high values of the given physical and mechanical parameters of composite materials and the duration of the process of obtaining coated fibers.

The objective of the present invention is to develop a method for producing sizing carbon fibers with a shorter duration of the sizing process, and polyetheretherketone composite materials with higher values of physical, mechanical and rheological properties, based on a matrix polymer polyetheretherketone (PEEK) filled with sizing carbon fiber (carbon fiber, CF).

This task is achieved by the fact that polyetheretherketone composite materials filled with carbon fibers are obtained by pre-treating the carbon fiber with a sizing composition, which is a mixture of copolyepoxyether based on diane, phenolphthalein and epichlorohydrin (SPEEDF) with a degree of polycondensation n=85÷90 and 2,4-toluylenediamine .

The 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 (mass %) of the components in the filler are taken:

Carbon fiber 95.5 SPEEDF 1.0÷3.5 2,4-TDA 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 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 in a mixture of methylene chloride and acetone.

The composite materials 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°C, 315°C, 355°C. The carbon fiber used was RK-306 (IFI Technical Production) and industrial grade PEEK 450 polyetheretherketone with a reduced viscosity of 0.32 dl/g measured for a 1% solution in concentrated sulfuric acid.

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

Example 1. Preparation of finished hydrocarbon with 1.0 wt. % SPEEDF and 3.5 wt. % 2,4-TDA.

23.875 g (95.5 wt%) of hydrocarbons with a fiber length of 0.2 mm are placed in a three-neck reaction flask equipped with a stirrer, a supply of nitrogen gas and a direct refrigerator, and a solution obtained by dissolving 0.25 g (1.0 wt.) is added. %) SPEEDF and 0.875 g (3.5 wt. %) 2,4-TDA in a mixture of 110 ml of acetone and 55 ml of methylene chloride (0.7% solution). The flask is placed in a water bath, the stirrer is turned on, the nitrogen supply is turned on, and kept at 20°C for 4 minutes. Then, the contents of the flask are heated and the solvents are distilled off according to the following regime: 27°C - 5 minutes; 33°C - 5 min.; 53°C - 4 min.; 63°C - 13 min.

The dressed fiber is dried in a drying cabinet under vacuum at 50-51°C for 2 hours.

Example 2. Preparation of finished hydrocarbon with 1.5 wt. % SPEEDF and 3.0 wt. % 2,4-TDA.

23.875 g (95.5 wt%) of a hydrocarbon with a fiber length of 0.2 mm is placed in a three-neck reaction flask equipped with a stirrer, a supply of nitrogen gas and a direct cooler, and the solution obtained by dissolving 0.375 g (1.5 wt%) is added. SPEEDF and 0.75 g (3.0 wt%) 2,4-TDA in a mixture of 110 ml of acetone and 55 ml of methylene chloride (0.7% solution). The flask is placed in a water bath, the stirrer is turned on, the nitrogen supply is turned on, and kept at 20°C for 4 minutes. Then, the contents of the flask are heated and the solvents are distilled off according to the following regime: 27°C - 5 minutes; 33°C - 5 min.; 53°C - 4 min.; 63°C - 13 min.

The dressed fiber is dried in a drying cabinet under vacuum at 50-51°C for 2 hours.

Example 3. Preparation of finished hydrocarbon with 2.0 wt. % SPEEDF and 2.5 wt. % 2,4-TDA.

23.875 g (95.5 wt%) of hydrocarbons with a fiber length of 0.2 mm are placed in a three-neck reaction flask equipped with a stirrer, a supply of nitrogen gas and a direct cooler, and a solution obtained by dissolving 0.5 g (2.0 wt.) is added. %) SPEEDF and 0.625 g (2.5 wt%) 2,4-TDA in a mixture of 110 ml of acetone and 55 ml of methylene chloride (0.7% solution). The flask is placed in a water bath, the stirrer is turned on, the nitrogen supply is turned on, and kept at 20°C for 4 minutes. Then, the contents of the flask are heated and the solvents are distilled off according to the following regime: 27°C - 5 minutes; 33°C - 5 min.; 53°C - 4 min.; 63°C - 13 min.

The dressed fiber is dried in a drying cabinet under vacuum at 50-51°C for 2 hours.

Example 4. Preparation of finished hydrocarbon with 2.5 wt. % SPEEDF and 2.0 wt. % 2,4-TDA.

In a three-neck reaction flask equipped with a stirrer, a supply of nitrogen gas and a direct refrigerator, 23.875 g (95.5 wt.%) of a hydrocarbon with a fiber length of 0.2 mm is placed and the solution obtained by dissolving 0.625 g (2.5 wt.%) is added. SPEEDF and 0.5 g (2.0 wt%) 2,4-TDA in a mixture of 110 ml of acetone and 55 ml of methylene chloride (0.7% solution). The flask is placed in a water bath, the stirrer is turned on, the nitrogen supply is turned on, and kept at 20°C for 4 minutes. Then, the contents of the flask are heated and the solvents are distilled off according to the following regime: 27°C - 5 minutes; 33°C - 5 min.; 53°C - 4 min.; 63°C - 13 min.

The dressed fiber is dried in a drying cabinet under vacuum at 50-51°C for 2 hours.

Example 5. Preparation of finished hydrocarbon with 3.0 wt. % SPEEDF and 1.5 wt. % 2,4-TDA.

In a three-neck reaction flask equipped with a stirrer, a supply of nitrogen gas and a direct refrigerator, 23.875 g (95.5 wt. %) of hydrocarbons with a fiber length of 0.2 mm is placed and a solution obtained by dissolving 0.75 g (3.0 wt. %) is added. %) SPEEDF and 0.375 g (1.5 wt%) 2,4-TDA in a mixture of 110 ml of acetone and 55 ml of methylene chloride (0.7% solution). The flask is placed in a water bath, the stirrer is turned on, the nitrogen supply is turned on, and kept at 20°C for 4 minutes. Then, the contents of the flask are heated and the solvents are distilled off according to the following regime: 27°C - 5 minutes; 33°C - 5 min.; 53°C - 4 min.; 63°C - 13 min.

The dressed fiber is dried in a drying cabinet under vacuum at 50-51°C for 2 hours.

Example 6. Preparation of finished hydrocarbon with 3.5 wt. % SPEEDF and 1.0 wt. % 2,4-TDA.

In a three-neck reaction flask equipped with a stirrer, a supply of nitrogen gas and a direct refrigerator, 23.875 g (95.5 wt.%) of a hydrocarbon with a fiber length of 0.2 mm is placed and the solution obtained by dissolving 0.875 g (3.5 wt.%) is added. SPEEDF and 0.25 g (1.0 wt%) 2,4-TDA in a mixture of 110 ml of acetone and 55 ml of methylene chloride (0.7% solution). The flask is placed in a water bath, the stirrer is turned on, the nitrogen supply is turned on, and kept at 20°C for 4 minutes. Then, the contents of the flask are heated and the solvents are distilled off according to the following regime: 27°C - 5 minutes; 33°C - 5 min.; 53°C - 4 min.; 63°C - 13 min.

The dressed fiber is dried in a drying cabinet under vacuum at 50-51°C for 2 hours.

Polyetheretherketone composite materials containing 10 wt. % of carbon fibers coated with a mixture of SPEEDF and 2,4-TDA.

Table 1 presents the compositions, as well as the rheological and physical-mechanical properties of polyetheretherketone composite materials with sizing carbon fibers according to examples 1-6, treated with various amounts of sizing composition.

Table 1 Compound PTR,
g/10 min _Ar , kJ/m²
11 J
s/n E _izg ,
MPa E _rise , GPa σ _rise,
MPa σ _flow,
MPa REEK 450 + 10% HC 0.2 mm unfinished 4.46 8.65 5.9 4.74 105 110.3 According to example 1 5.94 10.36 6.48 5.16 114.42 115.9 According to example 2 6.78 11.81 6.53 5.27 116.81 117.4 According to example 3 7.32 12.43 6.82 5.33 117.93 118.8 According to example 4 7.66 12.64 6.98 5.39 119.36 120.5 According to example 5 7.85 12.95 6.95 5.54 122.53 123.7 According to example 6 7.91 12.92 6.92 5.52 122.11 123.6

where, MTR is the melt flow index, A _p is the impact strength with a notch, E _bend is the elastic modulus in bending, σ _rise and E _rise is the breaking stress and tensile modulus of elasticity; σ _flow - tensile yield strength.

As can be seen from the results presented, polyetheretherketone composite materials with coated carbon fibers (No. 1-6) exhibit higher physical, mechanical and rheological properties compared to materials containing unfinished carbon fiber (first row of the table).

The technical result of the proposed invention is to reduce the duration of the carbon fiber sizing process, and improve the physical, mechanical and rheological properties created by polyetheretherketone composite materials due to the introduction of a sizing composition - copolyepoxyether based on diane, phenolphthalein and epichlorohydrin with a degree of polycondensation n=85÷90 and 2, 4-toluene diamine, which increases the wettability of the carbon fiber, and increases the interfacial interactions between the filler and the polyetheretherketone matrix.

Claims (4)

1. A method for producing sizing carbon fibers intended for special-purpose structural products in additive technologies based on sizing carbon fiber by applying a sizing composition from a solution, followed by drying in a drying oven under vacuum at 50-51°C, characterized in that the sizing composition , which is a mixture of copolyepoxyether based on diane, phenolphthalein and epichlorohydrin (SPEEDP) with 2,4-toluylenediamine (2,4-TDA), is applied from a solution with a mass concentration of 0.7% in a mixture of organic volatile solvents - acetone and methylene chloride, kept at 20°C for 4 minutes and carry out a stepwise increase in temperature with distillation of solvents according to the following regime: 27°C - 5 minutes; 33°C – 5 min; 53°C - 4 min; 63°C – 13 min, and the quantitative ratio of the components corresponds in wt.%: Carbon fiber 95.5 Copolyepoxyether based on diane, phenolphthalein and epichlorohydrin (SPEEDP) from 1.0 to 3.5 2,4-toluenediamine (2,4-TDA) from 3.5 to 1.0 2. Polyetheretherketone composite material as structural polymer materials, intended for the production of special-purpose products in additive technologies, based on polyetheretherketone and carbon fiber treated with a sizing composition, characterized in that sizing carbon fiber is used, obtained by the method according to claim 1, and quantitative The ratio of components in the polyetheretherketone composite material corresponds in wt.%: Polyetheretherketone 90 Finished carbon fiber 10