RU2850275C1 - Method of producing glazed carbon fibres and a polymer composition with polyether ether ketone - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of special-purpose structural articles in additive technologies. Disclosed is a method of producing glazed carbon fibre by applying a finishing agent, which is a mixture of copolyhydroxy ether from 4,4'-dioxydiphenylsulphone, 4,4'-dioxyphthalophenone, 3-chloro-1,2-epoxypropane with degree of polymerisation n = 65-70 and sulphon-oligomeric ether ether ketone based on 4,4'-dioxydiphenylsulphone and 4,4'-difluorodiphenylketone with degree of polycondensation n = 5-7, on carbon fibre from a solution with a mass concentration of 0.25 % in mixture of 128 ml of trichloromethane and 40 ml of 1,2-dichloroethane with subsequent stepwise raising of temperature and simultaneous distillation of solvents.

EFFECT: shorter process of producing glazed carbon fibres and improved physical-mechanical and rheological properties of the obtained polymer composition with polyether ether ketone.

1 cl, 1 tbl, 5 ex

Description

The invention relates to a method for producing coated carbon fibers and polymer compositions with polyetheretherketone and can be used for the production of special-purpose products in additive technology.

One of the ways to improve the performance characteristics of polyetheretherketone carbon fiber composites is to finish the surface of the carbon fiber, which allows modifying the structure of the interphase layer and increasing intermolecular adhesive interactions at the polymer-filler phase boundary.

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 (PEC) (not polyetheretherketone (PEEK)), aromatic polysulfone, and fillers, including carbon fiber.

Patent EP 0316681 A2 also describes fiber composite materials made of polyethersulfone, polyetherketone (not polyetheretherketone), and carbon fiber. Both patents describe composites obtained from a blend of two polymers—polyethersulfone and polyetherketone—filled with fibers. They do not provide information on finishing the carbon fibers to produce PCMs with enhanced mechanical properties.

Patent RU 2278126, published June 20, 2006, Bulletin No. 17, describes compositions used for crosslinking chains. This work proposes using a blend of polyetheretherketone (not PEEK) with terminal amine groups and copolymers of polyethersulfone (PES) and copolyetherethersulfone (PEES) with terminal anhydride groups. The mixture is dissolved in a high-boiling solvent, N-methylpyrrolidone, and carbon fibers are treated with it. A disadvantage of this solution is the use of a solvent with a high boiling point (203°C), which is difficult to remove from the composition. Its residues, at high operating temperatures, will lead to the formation of bubbles in the castings, resulting in a decrease in performance properties.

Various types of finishing additives used in the creation of polymer composite materials are known from the prior art. For example, patent RU 2057767 describes a polymer composite material comprising a polysulfone polymer and carbon fibers. The carbon fibers contain on the surface, as a finishing layer, a copolymer consisting of methacrylic acid units, 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 the fiber weight with the following ratio of components, by weight: carbon reinforcing fibers containing the copolymer, 25-75; polysulfone matrix, the remainder. According to the inventors, the use of the said copolymer as a finishing layer allows for a 1.8-2.2-fold increase in the interlaminar shear strength of polysulfone carbon fiber-reinforced plastics. The main drawback of the proposed solution is the use of an aqueous medium to apply the monomer mixture to the carbon tape. Since carbon fibers and tapes are hydrophobic, achieving uniform distribution of the aqueous monomer mixture is difficult. Incomplete monomer conversion is also possible during polymerization, which can lead to the formation and release of water during other stages of polymer composite production, leading to pore formation and reduced strength. The presence of benzenesulfonic acid in the aqueous medium will promote ion accumulation, which will degrade the dielectric properties of the materials.

According to Russian Patent No. 2201423, polymer composites were obtained from a polymer binder (sizing agent) and fiberglass or carbon filler. First, the binder (oligomer) is produced by reacting aromatic tetracarboxylic acid tetranitrile with aromatic bis-o-cyanamine at temperatures of 170-180°C. The binder is obtained in powder form. The main drawback of this solution is the complexity of the binder production process. If the monomers are not fully converted during synthesis, low-molecular-weight byproducts may be released during the combination of the binder and filler at elevated temperatures, resulting in the formation of voids in the composite material. This will lead to a deterioration in the strength properties of the material. Furthermore, powdered sizing agents may not coat the filler surface uniformly enough.

Polyetheretherketone composites are known from US Patent No. 4,049,613. To increase the wettability of carbon fiber by the polymer matrix, the authors propose soaking the filler in hot nitric acid for three days, which is unfavorable from a technological and economic standpoint.

The following patent describes a method for finishing carbon fiber, as described in Russian Patent No. 2054015, "Method for Finishing Carbon Fiber for the Production of Polysulfone Carbon Fiber Reinforced Plastic." The proposed method involves mixing a block copolymer with a solvent. The block copolymer, consisting of bismethacryloyloxy diethylene glycolphthalate and bismethacryloyloxy triethylene glycolphthalate units, is impregnated into a carbon filler, followed by drying to remove the solvent and polymerize the finishing film on the fiber. The method is distinguished by mixing in water while simultaneously exposed to ultrasonic radiation at a frequency of 15 to 44 kHz for a duration of 5 to 14 minutes. Disadvantages of this method include the use of aqueous solutions of block copolymers to wet the hydrophobic surfaces of the carbon fiber and the need for further polymerization on the filler surface. The consequence may be uneven wetting of the filler and, consequently, a decrease in the properties of the resulting carbon fiber.

The closest analogue is Russian Patent No. 2752625, "Polymer Composite Material Based on Polyetheretherketone and Carbon Fiber and a Method for its Production." Disadvantages of this patent include the relatively modest physical and mechanical properties of the composite materials and the lengthy process of producing the coated fibers.

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

The set task is achieved by the fact that the finished fibers are obtained by treatment with a finishing composition - a mixture of copolyhydroxyether from 4,4'-dioxydiphenylsulfone, 4,4'-dihydroxyphthalophenone, 3-chloro-1,2-epoxypropane (SPGESF) with a degree of polymerization n = 65÷70:

and sulfonoligomeric etheretherketone based on 4,4'-dioxydiphenylsulfone and 4,4'-difluorodiphenylketone (SOEEK) with a degree of polycondensation n = 5÷7:

in a mixture of trichloromethane and 1,2-dichloroethane upon heating and exposure to ultrasound with an operating frequency of 46 kHz.

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

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

Carbon fiber 97.0 SPGESF 0.5÷2.5 SOEK 2.5÷0.5

The amount of pre-treated carbon fiber in the composite material is 10% by weight. This treatment with a pre-treating compound increases the filler's wettability by the pre-treating compound and allows for repeated heat treatment of the resulting product, if necessary, without altering the properties of the pre-treating compound.

The finished fibers are obtained by treating carbon fiber with a finishing compound in a CD-4820 ultrasonic bath with an operating frequency of 46 kHz in a mixture of trichloromethane and 1,2-dichloroethane.

Polymer composites with polyetheretherketone according to the present invention are obtained by preliminary mixing of the polymer matrix and coated carbon fiber using a high-speed homogenizer Multi-function disintegrator VLM-40B. The polymer mixture is then extruded using a laboratory twin-screw extruder with three heating zones at processing temperatures of 200 °C, 315 °C, and 355 °C. The following were used: carbon fiber of the RK-306 brand (IFI Technical Production), industrial polyetheretherketone of the PEEK 450 brand with a reduced viscosity of 0.33 dl/g, measured for a 1% solution in concentrated sulfuric acid, trichloromethane, and 1,2-dichloroethane of the Ch grade.

Below are examples illustrating the method for producing treated carbon fibers.

Example 1. Obtaining a finished hydrocarbon with 0.5 wt.% SPGESF and 2.5 wt.% SOEK

In a three-necked reaction flask, 19.4 g (97.0 wt.%) of CF with a fiber length of 0.2 mm are placed and a solution obtained by dissolving 0.1 g (0.5 wt.%) of SPHESF and 0.5 g (2.5 wt.%) of SOEK in a mixture of 128 ml of trichloromethane and 40 ml of 1,2-dichloroethane (0.25% solution) is added. The flask is placed in a water bath of an ultrasonic bath at a temperature of 20 °C, the ultrasound is turned on and held for 3 minutes. After this, a stirrer is placed in the flask, a direct condenser is connected, and the supply of nitrogen gas is turned on. The stirrer is turned on, and the contents of the flask are heated and the solvents are distilled off according to the following regime: 32 °C - 3 min; 42 °C - 3 min; 52 °C - 3 min; 62 °C - 5 min, 85 °C - 10 min.

The finished fiber is dried in a drying oven under vacuum at 94÷95 °C for 85 min.

Example 2. Obtaining a finished hydrocarbon with 1.0 wt.% SPGES and 2.0 wt.% SOEK

In a three-necked reaction flask, 19.4 g (97.0 wt.%) of CF with a fiber length of 0.2 mm are placed and a solution obtained by dissolving 0.2 g (1.0 wt.%) of SPHESF and 0.4 g (2.0 wt.%) SOEK in a mixture of 128 ml of trichloromethane and 40 ml of 1,2-dichloroethane (0.25% solution) is added. The flask is placed in a water bath of an ultrasonic bath at a temperature of 20 °C, the ultrasound is turned on and held for 3 minutes. After this, a stirrer is placed in the flask, a direct condenser is connected, and the supply of nitrogen gas is turned on. The stirrer is turned on, the contents of the flask are heated and the solvents are distilled off according to the following regime: 32 °C - 3 min; 42 °C - 3 min; 52 °C - 3 min; 62 °C - 5 min, 85 °C - 10 min.

The finished fiber is dried in a drying oven under vacuum at 94÷95 °C for 85 min.

Example 3. Obtaining a finished hydrocarbon with 1.5 wt.% SPGESF and 1.5 wt.% SOEK

In a three-necked reaction flask, 19.4 g (97.0 wt.%) of CF with a fiber length of 0.2 mm are placed and a solution obtained by dissolving 0.3 g (1.5 wt.%) of SPHESF and 0.3 g (1.5 wt.%) of SOEK in a mixture of 128 ml of trichloromethane and 40 ml of 1,2-dichloroethane (0.25% solution) is added. The flask is placed in a water bath of an ultrasonic bath at a temperature of 20 °C, the ultrasound is turned on and held for 3 minutes. After this, a stirrer is placed in the flask, a direct condenser is connected, and the supply of gaseous nitrogen is turned on. The stirrer is turned on, the contents of the flask are heated and the solvents are distilled off according to the following regime: 32 °C - 3 min; 42 °C - 3 min; 52 °C - 3 min; 62 °C - 5 min, 85 °C - 10 min.

The finished fiber is dried in a drying oven under vacuum at 94÷95 °C for 85 min.

Example 4. Obtaining a finished hydrocarbon with 2.0 wt.% SPGES and 1.0 wt.% SOEK

In a three-necked reaction flask, 19.4 g (97.0 wt.%) of CF with a fiber length of 0.2 mm are placed and a solution obtained by dissolving 0.4 g (2.0 wt.%) of SPGESF and 0.2 g (1.0 wt.%) SOEK in a mixture of 128 ml of trichloromethane and 40 ml of 1,2-dichloroethane (0.25% solution) is added. The flask is placed in a water bath of an ultrasonic bath at a temperature of 20 °C, the ultrasound is turned on and held for 3 minutes. After this, a stirrer is placed in the flask, a direct condenser is connected, and the supply of nitrogen gas is turned on. The stirrer is turned on, and the contents of the flask are heated and the solvents are distilled off according to the following regime: 32 °C - 3 min; 42 °C - 3 min; 52 °C - 3 min; 62 °C - 5 min, 85 °C - 10 min.

The finished fiber is dried in a drying oven under vacuum at 94÷95 °C for 85 min.

Example 5. Obtaining a finished hydrocarbon with 2.5 wt.% SPGES and 0.5 wt.% SOEK

In a three-necked reaction flask, 19.4 g (97.0 wt %) of CF with a fiber length of 0.2 mm are placed and a solution obtained by dissolving 0.5 g (2.5 wt %) of SPGESF and 0.1 g (0.5 wt %) of SOEK in a mixture of 128 ml of trichloromethane and 40 ml of 1,2-dichloroethane (0.25% solution) is added. The flask is placed in a water bath of an ultrasonic bath at a temperature of 20 °C, the ultrasound is turned on and held for 3 minutes. After this, a stirrer is placed in the flask, a direct condenser is connected, and the supply of nitrogen gas is turned on. The stirrer is turned on, the contents of the flask are heated and the solvents are distilled off according to the following regime: 32 °C - 3 min; 42 °C - 3 min; 52 °C - 3 min; 62 °C - 5 min, 85 °C - 10 min.

The finished fiber is dried in a drying oven under vacuum at 94÷95 °C for 85 min.

Carbon fiber polymer composites with polyetheretherketone containing 10 wt.% of carbon fibers coated with a mixture of SPGESF and SOEK were obtained from coated CF and PEEK.

Table 1 presents the compositions and physical and mechanical properties of carbon fiber polymer composites with polyetheretherketone according to examples 1-5, treated with different amounts of finishing composition.

Table 1

Properties of carbon fiber polymer composites with polyetheretherketone

Compound MFR, g/10 min A _p , kJ/m ²
11 J
s/n E _izg , MPa E _rast , GPa σ _growth , MPa σ _тек , MPa PEEK 450 + 10% UV 0.2 mm untreated 4.46 8.65 5.9 4.74 105 110.3 According to example 1 6.68 11.67 6.64 5.66 125.4 127.3 According to example 2 7.91 12.83 7.35 5.71 126.5 128.4 According to example 3 8.46 13.74 7.57 5.76 127.7 129.6 According to example 4 9.85 14.56 7.53 5.81 128.8 130.9 According to example 5 9.89 14.32 7.48 5.80 128.6 130.5

where MFI is the melt flow index, A _p is the notched impact strength, _Ebend is the modulus of elasticity in bending, _Estr is the modulus of elasticity in tension, σstr _is the ultimate tensile strength, _σtek is the yield strength in tension.

As can be seen from the data provided, polymer compositions with polyetheretherketone containing coated carbon fibers (No. 1-5) exhibit higher physical, mechanical and rheological properties compared to a composition containing uncoated carbon fiber (first row of the table).

The technical result of the proposed invention consists in reducing the duration of the carbon fiber finishing process and improving the physical, mechanical and rheological properties of the created polymer composition with polyetheretherketone due to the introduction of a finishing composition - a copolyhydroxyether from 4,4'-dioxydiphenylsulfone, 4,4'-dioxyphthalophenone, 3-chloro-1,2-epoxypropane with a degree of polymerization n = 65÷70, and a sulfonoligomeric etheretherketone based on 4,4'-dioxydiphenylsulfone and 4,4'-difluorodiphenylketone with a degree of polycondensation n = 5÷7, which increases the wettability of the filler and increases the boundary interactions between the carbon filler and the polyetheretherketone matrix.

Claims (6)

A method for producing finished carbon fibers intended for special-purpose products in additive technologies, based on finishing carbon fiber by applying a finishing component from a solution followed by drying, characterized in that the finishing composition, which is a mixture of copolyhydroxyether from 4,4'-dioxydiphenylsulfone, 4,4'-dioxyphthalophenone, 3-chloro-1,2-epoxypropane (SPGESF) with a degree of polymerization n = 65-70 and a sulfonoligomeric etheretherketone based on 4,4'-dioxydiphenylsulfone and 4,4'-difluorodiphenylketone (SOEEK) with a degree of polycondensation n = 5-7, is applied from a solution with a mass concentration of 0.25% in a mixture of 128 ml of trichloromethane and 40 ml of 1,2-dichloroethane and a stepwise increase in temperature is carried out with simultaneous exposure to ultrasound with an operating frequency of 46 kHz with simultaneous distillation of solvents according to the following regime: 20 °C - 3 min; 32 °C - 3 min; 42 °C - 3 min; 52 °C - 3 min; 62 °C - 5 min, 85 °C - 10 min, followed by drying in a drying cabinet under vacuum at 94-95 °C, with the quantitative ratio of the components corresponding, mass %: Carbon fiber 97.0 SPGESF 0.5-2.5 SOEK 2.5-0.5, copolyhydroxyether (SPHESF) sulfonoligomeric etheretherketone (SOEEK).