RU2847493C2 - Method of producing glazed carbon fibres and polymer composite with polyetheretherketone - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of special-purpose structural articles in additive technologies. Disclosed is a method of producing sized carbon fibre by applying a finishing agent, which is a copolyepoxy ester based on epichlorohydrin, 4,4'-dixydiphenylsulphone and 4,4'-dioxyphthalophenone with degree of polymerisation n = 45–50, on carbon fibre from a solution with weight concentration of 0.2–0.4 % in 1,2-dichloroethane with subsequent stepped raising of temperature and simultaneous distillation of solvents.

EFFECT: shorter process of producing glazed carbon fibres and improved physical and mechanical properties of the formed carbon fibre polyetheretherketone polymer composite.

1 cl, 1 tbl, 5 ex

Description

The invention relates to a method for producing coated carbon fibers and polymer composites with polyetheretherketone, 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 allows for modification of the structure of the interphase layer and increase intermolecular adhesive interactions at the polymer-filler phase boundary.

Polymer composite materials containing polyether ketones are known.

Patent EP0224236A2 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 EP0316681A2 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. 2741505, "Polyetheretherketone Carbon Fiber Composite and Method for Its Production." Disadvantages of this patent include the lengthy process of producing the coated fibers and the relatively low values of the stated physical and mechanical properties of the composite materials.

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 and mechanical properties, based on a matrix polymer of polyetheretherketone (PEEK) filled with coated carbon fiber (CF).

The stated objective is achieved by the fact that polyetheretherketone polymer composites filled with carbon fibers are obtained by pre-treating the carbon fiber with a finishing component, which is a copolyepoxyether (SPEE) based on epichlorohydrin, 4,4'-doxydiphenylsulfone and 4,4'-dihydroxyphthalophenone with a degree of polymerization n = 45÷50:

The matrix polymer is polyetheretherketone, an industrial polymer PEEK 450, which is a product of polycondensation of 1,4-dihydroxybenzene and 4,4'-difluorodiphenylketone with a degree of condensation n = 147÷152:

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

Carbon fiber 96 ÷ 98 SPEE 4 ÷ 2

The amount of pre-treated carbon fiber in the composite material is 20% by weight. This treatment with a pre-treating compound increases the filler's wettability and allows for repeated heat treatment of the resulting product, if necessary, without altering the properties of the pre-treating compound.

The carbon filler is coated with a finishing composition by treatment in 1,2-dichloroethane, followed by drying to constant weight.

The polyetheretherketone composites of the present invention are obtained by pre-mixing the polymer matrix and coated carbon fiber using a VLM-40B Multi-function disintegrator high-speed homogenizer. 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 materials were used: RK-306 carbon fiber (IFI Technical Production), PEEK 450 industrial polyetheretherketone with a reduced viscosity of 0.31 dl/g, measured for a 1% solution in concentrated sulfuric acid, and grade "Ch" 1,2-dichloroethane.

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

Example 1

A three-necked round-bottomed flask equipped with a direct condenser, a device for supplying gaseous nitrogen, a heater and a mechanical stirrer is placed. 24.5 g (98 wt.%) of discrete CF with a fiber length of 0.2 mm are placed and a solution obtained by dissolving 0.5 g (2 wt.%) of SPEE in 199 ml of 1,2-dichloroethane (0.2% solution) is added. The stirrer and nitrogen supply are turned on and the mixture is stirred for 6 min at 20 °C. The contents of the flask are then heated and 1,2-dichloroethane is distilled off according to the following regime: 42 °C - 6 min.; 62 °C - 6 min.; 72 °C - 6 min.; 82 °C - 6 min., 90 °C - 6 min.

The finished fiber is dried in a drying oven under vacuum at 79-80 ^o C for 1.5 hours.

Example 2

In a three-necked round-bottomed flask equipped with a direct condenser, a device for feeding gaseous nitrogen, a heater and a mechanical stirrer, 24.375 g (97.5 wt.%) of discrete CF with a fiber length of 0.2 mm are placed and a solution obtained by dissolving 0.625 g (2.5 wt.%) of SPEE in 199 ml of 1,2-dichloroethane (0.25% solution) is added. The stirrer and nitrogen supply are turned on and the mixture is stirred for 6 min at 20 °C. Then the contents of the flask are heated and 1,2-dichloroethane is distilled off according to the following regime: 42 °C - 6 min.; 62 °C - 6 min.; 72 °C - 6 min.; 82 °C - 6 min., 90 °C - 6 min.

The finished fiber is dried in a drying oven under vacuum at 79-80 ^o C for 1.5 hours.

Example 3

In a three-necked round-bottomed flask equipped with a direct condenser, a device for supplying gaseous nitrogen, a heater and a mechanical stirrer, 24.25 g (97.0 wt.%) of discrete CF with a fiber length of 0.2 mm are placed and a solution obtained by dissolving 0.75 g (3 wt.%) of SPEE in 199 ml of 1,2-dichloroethane (0.3% solution) is added. The stirrer and nitrogen supply are turned on and the mixture is stirred for 6 min at 20 °C. Then the contents of the flask are heated and 1,2-dichloroethane is distilled off according to the following regime: 42 °C - 6 min.; 62 °C - 6 min.; 72 °C - 6 min.; 82 °C - 6 min., 90 °C - 6 min.

The finished fiber is dried in a drying oven under vacuum at 79-80 ^o C for 1.5 hours.

Example 4

In a three-necked round-bottomed flask equipped with a direct condenser, a device for supplying gaseous nitrogen, a heater and a mechanical stirrer, 24.125 g (96.5 wt.%) of discrete CF with a fiber length of 0.2 mm are placed and a solution obtained by dissolving 0.875 g (3.5 wt.%) of SPEE in 199 ml of 1,2-dichloroethane (0.35% solution) is added. The stirrer and nitrogen supply are turned on and the mixture is stirred for 6 min at 20 °C. Then the contents of the flask are heated and 1,2-dichloroethane is distilled off according to the following regime: 42 °C - 6 min.; 62 °C - 6 min.; 72 °C - 6 min.; 82 °C - 6 min., 90 °C - 6 min.

The finished fiber is dried in a drying oven under vacuum at 79-80 ^o C for 1.5 hours.

Example 5

A three-necked round-bottomed flask equipped with a direct condenser, a device for supplying gaseous nitrogen, a heater and a mechanical stirrer is placed. 24.0 g (96 wt.%) of discrete CF with a fiber length of 0.2 mm are placed and a solution obtained by dissolving 1.0 g (4 wt.%) of SPEE in 199 ml of 1,2-dichloroethane (0.4% solution) is added. The stirrer and nitrogen supply are turned on and the mixture is stirred for 6 min at 20 °C. The contents of the flask are then heated and 1,2-dichloroethane is distilled off according to the following regime: 42 °C - 6 min.; 62 °C - 6 min.; 72 °C - 6 min.; 82 °C - 6 min., 90 °C - 6 min.

The finished fiber is dried in a drying oven under vacuum at 79-80 ^o C for 1.5 hours.

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

Table 1

Properties of carbon fiber polyetheretherketone polymer composites

Compound E _izg ,
MPa σ _izg,
MPa E _rast, GPa σ _grows,
MPa PEEK 450 + 20% UV 0.2 mm, untreated 13.6 240.6 8.75 132.2 According to example 1 13.98 247.3 9.72 145.3 According to example 2 14.17 250.7 10.26 153.5 According to example 3 14.33 253.5 10.53 157.9 According to example 4 14.56 255.8 10.58 159.8 According to example 5 14.53 254.6 10.54 159.3

where σ _bend and E _bend are the ultimate stress and modulus of elasticity in bending; σ _stretch and E _stretch are the ultimate stress and modulus of elasticity in tension.

The data presented in the table show that polyetheretherketone polymer composites containing coated hydrocarbons (examples No. 1-5) have higher values of physical and mechanical properties compared to the uncoated sample (first row of the table).

The technical result of the proposed invention consists in reducing the duration of the process for obtaining coated carbon fibers, and improving the physical and mechanical properties of the created carbon fiber polyetheretherketone polymer composites by introducing copolyepoxyether based on epichlorohydrin, 4,4'-doxydiphenylsulfone and 4,4'-dioxyphthalophenone with a degree of polymerization n = 45÷50, which increases the wettability of the carbon fiber and increases intermolecular interactions between the filler and the polyetheretherketone matrix.

Claims (3)

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 copolyepoxy ether (CPEE) based on epichlorohydrin, 4,4'-doxydiphenylsulfone and 4,4'-dihydroxyphthalophenone with a degree of polymerization n=45-50, is applied from a solution with a mass concentration of 0.2-0.4% in 1,2-dichloroethane and a stepwise increase in temperature is carried out with simultaneous distillation of the solvent according to the following regime: 20 °C - 6 min; 42 °C - 6 min; 62 °C - 6 min; 72 °C - 6 min; 82 °C - 6 min, 90 °C - 6 min, followed by drying in a drying oven under vacuum at 79-80 °C, with the quantitative ratio of the components corresponding, wt.%: Carbon fiber 96-98 SPEE 4-2