RU2803746C2 - Method for obtaining dressed carbon fibers and polymer composite - Google Patents

Abstract

FIELD: production of carbon fibres and polymer compositions.

SUBSTANCE: invention is related to a method for producing finished carbon fibres and polymer compositions with inorganic, in particular carbon, fibres as fillers and can be used for production of special-purpose structural products in additive technologies. A method for producing finished carbon fibres intended for structural polymeric materials, based on the finishing of carbon fibre by applying a finishing component from a solution, followed by drying in an oven under vacuum at 68-69°C, whereas the sizing component is applied to a carbon fibre 3 mm long from solutions of polyetheretherketone (PEEK) based on bis(4-hydroxyphenyl)propane and bis(4-fluorophenyl)phenylketone with n=192-200 and bis(4-aminophenyl)propane (APP) with a concentration of 0.48 wt.%, obtained by dissolving in an organic solvent (chloroform), and a stepwise increase in temperature is carried out with simultaneous distillation of the solvent and exposure to ultrasound with an operating frequency of 46 kHz as follows: 20°C - 3 min; 40°C - 2 min; 50°C - 2 min; 60°C - 2 min; 64°C - 2 min, with the following quantitative ratio of components in wt.%: carbon fibre 96.0, PEEK 3.5 - 3.0, APP 0.5-1.0. The invention also relates to a polymer carbon fibre composite used in the manufacture of structural products in additive technologies, containing a polymer matrix based on polyesterimide and finished carbon fibre, obtained by the method of obtaining finished carbon fibres, with the following quantitative ratio of components in the polymer composite in wt.%: polyesterimide 80, finished carbon fibre 20.

EFFECT: improving the modulus of elasticity and tensile strength of the created polymer composite due to the introduction of a sizing composition - polyetheretherketone and bis(4-aminophenyl)propane, which increases the wettability of the filler and boundary interactions between the filler and the polyesterimide matrix.

2 cl, 1 tbl, 6 ex

Description

The invention relates to a method for producing finished carbon fibers and polymer composites with inorganic, in particular carbon fibers, as fillers, and can be used for the production of special-purpose structural products in additive technologies.

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

Various types of sizing additives used in the creation of polymer composite materials are known from the prior art. Thus, the patent for the invention RU 2057767 describes a polymer composite material that includes a polysulfone matrix and carbon fibers, and the 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% by weight of the fiber with the following ratio of components, wt.%: carbon reinforcing fibers containing a 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 can also lead to the accumulation of ions, which can deteriorate dielectric properties.

There are known polymer compositions according to RF patent No. 2201423, obtained on the basis of a polymer binder (sizing agent) and fiberglass or carbon filler. A binder, an oligomer, is first prepared by reacting aromatic tetracarboxylic acid tetranitrile and aromatic bis-o-cyanamine at a temperature of 170-180°C. The binder is obtained in powder form. The main disadvantage of the above solution is the complexity of the binder synthesis process. An incomplete degree of conversion of monomers during synthesis can lead to the release of by-products of low molecular weight reaction when combining a binder with a filler at elevated temperatures, and, consequently, to the formation of voids in the composite material, which 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.

Polyetherimide composites are known according to US patent No. 4049613. To increase the wettability of carbon fiber by the polymer matrix, the patent proposes keeping the filler in hot nitric acid for three days, which is technologically and economically unprofitable.

In the following work, according to RF patent No. 2054015 “Method of sizing carbon fiber for the production of polysulfone carbon fiber plastic,” it is proposed to mix a block copolymer consisting of units of bismethacryloyloxydiethylene glycol phthalate and bismethacryloyloxy-triethylene glycol phthalate with a solvent, impregnation of the carbon filler with subsequent drying to remove the solvent and polymerization of sizing film on 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 of 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, deterioration of the properties of the resulting carbon fiber reinforced plastic.

The closest analogue is the method of finishing carbon fiber according to RF patent No. 2712612 “Method for producing finished carbon fibers and composite materials based on them.” The disadvantage of the solution can be considered the relatively low values of tensile strength of polymer composites.

The objective of the present invention is to develop a method for producing coated carbon fibers and obtaining polymer composites with improved tensile strength values based on a matrix polymer polyetherimide (PEI) reinforced with coated carbon fiber (carbon fiber, CF) as a filler.

This task is achieved by the fact that polyetherimide composites filled with carbon filler are obtained by pre-treating the carbon fiber with a sizing composition - a mixture of polyetheretherketone (PEEK) based on bis(4-hydroxyphenyl)propane and bis(4-fluorophenyl)phenylketone of the formula:

and bis(4-aminophenyl)propane (AFP).

The matrix polymer is polyetherimide (PEI) brand ULTEM-1010, is a polycondensation product of 1,3-diaminobenzene and 2,2'-bis[4(3,4-dicarboxyphenoxy)phenyl]-propane dianhydride of the formula:

with a reduced viscosity of 0.61 dl/g, measured for a 0.5% solution in chloroform

In this case, the following ratios (wt.%) of the components in the filler (Carbon fiber + PEEK + AFP) are taken:

Carbon fiber 96.0 PEEK 3.5 ÷ 3.0 AFP 0.5 ÷ 1.0

The amount of sizing composition for carbon fiber corresponds to 4.0%. The amount of finished carbon fiber in the polymer composite is 20 wt. %. Treatment with such a sizing composition increases the wettability of carbon fiber by the matrix polyetherimide and allows repeated heat treatment of the resulting product, if necessary, without changing the properties of the sizing composition.

Finished fibers are produced by treating carbon fiber with a sizing composition in an ultrasonic bath CD-4820 with an operating frequency of 46 kHz. 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 ^o C, 315 ^o C, 355 ^o C. Glass fiber grade RK-306 (IFI Technical Production), bis(4-aminophenyl)- propane and chloroform, grade "chemical grade".

Below are examples illustrating a method for producing sizing carbon fibers using a sizing composition.

Example 1. Preparation of finished hydrocarbon with 3.5 wt. % PEEK and 0.5 wt. % AFP.

24 g (96 wt.%) CF with a fiber length of 3 mm is placed in a three-neck reaction flask and a solution obtained by dissolving 0.875 g (3.5 wt.%) PEEK and 0.125 g (0.5 wt.%) AFP in 140 is added. ml chloroform (0.48% solution). 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 refrigerator is connected, and the supply of nitrogen gas is turned on. Turn on the stirrer and nitrogen supply and heat the contents of the flask and distill off chloroform according to the following mode: 40 °C - 2 minutes; 50 °C - 2 min.; 60 °C - 2 min.; 64 °C - 2 min.

The dressed fiber is dried in a drying cabinet under vacuum at 68-69 ^o C for 2 hours.

Example 2. Preparation of finished hydrocarbon with 3.4 wt. % PEEK and 0.6 wt. % AFP.

24 g (96 wt%) of carbon fiber with a fiber length of 3 mm is placed in a three-neck reaction flask and a solution obtained by dissolving 0.85 g (3.4 wt%) of PEEK and 0.15 g (0.6 wt%) is added. ) AFP in 140 ml of chloroform (0.48% solution). 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 refrigerator is connected, and the supply of nitrogen gas is turned on. Turn on the stirrer and nitrogen supply and heat the contents of the flask and distill off chloroform according to the following mode: 40 °C - 2 minutes; 50 °C - 2 min.; 60 °C - 2 min.; 64 °C - 2 min.

The dressed fiber is dried in a drying cabinet under vacuum at 68-69 ^o C for 2 hours.

Example 3. Preparation of finished hydrocarbon with 3.3 wt. % PEEK and 0.7 wt. % AFP.

24 g (96 wt%) of carbon fiber with a fiber length of 3 mm is placed in a three-neck reaction flask and a solution obtained by dissolving 0.825 g (3.3 wt%) of PEEK and 0.175 g (0.7 wt%) of AFP in 140 is added. ml chloroform (0.48% solution). 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 refrigerator is connected, and the supply of nitrogen gas is turned on. Turn on the stirrer and nitrogen supply and heat the contents of the flask and distill off chloroform according to the following mode: 40 °C - 2 minutes; 50 °C - 2 min.; 60 °C - 2 min.; 64 °C - 2 min.

The dressed fiber is dried in a drying cabinet under vacuum at 68-69 ^o C for 2 hours.

Example 4. Preparation of finished hydrocarbon with 3.2 wt. % PEEK and 0.8 wt. % AFP.

24 g (96 wt %) of CF with a fiber length of 3 mm is placed in a three-neck reaction flask and a solution obtained by dissolving 0.8 g (3.2 wt %) of PEEK and 0.2 g (0.8 wt %) is added ) AFP in 140 ml of chloroform (0.48% solution). 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 refrigerator is connected, and the supply of nitrogen gas is turned on. Turn on the stirrer and nitrogen supply and heat the contents of the flask and distill off the chloroform according to the following mode: 64 °C - 2 min.

The dressed fiber is dried in a drying cabinet under vacuum at 68-69 ^o C for 2 hours.

Example 5. Preparation of finished hydrocarbon with 3.1 wt. % PEEK and 0.9 wt. % AFP.

24 g (96 wt %) of CF with a fiber length of 3 mm is placed in a three-neck reaction flask and a solution obtained by dissolving 0.775 g (3.1 wt %) of PEEK and 0.225 g (0.9 wt %) of AFP in 140 is added. ml chloroform (0.48% solution). 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 refrigerator is connected, and the supply of nitrogen gas is turned on. Turn on the stirrer and nitrogen supply and heat the contents of the flask and distill off chloroform according to the following mode: 40 °C - 2 minutes; 50 °C - 2 min.; 60 °C - 2 min.; 64 °C - 2 min.

The dressed fiber is dried in a drying cabinet under vacuum at 68-69 ^o C for 2 hours.

Example 6. Preparation of finished hydrocarbon with 3.0 wt. % PEEK and 1.0 wt. % AFP.

24 g (96 wt%) of carbon fiber with a fiber length of 3 mm is placed in a three-neck reaction flask and a solution obtained by dissolving 0.75 g (3.0 wt%) of PEEK and 0.25 g (1.0 wt%) is added. ) AFP in 140 ml of chloroform (0.48% solution). 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 refrigerator is connected, and the supply of nitrogen gas is turned on. Turn on the stirrer and nitrogen supply and heat the contents of the flask and distill off chloroform according to the following mode: 40 °C - 2 minutes; 50 °C - 2 min.; 60 °C - 2 min.; 64 °C - 2 min.

The dressed fiber is dried in a drying cabinet under vacuum at 68-69 ^o C for 2 hours.

Composite materials containing 20 wt. were obtained from finished CF and PEI. % of carbon fibers coated with a mixture of PEEK and AFP.

Table 1 presents the compositions, as well as the moduli of elasticity and tensile strength of composites containing finished carbon fibers according to examples 1-6.

Table 1

Composition (wt.%) E rise, GPa σ size, MPa PEI 2.8 88.0 PEI + 20% HC uncoated 6.4 142.0 According to example 1 7.09 160.1 According to example 2 7.20 163.11 According to example 3 7.42 166.03 According to example 4 7.68 174.27 According to example 5 7.66 172.36 According to example 6 7.55 167.33

where E _grow is the tensile modulus of elasticity, σ _break is the tensile strength.

As can be seen from the data presented, polymer composites with coated carbon fibers (No. 1-6) exhibit higher values of elastic modulus and tensile strength compared to a composite containing unfinished carbon fiber.

The technical result of the proposed invention is to improve the elastic modulus and tensile strength of the created polymer composite due to the introduction of a sizing composition - polyetheretherketone and bis(4-aminophenyl)propane, which increases the wettability of the filler and increases the boundary interactions between the filler and the polyetherimide matrix.

Claims (4)

1. A method for producing sizing carbon fibers intended for structural polymer materials, based on sizing carbon fiber by applying a sizing component from a solution, followed by drying in an oven under vacuum at 68-69°C, characterized in that the sizing component is applied to the carbon fiber 3 mm long from solutions of polyetheretherketone (PEEK) based on bis(4-hydroxyphenyl)propane and bis(4-fluorophenyl)phenylketone with n=192-200 and bis(4-aminophenyl)propane (AFP) with a concentration of 0.48 wt. % obtained by dissolving in an organic solvent - chloroform, and carry out a stepwise increase in temperature with simultaneous distillation of the solvent and exposure to ultrasound with an operating frequency of 46 kHz according to the mode: 20 ° C - 3 min; 40°C - 2 min; 50°C - 2 min; 60°C - 2 min; 64°C - 2 min, and the quantitative ratio of the components corresponds in wt.%: Carbon fiber 96.0 PEEK 3.5-3.0 AFP 0.5-1.0 2. Polymer carbon fiber composite used in the production of structural products in additive technologies, containing a polymer matrix based on polyetherimide and finished carbon fiber, characterized in that it uses finished carbon fiber obtained by the method according to claim 1, and the quantitative ratio of the components in the polymer composite corresponds to in wt.%: Polyetherimide 80 Finished carbon fiber 20