RU2796448C1 - Method for obtaining finished carbon fibers and polymer composite material - Google Patents

Abstract

FIELD: polymer materials.

SUBSTANCE: method for obtaining sized carbon fibers, and polymer composite materials intended as structural polymer materials in additive processes, including PEI and CF, sized. Manufacturing of structural products using additive processes. Obtaining sized carbon fiber by applying a sizing, which is 1-methyl-3,4-diaminobenzene 1.0-3.5 wt.%, onto carbon fiber from a solution with a mass concentration of 0.18-0.63% in acetone with subsequent stepwise rise in temperature up to 60°C and distillation of the solvent, the sized carbon fiber obtained by the proposed method, and a polymer composite material that contains 80 wt.% of the polymer matrix based on polyesterimide and 20 wt.% of the proposed sized carbon fiber.

EFFECT: improvement of compressive strength of the created polymer composite material due to the introduction of a sizing composition, which increases the wettability of the filler and increases the boundary interactions between the filler and the polyesterimide matrix.

3 cl, 1 tbl, 6 ex

Description

The invention relates to a method for producing finished carbon fibers and polymer composite materials 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 of polymeric carbon fiber composite materials is to finish the carbon fiber surface, which makes it possible to modify the structure of the interfacial layer and increase intermolecular adhesive interactions at the polymer-filler interface.

Couplings are substances that affect the structure, properties and length of the interfacial layer, which greatly increases the contact area of the fibrous filler with the binder. For the production of structural polymer composite materials with desired performance characteristics, it is necessary to purposefully select a sizing composition for a reinforcing fiber, taking into account the viscosity of the binder, its molecular weight, physicochemical properties, size and structure of pores in the filler. Thus, the development of sizing compositions for the production of polymer composite materials based on superstructural thermoplastics will improve the mechanical, heat-resistant, and operational properties of the material, which will lead to an increase in the service life of products.

From the prior art, various types of sizing additives are known that are used in the creation of a polymer composite material. So the patent for the invention RU 2057767 describes a polymer composite material, including 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 the amount of 0.52 - 5.0% by weight of the fiber in the following ratio, wt.%: carbon reinforcing fibers containing a copolymer, 25 - 75; polysulfone matrix rest. According to the authors of the invention, the use of said copolymer as a sizing layer makes it possible to increase the interlaminar shear strength of polysulfone carbon plastics by a factor of 1.8 - 2.2. The main disadvantage of the proposed solution is the use of an aqueous medium for applying a mixture of monomers to a carbon tape. Since carbon fibers and tapes are hydrophobic, it is difficult to achieve a uniform distribution of an aqueous solution of a mixture of monomers. 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 medium can also lead to the accumulation of ions, which can worsen the dielectric properties.

Known polymer compositions according to the patent of the Russian Federation No. 2201423, obtained on the basis of a polymer binder (sizing) and fiberglass or carbon filler. Preliminarily, a binder - oligomer is obtained 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 low-molecular by-products of the reaction when combining the binder with the filler at an elevated temperature, 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 finishes 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 a polymer matrix, the patent proposes to keep the filler in hot nitric acid for three days, which is technologically and economically disadvantageous.

In the following work - according to the patent of the Russian Federation No. 2054015 "Method of sizing carbon fiber for the production of polysulfone carbon fiber", it is proposed to mix with a solvent a block copolymer consisting of units of bismethacryloyloxydiethylene glycol phthalate and bismethacryloyloxy-triethylene glycol phthalate, impregnation of the carbon filler, followed by drying to remove the solvent and polymerization of the sizing film on the fiber , characterized in that the mixing is carried out in water with simultaneous exposure to ultrasonic radiation at a frequency of 15 to 44 kHz and an exposure time of 5 to 14 minutes. The disadvantages of this method are the use of aqueous solutions of block copolymers for wetting hydrophobic surfaces of carbon fiber and the need for further polymerization on the surface of the filler. The result may be uneven wetting of the filler, and, consequently, the deterioration of the properties of the resulting carbon fiber.

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

The objective of the present invention is to develop a method for producing finished carbon fibers and obtaining a polymeric carbon fiber composite material (CM) with improved compressive strength values based on a polyesterimide (PEI) matrix polymer reinforced with finished carbon fiber (CF) as a filler.

The task is achieved by the fact that a polymer composite material based on polyesterimide, reinforced with a carbon filler, is obtained by pre-treatment of carbon fiber with a sizing component - 1-methyl-3,4-diaminobenzene (MDAB).

Matrix polymer - industrial polyesterimide (PEI) brand ULTEM-1010, formulas:

is a polycondensation product of 1,3-diaminobenzene and 2,2'-bis[4(3,4-dicarboxyphenoxy)phenyl]propane dianhydride. The reduced viscosity is 0.63 dl/g, measured for a 0.5 wt% solution in chloroform.

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

MDAB 1 ÷ 3.5 HC 99 ÷ 96.5

The amount of finished carbon fiber in the polyesterimide composite is 20 wt.%. The treatment with such a sizing agent increases the wettability of the carbon fiber by the matrix polyesterimide, and makes it possible to heat-treat the resulting product repeatedly if necessary without changing the properties of the sizing composition.

Finished fibers are obtained by treating carbon fiber with a sizing agent - a solution of 1-methyl-3,4-diaminobenzene in acetone. The polymer composite materials of the present invention are obtained by pre-mixing the polymer matrix and sized carbon fiber using a high-speed homogenizer Multi function disintegrator VLM-40B. 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. Used carbon fiber brand RK-306 (IFI Technical Production), acetone, brand "HCh".

Below are examples illustrating the method of obtaining finished carbon fibers using a sizing component.

Example 1. Preparation of finished HC with 1.0 wt.% MDAB

24.75 g (99.0 wt.%) of HC with a fiber length of 3 mm is placed in a three-necked reaction flask equipped with a stirrer, a nitrogen gas supply system and a direct condenser, and the solution obtained by dissolving 0.25 g (1.0 wt. %) MDAB in 175 ml of acetone (0.18% solution). Include a stirrer, nitrogen supply, and incubated for 10 minutes at a temperature of 20°C. After that, the contents of the flask are heated and acetone is distilled off according to the regime: 30°C - 10 min; 40°C - 15 min; 50°C - 10 min; 60°C - 25 min.

Finished fiber is dried in a drying oven under vacuum at 76÷78°C for 2 hours.

Example 2. Preparation of finished HC with 1.5 wt.% MDAB

24.625 g (98.5 wt.%) of HC with a fiber length of 3 mm is placed in a three-necked reaction flask equipped with a stirrer, a nitrogen gas supply system and a direct condenser and a solution obtained by dissolving 0.375 g (1.5 wt.%) of MDAB in 175 ml of acetone (0.27% solution). Include a stirrer, nitrogen supply, and incubated for 10 minutes at a temperature of 20°C. After that, the contents of the flask are heated and acetone is distilled off according to the regime: 30°C - 10 min; 40°C - 15 min; 50°C - 10 min; 60°C - 25 min.

Finished fiber is dried in a drying oven under vacuum at 76÷78°C for 2 hours.

Example 3. Preparation of finished HC with 2.0 wt.% MDAB

24.5 g (98.0 wt.%) of HC with a fiber length of 3 mm is placed in a three-necked reaction flask equipped with a stirrer, a nitrogen gas supply system and a direct condenser, and the solution obtained by dissolving 0.5 g (2.0 wt. %) MDAB in 175 ml of acetone (0.36% solution). Include a stirrer, nitrogen supply, and incubated for 10 minutes at a temperature of 20°C. After that, the contents of the flask are heated and acetone is distilled off according to the regime: 30°C - 10 min; 40°C - 15 min; 50°C - 10 min; 60°C - 25 min.

Finished fiber is dried in a drying oven under vacuum at 76÷78°C for 2 hours.

Example 4. Preparation of finished HC with 2.5 wt.% MDAB

24.375 g (97.5 wt.%) of HC with a fiber length of 3 mm is placed in a three-necked reaction flask equipped with a stirrer, a nitrogen gas supply system and a direct condenser and a solution obtained by dissolving 0.625 g (2.5 wt.%) of MDAB in 175 ml of acetone (0.45% solution). Include a stirrer, nitrogen supply, and incubated for 10 minutes at a temperature of 20°C. After that, the contents of the flask are heated and acetone is distilled off according to the regime: 30°C - 10 min; 40°C - 15 min; 50°C - 10 min; 60C - 25 min.

Finished fiber is dried in a drying oven under vacuum at 76÷78°C for 2 hours.

Example 5. Preparation of finished HC with 3.0 wt.% MDAB

24.25 g (97.0 wt.%) of HC with a fiber length of 3 mm is placed in a three-necked reaction flask equipped with a stirrer, a nitrogen gas supply system and a direct condenser, and the solution obtained by dissolving 0.75 g (3.0 wt. %) MDAB in 175 ml of acetone (0.54% solution). Include a stirrer, nitrogen supply, and incubated for 10 minutes at a temperature of 20°C. After that, the contents of the flask are heated and acetone is distilled off according to the regime: 30°C - 10 min; 40°C - 15 min; 50°C - 10 min; 60°C - 25 min.

Finished fiber is dried in a drying oven under vacuum at 76÷78°C for 2 hours.

Example 6. Preparation of finished HC with 3.5 wt.% MDAB

24.125 g (96.5 wt.%) of HC with a fiber length of 3 mm is placed in a three-necked reaction flask equipped with a stirrer, a nitrogen gas supply system and a direct condenser and a solution obtained by dissolving 0.875 g (3.5 wt.%) of MDAB in 175 ml of acetone (0.63% solution). Include a stirrer, nitrogen supply, and incubated for 10 minutes at a temperature of 20°C. After that, the contents of the flask are heated and acetone is distilled off according to the regime: 30°C - 10 min; 40°C - 15 min; 50°C - 10 min; 60°C - 25 min.

Finished fiber is dried in a drying oven under vacuum at 76÷78°C for 2 hours.

From the finished hydrocarbons and PEI, polymer composite materials were obtained containing 20 wt.% of carbon fibers finished with 1-methyl-3,4-diaminobenzene.

Table 1 shows the compositions and compressive strength values of the composite materials of examples 1-6 treated with different amounts of sizing additive.

Table 1

Composition (wt%) σ _compression ,
MPa PEI + 20% HC raw 342 According to example 1 346 According to example 2 348 According to example 3 352 According to example 4 354 According to example 5 358 According to example 6 363

As can be seen from the above data, polymeric carbon fiber composite materials based on polyetherimide containing sized CFs (Nos. 1-6) exhibit higher compressive strength compared to a composite containing untreated carbon fiber.

The technical result of the invention is to improve the compressive strength of the created composite materials due to the introduction of a sizing compound - 1-methyl-3,4-diaminobenzene, which increases the wettability of the filler and increases the boundary interactions between the filler and the polyesterimide matrix.

Claims (5)

1. A method for producing sizing carbon fibers intended for structural polymeric materials based on sizing carbon (CF) fibers by applying a sizing component from a solution followed by drying in an oven under vacuum at 76-78 ° C, characterized in that the sizing, consisting of 1-methyl-3,4-diaminobenzene (MDAB) is applied from solutions with mass concentrations of 0.18-0.63% in an organic solvent of acetone and a stepwise increase in temperature and distillation of the solvent are carried out according to the regime: 20 ° C - 10 min; 30°С - 10 min; 40°C - 15 min; 50°C - 10 min; 60°C - 25 min, and the quantitative ratio of the components corresponds in wt.%: MDAB 1 - 3.5 HC 99 - 96.5 2. Finished carbon fiber for structural products in additive technologies, obtained by the method according to p. 1. 3. Polymer composite material used in the manufacture of products in additive technologies, containing a polymer matrix based on polyesterimide and finished carbon fiber, characterized in that the finished carbon fiber according to claim 2 is used, and the quantitative ratio of components in the composite material corresponds to wt.% : Polyetherimide 80 Finished carbon fiber 20