RU2793866C1 - Method for obtaining dressed carbon fibres and polyesterimide composite - Google Patents

Abstract

FIELD: carbon fibres.

SUBSTANCE: products manufactured using additive techniques. The method for obtaining dressed carbon fibres includes applying a dressing composition from a solution followed by drying. The dressing composition contains 1-methyl-2,5-diaminobenzene and polyetheretherketone based on 4,4'-dioxydiphenylpropane and 4,4'-difluorobenzophenone. A polyetherimide carbon fibre composite has also been proposed.

EFFECT: improving the elasticity and bending strength of the polyesterimide carbon fibre composite.

2 cl, 1 tbl, 6 ex

Description

The invention relates to a method for producing finished carbon fibers and polyesterimide 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 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, sizes 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. Previously, 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 side low-molecular reaction products when the binder is combined 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 this solution is the relatively low flexural strength of polymer composites.

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

The task is achieved by the fact that polyetherimide composites filled with carbon filler are obtained by pre-treatment of carbon fiber with a sizing compound - polyetheretherketone (PEEK) based on 4,4'-dioxydiphenylpropane and 4,4'-difluorobenzophenone of the formula:

with a reduced viscosity of 0.8 dl/g, measured for 0.5 wt. % solution in chloroform, and 1-methyl-2,5-diaminobenzene (MDAB).

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

with a reduced viscosity of 0.6 dl/g, measured for a 0.5% solution in chloroform.

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

Carbon fiber 97.5; PEEK 2.46 ÷ 2.08; MDAB 0.04 ÷ 0.42.

The amount of sizing composition to carbon fiber corresponds to 2.5%. The amount of finished carbon fiber in the composite material corresponds to 20 wt. %. Treatment with such a sizing composition increases the wettability of the carbon fiber with polyesterimide, and allows repeated, if necessary, heat treatment of the resulting product without changing the properties of the sizing composition.

Finished fibers are obtained by treating carbon fiber with a sizing composition - a solution of polyether ether ketone and 1-methyl-2,5-diaminobenzene in a mixture of methylene chloride and diethyl ether. Polyetherimide carbon fiber composites of the present invention are obtained by pre-mixing the polymer matrix and sized glass 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), methylene chloride and diethyl ether, brand "HCh".

Below are examples illustrating a method for obtaining sizing carbon fibers using a sizing composition, and the sizing is applied from a solution with a mass concentration of 0.36 wt. % in a mixture of volatile organic solvents.

Example 1. Preparation of finished HC with 2.46 wt. % PEEK and 0.04 wt. % MDAB.

23.4 g (97.5 wt.%) of HC with a fiber length of 3 mm is placed in a three-necked reaction flask and a solution obtained by dissolving 0.59 g (2.46 wt.%) of PEEK and 0.01 g (0. 04 wt.%) MDAB in a mixture of 80 ml of methylene chloride and 80 ml of diethyl ether (0.36 wt.% solution). The flask is placed in a water bath, the stirrer is turned on, nitrogen is supplied, and incubated for 10 minutes at a temperature of 20 °C. After that, the contents of the flask are heated and diethyl ether and methylene chloride are distilled off according to the regime: 25 ° C - 10 min.; 30 °С - 15 min.; 35 °С - 15 min.; 40 °С - 15 min.

The dressed fiber is dried in an oven under vacuum at 41-42°C for 1.5 hours.

Example 2. Preparation of finished HC with 2.38 wt. % PEEK and 0.12 wt. % MDAB.

23.4 g (97.5 wt.%) of HC with a fiber length of 3 mm is placed in a three-necked reaction flask and a solution obtained by dissolving 0.57 g (2.38 wt.%) of PEEK and 0.03 g (0. 12 wt.%) MDAB in a mixture of 80 ml of methylene chloride and 80 ml of diethyl ether (0.36 wt.% solution). The flask is placed in a water bath, the stirrer is turned on, nitrogen is supplied, and incubated for 10 minutes at a temperature of 20 °C. After that, the contents of the flask are heated and diethyl ether and methylene chloride are distilled off according to the regime: 25 ° C - 10 min.; 30 °С - 15 min.; 35 °С - 15 min.; 40 °С - 15 min.

The dressed fiber is dried in an oven under vacuum at 41-42°C for 1.5 hours.

Example 3. Preparation of finished HC with 2.29 wt. % PEEK and 0.21 wt. % MDAB.

23.4 g (97.5 wt.%) of HC with a fiber length of 3 mm is placed in a three-necked reaction flask and a solution obtained by dissolving 0.55 g (2.29 wt.%) of PEEK and 0.05 g (0. 21 wt.%) MDAB in a mixture of 80 ml of methylene chloride and 80 ml of diethyl ether (0.36 wt.% solution). The flask is placed in a water bath, the stirrer is turned on, nitrogen is supplied, and incubated for 10 minutes at a temperature of 20 °C. After that, the contents of the flask are heated and diethyl ether and methylene chloride are distilled off according to the regime: 25 ° C - 10 min.; 30 °С - 15 min.; 35 °С - 15 min.; 40 °С - 15 min.

The dressed fiber is dried in an oven under vacuum at 41-42°C for 1.5 hours.

Example 4. Preparation of finished HC with 2.21 wt. % PEEK and 0.29 wt. % MDAB.

23.4 g (97.5 wt.%) of HC with a fiber length of 3 mm is placed in a three-necked reaction flask and a solution obtained by dissolving 0.53 g (2.21 wt.%) of PEEK and 0.07 g (0. 29 wt.%) MDAB in a mixture of 80 ml of methylene chloride and 80 ml of diethyl ether (0.36 wt.% solution). The flask is placed in a water bath, the stirrer is turned on, nitrogen is supplied, and incubated for 10 minutes at a temperature of 20 °C. After that, the contents of the flask are heated and diethyl ether and methylene chloride are distilled off according to the regime: 25 ° C - 10 min.; 30 °С - 15 min.; 35 °С - 15 min.; 40 °С - 15 min.

The dressed fiber is dried in an oven under vacuum at 41-42°C for 1.5 hours.

Example 5. Preparation of finished HC with 2.12 wt. % PEEK and 0.38 wt. % MDAB.

23.4 g (97.5 wt.%) of HC with a fiber length of 3 mm is placed in a three-necked reaction flask and a solution obtained by dissolving 0.51 g (2.12 wt.%) of PEEK and 0.09 g (0. 38 wt.%) MDAB in a mixture of 80 ml of methylene chloride and 80 ml of diethyl ether (0.36 wt.% solution). The flask is placed in a water bath, the stirrer is turned on, nitrogen is supplied, and incubated for 10 minutes at a temperature of 20 °C. After that, the contents of the flask are heated and diethyl ether and methylene chloride are distilled off according to the regime: 25 ° C - 10 min.; 30 °С - 15 min.; 35 °С - 15 min.; 40 °С - 15 min.

The dressed fiber is dried in an oven under vacuum at 41-42°C for 1.5 hours.

Example 6. Preparation of finished HC with 2.08 wt. % PEEK and 0.42 wt. % MDAB.

23.4 g (97.5 wt.%) of HC with a fiber length of 3 mm is placed in a three-necked reaction flask and a solution obtained by dissolving 0.5 g (2.08 wt.%) of PEEK and 0.1 g (0. 42 wt.%) MDAB in a mixture of 80 ml of methylene chloride and 80 ml of diethyl ether (0.36 wt.% solution). The flask is placed in a water bath, the stirrer is turned on, nitrogen is supplied, and incubated for 10 minutes at a temperature of 20 °C. After that, the contents of the flask are heated and diethyl ether and methylene chloride are distilled off according to the regime: 25 ° C - 10 min.; 30 °С - 15 min.; 35 °С - 15 min.; 40 °С - 15 min.

The dressed fiber is dried in an oven under vacuum at 41-42°C for 1.5 hours.

Composite materials containing 20 wt. % finished with polyetheretherketone and 1-methyl-2,5-diaminobenzene carbon fibers.

Table 1 presents the compositions, as well as the moduli of elasticity and flexural strength of composites containing hydrocarbons, according to examples 1-6.

Table 1 Compound E izg,
GPa σ bend,
MPa PEI 3.63 112.4 PEI + 20% HC (3 mm)
unapplied 8.48 207.1 According to example 1 10.15 253.6 According to example 2 10.65 256.5 According to example 3 11.86 265.5 According to example 4 12.46 272.7 According to example 5 11.77 269.9 According to example 6 11.34 266.8

where, E izg - modulus of elasticity in bending, σ izg - ultimate strength in bending.

As can be seen from the above data, polyetherimide carbon fiber composites containing sized CFs (Nos. 1-6) exhibit higher values of the modulus of elasticity and flexural strength compared to the composite containing untreated carbon fiber.

The technical result of the invention is to improve the modulus of elasticity and flexural strength of the created polyesterimide carbon fiber composites due to the introduction of a sizing composition - polyetheretherketone and 1-methyl-2,5-diaminobenzene, which increases the wettability of the filler and increases the boundary interactions between the filler and the polyesterimide matrix.

Claims (6)

1. A method for producing sizing carbon fibers intended for structural polymeric materials, based on sizing carbon fiber by applying a sizing component from a solution, followed by drying in an oven under vacuum at 41-42 ° C, characterized in that the sizing is applied from a solution with a mass a concentration of 0.36 wt.% in a mixture of volatile organic solvents of methylene chloride and diethyl ether and carry out a stepwise rise in temperature and distillation of solvents according to the mode: 20°C - 10 min; 25°С - 10 min; 30°С - 15 min; 35°C - 15 min; 40°C - 15 min, where the quantitative ratio of the components corresponds to the mass. %: carbon fiber 97.5 polyetheretherketone (PEEK) 2.46 - 2.08 1-methyl-2,5-diaminobenzene 0.04 - 0.42 moreover, PEEK based on 4,4'-dioxydiphenylpropane and 4,4'-difluorobenzophenone of the formula is used:

. 2. Polyetherimide carbon fiber composite used in the manufacture of structural products in additive technologies, containing a polymer matrix based on polyesterimide and finished carbon fiber, characterized in that the finished carbon fiber is used, obtained by the method according to claim 1, and the quantitative ratio of components in the polymer composite corresponds to in mass %: polyetherimide 80 finished carbon fiber 20