RU2793762C1 - Method for obtaining finished carbon fibre and polyesterimide composite material - 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 p-toluylenediamine in isopropanol. A polyetherimide composite material is also proposed.

EFFECT: improving the rheological properties of a polyesterimide composite material containing a dressed carbon fibre.

2 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 characteristics of polyetherimide 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, 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 the solution can be considered not quite high values of the rheological properties of composite materials.

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

This task is achieved in that the polyesterimide composite material reinforced with carbon filler is obtained by pre-treatment of carbon fiber with a sizing component - p-toluenediamine (p-TDA). In this case, the following ratios (wt. %) of the components in the filler are taken:

carbon fiber 99.5÷97 p-toluenediamine (p-TDA) 0.5÷3.0

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 according to the present invention are obtained by treating carbon fibers with a sizing component - a solution of p-toluylenediamine in isopropanol, followed by distillation of the solvent. Composite materials are obtained by pre-mixing the polymer matrix - polyesterimide of the following formula and finished 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) and polyetherimide (PEI) brand ULTEM-1010, which 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 0.62 dl/g, measured for 0.5 wt. % solution in chloroform, and isopropanol brand "HCh".

Below are examples illustrating a method for obtaining sizing carbon fibers using a sizing component, and the sizing is applied from solutions with mass concentrations of 0.11-0.57 wt. % in an organic solvent.

Example 1. Obtaining finished CF with 0.5 wt. % p-TDA.

24.875 g (99.5 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 0.125 g (0.5 wt.%) p -TDA in 165 ml of isopropanol (0.1 wt.% solution). Include a stirrer, nitrogen supply, and incubated for 20 minutes at a temperature of 20°C. After that, the contents of the flask are heated and isopropanol is distilled off according to the regime: 45°C - 12 minutes; 55°С - 12 min.; 65°С - 12 min.; 70°С - 15 min.; 75°С - 15 min, 83°С - 20 min.

The dressed fiber is dried in an oven under vacuum at 85-86°C for 2 hours.

Example 2. Obtaining finished CF with 1 wt. % p-TDA.

In a three-necked reaction flask equipped with a stirrer, a nitrogen gas supply system and a direct condenser, 24.75 g (99 wt.%) HC with a fiber length of 3 mm is placed and a solution obtained by dissolving 0.25 g (1 wt.%) p -TDA in 165 ml of isopropanol (0.19 wt.% solution). Include a stirrer, nitrogen supply, and incubated for 20 minutes at a temperature of 20°C. After that, the contents of the flask are heated and isopropanol is distilled off according to the regime: 45°C - 12 minutes; 55°С - 12 min.; 65°С - 12 min.; 70°С - 15 min.; 75°С - 15 min, 85°С - 20 min.

The dressed fiber is dried in an oven under vacuum at 90-95°C for 2 hours.

Example 3. Obtaining finished CF with 1.5 wt. % p-TDA.

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.%) p -TDA in 165 ml of isopropanol (0.29 wt.% solution). Include a stirrer, nitrogen supply, and incubated for 20 minutes at a temperature of 20°C. After that, the contents of the flask are heated and isopropanol is distilled off according to the regime: 45°C - 12 minutes; 55°С - 12 min.; 65°С - 12 min.; 70°С - 15 min.; 75°С - 15 min, 83°С - 20 min.

The dressed fiber is dried in an oven under vacuum at 85-86°C for 2 hours.

Example 4. Obtaining finished HC with 2 wt. % p-TDA.

In a three-necked reaction flask equipped with a stirrer, a nitrogen gas supply system and a direct condenser, 24.5 g (98 wt.%) of HC with a fiber length of 3 mm is placed and a solution obtained by dissolving 0.5 g (2 wt.%) of p -TDA in 165 ml of isopropanol (0.38 wt.% solution). Include a stirrer, nitrogen supply, and incubated for 20 minutes at a temperature of 20°C. After that, the contents of the flask are heated and isopropanol is distilled off according to the regime: 45°C - 12 minutes; 55°С - 12 min.; 65°С - 12 min.; 70°С - 15 min.; 75°С - 15 min, 83°С - 20 min.

The dressed fiber is dried in an oven under vacuum at 85-86°C for 2 hours.

Example 5. Obtaining finished CF with 2.5 wt. % p-TDA.

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.%) p -TDA in 165 ml of isopropanol (0.48 wt.% solution). Include a stirrer, nitrogen supply, and incubated for 20 minutes at a temperature of 20°C. After that, the contents of the flask are heated and isopropanol is distilled off according to the regime: 45°C - 12 minutes; 55°С - 12 min.; 65°С - 12 min.; 70°С - 15 min.; 75°С - 15 min, 83°С - 20 min.

The dressed fiber is dried in an oven under vacuum at 85-86°C for 2 hours.

Example 6. Obtaining finished CF with 3 wt. % p-TDA.

In a three-necked reaction flask equipped with a stirrer, a nitrogen gas supply system and a direct condenser, 24.25 g (97 wt.%) HC with a fiber length of 3 mm is placed and a solution obtained by dissolving 0.75 g (3 wt.%) p -TDA in 165 ml of isopropanol (0.57 wt.% solution). Include a stirrer, nitrogen supply, and incubated for 30 minutes at a temperature of 20°C. After that, the contents of the flask are heated and isopropanol is distilled off according to the regime: 45°C - 12 minutes; 55°С - 12 min.; 65°С - 12 min.; 70°С - 15 min.; 75°С - 15 min, 83°С - 20 min.

The dressed fiber is dried in an oven under vacuum at 85-86°C for 2 hours.

Composite materials containing 20 wt. % of carbon fibers finished with p-toluenediamine.

Table 1 presents the compositions and rheological properties of composite materials containing HC according to examples 1-6, treated with various amounts of sizing component.

Table 1 Composition (wt.%) PTR,
g/10 min ε, % PEI 13.2 22.7 PEI + 20% HC raw 3.4 4.4 According to example 1 7.18 4.46 According to example 2 7.46 4.55 According to example 3 7.57 4.78 According to example 4 7.78 4.85 According to example 5 8.45 4.96 According to example 6 8.57 4.95

where, MFI - melt flow index, ε - relative elongation at break.

As can be seen from the data presented, polymer compositions containing sized CFs (nos. 1–6) exhibit higher rheological properties compared to a composite containing untreated carbon fiber.

The technical result of the invention is to improve the rheological properties created by polyesterimide composite materials due to the preliminary introduction of a sizing component - p-toluylenediamine, which increases the wettability of the filler and increases the intermolecular interaction forces between the carbon fiber and the polyesterimide matrix.

Claims (4)

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 85-86 ° C, characterized in that the sizing is applied from solutions with mass concentrations of 0.11-0.57 wt. % in an organic solvent of isopropanol and carry out a stepwise rise in temperature with simultaneous distillation of the solvent according to the regime: 20°C - 20 min; 45°C - 12 min; 55°C - 12 min; 65°C - 12 min; 70°C - 15 min; 75°C - 15 min; 83°C - 20 min, and the quantitative ratio of the components corresponds, wt. %: carbon fiber 99.5÷97 p-toluenediamine (TDA) 0.5÷3.0 2. Polyetherimide 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 a finished carbon fiber is used, obtained by the method according to claim 1, and the quantitative ratio of the components in the composite material corresponds to, wt. %: polyetherimide 80 finished carbon fiber 20