CN112210207B

CN112210207B - Preparation method of carbon fiber/polyamide composite powder material for laser sintering

Info

Publication number: CN112210207B
Application number: CN202011030889.XA
Authority: CN
Inventors: 孙茂银; 吴健; 古文全; 吴泽宏; 梁寅; 李英; 于云峰
Original assignee: Guizhou Senyuan Additive Manufacturing Technology Co ltd
Current assignee: Guizhou Senyuan Additive Manufacturing Technology Co ltd
Priority date: 2020-09-27
Filing date: 2020-09-27
Publication date: 2023-05-16
Anticipated expiration: 2040-09-27
Also published as: CN112210207A

Abstract

The invention discloses a preparation method of a carbon fiber/polyamide composite powder material for laser sintering, which specifically comprises the following steps: the surface of the carbon fiber is activated by a liquid-phase oxidation technology, so that organic functional groups such as-OH, -COOH and the like are formed on the surface of the carbon fiber; activating carboxyl end carboxyl on the surface of the carbon fiber by using a carboxyl activating reagent; then synthesizing amide on the surface of the carbon fiber in situ by using a catalyst; coating the carbon fiber surface with a thin layer of carbon fiber by a solvent precipitation method; the carbon fiber coated with polyamide is kept for 5 to 10 hours under the protection of nitrogen at the temperature of 10 to 20 ℃ below the melting point, so that the polyamide on the carbon fiber and the polyamide are polycondensed at high temperature; and then mechanically blending and sieving the polyamide spherical powder with 20 to 50 percent of polyamide spherical powder to obtain the polyamide carbon fiber composite powder material with high strength and high modulus. Solves the problems of low interface bonding strength, poor comprehensive mechanical property and the like of the existing material.

Description

Preparation method of carbon fiber/polyamide composite powder material for laser sintering

Technical field:

the invention relates to a polyamide carbon fiber composite powder material and a preparation method thereof, belonging to the field of carbon fiber composite material preparation.

The background technology is as follows:

3D printing is a product forming technology of layered manufacturing and layer-by-layer lamination; the rapid prototyping technology can integrally manufacture complex structural parts. In contrast to conventional machining techniques that reduce the base material by turning, milling, planing, grinding, etc., 3D printing is also referred to as additive manufacturing techniques. The selective laser sintering technology is a technology for preparing a product by melting and solidifying a powder material under the laser selection effect, and is the most widely applied 3D printing technology. The selective laser sintering products of high-performance materials such as metal, ceramic and the like are widely applied to the fields of mechanical industry, national defense, military, aerospace and the like. The polyamide semi-crystalline polymer material has the characteristics of low water absorption, small solidification deformation, stable thermodynamic performance and the like, and is the most widely used polymer laser sintering material at present. The selective laser sintering product of the existing polyamide powder material has the performance problems of low strength, small modulus, poor dimensional stability and the like, and prevents the selective laser sintering product from being popularized and applied in various fields such as aerospace and the like. The carbon fiber composite modification is an effective measure for improving the performance of the polymer material workpiece. The high-performance carbon fiber/resin composite material prepared by the traditional process is widely applied to the fields of aerospace and the like. The existing preparation technology of the carbon fiber polyamide/composite material for laser sintering is complex, and industrial application is difficult to realize; and the prepared polyamide resin material of the carbon fiber composite material has poor bonding strength between the carbon fiber and the matrix, small load transfer effect and low performance improvement amplitude.

The invention comprises the following steps:

aiming at the problems of low interface bonding strength, poor stress transfer effect and the like of the existing carbon fiber composite material, the invention provides a preparation method of a carbon fiber/polyamide composite material for laser sintering.

The preparation method of the carbon fiber/polyamide composite material provided by the invention can fully improve the compatibility of the carbon fiber and matrix resin, improve the interface strength, reduce the impact weakening effect of laser on the carbon fiber and the like, and can prepare the composite material with high strength, high modulus and uniform performance for laser sintering.

The preparation method of the carbon fiber/polyamide composite material provided by the invention comprises the following steps:

cleaning carbon fiber powder, and performing surface activation treatment on the carbon fiber by using one or more of gas phase oxidation, plasma treatment, liquid phase oxidation, anodic oxidation and the like, wherein the aim is to form organic functional groups such as-OH, -COOH and the like on the surface of the carbon fiber powder to obtain surface-organized carbon fiber; in the aspect of the treatment by liquid-phase oxidation, a method of oxidizing the treatment with a complex acid of 3 parts of concentrated nitric acid and 1 part of concentrated sulfuric acid is preferably employed. Immersing the carbon fiber into a mixed solution of concentrated HNO3 and concentrated H2SO4 (HNO 3: H2SO4=3:1), and carrying out reflux treatment at 60 ℃ for 1-2H. And (3) washing the acidified carbon fiber with deionized water until the PH value of the washing liquid is close to 7. The carbon fiber forms-OH and-COOH under the oxidation of concentrated nitric acid and concentrated sulfuric acid, as shown in figure 1.

The carbon fiber obtained in the previous step is immersed in a carboxyl activating reagent, preferably one of dicyclohexylcarbodiimide, diisopropylcarbodiimide and 1-ethyl-3 (3-dimethylpropylamine) carbodiimide. Adding 0.1-1% acetic acid, adjusting the pH value of the solution to the required pH value of the activator by hydrochloric acid, activating for 5-10 h at 20 ℃, taking out, and draining. The 1-ethyl-3 (3-dimethylpropylamine) carbodiimide is used for reacting with carbon fiber carboxyl end groups to form an intermediate unstable compound of the collar isourea, and the purpose of activating hydroxyl end groups is achieved, as shown in figure 2.

Immersing the carboxyl activated carbon fiber obtained in the previous step into one solution of ammonia compound or primary amine and secondary amine, adding a proper amount of one of 1-hydroxybenzotriazole, 4-dimethylaminopyridine and 4-pyrrolidinyl pyridine, stirring for 5-10 h at 20 ℃, taking out, washing with deionized water, and removing unreacted 1-ethyl-3 (3-dimethylpropylamine) carbodiimide, 1-hydroxybenzotriazole and the like on the surface to obtain the surface amidated carbon fiber. Taking PA12 as an example, carbon fiber-collar acyl isourea reacts with 12-aminododecanoic acid under the catalysis of 1-hydroxybenzotriazole to synthesize omega-dodecalactam monomer on the surface of the carbon fiber in situ, as shown in figures 3 and 4.

Immersing the surface amidated carbon fiber obtained in the previous step into a supersaturated solution of one or more of PA12, PA11, PA13, PA6, PA610, PA1010, PA1012 and PA1013 at 100-150 ℃ to slowly cool to 80-140 ℃, wherein one or more of PA12, PA11, PA13, PA6, PA610, PA1010, PA1012 and PA1013 is separated out by taking the surface amidated carbon fiber as a core part, thus obtaining the carbon fiber of the polyamide thin layer which is uniformly coated. In the case of PA12, the carbon fiber surface coating is shown in fig. 5.

And (3) placing the carbon fiber obtained in the last step into a nitrogen protection oven, and preserving heat for 5 hours at 170 ℃ to obtain the carbon fiber with the surface grafted with the polyamide. Taking PA12 as an example, the principle of in-situ synthesis of amide by carbon fiber and dehydration condensation polymerization of PA12 is shown in figure 6

Description of the drawings:

the carbon fiber of the attached figure 1 forms-COOH under the oxidation of concentrated nitric acid and concentrated sulfuric acid composite acid;

FIG. 2 shows that 1-ethyl-3 (3-dimethylpropylamine) carbodiimide is used for reacting carbon fiber carboxyl end groups to form an intermediate unstable compound of the collar isourea, so as to achieve the purpose of activating hydroxyl end groups;

FIG. 3 in situ synthesis of omega-dodecalactam monomer on the surface of carbon fiber by reacting carbon fiber-collar isourea with 12-aminododecanoic acid under the catalysis of 1-hydroxybenzotriazole;

FIG. 4 in situ synthesis of omega-dodecalactam molecular model by carbon fiber;

FIG. 5 is a schematic diagram of a film coating model on the surface of carbon fiber by a solvent precipitation method;

the omega-dodecalactam on the carbon fiber of fig. 6 is polycondensed with PA12 under the protection of high-temperature nitrogen.

The specific embodiment is as follows:

example 1

Immersing the carbon fiber into a mixed solution of concentrated HNO3 and concentrated H2SO4 (HNO 3: H2SO4=3:1), and carrying out reflux treatment at 60 ℃ for 1-2H. And (3) washing the acidified carbon fiber with deionized water until the PH value of the washing liquid is 7.

Immersing the carbon fiber in a dichloromethane solution of 1-ethyl-3 (3-dimethylpropylamine) carbodiimide, adding 0.1-1% acetic acid, adjusting the pH of the solution to be 4 by hydrochloric acid, activating at 20 ℃ for 5 hours, taking out, and draining. Then immersing the fiber into 12-aminododecanoic acid solution, adding a proper amount of 1-hydroxybenzotriazole, stirring for 5 hours at 20 ℃, taking out, washing with deionized water, and removing unreacted 1-ethyl-3 (3-dimethylpropylamine) carbodiimide, 1-hydroxybenzotriazole and the like on the surface to obtain the surface amidated carbon fiber.

And then immersing the surface amidated carbon fiber into a 150 ℃ PA12 supersaturated ethanol aqueous solution, slowly cooling to 140 ℃, and separating out the PA12 by taking the surface amidated carbon fiber as a core part to obtain the uniformly coated PA12 thin-layer carbon fiber.

Taking out, placing in a nitrogen protection oven, and preserving heat for 5 hours at 170 ℃ to obtain the carbon fiber with the surface grafted with PA 12.

Weighing 3kg of the carbon fiber prepared in the previous step, weighing 7kg of PA12 spherical powder, loading the powder into high-speed mixing equipment, adding 21g of N, N ' -bis- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexamethylenediamine, 21g of tris [2, 4-di-tert-butylphenyl ] phosphite, 7g of 2' - (2 ' -hydroxy-3 ' -tert-butyl-5 ' -methylphenyl) -5-chlorobenzotriazole, 14g of nano silicon dioxide and 14g of nano ATO, controlling the powder temperature to be 18-60 ℃ and intermittently stirring for 20min to obtain the carbon fiber/PA 12 composite material.

Adding the carbon fiber/PA 12 composite material powder obtained in the previous step into selective laser sintering equipment, wherein the preheating temperature of a forming cavity is 169 ℃, the laser scanning speed is 15m/s, the laser filling power is 85W, and the laser filling interval is 0.25mm. The test performance of the obtained product according to the national standard is shown in Table 1

Example 2

Weighing 4kg of the carbon fiber prepared in the previous step, weighing 6kg of PA12 spherical powder, loading the powder into high-speed mixing equipment, adding 18g of N, N ' -bis- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexamethylenediamine, 18g of tris [2, 4-di-tert-butylphenyl ] phosphite, 6g of 2' - (2 ' -hydroxy-3 ' -tert-butyl-5 ' -methylphenyl) -5-chlorobenzotriazole, 12g of nano silicon dioxide and 12g of nano ATO, controlling the temperature of the powder to be 18-60 ℃, and intermittently stirring for 20min to obtain the carbon fiber/PA 12 composite material.

Adding the carbon fiber/PA 12 composite material powder in the previous step into selective laser sintering equipment, wherein the preheating temperature of a forming cavity is 169 ℃, the laser scanning speed is 15m/s, the laser filling power is 85W, and the laser filling interval is 0.25mm. The test performance of the obtained product according to the national standard is shown in Table 1

Example 3

Weighing 5kg of the carbon fiber prepared in the previous step, weighing 5kg of PA12 spherical powder, loading the powder into high-speed mixing equipment, adding 15g of N, N ' -bis- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexamethylenediamine, 15g of tris [2, 4-di-tert-butylphenyl ] phosphite, 5g of 2' - (2 ' -hydroxy-3 ' -tert-butyl-5 ' -methylphenyl) -5-chlorobenzotriazole, 10g of nano silicon dioxide and 10g of nano ATO, controlling the temperature of the powder to be 18-60 ℃, and intermittently stirring for 20min to obtain the carbon fiber/PA 12 composite material.

Comparative example 1

10kg of PA12 spherical powder is weighed and put into high-speed mixing equipment, 30g of N, N ' -bis- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexamethylenediamine, 30g of tris [2, 4-di-tert-butylphenyl ] phosphite, 10g of 2' - (2 ' -hydroxy-3 ' -tert-butyl-5 ' -methylphenyl) -5-chlorobenzotriazole, 20g of nano silicon dioxide and 20g of nano ATO are added, the rotating speed is 1000-1500 r/min, the powder temperature is controlled to 18-60 ℃, and the intermittent stirring is carried out for 20min, thus obtaining the carbon fiber/PA 12 composite material.

Adding the PA12 material powder in the previous step into selective laser sintering equipment, wherein the preheating temperature of a forming cavity is 169 ℃, the laser scanning speed is 15m/s, the laser filling power is 85W, and the laser filling interval is 0.25mm. The test performance of the obtained product according to the national standard is shown in Table 1

TABLE 1 product Performance data (GBT 1040.1-2006, GBT 1040.2-2006)

	Tensile Strength/MPa	Tensile modulus/MPa
			Comparative example 1	46.3	1603
Example 1	52.5	4136
			Example 2	79.8	5806
Example 3	100.5	6538

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of a carbon fiber/polyamide composite powder material for laser sintering is characterized by comprising the following steps: the method comprises the following steps:

(1) Cleaning a carbon fiber powder raw material by using acetone, and then performing surface activation treatment on the carbon fiber by using one or more of gas phase oxidation, plasma treatment, liquid phase oxidation and anodic oxidation, wherein the aim is to form-OH, -COOH organic functional groups on the surface of the carbon fiber powder raw material to obtain surface-organized carbon fiber;

(2) Immersing the carbon fiber prepared in the previous step into a 1-ethyl-3 (3-dimethylpropylamine) carbodiimide solution, and activating carboxyl groups at the surface end of the carbon fiber to generate an unstable intermediate compound which is easy to react with amines, thereby obtaining carboxyl activated carbon fiber;

(3) Immersing the carbon fiber prepared in the previous step into an amine compound, and then adding a condensation reagent and a catalyst auxiliary agent to enable the carbon fiber to synthesize an amide polymer with small molecular weight on the surface of the carbon fiber in situ to obtain the surface grafted carbon fiber;

(4) Immersing the carbon fiber prepared in the previous step into a supersaturated polyamide solution, stirring, controlling a proper cooling rate, and coating a layer of uniform film on the surface of the carbon fiber by utilizing a heterogeneous preferential nucleation mechanism to obtain the carbon fiber with the surface coated with polyamide;

(5) Putting the carbon fiber prepared in the previous step into a baking oven, adopting nitrogen with oxygen content lower than 1% for protection, adding a small amount of cross-linking agent and condensation reagent auxiliary agent, and preserving heat at 170 ℃ for 5-10 h to enable an amide monomer or small molecular polymer on the carbon fiber to react with polyamide through dehydration condensation at high temperature, and slowly cooling to room temperature to obtain the polyamide composite carbon fiber;

(6) Weighing 30-50 parts of carbon fiber prepared in the previous step, weighing 50-70 parts of polyamide spherical powder, loading the powder into high-speed mixing equipment, adding 0.1-0.5% of antioxidant, 0.01-0.5% of light absorber, 0.05-0.2% of flow aid and 0.01-0.05% of antistatic agent processing aid, controlling the temperature of the powder to be 18-60 ℃, and intermittently stirring for 20min to obtain the carbon fiber/polyamide composite material.

2. The method for preparing a carbon fiber/polyamide composite powder material for laser sintering according to claim 1, wherein the carbon fiber powder has a diameter of 5 to 30 μm and a length of 50 to 300. Mu.m.

3. The method for producing a carbon fiber/polyamide composite powder material for laser sintering according to claim 1, wherein the polyamide in the step (6) comprises one or more of PA12, PA11, PA13, PA6, PA610, PA1010, PA1012, and PA 1013.