CN112813675B

CN112813675B - Metallized polyimide fiber and preparation method thereof

Info

Publication number: CN112813675B
Application number: CN202011555285.7A
Authority: CN
Inventors: 王彬; 刘大亮
Original assignee: Ganzhou Silver Metal Material Development Co ltd
Current assignee: Ganzhou Silver Metal Material Development Co ltd
Priority date: 2020-12-24
Filing date: 2020-12-24
Publication date: 2023-08-29
Anticipated expiration: 2040-12-24
Also published as: CN112813675A

Abstract

The invention discloses a metallized polyimide fiber and a preparation method thereof. The metallized polyimide fiber comprises a base material fiber and a composite metal layer coated on the surface of the base material fiber, wherein the base material fiber is polyimide fiber with fineness of 200D-2000D and breaking strength of more than or equal to 3.5 Gpa; the composite metal layer comprises an inner metal layer, an intermediate metal layer and an outer metal layer, wherein the metal of the inner metal layer is selected from one of silver, nickel, copper or tin; the metal of the interlayer metal layer is selected from one of silver, nickel, copper or tin; the metal of the outer metal layer is selected from one of silver, nickel, copper or tin, and the metals of the inner metal layer, the middle metal layer and the outer metal layer are different from each other. The metallized polyimide fiber has the characteristics of excellent performance, high strength, excellent conductivity, high temperature resistance, good flexibility, firm combination of metal layers and the like.

Description

Metallized polyimide fiber and preparation method thereof

Technical Field

The invention relates to the technical field of high-performance fibers, in particular to a metallized polyimide fiber and a preparation method thereof.

Background

With the rapid development of modern high and new technologies such as high-frequency communication, microelectronics, artificial intelligence, aerospace and the like, the requirements on the comprehensive performance of materials are also higher and higher, and the development is continuously carried out towards the directions of high performance, multifunction, light weight and the like. The polyimide fiber has the advantages of low density, high strength, corrosion resistance, radiation resistance, low expansion, good thermal stability and the like, and is an ideal matrix material for preparing conductive functional fiber materials. The conductive functional fiber material has the characteristics of light weight, softness, bending resistance and the like, has the functions of eliminating static electricity, electromagnetic shielding, detecting and transmitting electric signals and the like, is easy to process, shows excellent comprehensive performance, and has wide application prospect in the fields of aerospace, national defense and military industry, weapon equipment, high-frequency communication, microelectronics, artificial intelligence, medical treatment, protection and the like.

CN101446037B discloses a preparation method of conductive polyimide fiber, the technical route disclosed by the invention is as follows: pretreatment, washing, chemical roughening, sensitization, activation, dispergation, chemical copper plating, deionized water washing, sensitization, activation, dispergation, chemical nickel plating, water washing, drying and finished product, and the process flow is very complex and takes a long time, so that the method is not suitable for industrial production. CN106637934a discloses a polyimide fiber surface metallization processing method, which comprises the following process flows: the invention belongs to the traditional chemical plating process, in particular to a method for uniformly covering each fiber wire with a metal plating layer for a 600D-2000D crude fiber wire bundle, wherein the phenomenon of plating leakage exists for the crude fiber wire bundle. CN109989263a discloses a preparation method of high-performance silver-plated conductive fibers, which comprises the following process flows: deoiling and cleaning, modifying, presoaking, activating, debonding, chemical silvering, and plating leakage phenomenon also exists when a metal layer is plated on the crude fiber bundles.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the metallized polyimide fiber which has the characteristics of excellent performance, high strength, excellent conductivity, high temperature resistance, good flexibility, firm combination of metal layers and the like.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:

the metallized polyimide fiber comprises a base material fiber and a composite metal layer coated on the surface of the base material fiber, wherein the base material fiber is polyimide fiber with fineness of 200D-2000D and breaking strength of more than or equal to 3.5 Gpa; the composite metal layer comprises an inner metal layer, an intermediate metal layer and an outer metal layer, wherein the metal of the inner metal layer is selected from one of silver, nickel, copper or tin; the metal of the interlayer metal layer is selected from one of silver, nickel, copper or tin; the metal of the outer metal layer is selected from one of silver, nickel, copper or tin, and the metals of the inner metal layer, the middle metal layer and the outer metal layer are different from each other.

According to the invention, polyimide fiber with fineness of 200D-2000D and breaking strength of more than or equal to 3.5Gpa is selected as a base material fiber, and the composite metal layer is coated on the surface of the fiber, so that the prepared metallized polyimide fiber has the advantages of excellent performance, high strength (breaking strength of more than or equal to 3.0 GPa), excellent conductivity (length surface resistance of less than or equal to 2.0 ohm/m), high temperature resistance, good flexibility, firm combination of the metal layer and the like.

Preferably, the metal of the inner metal layer is copper, the metal of the middle metal layer is nickel, and the metal of the outer metal layer is silver, so that the conductivity of the fiber is improved.

Preferably, the thickness of the inner metal layer is 1-3 μm, which is beneficial to improving the conductivity of the fiber.

Preferably, the thickness of the middle layer metal layer is 2-6 μm, which is beneficial to improving the conductivity of the fiber.

Preferably, the thickness of the outer metal layer is 1-3 μm, which is beneficial to improving the conductivity of the fiber.

The invention also provides a preparation method of the metallized polyimide fiber, which comprises the following steps:

(1) Oil and gel removal: carrying out oil removal and glue removal treatment on the base material fiber, washing the base material fiber to be neutral by deionized water after the treatment is finished, and then drying;

(2) Surface modification: performing low-temperature plasma treatment on the polyimide fiber treated in the step (1), wherein the treatment power is 500-2500W, the treatment time is 2-20min, and the polyimide fiber is washed to be neutral by deionized water and then dried;

(3) Surface adjustment: carrying out surface adjustment treatment on the polyimide fiber treated in the step (2) by adopting an enamine cationic surfactant solution, washing the polyimide fiber to be neutral by deionized water after the treatment is finished, and then drying the polyimide fiber;

(4) And (3) metallization: carrying out metallization treatment on the surface of the polyimide fiber treated in the step (3), washing the surface with deionized water to be neutral after the treatment is finished, and then drying;

(5) Post protection: and (3) performing post-protection treatment on the surface of the polyimide fiber treated in the step (4), washing the surface to be neutral by deionized water after the treatment, and then drying to obtain a metallized polyimide fiber finished product.

In the preparation process flow, firstly, oil and glue removal treatment is carried out on the surface of the base material fiber to obtain a clean surface; then, modifying the fiber through low-temperature plasma treatment to obtain a surface with certain defects and roughness so as to facilitate the adhesion of subsequent conductive metal substances; then adopting enamine cationic surfactant to carry out surface adjustment on the modified fiber, so that the surface of the fiber is positively charged, thereby being beneficial to improving the hydrophilicity of the fiber surface and improving the deposition effect of conductive metal substances on the material surface; and finally, carrying out metallization processing on the modified polyimide fiber to obtain the metallized polyimide fiber. Compared with the traditional chemical plating process, the preparation process can ensure that each fiber wire of the 600D-2000D crude fiber bundle is uniformly covered with the metal plating layer, reduce the occurrence of the plating leakage phenomenon, and further be beneficial to improving the comprehensive performance of the fiber.

The preparation method has the advantages of simple preparation process, short time consumption, low cost, energy conservation, safety, environmental protection and easy realization of batch production.

Experiments show that compared with surface modification methods such as a chemical method, an electrochemical method, a coupling agent method, ultraviolet irradiation and the like, the method is beneficial to improving the roughness of the surface of the fiber by modifying the fiber through low-temperature plasma treatment so as to facilitate the adhesion of subsequent conductive metal substances.

Compared with other types of surfactants, the invention adopts enamine cationic surfactant solution to carry out surface adjustment treatment, which is more beneficial to the subsequent improvement of the deposition effect of conductive metal substances on the fiber surface.

Preferably, in the step (1), the method for removing oil and glue is selected from one or more of an organic solvent method, a high-temperature chemical method, a high-temperature alkali solution method and an electrochemical method, and the time for removing oil and glue is 1-10min.

Preferably, the specific process of the surface conditioning treatment in step (3) is: and (3) carrying out activation treatment on the polyimide fiber treated in the step (2) by adopting an enamine cationic surfactant solution, wherein the concentration of the enamine cationic surfactant in the enamine cationic surfactant solution is 40-60mL/L, the treatment temperature is 50-60 ℃, the treatment time is 2-7min, and mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration is assisted in the activation process to ensure that each monofilament in the polyimide fiber is treated in place.

The invention is beneficial to the subsequent improvement of the deposition effect of the conductive substance on the fiber surface by adding and optimizing the process steps and related process parameters of the surface adjustment treatment.

Preferably, the metallization treatment in step (4) specifically comprises the steps of:

(4.1) presoaking: pre-soaking the polyimide fiber treated in the step (3) for 1-10min, wherein mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration is assisted in the pre-soaking process to ensure that each monofilament in the polyimide fiber is treated in place;

(4.2) activation: performing activation treatment on the polyimide fiber treated in the step (4.1) for 1-10min, wherein mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration is assisted in the activation process to ensure that each monofilament in the polyimide fiber is treated in place;

(4.3) debonding: and (3) carrying out de-sizing treatment on the polyimide fiber treated in the step (4.2) for 1-10min, wherein mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration is assisted in the de-sizing process to ensure that each monofilament in the polyimide fiber is treated in place.

(4.4) electroless plating: placing the polyimide fibers treated in the step (4.4) into chemical plating solution, wherein the chemical plating solution is chemical silver plating, chemical nickel plating, chemical copper plating or chemical tin plating, and mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the chemical plating process, so that the polyimide fibers maintain a good dispersion state in the solution, each monofilament in the fiber bundle is ensured to be uniformly and continuously deposited with metal, an inner metal layer is obtained, the chemical plating temperature is 20-100 ℃, and the reaction time is 1-60min;

(4.5) repeating the steps (4.1-4.4) to obtain an intermediate metal layer and an outer metal layer respectively.

Compared with the prior art, the invention has the beneficial effects that:

1. the metallized polyimide fiber prepared by the invention has excellent performance, particularly, the crude fiber bundles of 600D-2000D can uniformly cover each fiber yarn with a metal coating, the phenomenon of plating omission of the crude fiber bundles in the actual production process is avoided, and the metallized polyimide fiber has the advantages of high strength (the breaking strength is more than or equal to 3.0 GPa), excellent conductivity (the length surface resistance is less than or equal to 2.0 ohm/m), high temperature resistance, good flexibility, firm combination of the metal layers and the like.

2. The preparation process of the metallized polyimide fiber is simple, short in time consumption, low in cost, energy-saving, safe, environment-friendly, free of strong oxidant and easy to realize batch production.

Drawings

Fig. 1 shows the copper-plated polyimide fiber (a) obtained by the method of example 1 and the copper-plated polyimide fiber (B) obtained by the method of comparative example 4, wherein the original drawing is a color drawing, the fiber bundle plating layer of fig. 1 (a) is uniform, and the fiber bundle on fig. 1 (B) has a plating omission phenomenon.

FIG. 2 is a metallographic photograph of a cross section of a metallized polyimide fiber prepared in example 1, wherein the fiber is uniformly coated with a metal coating;

FIG. 3 is a metallographic photograph of a cross section of a metallized polyimide fiber prepared in example 2, wherein the fiber is uniformly coated with a metal coating;

FIG. 4 is a metallographic photograph of a cross section of a metallized polyimide fiber prepared in example 3, wherein the fiber is uniformly coated with a metal coating;

FIG. 5 is a metallographic photograph of a cross section of a metallized polyimide fiber prepared in example 4, wherein the fiber is uniformly coated with a metal coating.

Detailed Description

For a better description of the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to the following specific examples. It will be appreciated by persons skilled in the art that the specific embodiments described herein are for purposes of illustration only and are not intended to be limiting.

In the examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used, unless otherwise specified, are commercially available.

Example 1

A preparation method of metallized polyimide fiber comprises the following steps:

(1) Oil and gel removal: polyimide fiber with fineness of 1000D and breaking strength of 3.5Gpa is selected as base material fiber, the base material fiber is subjected to oil and glue removal treatment, deionized water is used for washing to be neutral after the treatment is finished, and then the base material fiber is dried;

(2) Surface modification: performing low-temperature plasma treatment on the polyimide fiber treated in the step (1), wherein the treatment power is 1000W, the treatment time is 10min, and the polyimide fiber is washed to be neutral by deionized water and then dried;

(3) Surface adjustment: activating the polyimide fiber treated in the step (2) by adopting an enamine cationic surfactant solution, wherein the concentration of the enamine cationic surfactant in the enamine cationic surfactant solution is 50mL/L, the treatment temperature is 60 ℃, and the treatment time is 5min, and mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the activation process to ensure that each monofilament in the polyimide fiber is treated in place;

(4) And (3) metallization:

(4.1) presoaking: pre-soaking the polyimide fiber treated in the step (3) for 5min, wherein mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration is assisted in the pre-soaking process to ensure that each monofilament in the polyimide fiber is treated in place;

(4.2) activation: performing activation treatment on the polyimide fiber treated in the step (4.1) for 5min, wherein mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration is assisted in the activation process to ensure that each monofilament in the polyimide fiber is treated in place;

(4.3) debonding: carrying out de-colloid treatment on the polyimide fiber treated in the step (4.2) for 5min, wherein mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the de-colloid treatment process to ensure that each monofilament in the polyimide fiber is treated in place, and deionized water is used for washing until the treated monofilament is neutral, and then drying;

(4.4) electroless plating: placing the polyimide fiber treated in the step (4.3) into an electroless plating solution, wherein the electroless plating solution is electroless copper plating, mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the electroless plating process, so that the polyimide fiber is kept in a good dispersion state in the solution, each monofilament in the fiber bundle is ensured to be uniformly and continuously deposited with metal, an inner metal layer with the thickness of 2 mu m is obtained, the electroless plating temperature is 50 ℃, the reaction time is 10min, and the prepared copper-plated polyimide fiber is uniform and consistent in plating layer on the fiber and free of plating leakage as shown in the graph (A) of fig. 1;

(4.5) repeating the steps (4.1-4.4) to obtain an intermediate layer metal layer with the thickness of 2 mu m, wherein the electroless plating solution is electroless nickel, the electroless plating temperature is 80 ℃, and the reaction time is 2min;

(4.6) repeating the steps (4.1-4.4) to obtain an outer metal layer with the thickness of 1 mu m, wherein the electroless plating solution is electroless silver plating, the electroless plating temperature is 80 ℃, the reaction time is 2min, and the treated metal layer is washed to be neutral by deionized water and then dried;

Example 2

(3) Surface adjustment: activating the polyimide fiber treated in the step (2) by adopting an enamine cationic surfactant solution, wherein the concentration of the enamine cationic surfactant in the enamine cationic surfactant solution is 50mL/L, the treatment temperature is 60 ℃, and the treatment time is 5min, and mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the activation process to ensure that each monofilament in the polyimide fiber is treated in place; treating each monofilament in the imine fiber in place, washing the treated monofilament to be neutral by deionized water, and then drying;

(4) And (3) metallization:

(4.1) electroless plating: placing the polyimide fiber treated in the step (4.3) into an electroless plating solution, wherein the electroless plating solution is electroless copper plating, mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the electroless plating process, so that the polyimide fiber is kept in a good dispersion state in the solution, each monofilament in the fiber bundle is ensured to be uniformly and continuously deposited with metal, an inner metal layer with the thickness of 1 mu m is obtained, the electroless plating temperature is 50 ℃, and the reaction time is 3min;

(4.5) repeating the steps (4.1-4.4) to obtain an intermediate layer metal layer with the thickness of 2 mu m, wherein electroless nickel plating is selected as electroless plating solution, the electroless plating temperature is 60 ℃, and the reaction time is 5min;

(4.6) repeating the steps (4.1-4.4) to obtain an outer metal layer with the thickness of 1 mu m, wherein chemical plating solution is selected as chemical silver plating, the chemical plating temperature is 100 ℃, and the reaction time is 1min; washing the treated product to be neutral by deionized water, and then drying;

Example 3

(3) Surface adjustment: performing activation treatment on the polyimide fiber treated in the step (2), wherein the concentration of the enamine cationic surfactant in the enamine cationic surfactant solution is 50mL/L, the treatment temperature is 60 ℃, and the treatment time is 5min, and mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the activation process to ensure that each monofilament in the polyimide fiber is treated in place;

(4) And (3) metallization:

(4.4) electroless plating: placing the polyimide fiber treated in the step (4.3) into an electroless plating solution, wherein the electroless plating solution is electroless copper plating, mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the electroless plating process, so that the polyimide fiber is kept in a good dispersion state in the solution, each monofilament in the fiber bundle is ensured to be uniformly and continuously deposited with metal, an inner metal layer with the thickness of 3 mu m is obtained, the electroless plating temperature is 100 ℃, and the reaction time is 5min;

(4.5) repeating the steps (4.1-4.4) to obtain an intermediate layer metal layer with the thickness of 6 mu m, wherein the electroless plating solution is electroless nickel, the electroless plating temperature is 70 ℃, and the reaction time is 40min;

(4.6) repeating the steps (4.1-4.4) to obtain an outer metal layer with the thickness of 3 mu m, wherein the electroless plating solution is electroless silver plating, the electroless plating temperature is 60 ℃, the reaction time is 15min, and the treated metal layer is washed to be neutral by deionized water and then dried;

Example 4

(1) The method comprises the steps of deoiling and removing glue, wherein polyimide fiber with fineness of 1000D and breaking strength of 3.5Gpa is used as base material fiber, deoiling and removing glue is carried out on the base material fiber, deionized water is used for washing to be neutral after the treatment is finished, and then drying is carried out;

(3) Surface adjustment: activating the polyimide fiber treated in the step (2) by adopting an enamine cationic surfactant solution, wherein the concentration of the enamine cationic surfactant in the enamine cationic surfactant solution is 50mL/L, the treatment temperature is 60 ℃, and the treatment time is 5min, and mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the activation process to ensure that each monofilament in the polyimide fiber is treated in place; (4) metallization:

(4.2) activation: performing activation treatment on the polyimide fiber treated in the step (4.1), wherein the concentration of the enamine cationic surfactant in the enamine cationic surfactant solution is 50mL/L, the treatment temperature is 60 ℃, and the treatment time is 5min, and mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the activation process to ensure that each monofilament in the polyimide fiber is treated in place;

(4.4) electroless plating: placing the polyimide fiber treated in the step (4.3) into an electroless plating solution, wherein the electroless plating solution is electroless copper plating, mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the electroless plating process, so that the polyimide fiber is kept in a good dispersion state in the solution, each monofilament in the fiber bundle is ensured to be uniformly and continuously deposited with metal, an inner metal layer with the thickness of 1 mu m is obtained, the electroless plating temperature is 50 ℃, and the reaction time is 1min;

(4.5) repeating the steps (4.1-4.4) to obtain an intermediate layer metal layer with the thickness of 6 mu m, wherein the electroless plating solution is electroless nickel, the electroless plating temperature is 30 ℃, and the reaction time is 60min;

(4.6) repeating the steps (4.1-4.4) to obtain an outer metal layer with the thickness of 2 mu m, wherein the electroless plating solution is electroless silver plating, the electroless plating temperature is 50 ℃, the reaction time is 10min, and the treated metal layer is washed to be neutral by deionized water and then dried;

Example 5

(1) Oil and gel removal: polyimide fiber with fineness of 2000D and breaking strength of 3.5Gpa is selected as base material fiber, the base material fiber is subjected to oil and glue removal treatment, deionized water is used for washing to be neutral after the treatment is finished, and then the base material fiber is dried;

(2) Surface modification: performing low-temperature plasma treatment on the polyimide fiber treated in the step (1), wherein the treatment power is 500W, the treatment time is 20min, and the polyimide fiber is washed to be neutral by deionized water and then dried;

(3) Surface adjustment: activating the polyimide fiber treated in the step (2) by adopting an enamine cationic surfactant solution, wherein the concentration of the enamine cationic surfactant in the enamine cationic surfactant solution is 40mL/L, the treatment temperature is 50 ℃, and the treatment time is 7min, and mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the activation process to ensure that each monofilament in the polyimide fiber is treated in place; each monofilament in the amine fiber is treated in place, and the treated monofilament is washed to be neutral by deionized water and then dried;

(4) And (3) metallization:

(4.1) presoaking: pre-soaking the polyimide fiber treated in the step (3) for 1min, wherein mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration is assisted in the pre-soaking process to ensure that each monofilament in the polyimide fiber is treated in place;

(4.2) activation: performing activation treatment on the polyimide fiber treated in the step (4.1) for 7min, wherein mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration is assisted in the activation process to ensure that each monofilament in the polyimide fiber is treated in place;

(4.3) debonding: carrying out de-sizing treatment on the polyimide fiber treated in the step (4.2) for 1-10min, wherein mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the de-sizing process to ensure that each monofilament in the polyimide fiber is treated in place, and the polyimide fiber is washed to be neutral by deionized water after the treatment is finished and then dried;

(4.4) electroless plating: placing the polyimide fiber treated in the step (4.3) into an electroless plating solution, wherein the electroless plating solution is electroless copper plating, mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the electroless plating process, so that the polyimide fiber is kept in a good dispersion state in the solution, each monofilament in the fiber bundle is ensured to be uniformly and continuously deposited with metal, an inner metal layer with the thickness of 3 mu m is obtained, the electroless plating temperature is 50 ℃, and the reaction time is 15min;

(4.5) repeating the steps (4.1-4.4) to obtain an intermediate layer metal layer with the thickness of 4 mu m, wherein the electroless plating solution is electroless tin plating, the electroless plating temperature is 80 ℃, and the reaction time is 20min;

(4.6) repeating the steps (4.1-4.4) to obtain an outer metal layer with the thickness of 1 mu m, wherein the electroless plating solution is electroless silver plating, the electroless plating temperature is 55 ℃, the reaction time is 2min, and the treated metal layer is washed to be neutral by deionized water and then dried;

Example 6

(1) Oil and gel removal: polyimide fiber with fineness of 600D and breaking strength of 3.5Gpa is selected as base material fiber, the base material fiber is subjected to oil and glue removal treatment, deionized water is used for washing to be neutral after the treatment is finished, and then the base material fiber is dried;

(2) Surface modification: performing low-temperature plasma treatment on the polyimide fiber treated in the step (1), wherein the treatment power is 2500W, the treatment time is 2min, and the polyimide fiber is washed to be neutral by deionized water and then dried;

(3) Surface adjustment: activating the polyimide fiber treated in the step (2) by adopting an enamine cationic surfactant solution, wherein the concentration of the enamine cationic surfactant in the enamine cationic surfactant solution is 60mL/L, the treatment temperature is 60 ℃, and the treatment time is 2min, and mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the activation process to ensure that each monofilament in the polyimide fiber is treated in place; (4) metallization:

(4.1) presoaking: pre-soaking the polyimide fiber treated in the step (3) for 10min, wherein mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration is assisted in the pre-soaking process to ensure that each monofilament in the polyimide fiber is treated in place;

(4.2) activation: performing activation treatment on the polyimide fiber treated in the step (4.1) for 2min, wherein mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration is assisted in the activation process to ensure that each monofilament in the polyimide fiber is treated in place;

(4.4) electroless plating: placing the polyimide fiber treated in the step (4.3) into an electroless plating solution, wherein the electroless plating solution is electroless copper plating, mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the electroless plating process, so that the polyimide fiber is kept in a good dispersion state in the solution, each monofilament in the fiber bundle is ensured to be uniformly and continuously deposited with metal, an inner metal layer with the thickness of 2 mu m is obtained, the electroless plating temperature is 60 ℃, and the reaction time is 8min;

(4.5) repeating the steps (4.1-4.4) to obtain an intermediate layer metal layer with the thickness of 6 mu m, wherein the electroless plating solution is electroless nickel, the electroless plating temperature is 85 ℃, and the reaction time is 30min;

(4.6) repeating the steps (4.1-4.4) to obtain an outer metal layer with the thickness of 2 mu m, wherein the electroless plating solution is electroless silver plating, the electroless plating temperature is 70 ℃, the reaction time is 5min, and the treated metal layer is washed to be neutral by deionized water and then dried;

Comparative example 1

(4) And (3) metallization:

(4.1) electroless plating:

(4.4) placing the polyimide fibers treated in the step (4.3) into an electroless plating solution, wherein the electroless plating solution is electroless silver plating, mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the electroless plating process, so that the polyimide fibers maintain a good dispersion state in the solution, each monofilament in the fiber bundle is ensured to be uniformly and continuously deposited with metal, a metal layer with the thickness of 1 mu m is obtained, the electroless plating temperature is 80 ℃, the reaction time is 2min, deionized water is used for washing to be neutral after the treatment is completed, and then the fiber bundle is dried;

Comparative example 2

(2) Surface modification: modifying the polyimide fiber treated in the step (1) by adopting a silane coupling agent for 10min, washing the polyimide fiber to be neutral by deionized water after the treatment is finished, and then drying the polyimide fiber;

(4) And (3) metallization:

(4.4) electroless plating: placing the polyimide fiber treated in the step (4.3) into an electroless plating solution, wherein the electroless plating solution is electroless copper plating, mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the electroless plating process, so that the polyimide fiber is kept in a good dispersion state in the solution, each monofilament in the fiber bundle is ensured to be uniformly and continuously deposited with metal, an inner metal layer with the thickness of 2 mu m is obtained, the electroless plating temperature is 50 ℃, and the reaction time is 10min;

Comparative example 3

(1) Oil and gel removal: polyimide fiber with fineness of 100D and breaking strength of 2.5Gpa is selected as base material fiber, the base material fiber is subjected to oil and glue removal treatment, deionized water is used for washing to be neutral after the treatment is finished, and then the base material fiber is dried;

Comparative example 4

(1) Polyimide fiber with fineness of 1000D and breaking strength of 3.5Gpa is selected as a base material fiber, and the polyimide fiber is ultrasonically cleaned and dried in acetone;

(2) Coarsening polyimide fibers in a mixed solution of potassium permanganate and sodium hydroxide for 10min at 80 ℃, wherein the concentration of the potassium permanganate in the mixed solution of the potassium permanganate and the sodium hydroxide is 80g/L, and the concentration of the sodium hydroxide is 100g/L;

(3) Activating polyimide fiber in ionic palladium complex solution with the concentration of palladium ions of 250mg/L at 50 ℃ for 10min;

(4) Reducing polyimide fibers in a 5g/L dimethyl ammonia borane solution at 30 ℃ for 10min to reduce ionic palladium adsorbed on the surfaces of the fibers into metallic palladium;

(5) The polyimide fiber is placed in a chemical copper solution, chemical copper is deposited on the surface of the polyimide fiber for 20min at 40 ℃ by using a chemical copper electroplating method, and the copper-plated polyimide fiber is prepared, wherein the chemical copper solution consists of potassium sodium tartrate with the concentration of 60g/L, copper sulfate with the concentration of 10g/L, sodium hydroxide with the concentration of 15g/L, formaldehyde with the concentration of 15mL/L and nickel chloride with the concentration of 10 g/L.

As shown in FIG. 1 (B), the copper-plated polyimide fibers prepared in this comparative example were free from the phenomenon of missing plating in the crude fiber bundles, and each fiber yarn could not be uniformly coated with a metal plating.

The metallized polyimide fibers prepared in the above examples and comparative examples were tested for electrical conductivity and breaking strength, and the results are shown in table 1.

TABLE 1

Group of	Length surface resistance (omega/m)	Breaking strength (GPa)
			Example 1	1.92	3.3
Example 2	2.00	3.2
			Example 3	1.58	3.2
Example 4	1.74	3.3
			Example 5	1.78	3.4
Example 6	1.60	3.2
			Comparative example 1	3.94	3.2
Comparative example 2	2.38	3.2
			Comparative example 3	1.93	2.2

From the above results, it is clear that the metallized polyimide fibers prepared in examples 1 to 6 have both higher conductive properties and higher breaking strength than those of the comparative examples.

Fig. 2-5 are metallographic photographs of the sections of the metallized polyimide fibers prepared in example 1, example 2, example 3 and example 4, respectively, and it can be seen that each fiber wire can be uniformly coated with a metal coating, and no plating leakage phenomenon exists, so that the problem that the conventional electroless plating process is effective for 600-2000D thick fiber bundles, and the plating leakage phenomenon exists in the actual production process is solved.

Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted equally without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. The metallized polyimide fiber is characterized by comprising a base material fiber and a composite metal layer coated on the surface of the base material fiber, wherein the base material fiber is polyimide fiber with fineness of 200D-2000D and breaking strength of more than or equal to 3.5 Gpa; the composite metal layer comprises an inner metal layer, an intermediate metal layer and an outer metal layer, wherein the metal of the inner metal layer is selected from one of silver, nickel, copper or tin; the metal of the interlayer metal layer is selected from one of silver, nickel, copper or tin; the metal of the outer metal layer is selected from one of silver, nickel, copper or tin, and the metals of the inner metal layer, the middle metal layer and the outer metal layer are different from each other;

The thickness of the inner metal layer is 1-3 mu m, the thickness of the middle metal layer is 2-6 mu m, and the thickness of the outer metal layer is 1-3 mu m;

the polyimide fiber comprises low-temperature plasma treatment and surface adjustment treatment by using enamine cationic surfactant solution;

the metallization treatment comprises the step of placing the treated polyimide fibers into an electroless plating solution for electroless plating.

2. The method for preparing the metallized polyimide fiber according to claim 1, which comprises the following steps:

3. The method for producing a metallized polyimide fiber according to claim 2, wherein in the step (1), the degreasing and photoresist-removing treatment is performed for 1 to 10 minutes by one or more selected from the group consisting of an organic solvent method, a high-temperature chemical method, a high-temperature alkali solution method and an electrochemical method.

4. The method for producing a metallized polyimide fiber according to claim 2, wherein the specific process of the surface conditioning treatment in step (3) is:

and (3) carrying out activation treatment on the polyimide fiber treated in the step (2) by adopting an enamine cationic surfactant solution, wherein the concentration of the enamine cationic surfactant in the enamine cationic surfactant solution is 40-60mL/L, the treatment temperature is 50-60 ℃, the treatment time is 2-7min, and mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration is assisted in the activation process to ensure that each monofilament in the polyimide fiber is treated in place.

5. The method of producing a metallized polyimide fiber according to claim 4, wherein the metallization treatment in the step (4) comprises the steps of:

(4.3) debonding: carrying out de-sizing treatment on the polyimide fiber treated in the step (4.2) for 1-10min, wherein mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration is assisted in the de-sizing process to ensure that each monofilament in the polyimide fiber is treated in place;

(4.4) electroless plating: placing the polyimide fibers treated in the step (4.3) into chemical plating solution, wherein the chemical plating solution is chemical silver plating, chemical nickel plating, chemical copper plating or chemical tin plating, and mechanical stirring, air stirring, ultrasonic vibration or mechanical vibration are assisted in the chemical plating process, so that the polyimide fibers maintain a good dispersion state in the solution, each monofilament in the fiber bundle is ensured to be uniformly and continuously deposited with metal, an inner metal layer is obtained, the chemical plating temperature is 20-100 ℃, and the reaction time is 1-60min;

(4.5) repeating the above steps (4.1) to (4.4) to obtain an intermediate metal layer and an outer metal layer, respectively.