CN113072830A

CN113072830A - Preparation method and application of polyaniline carbon nanotube core-shell composite material

Info

Publication number: CN113072830A
Application number: CN202110376349.5A
Authority: CN
Inventors: 朱爱萍; 张金戈
Original assignee: Yangzhou University
Current assignee: Yangzhou University
Priority date: 2021-04-08
Filing date: 2021-04-08
Publication date: 2021-07-06

Abstract

A preparation method and application of a polyaniline carbon nanotube core-shell composite material belong to the technical field of preparation of functional nano composite materials, and a high-molecular hyperdispersant for a carbon nanotube is ultrasonically dispersed in water to obtain a suspension of the carbon nanotube; mixing the suspension of the carbon nano tube with aniline and hydrochloric acid, cooling to 0-5 ℃, then dropwise adding an ammonium persulfate aqueous solution to initiate aniline oxidative polymerization, filtering, washing, drying, grinding and sieving to obtain the polyaniline carbon nano tube core-shell composite material, wherein the polyaniline carbon nano tube core-shell composite material is applied to a coating and can endow the coating with excellent conductivity and metal corrosion resistance activity.

Description

Preparation method and application of polyaniline carbon nanotube core-shell composite material

Technical Field

The invention belongs to a preparation process of a functional nano composite material, and also relates to the technical field of production of functional metal anticorrosive paint.

Background

Carbon nanomaterials (such as graphene and carbon nanotubes) have high conductivity and large specific surface area, and thus have attracted extensive attention in the fields of antistatic agents and anticorrosion additives. Although, the application potential and prospect of the carbon nano-particles are very promising. However, since the carbon nanotubes have a high specific surface area with graphene, strong van der waals interaction and pi-pi stacking, aggregation inevitably occurs in an organic polymer matrix; meanwhile, the carbon nano particles lack functional groups and are difficult to form a good bonding interface with an organic matrix, so that the mechanical property and the function of the composite coating are influenced.

Polyaniline (PANI) is widely concerned by people in the field of conductive and green metal anticorrosion additives due to the simple and convenient synthesis method, unique reversible redox activity, and doping and dedoping characteristics. However, PANI has a rigid structure, is insoluble and infusible, has poor compatibility with general-purpose polymers, and is difficult to uniformly disperse in a polymer matrix. Furthermore, the conductivity and metal corrosion inhibiting activity of PANI as described above is lost when the pH of the corrosive medium is raised to 7.

The nano-composite technology provides an effective method for solving the above problems, and the composite of the carbon nano (carbon nano tube, graphene) material and the PANI can not only improve the dispersion of the single nano material, but also endow the single material with properties, such as conductivity and electrochemical activity in a high pH environment. As the properties of nanocomposites are due to their unique microstructure morphology and interfacial interactions.

Document CN201410321435.6 discloses that CNTs are first ultrasonically dispersed with an aqueous hydrochloric acid solution of sodium polystyrene sulfonate (PSS), the dispersion mechanism being: through the pi-pi interaction between the benzene ring on the PSS and the CNTs, the PSS molecular chain is wound on the surface of the CNTs, the aniline is further subjected to oxidative polymerization, and the prepared polyaniline/carbon nanotube composite material is a CNTs-PPS/PANI blend.

Patent documents CN 106496553B and CN 109384919 a both use carboxylated carbon nanotubes to realize that the electrostatic adsorption of anilinium salt cations and carboxylate anions can be utilized in the preparation process of the composite material to further obtain the conjugation of carbon nanotubes and aniline, and obtain the polymerization of aniline on the surface of carbon nanotubes. However, both methods require carboxylated CNTs, which not only have higher cost than CNT raw materials, but also have altered electronic structure and reduced conductivity, and the interaction between the prepared CNTs and PANI interfaces changes, thus affecting the properties of the composite material, such as conductivity and metal corrosion resistance activity.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a preparation method of a polyaniline carbon nanotube core-shell composite material with a core-shell microstructure morphology, so that the polyaniline carbon nanotube core-shell composite material can be used in a coating and can endow a coating with excellent conductivity and metal anticorrosion activity.

The preparation method comprises the following steps:

1) ultrasonically dispersing a macromolecular hyper-dispersant for the carbon nano tube into water to obtain a suspension of the carbon nano tube;

2) mixing the suspension of the carbon nano tube with aniline and hydrochloric acid, wherein the feeding mass ratio of the aniline to the carbon nano tube is 1-8: 1;

3) cooling the mixed system to 0-5 ℃, and then dropwise adding an ammonium persulfate aqueous solution to initiate aniline oxidation polymerization reaction;

4) and after the reaction is finished, filtering, washing, drying, grinding and sieving to obtain the polyaniline carbon nanotube core-shell composite material.

Compared with the document CN201410321435.6, the invention has very large difference in synthetic materials, methods and performances and application.

Compared with CN 106496553B and CN 109384919A, the carbon nano tube which is not modified by any chemical derivatization is used as a raw material, the weak pi electron interaction between the carbon nano tube and aniline salt is utilized, aniline monomer is adsorbed on the surface of the carbon nano tube, and oxidation polymerization reaction is carried out on the surface of the CNT under the action of an initiator, so that the composite material with the nano fiber appearance of the core-shell microstructure of the CNT surface coated with PANI is obtained. The microstructure of the formed polyaniline carbon nanotube core-shell composite material is characterized in that: the polyaniline shell layer directly grows on the surface of the carbon nano tube, so that a strong pi electron interface interaction is formed after the polyaniline is compounded with Polyaniline (PANI), and the polyaniline is doped through the electron interaction, so that the redox activity of the polyaniline is effectively expanded to be neutral, and the metal anticorrosion activity function of the PANI is effectively expanded to be neutral from acidity.

Furthermore, the process of the invention adopts the macromolecular hyperdispersant instead of other dispersants, and has the advantages that the anchoring group is combined with the CNT in the suspension, the CNT is stably dispersed in water by utilizing the principle of steric repulsion, and a large specific surface area is provided for the aniline salt monomer to assemble on the surface of the CNT.

The feeding mass ratio of the aniline to the carbon nano tubes is 1-8: 1. According to the invention, the thickness of the surface shell layer of the CNT is adjusted by adjusting the mass ratio of the aniline to the CNT to obtain the composite material with excellent conductive and metal anti-corrosion activities, and the PANI-CNT is easily dispersed in polymers such as epoxy, acrylate resin and the like, so that the excellent functions of nano barrier and metal anti-corrosion activities can be obtained with a small addition amount (0.1-3% by mass).

Further, the macromolecular hyperdispersant is a copolymer of styrene sulfonate and maleic anhydride, or an ammonium salt of the copolymer of styrene and acrylic acid.

When the feeding mass ratio of the aniline to the carbon nano tube is 1-2: 1, the composite material has excellent conductivity, excellent cathode inhibition and certain metal surface passivation metal corrosion prevention activity. When the ratio is less than 1:1, PANI can not completely coat the carbon nano tube; and when the ratio is more than 2-4: 1, the metal corrosion inhibition activity of the cathode disappears after the conductivity is weakened.

Furthermore, when the feeding mass ratio of the aniline to the carbon nano tubes is 4-8: 1, the composite material has excellent metal surface passivation metal corrosion prevention activity. When the ratio is higher than 8:1, the polyaniline-coated carbon nano tube is too thick, and the obtained composite material is not regular core-shell structure nano fiber any more.

Therefore, the nano composite material formed by the invention has different mechanisms of the dominant metal anticorrosion activity due to different proportions of two-phase components of aniline and carbon nano tubes. When the feeding mass ratio of the aniline to the carbon nano tube is 1-2: 1, the composite material mainly comprises nano barrier and cathode inhibition; when the mass ratio of the aniline to the carbon nano tube is 4-8: 1, the composite material is mainly composed of the nano barrier and the passivation of the metal surface.

Further, the dropping time of the ammonium persulfate aqueous solution is 30-40 min, and too fast or too slow dropping is not beneficial to regulating and controlling the polymerization speed initiated by aniline.

Further, the polymerization reaction is carried out at the temperature of 0-5 ℃, so that high molecular weight PANI is obtained, and the conductivity and metal corrosion prevention activity of the PANI-CNT are improved. The polymerization reaction time is 8-12 hours. Too short a reaction time may decrease the monomer polymerization conversion rate, and too long a reaction time may cause unnecessary waste of the preparation process.

Further, the temperature of the drying was 80 ℃. The temperature is lower than 80 ℃, the drying time is too long, and the temperature is higher than 80 ℃, so that the dispersibility of the hybrid composite material is influenced.

Further, the mesh size of the screen was 200 mesh when sieving. The yield of the powder is influenced by too large mesh number of the screen; too small a mesh size of the screen can result in an agglomerated hybrid composite, affecting the dispersion effect in the polymer.

The invention also aims to provide the application of the polyaniline carbon nanotube core-shell hybrid composite material prepared by the preparation method in metal anticorrosive paint.

The polyaniline carbon nanotube core-shell composite material is used as a metal anticorrosion additive for water-based, oil-based or powder coatings.

Repeated tests prove that the PANI based on the shell layer has-NH functional groups, the composite material is very easy to disperse in oily or aqueous polymer resin such as epoxy resin, the dispersion of CNT in a coating matrix can be effectively improved, and the conductivity and the metal corrosion resistance of the obtained nano coating are remarkably improved compared with the coating without the composite material, so that the composite material can be applied to aqueous coating, oily coating and powder coating, can be widely applied to the fields of electrical appliances, electronic products and the like, and is more suitable for static conduction and corrosion prevention in the fields of petroleum, chemical oil storage and oil transportation with serious corrosion environment.

Further, the solid mass ratio of the composite material to the metal anticorrosive paint is 0.1-3: 100. The low static electricity conduction and the metal corrosion prevention activity are not obvious, and the high dispersion stability is influenced, so that the function exertion is influenced.

Drawings

Fig. 1 is a TEM image of polyaniline carbon nanotube core-shell hybrid composite (PANI-CNT (1: 1)) prepared in example 1.

Fig. 2 is a TEM image of polyaniline carbon nanotube core-shell hybrid composite (PANI-CNT (2: 1)) prepared in example 2.

Fig. 3 is a TEM image of polyaniline carbon nanotube core-shell hybrid composite (PANI-CNT (4: 1)) prepared in example 3.

Fig. 4 is a TEM image of polyaniline carbon nanotube core-shell hybrid composite (PANI-CNT (8: 1)) prepared in example 4.

Fig. 5 is a redox activity diagram of the polyaniline carbon nanotube core-shell hybrid composite material prepared by the methods of examples 1 to 4 under an acidic medium.

Fig. 6 is a redox activity diagram of the polyaniline carbon nanotube core-shell hybrid composite material prepared by the methods of examples 1 to 4 under a neutral medium.

Detailed Description

Firstly, preparing a composite material:

example 1:

dissolving 0.986g of concentrated hydrochloric acid in 20g of water to prepare a hydrochloric acid aqueous solution, dissolving 1.35g of initiator ammonium persulfate in 30g of water to prepare an ammonium persulfate aqueous solution, weighing 0.465g of 1wt% styrene sulfonate maleic anhydride copolymer aqueous solution, 0.465g of CNT and 50g of water, and performing ultrasonic treatment to obtain a uniformly dispersed CNT suspension; and transferring the suspension into a three-necked bottle, adding 0.465g of aniline monomer and the prepared hydrochloric acid aqueous solution, placing the three-necked bottle in an ice bath, dropwise adding the prepared ammonium persulfate aqueous solution for 30min, and keeping the ice bath environment to continue to react for 8 h. After the reaction is finished, filtering, washing the filter cake for 3 times by using ethanol and distilled water in sequence, respectively, drying the obtained filter cake for 12 hours in vacuum at the temperature of 80 ℃, grinding and sieving to obtain composite particle powder which is marked as PANI-CNT (1: 1).

Comparative example 1:

dissolving 0.986g of concentrated hydrochloric acid in 20g of water to prepare a hydrochloric acid aqueous solution, dissolving 1.35g of initiator ammonium persulfate in 30g of water to prepare an ammonium persulfate aqueous solution, weighing 0.465g of 1wt% styrene sulfonate maleic anhydride copolymer aqueous solution, 0.465g of carboxylated CNT and 50g of water, and performing ultrasonic treatment to obtain a uniformly dispersed CNT suspension; and transferring the suspension into a three-necked bottle, adding 0.465g of aniline monomer and the prepared hydrochloric acid aqueous solution, placing the three-necked bottle in an ice bath, dropwise adding the prepared ammonium persulfate aqueous solution for 30min, and keeping the ice bath environment to continue to react for 8 h. After the reaction is finished, filtering, washing the filter cake for 3 times by using ethanol and distilled water in sequence, respectively, drying the obtained filter cake for 12 hours in vacuum at the temperature of 80 ℃, grinding and sieving to obtain composite particle powder which is marked as PANI/CNT-COOH (1: 1).

Example 2:

dissolving 1.972g of concentrated hydrochloric acid in 20g of water to prepare a hydrochloric acid aqueous solution, dissolving 2.7g of initiator ammonium persulfate in 30g of water to prepare an ammonium persulfate aqueous solution, weighing 0.465g of an ammonium salt aqueous solution of a styrene maleic anhydride copolymer with the concentration of 1wt%, 0.465g of CNT and 50g of water, and performing ultrasonic treatment to obtain a uniformly dispersed CNT suspension; and transferring the suspension into a three-necked bottle, adding 0.93g of aniline monomer into the prepared hydrochloric acid aqueous solution, placing the mixture into an ice bath, dropwise adding the prepared ammonium persulfate aqueous solution for 30min, and keeping the ice bath for further reaction for 12 h. Filtering, washing the filter cake with ethanol and distilled water for 3 times respectively, drying the obtained filter cake at 80 deg.C for 12h, grinding, and sieving to obtain composite particle powder (PANI-CNT (2: 1)).

Example 3:

3.944g of concentrated hydrochloric acid is dissolved in 20g of water to prepare a hydrochloric acid aqueous solution, 5.4g of initiator ammonium persulfate is dissolved in 30g of water to prepare an ammonium persulfate aqueous solution, 0.465g of styrene sulfonate maleic anhydride copolymer aqueous solution with the concentration of 1wt%, 0.465g of CNT and 50g of water are weighed, and uniformly dispersed CNT suspension is obtained by ultrasonic treatment; and transferring the suspension into a three-necked bottle, adding 1.86g of aniline monomer into 3.944g of concentrated hydrochloric acid 20g of aqueous solution, uniformly stirring the 2 mixed solutions, dropwise adding the prepared ammonium persulfate aqueous solution in an ice bath for 30min, and keeping the reaction for 10 h under the ice bath. Filtering, washing the filter cake with ethanol and distilled water for 3 times respectively, vacuum drying the obtained filter cake at 80 deg.C for 12h, grinding, and sieving to obtain composite particle powder, which is marked as PANI-CNT (4: 1).

Example 4

7.888g of concentrated hydrochloric acid is dissolved in 20g of water to prepare a hydrochloric acid aqueous solution, 10.8g of initiator ammonium persulfate is dissolved in 30g of water to prepare an ammonium persulfate aqueous solution, 0.465g of an ammonium salt aqueous solution of styrene acrylic copolymer with the concentration of 1wt%, 0.465g of CNT and 50g of water are weighed, and uniformly dispersed CNT suspension is obtained by ultrasonic treatment; and transferring the suspension into a three-necked bottle, adding 3.72g of aniline monomer into 7.888g of concentrated hydrochloric acid 20g of aqueous solution, uniformly stirring the 2 mixed solutions, dropwise adding the prepared ammonium persulfate aqueous solution in an ice bath for 30min, and keeping the reaction for further 12h in the ice bath. Filtering, washing the filter cake with ethanol and distilled water for 3 times respectively, vacuum drying the obtained filter cake at 80 deg.C for 12h, grinding, and sieving to obtain composite particle powder, which is recorded as PANI-CNT (8: 1).

Fig. 1, fig. 2, fig. 3, and fig. 4 respectively show transmission electron microscope images of the PANI-CNT composite material prepared by the above method, and the results show that the composite material exhibits an obvious microstructure of the core-shell structured nanofiber in which the PANI coats the CNT. And the thickness of the PANI shell layer is increased along with the increase of the mass ratio of the aniline to the carbon nano tube.

Fig. 5 and 6 are graphs showing the redox activity of the PANI-CNT composite material prepared by the above method, respectively. The results show that the PANI-CNT composite material shows two pairs of redox peaks in an acidic medium and still shows one pair of redox peaks in a neutral medium, because the combination of CNTs forms the nanofiber microstructure morphology of the PANI shell CNT core, and pi-pi interactions are formed to different degrees between the shell-core interfaces, so that the PANI can be greatly weakened by the dependence on acid doping through electron doping, and therefore, the PANI/CNT still maintains one pair of redox peaks even in an environment with a pH of 7.

Table 1 shows the electrical conductivity of the prepared PANI-CNT composite.

TABLE 1

As can be seen from table 1, the conductivity of the PANI-CNT gradually decreases as the PANI thickness on the CNT surface increases, because the CNT has a stronger electron-transporting ability than the PANI, and the pi-pi electron interaction between the CNT and the PANI interface also affects the conductivity of the composite. The conductivity of PANI/CNT (1:1) reached 10s/cm, which was 10 times higher than that of PANI prepared under the same conditions. The PANI/CNT-COOH (1:1) prepared with carboxylated CNTs was significantly lower than the PANI/CNT (1:1), indicating that the present invention well avoids the low conductivity of chemically derivatized CNTs.

The PANI-CNT composite powder shows excellent metal corrosion prevention activity, the conductivity of the PANI-CNT composite powder is closely related to the redox activity, the PANI-CNT composite powder has metal corrosion prevention activity based on a cathode inhibition and metal surface catalytic passivation action mechanism, the two-phase component proportion is different, and the dominant mechanism of the metal corrosion prevention activity is different.

Secondly, application:

PANI-CNT (1:1) was dispersed at high speed into a solvent free epoxy coating such that PANI-CNT (1:1) accounted for 0.5% of the coating solids, yielding coating 1. The coating 1 is sprayed on a sand-blasting steel plate and cured to prepare a salt spray sample plate 1 (sample plate 1 for short) with the coating thickness of 100 mu m.

The solvent-free epoxy coating is sprayed on a sand-blasting steel plate and cured to prepare a comparative salt spray sample plate 1 (referred to as a comparative sample plate 1 for short) with the coating thickness of 100 mu m.

PANI-CNT (2:1) was added to the epoxy powder coating such that PANI-CNT (2:1) accounted for 1% of the epoxy powder coating solids, resulting in coating 2. The coating 2 is electrostatically sprayed on a sand-blasting steel plate and sintered to prepare a salt spray sample plate 2 (sample plate 2 for short) with the coating thickness of 100 mu m.

The epoxy powder coating is electrostatically sprayed on a sand-blasting steel plate and sintered to prepare a comparative salt spray sample plate 2 (referred to as a comparative sample plate 2 for short) with the coating thickness of 100 mu m.

The aqueous PANI-CNT (4:1) slurry was added to the aqueous epoxy coating such that the PANI-CNT (4:1) accounted for 1.5% of the solids of the aqueous epoxy coating, yielding coating 3. The coating 3 is brushed on a sand-blasting steel plate, and after drying and curing, a salt spray sample plate 3 (sample plate 3 for short) with the coating thickness of 50 mu m is prepared.

The water-based epoxy paint is brushed on a sand-blasting steel plate, and after drying and curing, a comparative salt spray sample plate 3 (referred to as a comparative sample plate 3 for short) with the thickness of 50 mu m is prepared.

The PANI-CNT (8:1) aqueous slurry was added to the aqueous acrylate/amino resin such that the PANI-CNT (8:1) accounted for 3% of the aqueous acrylate/amino paint solids, yielding paint 4. The coating 4 is sprayed on a sand-blasting steel plate and baked to prepare a salt spray sample plate 4 (sample plate 4 for short) with the coating thickness of 50 mu m.

The water-based acrylate/amino resin is sprayed on a sand-blasting steel plate and baked to prepare a comparative salt spray sample plate 4 (referred to as a comparative sample plate 4 for short) with the thickness of 50 mu m.

The salt spray resistance test method is according to the national standard GB/T1771-2007.

The salt spray resistant time ratios of the respective salt spray samples obtained in the above examples by the above salt spray test method are shown in table 2.

TABLE 2

To summarize: the PANI-CNT composite material is used as a preservative and added into the coating of different systems, and the salt spray resistance time is improved by 1-3 times compared with that of the coating without the PANI-CNT composite material.

Claims

1. The preparation method of the polyaniline carbon nanotube core-shell composite material is characterized by comprising the following steps:

2. The method according to claim 1, wherein the polymeric hyperdispersant is a copolymer of styrene sulfonate and maleic anhydride, or an ammonium salt of a copolymer of styrene and acrylic acid.

3. The preparation method according to claim 1, wherein the mass ratio of the aniline to the carbon nanotubes is 1-2: 1.

4. The preparation method according to claim 1, wherein the mass ratio of the aniline to the carbon nanotubes is 4-8: 1.

5. The preparation method according to claim 1, wherein the aqueous solution of ammonium persulfate is added by a dropping process for 30-40 min.

6. The process according to claim 1, wherein the polymerization is continued at 0 to 5 ℃ for 8 to 12 hours after the completion of the dropwise addition of the initiator.

7. The method according to claim 1, wherein the drying temperature is 80 ℃.

8. The method according to claim 1, wherein the mesh size of the screen during the sieving is 200 mesh.

9. The polyaniline carbon nanotube core-shell composite material obtained by the preparation method according to claim 1 is applied to metal anticorrosive coatings, and the polyaniline carbon nanotube core-shell composite material is used as an anticorrosive additive of water-based, oil-based or powder metal coatings.

10. The application of the metal anticorrosive paint according to claim 9, wherein the solid mass ratio of the composite material to the metal anticorrosive paint is 0.1-3: 100.