CN112680076A

CN112680076A - Preparation method of functional graphene reinforced waterborne polyurethane anticorrosive coating

Info

Publication number: CN112680076A
Application number: CN201910987015.4A
Authority: CN
Inventors: 耿宏章; 温建功; 赵惠; 袁晓彤; 景立超; 王涛
Original assignee: Tianjin Polytechnic University
Current assignee: Tianjin Polytechnic University
Priority date: 2019-10-18
Filing date: 2019-10-18
Publication date: 2021-04-20

Abstract

The invention discloses a preparation method of a functional graphene reinforced waterborne polyurethane anticorrosive coating. The preparation method mainly comprises the steps of preparing Graphite Oxide (GO) and performing functional modification on the graphite oxide, doping the functionalized graphene oxide into the waterborne polyurethane coating, and finally coating the composite coating on the surface of metal by using a bar coating or spraying method. The method is characterized in that: (1) the graphene anticorrosive coating with high anticorrosive efficiency is prepared by taking functionalized graphene oxide as a reinforcement and aqueous polyurethane as a matrix: (2) the modified graphene oxide has good dispersibility and compatibility in waterborne polyurethane; (3) the anticorrosive effect of the modified anticorrosive coating is greatly improved compared with that of pure water polyurethane; (4) the functionalized graphene can be used as doped particles of a water-based paint and coated on a protected metal surface in a brush coating or spraying manner.

Description

Preparation method of functional graphene reinforced waterborne polyurethane anticorrosive coating

Technical Field

The invention belongs to the technical field of preparation of graphene anticorrosive coatings, and particularly relates to a modification of a functionalized graphene material and a preparation process of a waterborne polyurethane anticorrosive coating.

Background

Corrosion of metal surfaces, particularly automobiles, ships, high-speed railways and other metal equipment, has been one of the most urgent problems in metal protection, causing enormous economic losses to countries each year. Metal corrosion often occurs at the metal/electrolyte solution interface, and the most effective methods of protection include coating techniques and surface treatments. The invention mainly researches the anticorrosion performance of the functional graphene reinforced waterborne polyurethane. Graphene as a two-dimensional graphite carbon material has high specific surface area, high mechanical properties and excellent barrier properties. However, graphene sheets are not well dispersed in organic coatings due to strong van der waals forces between the graphene sheets. And the compatibility between the inorganic nano graphene and the high molecular polymer is poor, and the interface bonding force is weak, so in order to improve the dispersion compatibility and the interface bonding force of the graphene and the polymer, diisocyanate and hydroxyl and carboxyl on the surface of the diisocyanate form a urethane bond to be grafted to the surface of graphene oxide, and then the graphene oxide functionalized by polyisocyanate is bonded into an aqueous polyurethane matrix, so that the barrier property of the graphene is better exerted, and the corrosion resistance and the mechanical property of the composite coating are improved.

Disclosure of Invention

The invention aims to provide a preparation method of a functional graphene reinforced waterborne polyurethane anticorrosive coating, and the modified graphene oxide reinforced waterborne polyurethane remarkably improves the anticorrosive performance of the coating.

The technical scheme of the invention is as follows: firstly, preparing graphene oxide by adopting an improved Hummers method, then carrying out functional modification on the graphene oxide by using isophorone diisocyanate through a thermal reflux method, and then further modifying the graphene oxide by using nitrogen-nitrogen dimethylethanolamine. And finally, dissolving the obtained functionalized graphene in an aqueous solution, and adding a certain amount of SDBS into the aqueous polyurethane. Stirring for a certain time, standing for a certain time, and then carrying out vacuum defoaming. The coating is uniformly coated on a metal substrate by adopting a brush coating method, and is dried for 1-1.5 hours at the temperature of 115 ℃ and 125 ℃ after being cured for 1-1.5 hours at normal temperature, so that the coating with excellent corrosion resistance can be obtained.

The main innovation points of the invention are as follows: the IPDI and DMEA covalently modified graphene oxide reduces the self-agglomeration of the graphene oxide in the polymer, improves the dispersibility and compatibility of the graphene oxide in the polymer and enables the graphene oxide to play the greatest shielding role.

The method for preparing the functionalized graphene comprises the following steps: the method is characterized in that crystalline flake graphite is used as a raw material, and an improved Hummers method is adopted to prepare graphene oxide. Preparing graphene oxide powder into a graphene oxide allyl ketone solution with a certain concentration, performing ultrasonic dispersion for 0.5-1.5 hours, adding a certain amount of isophorone diisocyanate, refluxing for 11-13 hours at a certain temperature, then adding 20-30g of N-dimethyl ethanolamine, continuing heating for a certain time, and finally performing suction filtration, washing and freeze drying to obtain functionalized graphene powder (GO-IP).

The preparation process of the functionalized graphene anticorrosive paint in the method is as follows: dissolving the obtained functionalized graphene in an aqueous solution, adding a certain amount of SDBS (sodium dodecyl benzene sulfonate) for water bath and ultrasonic treatment for a certain time, adding waterborne polyurethane for mechanical stirring for a certain time, and adding a film-forming assistant to obtain the anticorrosive coating.

The preparation process of the functionalized graphene oxide anticorrosive coating in the method is as follows: the coating is brushed on the treated metal substrate by a brushing method, and is cured for 1-1.5 hours at room temperature, and is dried for 0.5-1.5 hours at the temperature of 115 ℃ and 125 ℃ to obtain the coating with excellent corrosion resistance.

According to the invention, a scanning electron microscope is adopted to represent good dispersion compatibility of the functionalized graphene in the waterborne polyurethane, and an electrochemical workstation is used to represent excellent anticorrosion performance of the anticorrosion coating.

Drawings

FIG. 1 is a diagram of the corrosion prevention mechanism for preparing a coating.

Fig. 2 is a cross-sectional SEM image of the corrosion protection coating.

Fig. 3 is a plot of the frequency of breakpoints of the corrosion protection coating.

Fig. 4 is a water absorption diagram of the anticorrosive coating.

Detailed Description

The present invention will be described in detail with reference to specific examples.

Example 1:

an improved Hummers method is adopted, and crystalline flake graphite is used as a raw material to prepare the graphene oxide dispersion liquid. Preparing functionalized graphene, namely freeze-drying the prepared graphene oxide into powder. 0.7g of GO powder was weighed into a beaker, followed by 200ml of acetone solution, sonicated (200w) in a sonicator for 1h, and then transferred to a 500ml three-necked flask. 0.1ml of dibutyltin dilaurate and 80g of IPDI were added with magnetic stirring and the mixture was heated to 85 ℃ under nitrogen protection for 10 h. Then, the temperature was lowered to 65 ℃ and 25g of DMEA was added and the reaction was continued for 2 h. And washing the residual reactant with acetone, and freeze-drying to obtain GO-IP powder. IP-GO (0.03g) and SDBS (0.03g) were dispersed in 8.5mL of ethanol solution (5%), sonicated for 1h, then 10g of WPU was added and vigorously stirred on a magnetic stirrer for 1 hour. Then, a WPU paint having a solid content of 20% was obtained. And (3) defoaming in vacuum for 30 minutes, brushing the coating on the treated metal substrate, curing at room temperature for 1 hour, and drying at 120 ℃ for 1 hour to obtain a coating with excellent corrosion resistance on the metal surface.

Example 2:

an improved Hummers method is adopted, and crystalline flake graphite is used as a raw material to prepare the graphene oxide dispersion liquid. Preparing functionalized graphene oxide, and freeze-drying the prepared graphene oxide into powder. 0.7g of GO powder was weighed into a beaker, followed by 200ml of acetone solution, sonicated (250w) in a sonicator for 1h, and then transferred to a 500ml three-necked flask. 0.1ml of dibutyltin dilaurate and 80g of IPDI were added with magnetic stirring, and the temperature was raised to 85 ℃ under the protection of nitrogen for reaction for 15 h. Then, the temperature was lowered to 65 ℃ and 25g of DMEA was added and the reaction was continued for 3 h. And washing the residual reactant with acetone, and freeze-drying to obtain GO-IP powder. IP-GO (0.05g) and SDBS (0.05g) were dispersed in 8.5mL ethanol solution (3%), sonicated for 1h, then 10g WPU was added and vigorously stirred on a magnetic stirrer for 1 hour. Then, a WPU paint having a solid content of 20% was obtained. And (3) defoaming in vacuum for 30min, brushing the coating on the treated metal substrate, curing at room temperature for 1h, and drying at 120 ℃ for 1.5 h to obtain a coating with excellent corrosion resistance on the metal surface. And finally, respectively using pure water polyurethane, graphite oxide and reduced graphene oxide reinforced waterborne polyurethane (namely WPU, GO/WPU and RGO/WPU) to perform anticorrosion test comparison with functionalized graphene reinforced waterborne polyurethane (GO-IP/WPU).

Claims

1. A preparation method of a functionalized graphene reinforced waterborne polyurethane anticorrosive coating mainly comprises the steps of dispersing oxidized graphene in acetone in an ultrasonic mode, adding a certain amount of isophorone diisocyanate (IPDI) at a certain temperature, mechanically stirring for 10-24 hours, adding a certain amount of N-dimethyl ethanolamine (DMEA), thermally refluxing for a certain time, washing and drying to obtain functionalized graphene powder. Dispersing the obtained functional graphene oxide powder and SDBS in an ethanol solution with a certain concentration according to a certain mass ratio, adding a certain amount of waterborne polyurethane, simply and mechanically stirring, and then coating the functional graphene oxide powder and the SDBS on the surface of a protected metal by a brush coating or spraying method. And placing the coated coating for 1-5h at normal temperature, and then placing the coating into a drying oven to be dried at a certain temperature. The problem of interlayer aggregation of graphene sheets is solved by a covalent grafting method, and the problem of compatibility between inorganic nanoparticles and high molecular polymers is also solved. The problem of dispersibility of the functionalized graphene in the water-based paint is further solved by a non-covalent grafting method. The electrochemical workstation test, the salt spray test and the results show that the anticorrosion effect of the modified anticorrosion coating is greatly improved compared with that of pure water polyurethane.

2. The method according to claim 1, wherein the number of graphene layers prepared by the modified hummer method is less than 2, and the sheet diameter is 1-10 μm. The number of the functionalized graphene layers is less than 3, and the sheet diameter is 1-5 mu m.

3. The method of claim 1, wherein the graphene oxide is non-covalently modified with SDBS by covalent modification with IPDI and DMEA by thermal refluxing.

4. The process of claim 1, wherein GO is reacted with IPDI at 80-90 ℃ for 10-24h and 3-6h with DMEA at 60-70 ℃.

5. The method of claim 1, conditions for ultrasonically dispersing graphene oxide and functionalized graphene: the power is 200-; the mass ratio of the SDBS to the functionalized graphene is 0.9-1: 1.

6. The method of claim 1, wherein the functionalized graphene is dispersed with an ethanol concentration of 3-7%.

7. The method of claim 1, wherein the functionalized graphene is uniformly dispersed in water, and then the aqueous polyurethane with the solid content of 37% is diluted into the aqueous polyurethane with the solid content of 18-22% by using the dispersion liquid.

8. The method of claim 1, wherein the functionalized graphene aqueous polyurethane mixed solution is coated on the surface of the protected metal after being stirred for 1.5-2.5 hours.

9. The heating temperature of the coating in the oven was 115-125 ℃.

10. A method according to claim 1, characterized in that a spray or bar coating method is used.