A hydrogen barrier coating applicable to the inner surface of a hydrogen delivery pipeline and a type IV hydrogen storage cylinder and a preparation method thereof

Abstract

The application discloses a hydrogen-blocking coating applicable to the inner surface of a hydrogen conveying pipeline and a type IV hydrogen storage cylinder and a preparation method thereof. The coating takes ethylene-vinyl alcohol copolymer (EVOH) as a main raw material, takes polyethylene imine (PEI) modified graphene oxide (GO) as a filler, and adopts a solution compounding method to prepare a coating stock solution. The composition of the coating stock solution is (PEI-GO) X EVOH (X=0, 0.25%, 1%, 2%, 4%). With nylon 6 as a base, after being cleaned and air-dried, a layer of nylon treatment agent is coated to improve the adhesion between the barrier coating and the base, and after being air-dried at room temperature, the compounding solution is uniformly poured on the base. The coating preparation method is simple, the coating can be dried at 35 DEG C and then solidified at room temperature, and a high temperature is not needed. The compounding solution has good dispersity and stability, and the compounding coating has excellent tensile property and hydrogen barrier property.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology for hydrogen pipelines and Type IV hydrogen storage cylinders, and particularly to a method for preparing a hydrogen barrier coating. Background Technology

[0002] The development of renewable and non-polluting energy sources is a crucial issue in the energy sector at present, and hydrogen energy is an ideal medium for the large-scale development of renewable energy, as renewable energy can be converted into hydrogen for storage. For the large-scale application of hydrogen energy, "hydrogen transportation" is a vital link.

[0003] Currently, hydrogen is mainly transported in China via long-tube trailers and pipelines. Long-tube trailer hydrogen storage cylinders are mainly divided into four types: I, II, III, and IV. The first three types all have metal liners, with the inner lining material mostly made of steel. This means the hydrogen storage cylinder itself is relatively heavy, limiting the hydrogen storage density. Furthermore, the accumulation and diffusion of hydrogen atoms within the metal liner can lead to "hydrogen embrittlement," easily causing material failure and safety issues. Type IV hydrogen storage cylinders differ from the first three types in that, to further reduce the weight of the high-pressure hydrogen storage container, increase the system's hydrogen storage density, and avoid the "hydrogen embrittlement" problem, the metal lining is replaced with a plastic lining. The plastic lining of Type IV cylinders is mainly made of high-density polyethylene (HDPE), polyamide (nylon PA6), or polyethylene terephthalate (PET). Pipeline transportation is divided into metal pipelines and non-metallic plastic composite pipelines. Similar to metal-lined hydrogen storage cylinders, metal pipelines also face the problem of shortened equipment lifespan and safety issues caused by hydrogen embrittlement. The market will increasingly demand lighter, more cost-effective, and safer non-metallic hydrogen pipelines in the future. However, whether it's a Type IV hydrogen storage cylinder or a non-metallic hydrogen pipeline, a non-metallic plastic liner alone is insufficient for long-term H2 storage and transportation. Applying a high-barrier coating to the liner is an effective way to reduce hydrogen permeation. Summary of the Invention

[0004] The purpose of this invention is to provide a hydrogen barrier coating suitable for the inner surface of hydrogen pipelines and Type IV hydrogen storage cylinders, and its preparation method, which uses surface treatment technology to reduce the hydrogen permeability of the material.

[0005] A hydrogen-barrier coating for use on the inner surface of hydrogen pipelines and Type IV hydrogen storage tanks is formed on a nylon 6 matrix and is composed of polyethyleneimine (PEI) modified graphene oxide (GO) and ethylene-vinyl alcohol copolymer (EVOH), with the composition (PEI-GO). X -EVOH(0%≤X≤4%), where X is the mass percentage of PEI-GO to EVOH.

[0006] Furthermore, the method for preparing the polyethyleneimine (PEI) modified graphene oxide (GO) is as follows:

[0007] Step G1: Graphene oxide is ultrasonically dispersed in deionized water at a concentration of 1 mg / ml and ultrasonicated at room temperature for 1.5 h to ensure complete dispersion.

[0008] Step G2: Polyethyleneimine is dissolved in deionized water at a concentration of 10 mg / ml and stirred at room temperature for 1 hour. Then it is slowly added dropwise to a continuously stirred graphene oxide solution, and the dropping rate is controlled at 3 s / drop using a separatory funnel.

[0009] Step G3: Adjust the pH of the mixed solution to 12 using 0.25 mol / L NaOH solution, and then stir the mixed solution at 80°C for 12 hours.

[0010] Step G4: Wash the product from step G3 three times by centrifugation with deionized water, filter it, and then freeze-dry it under vacuum for 12 hours.

[0011] Step G5: Grind the product and sieve it through a 200-mesh sieve to obtain the final product PEI-GO powder.

[0012] Furthermore, the composite solution (PEI-GO) X The preparation method of -EVOH (0% ≤ X ≤ 4%) is as follows:

[0013] Step S1: At 80°C, EVOH solid particles are dissolved in 90% glacial acetic acid, with an EVOH mass fraction of 3.33%.

[0014] Step S2: Disperse PEI-GO powder ultrasonically in 90% glacial acetic acid, wherein the concentration of PEI-GO is 1 mg / ml;

[0015] Step S3: Add different masses of PEI-GO dispersion to the EVOH solution described in step S1, wherein the mass percentages of PEI-GO and EVOH are 0%, 0.25%, 1%, 2%, and 4%, respectively. Stir the mixed solution at 45°C for 2 hours, and then sonicate it at room temperature and 80W for 2 hours to obtain a pure EVOH solution and (PEI-GO). 0.25％ -EVOH, (PEI-GO) 1％ -EVOH, (PEI-GO) 2％ -EVOH, (PEI-GO) 4％ -EVOH mixed solution.

[0016] Furthermore, the hydrogen-barrier coating formed on the nylon 6 substrate is prepared by the following method:

[0017] Step R1: The nylon 6 substrate is ultrasonically cleaned three times with deionized water and ethanol respectively, and then left to air dry at room temperature for 48 hours.

[0018] Step R2: Place the nylon 6 substrate from step R1 on a flat surface, and evenly brush a layer of nylon treatment agent onto it to form an adhesion layer on the nylon surface. Let it air dry at room temperature for 30 minutes.

[0019] Step R3: Take an appropriate volume of EVOH and (PEI-GO). 0.25％ -EVOH, (PEI-GO) 1％ -EVOH, (PEI-GO) 2％ -EVOH, (PEI-GO) 4％ - The EVOH solution was uniformly poured onto the nylon substrate in step R2, vacuum dried at 35°C for 6 hours, and then cured at room temperature for 36 hours to form a barrier layer on the nylon surface.

[0020] Furthermore, the nylon treatment agent described in step R2 mainly consists of resin and curing agent, wherein the resin is one or more of epoxy resin, acrylic resin or bisphenol A resin.

[0021] Furthermore, the thickness of the adhesion layer described in step R2 is 30-50 μm.

[0022] Furthermore, the thickness of the barrier layer described in step R3 is 150-200 μm.

[0023] This invention uses ethylene-vinyl alcohol copolymer as the main polymer material. Based on the principle of "like dissolves like," it utilizes the poor solubility between the polar "hydroxyl" groups in the ethylene-vinyl alcohol copolymer and the nonpolar "hydrogen" molecules to achieve a hydrogen-blocking effect at the dissolution level. Simultaneously, modified graphene oxide is introduced to construct a "brick wall structure" within the ethylene-vinyl alcohol copolymer, achieving a hydrogen-blocking effect at the diffusion level. Compared with existing technologies, this invention has the following advantages and outstanding effects: the coating preparation method is simple; the coating can be dried at 35°C and then cured at room temperature, without requiring excessively high temperatures; the coating thickness can be controlled by adjusting the amount of composite solution poured; the coating has sufficient tensile strength, capable of withstanding tensile forces encountered in application without cracking; the coating exhibits excellent elongation at break, meaning it has good flexibility and can adapt to the thermal expansion and contraction of the substrate without cracking; the coating has a significant hydrogen-blocking effect, with the hydrogen permeability of the hydrogen storage and transportation equipment substrate material coated with this coating reduced by more than 45% compared to the uncoated substrate material under conditions of 23°C and 0.1 MPa pressure. Attached Figure Description

[0024] Figure 1 In Example 1 (PEI-GO) 0.25％ Cross-sectional morphology of the -EVOH composite coating under a scanning electron microscope (SEM). Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0026] Example 1: (PEI-GO) 0.25％ -EVOH composite coating

[0027] First, polyethyleneimine-modified graphene oxide (PEI-GO) is prepared. The specific steps are as follows:

[0028] Step G1: Take 300mg of graphene oxide and ultrasonically disperse it in 300ml of deionized water at a concentration of 1mg / ml. Sonicate at room temperature for 1.5h to ensure complete dispersion.

[0029] Step G2: Dissolve polyethyleneimine in deionized water at a concentration of 10 mg / ml and stir at room temperature for 1 hour. Then, take 30 ml of polyethyleneimine solution and slowly add it dropwise to the continuously stirred graphene oxide solution, using a separatory funnel to control the dropping rate at 3 s / drop.

[0030] Step G3: Adjust the pH of the mixed solution to 12 using 0.25 mol / L NaOH solution, and then stir the mixed solution at 80°C for 12 hours.

[0031] Step G4: Wash the product from step G3 three times by centrifugation with deionized water, filter it, and then freeze-dry it under vacuum for 12 hours.

[0032] Step G5: Grind the product and sieve it through a 200-mesh sieve to obtain the final product PEI-GO powder.

[0033] Next, prepare (PEI-GO). 0.25％ The specific steps for preparing the -EVOH complex solution are as follows:

[0034] Step S1: At 80°C, EVOH solid particles are dissolved in 90% glacial acetic acid, with an EVOH mass fraction of 3.33%.

[0035] Step S2: Disperse PEI-GO powder ultrasonically in 90% glacial acetic acid, wherein the concentration of PEI-GO is 1 mg / ml;

[0036] Step S3: Add the PEI-GO dispersion to the EVOH solution described in step S1, wherein the mass percentage of PEI-GO to EVOH is 0.25%. Stir the mixed solution at 45°C for 2 hours, and then sonicate it at room temperature and 80W for 2 hours to obtain (PEI-GO). 0.25％ -EVOH mixed solution.

[0037] Finally, PEI-GO is coated onto the nylon substrate. 0.25％-EVOH composite coating, the specific steps are as follows:

[0038] Step R1: The nylon 6 substrate is ultrasonically cleaned three times with deionized water and ethanol respectively, and then left to air dry at room temperature for 48 hours.

[0039] Step R2: Place the nylon 6 substrate from step R1 on a flat surface, and evenly brush a layer of nylon treatment agent onto it to form an adhesion layer on the nylon surface. Let it air dry at room temperature for 30 minutes. The thickness of the adhesion layer is 30-50 μm.

[0040] Step R3: Take an appropriate volume of (PEI-GO) 0.25％ - The EVOH solution is uniformly poured onto the nylon substrate in step R2, vacuum dried at 35°C for 6 hours, and then cured at room temperature for 36 hours to form a barrier layer on the nylon surface with a thickness of 150-200 μm.

[0041] Please see Figure 1 (PEI-GO) was studied using a scanning electron microscope. 0.25％ The cross-sectional morphology of the EVOH composite film was characterized, and a distinct layered structure can be observed in the figure. This is because the modified graphene oxide forms a significant "brick wall structure" in EVOH, thereby increasing the hydrogen diffusion path and slowing down the diffusion rate.

[0042] Example 2: (PEI-GO) 1％ -EVOH composite coating

[0043] Same as Example 1, except that the mass percentage of PEI-GO and EVOH in step S3 is 1%.

[0044] Example 3: Pure EVOH coating

[0045] Step 1: Dissolve solid EVOH particles in 90% glacial acetic acid at 80°C, with an EVOH mass fraction of 3.33%.

[0046] Step 2: The nylon 6 substrate was ultrasonically cleaned three times with deionized water and ethanol respectively, and then left to air dry at room temperature for 48 hours.

[0047] Step 3: Place the nylon 6 substrate described in Step 2 on a flat table, and evenly brush a layer of nylon treatment agent onto it to form an adhesion layer on the nylon surface. Let it air dry at room temperature for 30 minutes. The thickness of the adhesion layer is 30-50 μm.

[0048] Step 4: Take an appropriate volume of pure EVOH solution and pour it evenly onto the nylon substrate described in Step 3. Vacuum dry at 35°C for 6 hours, then remove and cure at room temperature for 36 hours to form a barrier layer on the nylon surface. The thickness of the barrier layer is 150-200 μm.

[0049] It should be noted that the present invention includes, but is not limited to, the above-described embodiments. Any modifications and improvements made based on the concept of the present invention are within the scope of protection of the present invention.

Claims

1. A hydrogen barrier coating suitable for use on the inner surface of a hydrogen delivery pipe and a Type IV hydrogen storage tank, characterized in that, The graphene oxide modified by polyethylene imine (PEI-GO) is compounded with ethylene-vinyl alcohol copolymer (EVOH) to form a coating on a nylon 6 substrate; The preparation method of the hydrogen barrier coating is as follows: First, the graphene oxide modified by polyethylene imine (PEI-GO) is prepared, and the specific steps are as follows: Step G1: graphene oxide is ultrasonically dispersed in deionized water at a concentration of 1 mg / mL, and ultrasonic treatment is performed at room temperature for 1.5 h to ensure sufficient dispersion; Step G2: polyethylene imine is dissolved in deionized water at a concentration of 10 mg / mL, and stirred at room temperature for 1 h, and then slowly added into the continuously stirred graphene oxide solution, and the dropping rate is controlled at 3 s / drop by using a separatory funnel; Step G3: 0.25 mol / L NaOH solution is used to adjust the pH value of the mixed solution to 12, and then the mixed solution is stirred at 80℃ for 12 h; Step G4: the product of step G3 is washed with deionized water by centrifugation for 3 times, and then vacuum freeze-dried for 12 h; Step G5: the product is ground and sieved through a 200 mesh sieve to obtain the final product PEI-GO powder; Secondly, the composite solution of PEI-GO and EVOH is prepared, and the specific steps are as follows: Step S1: EVOH solid particles are dissolved in 90% glacial acetic acid at 80℃ to obtain an EVOH solution, and the mass fraction of EVOH is 3.33%; Step S2: PEI-GO powder is ultrasonically dispersed in 90% glacial acetic acid to obtain a PEI-GO dispersion, and the concentration of PEI-GO is 1 mg / mL; Step S3, take PEI-GO dispersion liquid into the EVOH solution obtained in step S1, wherein the mass percentage of PEI-GO and EVOH is 0.25%, 1%, 2% or 4%, mix the solution and stir at 45°C for 2h, and then ultrasonic at room temperature under the condition of 80W for 2h to obtain (PEI-GO) 0.25% -EVOH composite solution, (PEI-GO) 1% -EVOH composite solution, (PEI-GO) 2% -EVOH composite solution or (PEI-GO) 4% -EVOH composite solution; Finally, the composite coating is coated on the nylon substrate, and the specific steps are as follows: Step R1: the nylon 6 substrate is ultrasonically cleaned with deionized water and ethanol for three times respectively, and is left to air dry at room temperature for 48 h; Step R2: the nylon 6 substrate in step R1 is placed on a flat table, and a layer of nylon treatment agent is uniformly brushed on the surface of the nylon to form an adhesive layer, and is left to air dry at room temperature for 30 min; Step R3, take appropriate volume (PEI-GO) 0.25% -EVOH composite solution, (PEI-GO) 1% -EVOH composite solution, (PEI-GO) 2% -EVOH composite solution or (PEI-GO) 4% -EVOH composite solution is evenly poured on the nylon substrate of step R2, vacuum drying at 35℃ for 6h, after taking out, curing at room temperature for 36h, forming a barrier layer on the surface of the nylon.

2. The hydrogen barrier coating according to claim 1, wherein the main components of the nylon treatment agent are resin and curing agent, and the resin is one or more of epoxy resin and acrylic resin.

3. The hydrogen barrier coating according to claim 1, wherein the thickness of the adhesive layer is 30-50 um.

4. The hydrogen barrier coating according to claim 1, wherein the thickness of the barrier layer is 150-200 um.

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