A plastic liner of a type IV hydrogen storage bottle and its preparation method

Abstract

The present application discloses a type IV hydrogen storage bottle plastic liner and its preparation method, belonging to the technical field of high-pressure hydrogen storage containers. The preparation method of the type IV hydrogen storage bottle plastic liner comprises: uniformly mixing thermoplastic plastic, masterbatch and silane coupling agent to form a premix, then placing the premix into a twin-screw extruder for extrusion and granulation, the screw temperature is 220-240°C, and the speed is 100-120rpm; grinding the prepared pellets and passing them through a 40-60 mesh sieve to obtain rotational molding material, then drying the rotational molding material at 80-90°C for 5-8 hours, and then rotationally molding at 5-25rpm and 200-350°C for 8-15 minutes; annealing the molded workpiece, and then air cooling it to room temperature to obtain the type IV hydrogen storage bottle plastic liner. The liner has good hydrogen permeability and mechanical properties, so it is not easy to fail during the hydrogen charging and discharging process and under load impact, thus avoiding accidents.

Description

Technical Field

[0001] The present application relates to a plastic liner of a type IV hydrogen storage bottle and a preparation method thereof, belonging to the technical field of high-pressure hydrogen storage containers. Background Art

[0002] Type IV hydrogen storage bottles use a plastic liner as a barrier layer, which has many advantages such as light weight, low cost, long service life, corrosion resistance, and fatigue resistance. Especially under high-pressure hydrogen storage conditions, the hydrogen storage density can be increased to more than 5wt%.

[0003] The high-pressure gas stored in the IV type hydrogen storage bottle will cause great stress to the bottle body of the hydrogen storage bottle. Usually, during the fiber winding process of the IV type hydrogen storage bottle, a pre-tightening force will be applied to ensure that the inner liner and the fiber composite material layer are tightly fitted, while reducing the stress on the inner liner when storing high-pressure hydrogen, and making most of the stress be borne by the carbon fiber composite material layer. However, as the inner liner is mainly used to prevent hydrogen leakage, it will also be subject to large stresses, including static stress directly generated by high pressure during operation, stress cycles caused by rapid hydrogen charging and discharging, and impact on the inner liner during collisions. In addition, under the influence of hydrogen permeation, the high-pressure hydrogen dissolved in the composite material and the high-pressure hydrogen that penetrates into the interface between the inner liner and the carbon fiber composite material layer will respectively cause "bubble" rupture and inner liner collapse during the rapid decompression process. Therefore, how to reduce hydrogen permeation and improve the mechanical properties of the plastic inner liner is a difficult problem that needs to be urgently solved in the integrated molding process of the inner liner of the IV type hydrogen storage bottle. Summary of the Invention

[0004] In order to solve the above problems, a type IV hydrogen storage bottle plastic liner and a preparation method thereof are provided. The liner has good hydrogen permeation resistance and mechanical properties, so it is not easy to fail during the hydrogen charging and discharging process and under load impact, thus avoiding accidents.

[0005] The technical solution adopted in the present invention is:

[0006] According to one aspect of the present application, a method for preparing a plastic liner of a type IV hydrogen storage bottle is provided, comprising the following steps:

[0007] (1) The thermoplastic plastic, masterbatch and silane coupling agent are uniformly mixed to form a premix, and then the premix is ​​placed in a twin-screw extruder for extrusion and granulation, with the screw temperature being 220-240°C and the screw speed being 100-120 rpm;

[0008] (2) Grinding the prepared pellets and passing them through a 40-60 mesh sieve to obtain the rotomolding material, then drying the rotomolding material at 80-90°C for 5-8 hours, and then rotomolding the rotomolding material at 5-25 rpm and 200-350°C for 8-15 minutes;

[0009] (3) Annealing the formed workpiece and then air-cooling it to room temperature to obtain a plastic liner of a type IV hydrogen storage bottle;

[0010] Among them, the addition amount of masterbatch is 2-6wt% of thermoplastic;

[0011] The added amount of the silane coupling agent is 0.3 to 0.8 wt% of the thermoplastic plastic.

[0012] Optionally, in step (1), the method for preparing the masterbatch comprises the following steps:

[0013] S1. Dispersing carboxylated multi-walled carbon nanotubes in deionized water, then adding modified hydrotalcite, magnetically stirring for 10 to 30 minutes, and then ultrasonically dispersing for 30 to 50 minutes. The resulting dispersion is then frozen in liquid nitrogen and freeze-dried at -90 to -70°C for 60 to 80 hours to obtain a mixed filler powder.

[0014] S2. Dissolve the thermoplastic plastic in an organic solvent, stir and dissolve at 40-60°C, then add 1-4wt% of mixed filler powder and disperse evenly, and freeze-dry for 3-6 days to obtain a masterbatch.

[0015] Optionally, in step S1, the mass ratio of the carboxylated multi-walled carbon nanotubes to the modified hydrotalcite is 1:(1-5).

[0016] Optionally, in step S2, the organic solvent is at least one of dimethylformamide, dimethylacetamide and chloroform.

[0017] Optionally, in step S1, the method for preparing the modified hydrotalcite comprises the following steps:

[0018] A mixed solution of MgSO4·7H2O and Al2(SO4)3·18H2O is fully mixed with a mixed solution of NaOH and Na2CO3, refluxed and crystallized at 70-100°C for 4-6 hours, filtered, and washed with water until the pH value is less than 8 to obtain a hydrotalcite slurry; then, 5-8wt% of polyethylene glycol is added to the hydrotalcite slurry, stirred at 70-90°C for 20-40 minutes, filtered, and dried to obtain a modified hydrotalcite.

[0019] Optionally, the mass ratio of MgSO4·7H2O to Al2(SO4)3·18H2O is (1.0-4.0):1;

[0020] The amount of NaOH added is 1.5-3 wt% of the total mass of MgSO4·7H2O and Al2(SO4)3·18H2O;

[0021] The amount of Na2CO3 added is 2 to 4 wt% of the total mass of MgSO4·7H2O and Al2(SO4)3·18H2O.

[0022] Optionally, the thermoplastic is at least one of polyamide, polyamide 6 and polyamide 12.

[0023] Optionally, in step (3), the annealing treatment temperature is 80-120° C. and the time is 2-5 hours.

[0024] Optionally, in step (1), the silane coupling agent is at least one of KH540, KH550 and KH792.

[0025] According to another aspect of the present application, there is provided a type IV hydrogen storage bottle plastic liner, which is prepared by any of the above-mentioned methods for preparing the type IV hydrogen storage bottle plastic liner;

[0026] A reinforcing rib is provided on the inner side of the plastic liner. The reinforcing rib is a regular polygon. The regular polygon is an equilateral triangle, a square or a regular hexagon.

[0027] Optionally, the thickness of the reinforcing rib is 20-40% of the thickness of the plastic liner;

[0028] The spacing between the center points of adjacent reinforcing ribs is 8-15% of the diameter of the plastic liner cylinder.

[0029] In this application, "polyethylene glycol" has an average molecular weight of 200;

[0030] "Room temperature" refers to 20-30℃.

[0031] The beneficial effects of this application include but are not limited to:

[0032] 1. The present invention discloses a method for preparing a plastic liner for a Type IV hydrogen storage bottle, which features a simple process. Roto-molding not only achieves the integrated molding of the end cap and barrel, eliminating any welds and internal stresses, but also ensures a reliable connection to the metal bottle valve seat. By uniformly filling an appropriate amount of masterbatch into the thermoplastic, silver streaks and shear bands are generated when subjected to external impact, absorbing significant impact energy and preventing further crack expansion, thereby producing a nano-enhancement effect and improving impact resistance. The annealing process activates and rearranges the molecular chains of the semi-crystalline polymer material, causing some crystals to melt and recrystallize, forming a more complete crystal structure and increasing crystallinity, thereby improving the barrier properties of the product. Furthermore, annealing effectively eliminates residual stress and micro-defects within the workpiece, enhancing the mechanical properties of the material. This method for preparing a plastic liner for a Type IV hydrogen storage bottle significantly improves its strength, toughness, and hydrogen permeability resistance by optimizing the liner's material composition and processing technology, ensuring its reliability and durability in high-pressure hydrogen storage environments.

[0033] 2. The present invention discloses a method for preparing a plastic liner for a Type IV hydrogen storage bottle. Due to the electrostatic interaction between negatively charged carbon nanotubes and positively charged hydrotalcite, the carbon nanotubes are surrounded by exfoliated hydrotalcite sheets. Furthermore, the enhanced interfacial interaction between the masterbatch and the thermoplastic results in freeze-drying and masterbatch-based melt blending, resulting in a microstructure composed of one-dimensional carbon nanotubes and two-dimensional hydrotalcite sheets, forming a well-distributed three-dimensional network. The numerous microcracks formed during stretching prevent rapid matrix fracture, thereby improving the toughness of the liner. Furthermore, the improved interfacial interaction between the mixed filler powder and the thermoplastic matrix promotes stress transfer from the matrix to the filler, dissipating more pull-out energy and shortening the critical length of the carbon nanotubes, thereby enhancing the material's strength and modulus.

[0034] 3. In the present invention's method for preparing a plastic liner for a Type IV hydrogen storage bottle, both carboxylated multi-walled carbon nanotubes and modified hydrotalcite exhibit excellent compatibility with thermoplastics. The carboxyl groups in the carboxylated multi-walled carbon nanotubes can form hydrogen bonds with amide groups in the thermoplastic, while the hydroxyl groups in the modified hydrotalcite can form hydrogen bonds with amide groups in the thermoplastic, enhancing interfacial bonding. The two fillers work synergistically, enabling uniform dispersion in the matrix and further enhancing interfacial interactions with the matrix. This not only ensures the liner's mechanical properties, but also extends the hydrogen permeation path, increases permeation resistance, and reduces eddy currents or localized pressure concentrations, resulting in a plastic liner with improved quality and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0036] Figure 1 This is a schematic structural diagram of the plastic liner of a Type IV hydrogen storage bottle involved in an embodiment of the present application.

[0037] Figure 2 This is another structural schematic diagram of the plastic liner of the Type IV hydrogen storage bottle involved in an embodiment of the present application.

[0038] Figure 3 This is another structural schematic diagram of the plastic liner of the Type IV hydrogen storage bottle involved in the embodiment of the present application.

[0039] List of parts and reference numerals:

[0040] 1. Strengthen the ribs. DETAILED DESCRIPTION

[0041] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0042] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. The raw materials or instruments used, if the manufacturers are not specified, are all conventional products that can be purchased commercially.

[0043] The carboxylated multi-walled carbon nanotubes involved in the following examples and comparative examples were purchased from Hangzhou Chuangshi Biotechnology Co., Ltd.

[0044] like Figure 1-3 As shown, the present application provides a type IV hydrogen storage bottle plastic liner, the inner side of the plastic liner is provided with a reinforcing rib, the reinforcing rib is a regular polygon, and the regular polygon is an equilateral triangle (see Figure 3 ) or square (see Figure 2 ) or a regular hexagon (see Figure 1 ); Preferably, the regular polygon is a regular hexagon; it can effectively disperse pressure and reduce local stress concentration, thereby enhancing the bearing capacity of the inner liner under high pressure environment, reducing its cracking risk, and preventing hydrogen leakage.

[0045] Furthermore, the thickness of the reinforcing rib is 20-40% of the thickness of the plastic liner, preferably 30%;

[0046] The spacing between the center points of adjacent reinforcing ribs is 8-15% of the diameter of the plastic liner, preferably 10%;

[0047] By optimizing the thickness and spacing of the reinforcing ribs, the strength, toughness and barrier properties of the hydrogen storage bottle liner are ensured while achieving a lightweight design.

[0048] Example 1

[0049] A method for preparing a plastic liner of a type IV hydrogen storage bottle comprises the following steps:

[0050] (1) Polyamide, 2 wt% masterbatch and 0.3 wt% silane coupling agent KH540 were uniformly mixed to form a premix, and then the premix was placed in a twin-screw extruder for extrusion and pelletization. The screw temperature was 220 °C and the speed was 100 rpm.

[0051] (2) Grind the prepared pellets and pass them through a 40-mesh sieve to obtain the rotomolding material. Then, dry the rotomolding material at 80°C for 5 h, and then rotomold it at 5 rpm and 200°C for 8 min.

[0052] (3) Annealing the formed workpiece at 80°C for 5 hours, and then air-cooling it to room temperature to obtain a plastic liner of a type IV hydrogen storage bottle;

[0053] The preparation method of the masterbatch comprises the following steps:

[0054] S1. A mixed solution of MgSO4·7H2O and Al2(SO4)3·18H2O in a mass ratio of 1:1 was fully mixed with a mixed solution of 1.5wt% NaOH and 2wt% Na2CO3, refluxed and crystallized at 70°C for 4h, filtered, and washed with water until the pH value was 7 to obtain a hydrotalcite slurry; then 5wt% polyethylene glycol was added to the hydrotalcite slurry, stirred at 70°C for 20min, filtered, and dried to obtain a modified hydrotalcite;

[0055] S2. Dispersing the carboxylated multi-walled carbon nanotubes in deionized water, and then adding the modified hydrotalcite in a mass ratio of 1:1. After magnetic stirring for 10 minutes, ultrasonic dispersion was performed for 30 minutes. The obtained dispersion was then frozen in liquid nitrogen and freeze-dried at -90°C for 60 hours to obtain a mixed filler powder.

[0056] S3. Dissolve polyamide in dimethylformamide, stir and dissolve at 40°C, then add 1wt% mixed filler powder and disperse evenly. After freeze-drying for 3 days, obtain masterbatch.

[0057] Example 2

[0058] A method for preparing a plastic liner of a type IV hydrogen storage bottle comprises the following steps:

[0059] (1) Polyamide 12, 6 wt% masterbatch and 0.8 wt% silane coupling agent KH792 were uniformly mixed to form a premix, and then the premix was placed in a twin-screw extruder for extrusion and pelletization. The screw temperature was 240 °C and the speed was 120 rpm.

[0060] (2) Grind the prepared pellets and pass them through a 60-mesh sieve to obtain the rotomolding material. Then, dry the rotomolding material at 90°C for 8 h, and then rotomold it at 25 rpm and 350°C for 15 min.

[0061] (3) Annealing the formed workpiece at 120°C for 2 h, and then air-cooling it to room temperature to obtain a plastic liner for a type IV hydrogen storage bottle;

[0062] The preparation method of the masterbatch comprises the following steps:

[0063] S1. A mixed solution of MgSO4·7H2O and Al2(SO4)3·18H2O in a mass ratio of 4:1 was fully mixed with a mixed solution of 3wt% NaOH and 4wt% Na2CO3, refluxed and crystallized at 100°C for 6 hours, filtered, and washed with water until the pH value was 7 to obtain a hydrotalcite slurry; then 8wt% polyethylene glycol was added to the hydrotalcite slurry, stirred at 90°C for 40 minutes, filtered, and dried to obtain a modified hydrotalcite;

[0064] S2. Dispersing carboxylated multi-walled carbon nanotubes in deionized water, and then adding modified hydrotalcite in a mass ratio of carboxylated multi-walled carbon nanotubes to modified hydrotalcite of 1:5. After magnetic stirring for 30 minutes, ultrasonic dispersion was performed for 50 minutes. The obtained dispersion was then frozen in liquid nitrogen and freeze-dried at -70°C for 80 hours to obtain a mixed filler powder.

[0065] S3. Dissolve polyamide 12 in dimethylacetamide, stir and dissolve at 60°C, then add 4wt% mixed filler powder and disperse evenly. After freeze-drying for 6 days, obtain masterbatch.

[0066] Example 3

[0067] A method for preparing a plastic liner of a type IV hydrogen storage bottle comprises the following steps:

[0068] (1) Polyamide 6, 4 wt% masterbatch and 0.5 wt% silane coupling agent KH550 were uniformly mixed to form a premix, and then the premix was placed in a twin-screw extruder for extrusion and pelletization. The screw temperature was 230 °C and the speed was 110 rpm.

[0069] (2) Grind the prepared pellets and pass them through a 50-mesh sieve to obtain the rotomolding material. Then, dry the rotomolding material at 85°C for 6.5 h, and then rotomold it at 15 rpm and 280°C for 10 min.

[0070] (3) Annealing the formed workpiece at 100°C for 3.5 hours, and then air-cooling it to room temperature to obtain a plastic liner for a type IV hydrogen storage bottle;

[0071] The preparation method of the masterbatch comprises the following steps:

[0072] S1. A mixed solution of MgSO4·7H2O and Al2(SO4)3·18H2O in a mass ratio of 2.5:1 was fully mixed with a mixed solution of 2wt% NaOH and 3wt% Na2CO3, refluxed and crystallized at 85°C for 5h, filtered, and washed with water until the pH value was 7 to obtain a hydrotalcite slurry; then 6.5wt% polyethylene glycol was added to the hydrotalcite slurry, stirred at 80°C for 30min, filtered, and dried to obtain a modified hydrotalcite;

[0073] S2. Dispersing carboxylated multi-walled carbon nanotubes in deionized water, and then adding modified hydrotalcite in a mass ratio of carboxylated multi-walled carbon nanotubes to modified hydrotalcite of 1:3. After magnetic stirring for 20 minutes, ultrasonic dispersion was performed for 40 minutes. The obtained dispersion was then frozen in liquid nitrogen and freeze-dried at -80°C for 70 hours to obtain a mixed filler powder.

[0074] S3. Dissolve polyamide 6 in chloroform, stir and dissolve at 50°C, then add 3wt% mixed filler powder and disperse evenly. After freeze-drying for 5 days, obtain masterbatch.

[0075] Example 4

[0076] The difference from Example 3 is that step (3) is not included, that is, the formed workpiece is not annealed.

[0077] Example 5

[0078] The difference from Example 3 is that the preparation method of the masterbatch includes the following steps:

[0079] S1. A mixed solution of MgSO4·7H2O and Al2(SO4)3·18H2O in a mass ratio of 2.5:1 was fully mixed with a mixed solution of 2wt% NaOH and 3wt% Na2CO3, refluxed and crystallized at 85°C for 5h, filtered, washed with water until the pH value was 7 to obtain a hydrotalcite slurry, filtered, and dried to obtain hydrotalcite;

[0080] S2. Dispersing the carboxylated multi-walled carbon nanotubes in deionized water, and then adding hydrotalcite in a mass ratio of 1:3. After magnetic stirring for 20 minutes, ultrasonic dispersion was performed for 40 minutes. The obtained dispersion was then frozen in liquid nitrogen and freeze-dried at -80°C for 70 hours to obtain a mixed filler powder.

[0081] S3. Dissolve polyamide 6 in chloroform, stir and dissolve at 50°C, then add 3wt% mixed filler powder and disperse evenly. After freeze-drying for 5 days, obtain masterbatch.

[0082] Example 6

[0083] The difference from Example 3 is that the carboxylated multi-walled carbon nanotubes are replaced by carbon nanotubes.

[0084] Comparative Example 1

[0085] The difference from Example 3 is that the preparation method of the masterbatch includes the following steps:

[0086] Polyamide 6 was dissolved in chloroform and stirred at 50°C to dissolve, and then 3 wt% montmorillonite was added and dispersed evenly. After freeze-drying for 5 days, a masterbatch was obtained.

[0087] Comparative Example 2

[0088] The difference from Example 3 is that the preparation method of the masterbatch includes the following steps:

[0089] Polyamide 6 was dissolved in chloroform and stirred at 50° C., and then 3 wt % of carboxylated multi-walled carbon nanotubes were added and dispersed evenly. After freeze-drying for 5 days, a masterbatch was obtained.

[0090] Comparative Example 3

[0091] The difference from Example 3 is that the preparation method of the masterbatch includes the following steps:

[0092] S1. A mixed solution of MgSO4·7H2O and Al2(SO4)3·18H2O in a mass ratio of 2.5:1 was fully mixed with a mixed solution of 2wt% NaOH and 3wt% Na2CO3, refluxed and crystallized at 85°C for 5h, filtered, and washed with water until the pH value was 7 to obtain a hydrotalcite slurry; then 6.5wt% polyethylene glycol was added to the hydrotalcite slurry, stirred at 80°C for 30min, filtered, and dried to obtain a modified hydrotalcite;

[0093] S2. Dissolve polyamide 6 in chloroform, stir and dissolve at 50°C, then add 3 wt% modified hydrotalcite and disperse evenly. After freeze-drying for 5 days, obtain masterbatch.

[0094] Comparative Example 4

[0095] A method for preparing a plastic liner of a type IV hydrogen storage bottle comprises the following steps:

[0096] (1) Polyamide 6 was placed in a twin-screw extruder for extrusion and pelletization. The screw temperature was 230°C and the speed was 110 rpm.

[0097] (2) The prepared pellets were ground and passed through a 50-mesh sieve to obtain the roto-molding material. The roto-molding material was then dried at 85°C for 6.5 h and then roto-molded at 15 rpm and 280°C for 10 min. After the roto-molding process, the material was air-cooled to room temperature to obtain the plastic liner of the Type IV hydrogen storage bottle.

[0098] Tensile and impact mechanical test specimens were prepared circumferentially at the head and cylinder. The specimen thickness was 2.5 mm, of which the thickness of the reinforcement ribs was 0.5 mm. Mechanical property tests were carried out and the results were taken as the average value at the head and cylinder.

[0099] There is no testing organization in China that can measure hydrogen permeability. The molecular diameter of helium is second only to hydrogen. Therefore, the helium permeability of the sample is measured by using a differential pressure gas permeometer to evaluate the gas barrier performance of the sample. The result is taken as the average value at the head and cylinder.

[0100] The test results of the plastic liner samples of Examples 1-6 and Comparative Examples 1-4 are shown in Table 1.

[0101] Table 1

[0102]

[0103] The foregoing is merely an embodiment of the present application, and the scope of protection of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the technical ideas and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for preparing a plastic liner of a type IV hydrogen storage bottle, characterized in that: The following steps are involved: (1) The thermoplastic plastic, masterbatch and silane coupling agent are uniformly mixed to form a premix, and then the premix is ​​placed in a twin-screw extruder for extrusion and granulation, with the screw temperature being 220-240°C and the screw speed being 100-120 rpm; (2) Grinding the prepared pellets and passing them through a 40-60 mesh sieve to obtain the rotomolding material, then drying the rotomolding material at 80-90°C for 5-8 hours, and then rotomolding the rotomolding material at 5-25 rpm and 200-350°C for 8-15 minutes; (3) Annealing the formed workpiece and then air-cooling it to room temperature to obtain a plastic liner of a type IV hydrogen storage bottle; Among them, the addition amount of masterbatch is 2-6wt% of thermoplastic; The amount of silane coupling agent added is 0.3-0.8wt% of the thermoplastic; In step (1), the method for preparing the masterbatch comprises the following steps: S1. Dispersing carboxylated multi-walled carbon nanotubes in deionized water, then adding modified hydrotalcite, magnetically stirring for 10 to 30 minutes, and then ultrasonically dispersing for 30 to 50 minutes. The resulting dispersion is then frozen in liquid nitrogen and freeze-dried at -90 to -70°C for 60 to 80 hours to obtain a mixed filler powder. S2. Dissolve the thermoplastic plastic in an organic solvent, stir and dissolve at 40-60°C, then add 1-4wt% of mixed filler powder and disperse evenly, and freeze-dry for 3-6 days to obtain a masterbatch.

2. The method for preparing the plastic liner of type IV hydrogen storage bottle according to claim 1, characterized in that: In step S1, the mass ratio of the carboxylated multi-walled carbon nanotubes to the modified hydrotalcite is 1:(1-5).

3. The method for preparing the plastic liner of type IV hydrogen storage bottle according to claim 1, characterized in that: In step S2, the organic solvent is at least one of dimethylformamide, dimethylacetamide and chloroform.

4. The method for preparing the plastic liner of type IV hydrogen storage bottle according to claim 1, characterized in that: In step S1, the preparation method of the modified hydrotalcite comprises the following steps: A mixed solution of MgSO4·7H2O and Al2(SO4)3·18H2O is fully mixed with a mixed solution of NaOH and Na2CO3, refluxed and crystallized at 70-100°C for 4-6 hours, filtered, and washed with water until the pH value is less than 8 to obtain a hydrotalcite slurry; then, 5-8wt% of polyethylene glycol is added to the hydrotalcite slurry, stirred at 70-90°C for 20-40 minutes, filtered, and dried to obtain a modified hydrotalcite.

5. The method for preparing the plastic liner of type IV hydrogen storage bottle according to claim 4, characterized in that: The mass ratio of MgSO4·7H2O and Al2(SO4)3·18H2O is (1.0-4.0):1; The amount of NaOH added is 1.5-3 wt% of the total mass of MgSO4·7H2O and Al2(SO4)3·18H2O; The amount of Na2CO3 added is 2 to 4 wt% of the total mass of MgSO4·7H2O and Al2(SO4)3·18H2O.

6. The method for preparing the plastic liner of type IV hydrogen storage bottle according to claim 1, characterized in that: The thermoplastic is polyamide.

7. The method for preparing the plastic liner of type IV hydrogen storage bottle according to claim 1, characterized in that: In step (3), the annealing temperature is 80-120° C. and the time is 2-5 hours.

8. The method for preparing the plastic liner of type IV hydrogen storage bottle according to claim 1, characterized in that: In step (1), the silane coupling agent is at least one of KH540, KH550 and KH792.

9. A plastic liner for a type IV hydrogen storage bottle, characterized in that: Prepared by the preparation method of the IV type hydrogen storage bottle plastic liner according to any one of claims 1 to 8; A reinforcing rib is provided on the inner side of the plastic liner. The reinforcing rib is a regular polygon. The regular polygon is an equilateral triangle, a square or a regular hexagon.

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