Hydrogen IV type bottle inner container for new energy automobile and preparation method of hydrogen IV type bottle inner container

Abstract

The invention relates to the technical field of high-pressure hydrogen cylinders, in particular to an IV-type hydrogen cylinder liner for a new energy automobile and a preparation method of the IV-type hydrogen cylinder liner. The hydrogen cylinder is of an assembly type and comprises an inner container, a metal seal head and an assembly connector, a bottle opening is hemispherical, a spherical pit which is concave inwards is formed in the center of the bottle opening, the metal seal head is arranged in the middle of the bottle wall of the spherical pit, the assembly connector is screwed on the metal seal head in a threaded mode, and the hydrogen cylinder inner container mainly comprises 50-70% of high-density polyethylene, 10-30% of linear low-density polyethylene, 10-30% of polyethylene, 5-10% of polyethylene, 5-10% of polyethylene, 5-10% of polyethylene and 5-10% of polyethylene. The invention relates to an anti-hydrogen-permeation sealant which comprises the following components in percentage by weight: 0.5-2% of a coupling agent, 0.1-1% of an antioxidant, 0.5-1.5% of a light stabilizer and 1-3% of an anti- A rotational molding process is adopted for machining, a gas conveying pipeline towards a mold inner cavity is additionally arranged, and the tail end of the gas conveying pipeline is connected with a vacuum pump and a high-pressure gas pump. During processing, firstly negative pressure rotational molding is adopted, bubbles in the wall of the hydrogen cylinder inner container in the forming process are removed, then positive pressure rotational molding is adopted, high-pressure air is filled into the hydrogen cylinder inner container, the density of the hydrogen cylinder inner container is improved through high pressure, and bubbles possibly remaining on the wall of the inner container are extruded out.

Description

Technical Field

[0001] The present invention relates to the technical field of high-pressure hydrogen cylinders, and particularly relates to a hydrogen type-IV cylinder inner liner for new energy vehicles and a preparation method thereof. Background Art

[0002] Hydrogen fuel cell vehicles are gradually becoming the main force of future new energy vehicles due to their "zero emission" characteristics. On-board hydrogen storage technology, as a key link in the development of hydrogen fuel vehicles, is directly related to the endurance, cost, and safety of fuel cell vehicles, and is also a key breakthrough link in the future development of hydrogen fuel cell vehicles.

[0003] Currently, the on-board hydrogen storage technology mainly follows the high-pressure gaseous hydrogen storage technology route, using hydrogen storage cylinders as hydrogen storage containers. High-pressure gaseous hydrogen storage has advantages such as fast hydrogen charging and discharging speed and simple container structure, and is the main hydrogen storage method at present; with the development of hydrogen energy, the requirements for the bearing capacity of the container in high-pressure hydrogen storage technology increase. The existing types of hydrogen storage cylinders are mainly divided into metal gas cylinders (type I), metal inner liner fiber hoop-wound gas cylinders (type II), metal inner liner fiber fully-wound gas cylinders (type III), and non-metal inner liner fiber fully-wound gas cylinders (type IV). Among them, type I and type II cylinders have low hydrogen storage density and poor safety performance, and it is difficult to meet the requirements of on-board hydrogen storage density; type III and type IV cylinders have advantages such as improved safety, reduced weight, increased mass hydrogen storage density, etc., and thus are widely used. Compared with type III cylinders, type IV cylinders have become the "new favorite" leading the development direction of high-pressure hydrogen storage containers for international hydrogen energy vehicles due to their excellent anti-hydrogen embrittlement corrosion resistance, lighter weight, lower cost, higher mass hydrogen storage density, and longer cycle life.

[0004] In the domestic market, due to factors such as technical bottlenecks, regulatory restrictions, dependence on imported key materials carbon fiber, low demand, and unqualified supporting technologies, the mainstream products in on-board hydrogen storage cylinders on the market are still 35 MPa type III cylinders and 35 MPa type IV cylinders. The manufacturing process of 70 MPa type IV cylinders is still immature.

[0005] The greatest risk faced by on-board hydrogen cylinders during use is long-term safety, including the interfacial bonding strength of composite materials related to fatigue resistance, hydrogen leakage related to airtightness, surface flame retardancy and heat insulation related to fire safety, and surface abrasion resistance of the winding layer related to fiber performance retention. The ultimate performance and service life of on-board hydrogen cylinders are closely related to their preparation methods and processes.

[0006] The most crucial part of an on-vehicle hydrogen cylinder is the quality of the inner liner manufacturing. Due to its non-metallic material, the sealing performance of the combination of the metal hydrogen cylinder head and the cylinder body is affected by different coefficients of thermal expansion and contraction, making the manufacturing difficult. At the same time, there should be no bubbles in the finished non-metallic inner liner, which poses a major challenge to the current manufacturing process. Facing the current situation that the manufacturing process of 70 MPa type-IV cylinders in China is not yet mature, we have developed a new manufacturing process for 70 MPa type-IV cylinders, which can meet the technical requirements of 70 MPa type-IV hydrogen cylinders. Summary of the Invention

[0007] The main purpose of the present invention is to provide a hydrogen type-IV cylinder inner liner for new energy vehicles and its preparation method, so as to effectively solve the problems mentioned in the background technology.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions: A hydrogen type-IV cylinder inner liner for new energy vehicles includes an inner liner, a metal head, and an assembly joint. The inner liner is a columnar hollow bottle made of non-metallic material, with both ends open, and the bottle mouth is hemispherical. There is a spherical pit recessed inward at the center of the bottle mouth. A metal head is arranged in the middle of the bottle wall of the spherical pit. The metal head is a thick-walled metal tube, and there is a metal disc and several raised rings on the outer side of the metal tube. The metal disc and several raised rings are both located in the middle of the bottle wall of the spherical pit at the bottle mouth of the inner liner, and part of the metal tube extends out of the spherical pit; The assembly joint is made of the same material as the inner liner and is screwed onto the metal tube of the metal head extending out of the spherical concave pit at the bottle mouth. Its contact surface with the inner liner is a spherical convex surface adapted to the spherical concave pit, and the other end structure is adapted to the inflation joint of the gas filling station. The inner hole is communicated with the inner hole of the metal head. After its installation is completed, it forms a hemispherical shape with the appearance of the bottle mouth of the bottle liner, and the center is adapted to the inflation joint of the gas filling station;

[0009] The present invention is manufactured by rotational molding process. As part of the process for manufacturing the hydrogen cylinder inner liner, the present invention has modified the general rotational molding tooling and molds, and added a gas pipeline leading to the inner cavity of the mold: A pipe joint is hermetically connected to the metal head of the embedded part, a high-pressure gas pipe is connected to the pipe joint, the high-pressure gas pipe is connected to a gas pipe rotary joint that can rotate 360 degrees, and then the high-pressure gas pipe passes through the center of the transverse rotary mold driven bevel gear of the rotational molding mold, turns 90 degrees and then passes through the inner hole provided at the center of the driving bevel gear, and is respectively connected to a vacuum pump and a high-pressure gas pump through the driving shaft tube;

[0010] The assembly joint is manufactured separately by the ordinary rotational molding process;

[0011] The main components of this hydrogen cylinder inner liner are composed of high-density polyethylene, linear low-density polyethylene, coupling agent, antioxidant, light stabilizer, and hydrogen permeation resistance barrier agent according to their respective mass percentages;

[0012] A further improvement of the technical solution of the present invention lies in that the component contents of the hydrogen cylinder inner liner are 50-70% high-density polyethylene, 10-30% linear low-density polyethylene, 0.5-2% coupling agent, 0.1-1% antioxidant, 0.5-1.5% light stabilizer, and 1-3% hydrogen permeation resistance barrier agent.

[0013] A method for preparing the inner liner of a hydrogen Type IV cylinder for new energy vehicles includes the following steps:

[0014] Step 1: The component contents of the hydrogen cylinder inner liner, 50-70% high-density polyethylene, 10-30% linear low-density polyethylene, 0.5-2% coupling agent, 0.1-1% antioxidant, 0.5-1.5% light stabilizer, and 1-3% hydrogen permeation resistance barrier agent, are fully mixed and homogenized in a container to obtain a mixed material.

[0015] Step 2: After calibrating the equipment and setting the process parameters, the heating temperature of the mixed material is 240-260 degrees, and it is granulated with a twin-screw extruder. After cooling to room temperature, it is ground into a powder with a particle size of 60-80 meshes by a grinding mill with cooling.

[0016] Step 3: Negative pressure rotational molding: Before the powder enters the mold, first install the embedded part metal head of the bottle mouth. The metal head is connected to the pipe joint of the gas pipeline in the mold cavity. After uniformly filling the material, close the mold. Close the high-pressure air pump. The rotational molding machine rotates at a temperature of 250-280 degrees in the mold cavity for 3 minutes to seal the possible air leakage gaps in the mold. Then, turn on the vacuum pump to evacuate the mold cavity to remove the bubbles in the inner wall of the hydrogen cylinder liner during the molding process. The vacuum negative pressure is -0.05 to -0.1 MP, and the powder rotates uniformly in the mold cavity for 30-60 minutes for molding, and the mold cavity temperature is 250-280 degrees.

[0017] Step 4: Positive pressure rotational molding: Close the vacuum pump, turn on the high-pressure pump, and fill the inside of the hydrogen cylinder liner with high-pressure air at a pressure of 0.2-0.3 MP. The mold cavity temperature is 250-280 degrees, and it continues to rotate uniformly for 20-30 minutes for molding. The density of the hydrogen cylinder liner is increased by high pressure to extrude the possible bubbles remaining in the inner wall of the liner.

[0018] Step 5: After heating is completed, enter the air-cooling chamber. When the surface temperature of the mold drops to 40 degrees, take out the mold and remove the mold.

[0019] Step 6: Take out the product from the mold cavity, fill the product with air at a pressure of 0.3 MP, and if there is no leakage after standing for 3 hours, it is qualified.

[0020] Step 7: Quality inspection: The thickness of the hydrogen cylinder liner is 7.5 ± 0.5 mm, and the quality inspection of the product is carried out according to relevant requirements for the rest; there shall be no impurities, bubbles, or cracks on the inner wall of the liner.

[0021] A further improvement of the technical solution of the present invention lies in: in step 1, the component contents of the hydrogen cylinder inner liner are 70% high-density polyethylene, 25.5% linear low-density polyethylene, 1% coupling agent, 0.5% antioxidant, 1% light stabilizer, and 2% hydrogen permeation resistance barrier agent. They are fully mixed and evenly stirred in a container for 40 - 60 minutes to obtain a mixed material.

[0022] A further improvement of the technical solution of the present invention lies in: in step 1, the component contents of the hydrogen cylinder inner liner are 65% high-density polyethylene, 30.5% linear low-density polyethylene, 1% coupling agent, 0.5% antioxidant, 1% light stabilizer, and 2% hydrogen permeation resistance barrier agent. They are fully mixed and evenly stirred in a container for 40 - 60 minutes to obtain a mixed material.

[0023] Compared with the prior art, the beneficial effects of a type-IV hydrogen cylinder inner liner for new energy vehicles and its preparation method provided by the present invention are as follows:

[0024] 1. The present invention provides a type-IV hydrogen cylinder inner liner for new energy vehicles and its preparation method. Aiming at the structural requirements of low hydrogen permeability and impact resistance of the inner liner, using high-density polyethylene and linear low-density polyethylene as the base materials, its comprehensive performance is optimized and modified, and its internal action mechanism is studied. Based on polyethylene as the basic material, through the synthesis and physical blending modification of the inner liner polyethylene, a new inner liner polymer composite material is developed. The medium compatibility, material applicability, and use safety of the inner liner material for a 70 MPa high-pressure hydrogen cylinder are improved.

[0025] 2. The present invention provides a type-IV hydrogen cylinder inner liner for new energy vehicles and its preparation method. The component contents of the hydrogen cylinder inner liner are uniformly mixed and heated to 240 - 260 degrees to obtain a high-pressure composite material, which reduces the weight of the hydrogen storage cylinder, improves the overall strength and rigidity of the inner liner of the gas cylinder, makes its performance better, and is safer and more reliable under high pressure.

[0026] 3. The present invention provides a type-IV hydrogen cylinder inner liner for new energy vehicles and its preparation method. This preparation method provides a new process of negative pressure rotational molding and positive pressure rotational molding. Negative pressure rotational molding provides favorable conditions for eliminating bubbles during the forming process of the bottle wall under the negative pressure state of the inner cavity of the hydrogen cylinder mold, and then converts to positive pressure rotational molding, which improves the material density of the inner wall of the hydrogen cylinder, and thus improves the compressive strength of the bottle wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Attached Figure 1 is a schematic diagram of the mold and tooling structure of the present invention.

[0028] Attached Figure 2 is a schematic diagram of the structure of the combined part of the hydrogen cylinder and the metal head of the present invention.

[0029] Attached Figure 1-2Among them, lower mold 1, upper mold 2, air pipe 3, air pipe rotary joint 4, mold inner cavity 5, driving shaft tube 6, pipe joint 7, assembly joint 8, metal head 9, bottle liner 10, pressure gauge 11, pipe plug 12, bracket 13, driving bearing 14, driving bevel gear 15, driven bevel gear 16, driven bearing 17. Specific embodiments

[0030] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] Appendix Figure 1 、 2 Among them, as part of the process for manufacturing hydrogen bottle liners, the present invention has modified the general rotational molding tooling and molds, adding a gas pipeline for injecting gas into the mold inner cavity: the lower mold 1 and the upper mold 2 are buckled to form the mold inner cavity 5. The mold is provided with a pipe plug 12 at the tail end to seal the inner cavity, and a pipe joint 7 is hermetically connected to the metal head 9 embedded at the front end. A high-pressure air pipe 3 is connected to the pipe joint 7, and the high-pressure air pipe is connected to a 360-degree rotatable air pipe rotary joint 4. Then, the high-pressure air pipe 3 passes through the center of the driven bevel gear 16 of the rotational molding mold bracket 13, turns 90 degrees and then passes through the inner hole provided in the center of the driving bevel gear 15, and is respectively connected to a vacuum pump and a high-pressure air pump through the driving shaft tube 6; the driving bevel gear 15 is fixed in the front end hole of the driving shaft tube 6 with the driving bearing 14, the driven bevel gear 16 is fixed at the center of the mold bracket 13 with the driven bearing 17, and the lower mold 1 and the upper mold 2 are fixed on the mold bracket 13 after being closed; a pressure gauge 11 is provided on the high-pressure air pipe 3 between the air pipe rotary joint 4 and the pipe joint 7; the assembly joint 8 is separately manufactured by the ordinary rotational molding process;

[0032] Appendix Figure 2 This is a schematic structural diagram of the combined part of the hydrogen bottle of the present invention and the metal head. Two metal heads 9 are arranged at both ends of the inner wall of the bottle liner 10. The assembly joint 8 is screwed onto the metal head 9 and is in close fit with the spherical pit at the air outlet of the bottle liner 10.

[0033] Embodiment 1

[0034] A preparation method for the inner liner of a hydrogen type IV bottle for new energy vehicles includes the following steps:

[0035] Step 1, the component contents of the hydrogen bottle inner liner are 70% high-density polyethylene, 25.5% linear low-density polyethylene, 1% coupling agent, 0.5% antioxidant, 1% light stabilizer, and 2% hydrogen permeation resistance barrier agent. After being fully mixed and evenly stirred in a container for 50 minutes, a mixed material is obtained;

[0036] Step 2, after calibrating the equipment and setting the process parameters, the mixed material is heated to 250 degrees, and then the mixed material is stretched and pelletized, and then ground into 70 mesh powder after cooling at room temperature;

[0037] Step 3, negative pressure rotational molding: before the powder is put into the mold, the embedded metal head of the bottle mouth is installed first, and the metal head is connected to the pipe joint of the gas pipeline in the mold cavity. After filling at a uniform speed, the mold is closed, and the high-pressure air pump is turned off. The rotational molding machine rotates at a mold cavity temperature of 260 degrees for 3 minutes to close the gaps in the mold that may leak, and then the vacuum pump is turned on to evacuate the mold cavity to eliminate bubbles in the inner wall of the hydrogen bottle during the molding process. The vacuum negative pressure is -0.08MP, and the powder is rotated at a uniform speed in the mold cavity for 50 minutes, and the mold cavity temperature is 260 degrees;

[0038] Step 4, positive pressure rotational molding: turn off the vacuum pump, turn on the high-pressure pump, fill the inner liner of the hydrogen cylinder with high-pressure air, the air pressure is 0.25MP, the mold cavity temperature is 260 degrees, and continue to rotate at a constant speed for 23 minutes to form. The density of the inner liner of the hydrogen cylinder is increased by high pressure, and the bubbles that may remain on the wall of the inner liner are squeezed out;

[0039] Step 5: After heating is completed, the mold enters the air cooling chamber and when the mold surface temperature drops to 40 degrees, it is taken out of the oven and demolded;

[0040] Step 6, take the product out of the mold cavity, fill the product with air at a pressure of 0.3MP, and if there is no leakage after standing for 3 hours, it is qualified;

[0041] Step 7, quality inspection: The thickness of the inner liner of the hydrogen cylinder is 7.5±0.5mm, and the rest of the product quality inspection shall be carried out in accordance with relevant requirements; there shall be no impurities, bubbles or cracks on the inner liner wall.

[0042] Example 2

[0043] A method for preparing a hydrogen type IV bottle liner for new energy vehicles comprises the following steps:

[0044] The components of the hydrogen cylinder liner, including 65% high-density polyethylene, 30.5% linear low-density polyethylene, 1% coupling agent, 0.5% antioxidant, 1% light stabilizer and 2% anti-hydrogen penetration barrier, are fully and evenly mixed in a container and stirred for 50 minutes to obtain a mixture.

[0045] Step 1, the components of the hydrogen cylinder liner are 65% high-density polyethylene, 30.5% linear low-density polyethylene, 1% coupling agent, 0.5% antioxidant, 1% light stabilizer, and 2% anti-hydrogen permeation barrier, which are fully mixed and stirred in a container for 50 minutes to obtain a mixture;

[0046] Step 2: After calibrating the equipment and setting the process parameters, when the mixing heating temperature reaches 250°C, draw and pelletize, and then grind into 70-mesh powder after cooling to room temperature;

[0047] Step 3: Negative pressure rotational molding: Before the powder enters the mold, first install the metal head of the embedded part at the bottle mouth. The metal head is connected to the pipe joint of the gas pipeline in the mold cavity. After uniformly filling the material, close the mold, turn off the high-pressure air pump. The rotational molding machine rotates at a mold cavity temperature of 260°C for 3 minutes to seal the possible air leakage gaps in the mold. Then, turn on the vacuum pump to evacuate the mold cavity to remove the bubbles in the inner wall of the hydrogen cylinder liner during the molding process. The vacuum negative pressure is -0.09MP, and the powder rotates uniformly in the mold cavity for 45 minutes for molding, and its mold cavity temperature is 260°C;

[0048] Step 4: Positive pressure rotational molding: Turn off the vacuum pump and turn on the high-pressure pump to fill the inside of the hydrogen cylinder liner with high-pressure air at a pressure of 0.25MP. Its mold cavity temperature is 260°C, and continue to rotate uniformly for 25 minutes for molding. Increase the density of the hydrogen cylinder liner through high pressure and extrude the possible bubbles remaining on the inner wall of the liner;

[0049] Step 5: After heating is completed, enter the air-cooling chamber. When the surface temperature of the mold drops to 40°C, take out of the furnace and remove the mold;

[0050] Step 6: Take out the product from the mold cavity, fill the product with air pressure of 0.3MP, and it is qualified if there is no leakage after standing for 3 hours;

[0051] Step 7: Quality inspection: The thickness of the inner liner of the hydrogen cylinder is 7.5±0.5mm, and the quality inspection of the product is carried out according to relevant requirements for the rest; there shall be no impurities, bubbles, or cracks on the inner wall of the liner.

[0052] The quality inspection indicators of the above Examples 1 and 2 all meet the requirements of each standard in the National Standard for Plastic Inner Liner Carbon Fiber Fully Wound Cylinders for Vehicle Compressed Hydrogen - Draft for Comment, and comply with the requirements of the Group Standard of China Industrial Gas Industry Association - T / CCGA 40007 2021.

[0053] Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A hydrogen type-IV bottle inner liner for new energy vehicles, characterized in that: It includes an inner liner, a metal closure head, and an assembly joint. The inner liner is a cylindrical hollow bottle made of non-metallic material, with openings at both ends and a hemispherical bottle mouth. A spherical pit recessed inwardly is arranged at the center of the bottle mouth, and a metal closure head is arranged in the middle of the bottle wall of the spherical pit. The metal closure head is a thick-walled metal tube. A metal disc and several raised rings are arranged on the outside of the metal tube, and the metal disc and several raised rings are all located in the middle of the bottle wall of the spherical pit of the inner liner bottle mouth, and part of the metal tube protrudes from the spherical pit; the assembly joint is made of the same material as the inner liner, and is threadedly screwed on the metal tube of the metal closure head protruding from the spherical pit of the bottle mouth. Its contact surface with the inner liner is a spherical convex surface adapted to the spherical pit, and the other end structure is adapted to the inflation joint of the inflation station, and the inner hole is connected to the inner hole of the metal closure head. After installation, it forms a hemispherical shape with the appearance of the bottle mouth of the bottle liner, and the center is adapted to the inflation joint of the inflation station.

2. The inner liner of a type-IV hydrogen cylinder for new energy vehicles according to claim 1, wherein: The main components of the hydrogen cylinder liner are high-density polyethylene, linear low-density polyethylene, coupling agent, antioxidant, light stabilizer and anti-hydrogen penetration barrier in respective mass percentages; the content of each component of the hydrogen cylinder liner is 50-70% high-density polyethylene, 10-30% linear low-density polyethylene, 0.5-2% coupling agent, 0.1-1% antioxidant, 0.5-1.5% light stabilizer and 1-3% anti-hydrogen penetration barrier.

3. A hydrogen type IV cylinder inner liner for new energy vehicles according to claim 1, characterized in that: The assembly joint is manufactured separately by ordinary rotational molding process and has the same composition as the inner liner.

4. A method for preparing the inner liner of a Type IV hydrogen cylinder for new energy vehicles, characterized in that: The invention adopts the rotational molding process to manufacture the hydrogen cylinder liner. As a part of the process for manufacturing the hydrogen cylinder liner, the invention transforms the general rotational molding tool and mold, and adds a gas transmission pipeline to the inner cavity of the mold: a pipe joint is sealed and connected to the metal head of the embedded part, a high-pressure air pipe is connected to the pipe joint, the high-pressure air pipe is connected to a 360-degree rotatable air pipe rotating joint, and then the high-pressure air pipe passes through the center of the driven bevel gear of the horizontal rotating mold of the rotational molding mold, passes through the inner hole set in the center of the active bevel gear after turning 90 degrees, and is respectively connected to the vacuum pump and the high-pressure air pump through the active shaft tube.

5. According to claims 1, 2, and 4, a hydrogen IV type bottle liner for new energy vehicles, the preparation method comprises the following steps: Step 1, the components of the hydrogen cylinder liner, including 50-70% high-density polyethylene, 10-30% linear low-density polyethylene, 0.5-2% coupling agent, 0.1-1% antioxidant, 0.5-1.5% light stabilizer, and 1-3% anti-hydrogen permeation barrier, are fully mixed in a container to obtain a mixture; Step 2, after calibrating the equipment and setting the process parameters, the mixing heating temperature is 240-260 degrees, granulation is carried out by a twin-screw extruder, and after cooling to room temperature, grinding is carried out by a cooling mill into a powder of 60-80 mesh; Step 3, negative pressure rotational molding: Before the powder is put into the mold, first install the embedded metal head of the bottle mouth. The metal head is connected to the pipe joint of the air pipeline in the inner cavity of the mold. After uniformly filling the material, close the mold. Then turn off the high-pressure air pump. The rotational molding machine rotates at a temperature of 250-280°C in the mold cavity for 3 minutes to seal the gaps in the mold that may leak air. Then turn on the vacuum pump to evacuate the inner cavity of the mold, removing the bubbles in the inner wall of the hydrogen cylinder liner during the molding process. The vacuum negative pressure is -0.05 to -0.1 MP, and the powder rotates uniformly in the mold cavity for 30-60 minutes for molding, with the mold cavity temperature being 250-280°C; Step 4, positive pressure rotational molding: Turn off the vacuum pump and turn on the high-pressure pump to fill the inside of the hydrogen cylinder liner with high-pressure air at a pressure of 0.2-0.3 MP. The mold cavity temperature is 250-280°C, and continue to rotate uniformly for 20-30 minutes for molding. Increase the density of the hydrogen cylinder liner by high pressure and extrude the bubbles that may remain in the inner wall of the liner; Step 5, after the heating is completed, enter the air-cooling chamber. When the surface temperature of the mold drops to 40°C, take out the mold from the furnace and remove the mold; Step 6, take out the product from the mold cavity, fill the product with air pressure of 0.3 MP, and if there is no leakage after standing for 3 hours, it is qualified; Step 7, quality inspection: The thickness of the inner liner of the hydrogen cylinder is 7.5±0.5 mm, and the quality inspection of the product is carried out according to relevant requirements for the rest; there shall be no impurities, bubbles or cracks on the inner wall of the liner.

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