A method for producing a dense high-pressure gas cylinder plastic liner by using a rotational molding process

Abstract

The application relates to a method for producing a dense high-pressure gas cylinder plastic liner by using a rotational molding process, which comprises the following steps: performing a particle size distribution test on plastic powder according to the ASTM D1921 standard, screening out the plastic powder with a particle size distribution that contains no more than 10% of particles with a particle size greater than 500 mu m and no more than 20% of particles with a particle size less than 125 mu m; performing a bulk density test on the screened plastic powder according to the GB / T 1636 standard, and selecting the plastic powder with a bulk density greater than or equal to 0.32 g / cm 3 ; putting qualified plastic powder into a rotational molding mold, ensuring that a plastic film coating can be uniformly coated on the entire surface of the rotational molding mold; closing the rotational molding mold and setting the rotational speed of the main shaft and the auxiliary shaft of the rotational molding equipment, the heating time and the temperature; after the heating program is completed, performing cooling treatment on the rotational molding mold to make the molten plastic powder cool and crystallize; opening the rotational molding mold after the cooling is completed, taking out the plastic liner, and checking whether the surface of the plastic liner is smooth and free of bubbles, so that a high-pressure gas cylinder plastic liner with small internal stress and good stability is manufactured.

Description

Technical Field

[0001] This invention relates to the technical field of high-pressure gas cylinder manufacturing, and in particular to a method for producing a dense plastic liner for high-pressure gas cylinders using rotational molding. Background Technology

[0002] Against the backdrop of global energy structure transformation and sustainable development, hydrogen energy, with its clean, efficient, and renewable characteristics, is gradually becoming a new favorite in the energy sector. The development of the hydrogen energy industry is not only related to energy security but also a crucial engine for economic growth. The hydrogen energy industry chain, encompassing hydrogen production, storage and transportation, hydrogen refueling station construction, and hydrogen fuel cell applications, hinges on breakthroughs in storage and transportation technologies, which directly determine whether the hydrogen energy industry can achieve large-scale commercial application.

[0003] Currently, on-board hydrogen storage technologies for hydrogen fuel cell vehicles mainly include various forms such as high-pressure gaseous hydrogen storage, cryogenic liquid hydrogen storage, high-pressure cryogenic liquid hydrogen storage, metal hydride hydrogen storage, and organic liquid hydrogen storage. Among these technologies, high-pressure gaseous hydrogen storage technology has become the industry's recognized preferred solution for on-board hydrogen storage due to its advantages such as high cost-effectiveness and low energy consumption. In particular, Type IV plastic-lined hydrogen storage cylinders are considered the most ideal choice for high-pressure on-board hydrogen storage technology due to their high hydrogen storage density, excellent fatigue resistance, and cost-effectiveness.

[0004] In the manufacturing process of Type IV bottle plastic liners, rotational molding technology stands out due to its unique advantages. This process uses an atmospheric pressure preparation method, which places less pressure on the rotational molding mold, thereby reducing the risk of mold damage. Simultaneously, the low internal stress of the plastic liner results in better dimensional stability. However, the selection and processing of plastic powder in the rotational molding process has a decisive impact on product quality. For example, excessive use of fine particles may lead to too many air bubbles inside the plastic liner, affecting its mechanical properties; while excessive use of large particles may cause uneven melting of the plastic powder, resulting in lumps on the surface of the plastic liner; insufficiently rounded plastic powder shapes (with "appendage-like protrusions") will cause these protrusions to melt and bond first, preventing unmelted powder from approaching the rotational molding mold, ultimately resulting in a rough plastic liner. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for fixing an integrated rotationally molded reinforced bonded metal valve seat. To achieve the above objectives, the technical solution adopted by this invention includes: a method for producing a dense high-pressure gas cylinder plastic liner using rotational molding, comprising the following steps:

[0006] According to the ASTM D1921 standard, the particle size distribution test of the plastic powder was carried out, and the plastic powder with a particle size distribution of no more than 10% of the particles larger than 500μm and no more than 20% of the particles smaller than 125μm was selected.

[0007] According to GB / T 1636 standard, the bulk density test was carried out on the screened plastic powder, and plastic powder with a bulk density greater than or equal to 0.32 g / cm³ was selected.

[0008] Place a suitable amount of qualified plastic powder into the rotational molding mold, ensuring that the plastic film coating is evenly applied to the entire surface of the rotational molding mold;

[0009] Close the rotational molding mold and set the rotational molding equipment's main and auxiliary shaft speeds, heating time, and temperature;

[0010] After the heating process is completed, the rotational molding mold is cooled to allow the molten plastic powder to cool and crystallize.

[0011] After cooling, open the rotational molding mold, remove the plastic inner liner, and check whether the surface of the plastic inner liner is smooth and free of air bubbles.

[0012] Furthermore, after screening, the powder can be selected by eye and / or microscope to remove powder particles without appendage-like protrusions.

[0013] Furthermore, the bulk density test is determined by measuring the volume and mass of the plastic powder in a standard container.

[0014] Furthermore, the heating process of rotational molding includes two stages: heating and melting. The temperature and time of each stage are optimized according to the characteristics of the plastic powder.

[0015] Furthermore, the cooling process combines air cooling and circulating air cooling to accelerate the cooling rate and ensure the dimensional stability of the plastic liner.

[0016] Furthermore, the surface quality of the plastic liner is inspected using high-resolution 3D scanning technology to ensure that there are no obvious defects on the surface.

[0017] Furthermore, during the heating phase, the main and auxiliary shaft speed ratio is set to 4.8:4.

[0018] Furthermore, the temperature during the heating stage is set to constant, and the duration is set to 15-30 minutes; the constant temperature range during the melting stage is set to 190 degrees to 220 degrees.

[0019] The second aspect provides a dense high-pressure gas cylinder plastic liner produced by rotational molding, including a high-pressure gas cylinder plastic liner obtained by any of the aforementioned methods.

[0020] The beneficial effects of this invention are as follows: By precisely controlling the particle size distribution of the plastic powder, this invention ensures that the content of particles larger than 500 μm does not exceed 10%, while the content of particles smaller than 125 μm is controlled within 20%, effectively preventing defects such as internal bubbles and unstable mechanical properties. Furthermore, the high bulk density of the plastic powder (≥0.32 g / cm³) promotes rapid and uniform melting during the heating process, reducing uneven melting and localized overheating, thereby significantly improving the density and uniformity of the plastic liner. The high-pressure gas cylinder plastic liner produced by the method of this invention has a smooth, bubble-free surface, ensuring its surface quality and meeting the mechanical performance requirements of the high-pressure gas cylinder plastic liner. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the process for producing a dense high-pressure gas cylinder plastic liner using rotational molding, according to the present invention.

[0022] Figure 2 This is a schematic diagram of the dense high-pressure gas cylinder plastic liner structure produced by rotational molding process according to the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the test cases of this invention clearer, the technical solutions in the test cases of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described test cases are only a part of the embodiments of this invention, not all of them. The components of the embodiments of this invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0024] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0025] The first aspect of this invention relates to a method for producing a dense plastic liner for a high-pressure gas cylinder using rotational molding, the process being as follows: Figure 1 The method shown includes:

[0026] The plastic powder used in the following test cases and comparative examples is HD253P high-density polyethylene produced by Zhejiang Ruitang Plastics Technology Co., Ltd.

[0027] Step 1: Add 20-24 kg of polyethylene plastic powder to the rotational molding mold so that the polyethylene plastic powder can be evenly coated on the entire surface of the rotational molding mold.

[0028] Step 2: Heating stage of rotational molding mold, set spindle speed to 3 to 10 rpm, spindle speed ratio to counterspindle 4.8:4, constant temperature 150℃ to 170℃, duration 15 to 30 minutes;

[0029] Step 3: Melt the heated rotational molding mold, set the spindle speed to 3 to 10 rpm, the spindle speed ratio to counterspindle speed to 4.8:4, maintain the temperature at 190℃ to 220℃, and the duration to 25 to 40 minutes;

[0030] Step 4: Cool the molten rotational molding die, set the spindle speed to 3 to 10 rpm, and the spindle speed ratio to counterspindle to 4.8:4;

[0031] Step 5: The cooling stage uses both air cooling and circulating air cooling. The air cooling stage lasts for 60 to 90 minutes, and the circulating air cooling stage lasts for 60 to 90 minutes.

[0032] Step 6: After cooling, open the rotational molding mold and remove the plastic inner liner for inspection.

[0033] Test Case 1: The particle size distribution of the plastic powder is greater than 500μm=5% and less than 125μm=10%; the bulk density is 0.40 g / cm³; there is no "appendage-like protrusion" plastic powder.

[0034] Test Case 2: The particle size distribution of the plastic powder is greater than 500μm = 5% and less than 125μm = 20%; the bulk density is 0.42 g / cm³; there is no "appendage-like protrusion" plastic powder.

[0035] Test Case 3: The particle size distribution of the plastic powder is greater than 500μm=10% and less than 125μm=10%; the bulk density is 0.39 g / cm³; there is no "appendage-like protrusion" plastic powder.

[0036] Test Case 4: The particle size distribution of the plastic powder is greater than 500μm=10% and less than 125μm=20%; the bulk density is 0.40 g / cm³; there is no "appendage-like protrusion" plastic powder.

[0037] Comparative Example 1: The powder particle size distribution is greater than 500μm = 5% and less than 125μm = 10%; the bulk density is 0.31 g / cm³; the powder has "appendage-like protrusions".

[0038] Comparative Example 2: The powder particle size distribution was greater than 500μm = 30% and less than 125μm = 10%; the bulk density was 0.35 g / cm³; there were no "appendage-like protrusions" in the powder.

[0039] Comparative Example 3: The particle size distribution of the plastic powder is greater than 500μm = 5% and less than 125μm = 40%; the bulk density is 0.43 g / cm³; there is no "appendage-like protrusion" plastic powder.

[0040] Comparative Example 4: The particle size distribution of the plastic powder was greater than 500μm = 0% and less than 125μm = 40%; the bulk density was 0.42 g / cm³; there was no "appendage-like protrusions" in the plastic powder.

[0041]

[0042] Table 1. Results of the influence of plastic powders with different particle size distributions and shapes on the finished plastic liner.

[0043] The product parameters obtained from the test cases and comparative examples of this invention show that when the particle size distribution of the plastic powder is greater than 500μm ≤ 10% and the particle size is less than 125μm ≤ 20%, and the shape of the plastic powder is regular without "appendage protrusions", and the bulk density is ≥ 0.32g / cm³, the surface of the plastic liner produced by rotational molding is smooth, without obvious bubbles, and the plastic liner is dense.

[0044] The second aspect of this invention relates to a dense high-pressure gas cylinder plastic liner produced using a rotational molding process, such as... Figure 2 As shown, this includes a dense high-pressure gas cylinder plastic liner manufactured using any of the aforementioned methods.

[0045] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for producing a dense high-pressure gas cylinder plastic liner using rotational molding, characterized in that, Includes the following steps: a. According to ASTM D1921 standard, the particle size distribution test of the plastic powder was carried out, and the plastic powder with a particle size distribution of no more than 10% of the particles larger than 500μm and no more than 20% of the particles smaller than 125μm was selected. b. Conduct a bulk density test on the screened plastic powder according to GB / T 1636 standard, and select plastic powder with a bulk density greater than or equal to 0.32 g / cm³; c. Place the appropriate amount of qualified plastic powder into the rotational molding mold to ensure that the plastic film coating can be evenly coated on the entire surface of the rotational molding mold; d. Seal the rotational molding mold and set the rotational molding equipment's main and auxiliary shaft speeds, heating time, and temperature; e. After the heating process is completed, the rotational molding mold is cooled to allow the molten plastic powder to cool and crystallize; f. After cooling, open the rotational molding mold, remove the plastic inner liner, and check whether the surface of the plastic inner liner is smooth and free of air bubbles.

2. The method according to claim 1, characterized in that, After screening, the powder can be selected by eye and / or microscope to remove powder particles without appendage-like protrusions.

3. The method according to claim 1, characterized in that, Bulk density is determined by measuring the volume and mass of the plastic powder in a standard container.

4. The method according to claim 1, characterized in that, The heating process of rotational molding molds includes two stages: heating and melting. The temperature and time of each stage are optimized according to the characteristics of the plastic powder.

5. The method according to claim 1, characterized in that, The cooling process combines air cooling and circulating air cooling to accelerate the cooling rate and ensure the dimensional stability of the plastic liner.

6. The method according to claim 1, characterized in that, The surface quality of the plastic liner is inspected using high-resolution 3D scanning technology to ensure that there are no obvious defects on the surface.

7. The method according to claim 1, characterized in that, During the heating phase, the main and auxiliary shaft speed ratio is set to 4.8:

4.

8. The method according to claim 1, characterized in that, The temperature during the heating stage is set to constant, and the duration is set to 15-30 minutes; the constant temperature range during the melting stage is 190 degrees to 220 degrees.

9. A dense high-pressure gas cylinder plastic liner produced by rotational molding process, characterized in that, This includes manufacturing a dense high-pressure gas cylinder plastic liner using any of the methods described in claims 1-8.

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