Forming process of plastic inner container of small vehicle-mounted hydrogen storage bottle

Abstract

The invention discloses a forming process of a plastic inner container of a small vehicle-mounted hydrogen storage bottle, and belongs to the technical field of high-pressure containers. The forming process of the plastic inner container of the small vehicle-mounted hydrogen storage bottle comprises the steps that thermoplastic plastic serves as a raw material, a first sealing head and a second sealing head are formed through injection molding, one end of the first sealing head is provided with a first welding structure, and one end of the second sealing head is provided with a second welding structure; coating the corresponding surfaces of the first welding structure and the second welding structure with an interface sealant, and then connecting the corresponding surfaces of the first welding structure and the second welding structure to form a welding surface; welding sealing is conducted on the welding face, and heating is conducted through an infrared lamp tube with the power ranging from 10 KW to 30 KW; and the welded workpiece is fed into a material waiting position, redundant materials are removed through cutting, and the plastic inner container of the small vehicle-mounted hydrogen storage cylinder is obtained. The mechanical strength of the weld joint is improved, the barrier property of the weld joint is remarkably improved, hydrogen permeation is prevented, and the hydrogen leakage loss of the hydrogen energy automobile is reduced.

Description

Technical Field

[0001] The present application relates to a forming process for the plastic inner liner of a small vehicle-mounted hydrogen storage cylinder, belonging to the technical field of high-pressure containers. Background Art

[0002] Hydrogen fuel cell vehicles are regarded as an important development direction for future vehicles due to their advantages such as zero emissions, long driving range, and short hydrogen refueling time. Small vehicle-mounted hydrogen storage cylinders are key components of hydrogen fuel cell vehicles, directly determining the hydrogen storage capacity and driving range of the vehicles. Type IV hydrogen storage cylinders are pressure vessels made of plastic inner liners completely wrapped by fiber resin composites, which are characterized by low cost, light weight, fatigue resistance, high hydrogen storage density, and no risk of hydrogen embrittlement. Therefore, Type IV hydrogen storage cylinders are gradually becoming the development trend of the future hydrogen fuel cell vehicle industry.

[0003] The plastic inner liner of the Type IV hydrogen storage cylinder plays a core role in the hydrogen storage cylinder, so there are relatively high requirements for the preparation process of the plastic inner liner. At present, the preparation processes of the inner liners of Type IV hydrogen storage cylinders are mainly divided into integral forming and split forming. The integral forming process is simple, does not require post-decoration processing, and the obtained plastic inner liner has no seams. However, due to technical and other factors, the wall thickness uniformity and mechanical properties of the products are poor. The split forming process usually requires welding treatment, has a short forming time, good impact toughness, etc., and the product size is stable. However, due to the need for welding, there are defects such as weld seams, resulting in a decrease in the local performance of the product, especially the strength at the weld seams is likely to be insufficient, leading to weld cracking, hydrogen leakage, and extremely easy to explode. Summary of the Invention

[0004] In order to solve the above problems, a forming process for the plastic inner liner of a small vehicle-mounted hydrogen storage cylinder is provided, which improves the mechanical strength at the weld seam, significantly enhances its barrier performance, prevents hydrogen penetration, and reduces the hydrogen leakage loss of hydrogen energy vehicles.

[0005] The present application provides a forming process for the plastic inner liner of a small vehicle-mounted hydrogen storage cylinder, including the following steps:

[0006] (1) Using thermoplastic as the raw material, respectively injection-molding to form a first head and a second head. One end of the first head has a first welding structure, and one end of the second head has a second welding structure;

[0007] (2) Coating an interface sealant on the surfaces corresponding to the first welding structure and the second welding structure, and then connecting the surfaces corresponding to the first welding structure and the second welding structure to form a welding surface;

[0008] (3) Welding and sealing the welding surface, wherein heating is carried out by an infrared lamp tube with a power of 10 - 30 KW;

[0009] (4) Feed the welded workpiece to the waiting material position, and remove the excess material by cutting to obtain the plastic inner liner of the small vehicle-mounted hydrogen storage bottle.

[0010] Optionally, the coating thickness of the interface sealant is 0.5 - 2 mm.

[0011] Optionally, during the welding process in step (3), the heating temperature of the infrared lamp tube is 200 - 1000 °C, and the heating time is 20 - 50 s.

[0012] Preferably, during the welding process in step (3), the heating temperature of the workpiece is 200 - 400 °C, and the heating time is 20 - 50 s.

[0013] Optionally, during the welding process in step (3), the melting depth is 1.2 - 2.5 mm, the welding pressure is 0.3 - 1 MPa, and the welding time is 2 - 6 min.

[0014] Optionally, in step (1), the thermoplastic is at least one of polyamide, polyamide 6, and polyamide 12.

[0015] Optionally, during the injection molding process in step (1), the injection molding temperature is 240 - 300 °C, and the injection molding pressure is 80 - 120 MPa.

[0016] Optionally, in step (2), the preparation method of the interface sealant includes the following steps:

[0017] S1. Heat the epoxy resin to 50 - 65 °C, then add 4 - 6 wt% of the modifier and react for 3 - 6 h to obtain the modified epoxy resin;

[0018] S2. Disperse the pretreated mica flakes in xylene to obtain a mica flake dispersion liquid, disperse the pretreated nano - SiO₂ particles in deionized water to obtain a nano - SiO₂ particle dispersion liquid, add the nano - SiO₂ particle dispersion liquid to the mica flake dispersion liquid, stir and mix for 40 - 80 min, and after centrifugation, washing, and drying, obtain the nano - SiO₂ modified mica flakes;

[0019] S3. Mix the modified epoxy resin, xylene, and absolute ethanol in a mass ratio of (4 - 7)∶(1 - 3)∶1, and magnetically stir for 30 - 60 min, then add 20 - 30 wt% of the nano - SiO₂ modified mica flakes and 0.1 - 0.3 wt% of the defoaming agent, and continue to magnetically stir for 50 - 80 min to obtain the interface sealant;

[0020] Wherein, the addition amount of the pretreated nano - SiO₂ particles is 0.3 - 0.8 wt% of the pretreated mica flakes.

[0021] Optionally, the epoxy resin is at least one of epoxy resin E-42, epoxy resin E-20, and epoxy resin E-51.

[0022] Optionally, in step S1, the modifier includes one or a combination of 3-isocyanatopropylmethyldimethoxysilane, 3-isocyanatopropylmethyldiethoxysilane, or 3-isocyanatopropyltriisopropoxysilane.

[0023] Optionally, in step S2, the preparation method of the pretreated mica flakes includes the following steps:

[0024] Add the silane coupling agent to the mixed solution of anhydrous ethanol and deionized water, adjust the pH to 3-5, and stir for 1.5-3 h to obtain the hydrolyzed solution of the silane coupling agent.

[0025] Put the mica into a high-pressure hydraulic crusher to crush it into mica flakes. Take the mica flakes with a particle size of 5-20 μm and disperse them in xylene at 60-80 °C. Then add the hydrolyzed solution of the silane coupling agent and stir at 80-120 °C for 60-200 min. After washing and drying, the pretreated mica flakes are obtained.

[0026] Wherein, the mass ratio of the silane coupling agent to the mica flakes is (0.4-0.6):1.

[0027] Optionally, in step S2, the preparation method of the pretreated nano-SiO2 particles includes the following steps:

[0028] Disperse the nano-SiO2 particles in the mixed solution of anhydrous ethanol and deionized water, then add 3-6 wt% of the silane coupling agent and stir for 50-80 min. After centrifugation and drying, the pretreated nano-SiO2 particles are obtained.

[0029] Optionally, the silane coupling agent is at least one of KH540, KH602, and KH792.

[0030] The beneficial effects of this application include but are not limited to:

[0031] 1. The forming process of the plastic inner liner of a small vehicle-mounted hydrogen storage cylinder in this application, by setting the mutually cooperating first welding structure and the second welding structure, increases the contact area of the corresponding surfaces of the first head and the second head. Therefore, more interface sealant can be incorporated into the connection between the two. By coating the interface sealant, during the heating welding process, the interface sealant can be melted and connected between the first head and the second head. Among them, mica flakes have a lamellar structure and can form a physical barrier at the interface. Nano-SiO2 particles can fill the microscopic gaps of mica flakes, further reducing interface defects and preventing hydrogen permeation; the combined action of nano-SiO2 modified mica flakes and modified epoxy resin can form a high-strength interface layer, effectively dispersing stress, ensuring welding strength and tightness, and being beneficial to improving the overall structural stability and safety of the plastic inner liner of the hydrogen storage cylinder. By optimizing the welding process, the temperature and melting depth of the welding end face of the inner liner are adjustable and used in combination with the welding structure and the interface sealant, which can make the connection between the two ends of the head more dense, reduce hydrogen permeation, and at the same time improve the interface bonding strength, achieving a leap-forward breakthrough in the qualified rate of the inner liner products of type IV cylinders. It is especially suitable for high-pressure environments and is beneficial to extending the service life of the plastic inner liner of small vehicle-mounted hydrogen storage cylinders.

[0032] 2. The forming process of the plastic inner liner of a small vehicle-mounted hydrogen storage cylinder in this application, when modifying epoxy resin, the hydroxyl group in epoxy resin reacts with the isocyanate group in the modifier to generate a urethane bond with high chemical stability and mechanical strength. Although the alkoxy group in the modifier does not directly participate in the reaction during the modification process, it can form silanol by subsequent hydrolysis, and then the silanols condense with each other to form a -(Si-O-Si)n- network, increasing the density of the film layer and being able to reduce hydrogen permeation.

[0033] 3. The forming process of the plastic inner liner of a small vehicle-mounted hydrogen storage cylinder in this application, the pretreated nano-SiO2 particles have good dispersibility and can be evenly distributed on the surface of mica flakes. The alkoxysilane in the silane coupling agent is used to react between mica flakes and nano-SiO2 to form a covalent bond, and then the amino group is used to carry out a ring-opening reaction with the epoxy group in epoxy resin to form a chemical bond. The nano-SiO2 particles are tightly connected to mica flakes / epoxy resin and play an anchoring role between the two, making the interface sealant have good stability and tightness and being able to prevent the situation of interface separation and resulting in seal failure during use. Description of the Drawings

[0034] The drawings described herein are used to provide a further understanding of this application and constitute a part of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation of this application. In the drawings:

[0035] Figure 1Schematic diagram of the structure of the plastic liner of a small vehicle-mounted hydrogen storage cylinder according to an embodiment of the present application.

[0036] Figure 2 is Figure 1 Schematic diagram of area A in enlarged to 100 times.

[0037] List of components and reference numerals:

[0038] 1. First head, 2. Second head, 3. Welding surface, 4. First welding structure, 5. Second welding structure. Detailed implementation manners

[0039] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0040] For those not specified with specific conditions in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For raw materials or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0041] The defoaming agent used in the embodiments and comparative examples of the present invention is an organosilicon defoaming agent with the trade name BYK-085.

[0042] As Figure 1 and Figure 2 shown, the present application provides a plastic liner for a small vehicle-mounted hydrogen storage cylinder, including a first head 1 and a second head 2. One end of the first head 1 is provided with a first welding structure 4, and one end of the second head 2 is provided with a second welding structure 5. The surfaces of the first welding structure 4 and the second welding structure 5 corresponding to each other are connected to form a welding surface 3, and the welding surface 3 is a bent surface, which can not only evenly distribute stress, reduce stress concentration at the welding place, but also increase the welding contact area, improve the welding strength and sealing performance, thereby reducing the risk of hydrogen leakage and extending the service life of the liner.

[0043] Example 1

[0044] A molding process for the plastic liner of a small vehicle-mounted hydrogen storage cylinder includes the following steps:

[0045] (1) Using polyamide 12 as the raw material, respectively injection-molding the first head and the second head, the injection temperature is 240 °C, the injection pressure is 120 MPa, one end of the first head has a first welding structure, and one end of the second head has a second welding structure;

[0046] (2) Coat the corresponding surfaces of the first welding structure and the second welding structure with an interface sealant having a thickness of 0.5 mm, and then connect the corresponding surfaces of the first welding structure and the second welding structure to form a welding surface;

[0047] (3) Perform welding and sealing on the welding surface. The welding pressure is 0.3 MPa and the welding time is 6 min. Among them, it is heated by an infrared lamp tube with a power of 30 KW. The heating temperature of the workpiece is 300 °C, the heating time is 20 s, and the melting depth is 1.2 mm;

[0048] (4) Send the welded workpiece to the waiting position, and remove the excess material by cutting to obtain a plastic inner liner for a small vehicle-mounted hydrogen storage cylinder;

[0049] In step (2), the preparation method of the interface sealant includes the following steps:

[0050] S1. Heat epoxy resin E-20 to 50 °C, and then add 4 wt% 3-isocyanatopropylmethyldiethoxysilane and react for 3 h to obtain modified epoxy resin E-20;

[0051] S2. Add silane coupling agent KH602 to a mixed solution of anhydrous ethanol and deionized water (volume ratio 7:3), adjust the pH to 3, and stir for 3 h to obtain a hydrolyzed solution of silane coupling agent KH602;

[0052] Put mica into a high-pressure hydraulic crusher to crush it into mica flakes. Take mica flakes with a particle size of 5 μm and disperse them in xylene at 80 °C, then add the hydrolyzed solution of silane coupling agent KH602, and stir at 120 °C for 60 min. The mass ratio of silane coupling agent KH602 to mica flakes is 0.4:1. After washing and drying, obtain pretreated mica flakes;

[0053] Disperse nano-SiO2 particles in a mixed solution of anhydrous ethanol and deionized water (volume ratio 7:3), then add 3 wt% silane coupling agent KH602 and stir for 50 min. After centrifugation and drying, obtain pretreated nano-SiO2 particles;

[0054] Disperse the pretreated mica flakes in xylene to obtain a mica flake dispersion liquid, disperse the pretreated nano-SiO2 particles in deionized water to obtain a nano-SiO2 particle dispersion liquid, add the nano-SiO2 particle dispersion liquid to the mica flake dispersion liquid, stir and mix for 40 min. The addition amount of the pretreated nano-SiO2 particles is 0.3 wt% of the pretreated mica flakes. After centrifugation, washing and drying, obtain nano-SiO2 modified mica flakes;

[0055] S3. Mix modified epoxy resin E-20, xylene, and absolute ethanol in a mass ratio of 7:3:1, and magnetically stir for 30 min. Then add 20 wt% nano-SiO₂ modified mica flakes and 0.1 wt% defoamer, and continue to magnetically stir for 50 min to obtain an interface sealant.

[0056] Example 2

[0057] A molding process for the plastic inner liner of a small vehicle-mounted hydrogen storage cylinder includes the following steps:

[0058] (1) Using polyamide 6 as the raw material, injection mold the first head and the second head respectively. The injection temperature is 300 °C, and the injection pressure is 80 MPa. One end of the first head has a first welding structure, and one end of the second head has a second welding structure.

[0059] (2) Coat an interface sealant with a thickness of 2 mm on the surfaces of the first welding structure and the second welding structure corresponding to each other, and then connect the surfaces of the first welding structure and the second welding structure corresponding to each other to form a welding surface.

[0060] (3) Weld and seal the welding surface. The welding pressure is 1 MPa, and the welding time is 2 min. Among them, it is heated by an infrared lamp tube with a power of 30 KW. The heating temperature of the workpiece is 400 °C, the heating time is 20 s, and the melting depth is 2.5 mm.

[0061] (4) Send the welded workpiece to the waiting position, and remove the excess material by cutting to obtain the plastic inner liner of the small vehicle-mounted hydrogen storage cylinder.

[0062] In step (2), the preparation method of the interface sealant includes the following steps:

[0063] S1. Heat epoxy resin E-51 to 65 °C, and then add 6 wt% 3-isocyanatopropyltriisopropoxysilane, and react for 6 h to obtain modified epoxy resin E-51.

[0064] S2. Add silane coupling agent KH792 to a mixed solution of absolute ethanol and deionized water (volume ratio 7:3), adjust the pH to 5, and stir for 1.5 h to obtain a hydrolysis solution of silane coupling agent KH792.

[0065] Put mica into a high-pressure hydraulic crusher to crush it into mica flakes. Take mica flakes with a particle size of 20 μm and disperse them in xylene at 60 °C. Then add the hydrolysis solution of silane coupling agent KH792, and stir at 80 °C for 200 min. The mass ratio of silane coupling agent KH792 to mica flakes is 0.6:1. After washing and drying, obtain pretreated mica flakes.

[0066] Disperse nano-SiO2 particles in a mixed solution of absolute ethanol and deionized water (volume ratio 7:3), then add 6 wt% silane coupling agent KH792 and stir for 80 min. After centrifugation and drying, pretreated nano-SiO2 particles are obtained;

[0067] Disperse the pretreated mica flakes in xylene to obtain a mica flake dispersion. Disperse the pretreated nano-SiO2 particles in deionized water to obtain a nano-SiO2 particle dispersion. Add the nano-SiO2 particle dispersion to the mica flake dispersion and stir and mix for 80 min. The addition amount of the pretreated nano-SiO2 particles is 0.8 wt% of the pretreated mica flakes. After centrifugation, washing, and drying, nano-SiO2 modified mica flakes are obtained;

[0068] S3. Mix modified epoxy resin E-51, xylene, and absolute ethanol according to a mass ratio of 4:1:1 and magnetically stir for 60 min. Then add 30 wt% nano-SiO2 modified mica flakes and 0.3 wt% defoamer, and continue to magnetically stir for 80 min to obtain an interface sealant.

[0069] Example 3

[0070] A forming process for the plastic inner liner of a small vehicle-mounted hydrogen storage cylinder includes the following steps:

[0071] (1) Using polyamide as the raw material, injection mold the first head and the second head respectively. The injection temperature is 270 °C, the injection pressure is 100 MPa. One end of the first head has a first welding structure, and one end of the second head has a second welding structure;

[0072] (2) Coat an interface sealant with a thickness of 1.2 mm on the surfaces of the first welding structure and the second welding structure corresponding to each other, and then connect the surfaces of the first welding structure and the second welding structure corresponding to each other to form a welding surface;

[0073] (3) Weld and seal the welding surface. The welding pressure is 0.7 MPa, and the welding time is 4 min. Among them, heat is applied through an infrared lamp tube with a power of 20 KW. The heating temperature of the workpiece is 300 °C, the heating time is 35 s, and the melting depth is 2 mm;

[0074] (4) Send the welded workpiece to the waiting position and remove the excess material by cutting to obtain the plastic inner liner of the small vehicle-mounted hydrogen storage cylinder;

[0075] In step (2), the preparation method of the interface sealant includes the following steps:

[0076] S1. Heat epoxy resin E-42 to 60 °C, then add 5 wt% 3-isocyanatopropylmethyldimethoxysilane and react for 5 h to obtain modified epoxy resin E-42;

[0077] S2. Add the silane coupling agent KH540 into a mixed solution of absolute ethanol and deionized water (volume ratio 7:3), adjust the pH to 4, and stir for 2 h to obtain a hydrolysis solution of the silane coupling agent KH540.

[0078] Put mica into a high-pressure hydraulic crusher to crush it into mica flakes. Take mica flakes with a particle size of 10 μm and disperse them in xylene at 70 °C. Then add the hydrolysis solution of the silane coupling agent KH540, and stir at 100 °C for 120 min. The mass ratio of the silane coupling agent KH540 to the mica flakes is 0.5:1. After washing and drying, obtain pretreated mica flakes.

[0079] Disperse nano-SiO₂ particles in a mixed solution of absolute ethanol and deionized water (volume ratio 7:3), then add 5 wt% of the silane coupling agent KH540 and stir for 70 min. After centrifugation and drying, obtain pretreated nano-SiO₂ particles.

[0080] Disperse the pretreated mica flakes in xylene to obtain a mica flake dispersion. Disperse the pretreated nano-SiO₂ particles in deionized water to obtain a nano-SiO₂ particle dispersion. Add the nano-SiO₂ particle dispersion into the mica flake dispersion and stir and mix for 60 min. The addition amount of the pretreated nano-SiO₂ particles is 0.6 wt% of the pretreated mica flakes. After centrifugation, washing and drying, obtain nano-SiO₂ modified mica flakes.

[0081] S3. Mix the modified epoxy resin E-42, xylene and absolute ethanol according to a mass ratio of 6:2:1, and stir magnetically for 50 min. Then add 25 wt% of nano-SiO₂ modified mica flakes and 0.2 wt% of defoamer, and continue to stir magnetically for 60 min to obtain an interface sealant.

[0082] Example 4

[0083] The difference from Example 3 is as follows:

[0084] During the welding process in step (3), the heating temperature of the workpiece is 250 °C and the heating time is 40 s.

[0085] Example 5

[0086] The difference from Example 3 is as follows:

[0087] During the welding process in step (3), the heating temperature of the workpiece is 350 °C and the heating time is 30 s.

[0088] Example 6

[0089] It is different from Example 3 in that: 3-isocyanatopropylmethyldimethoxysilane in step S1 is replaced by silane coupling agent KH540.

[0090] Example 7

[0091] It is different from Example 3 in that:

[0092] In step (2), the preparation method of the interface sealant includes the following steps:

[0093] S1. Heat epoxy resin E-42 to 60 °C, then add 5 wt% 3-isocyanatopropylmethyldimethoxysilane and react for 5 h to obtain modified epoxy resin E-42;

[0094] S2. Add silane coupling agent KH540 to a mixed solution of absolute ethanol and deionized water (volume ratio 7:3), adjust the pH to 4, and stir for 2 h to obtain a hydrolysis solution of silane coupling agent KH540;

[0095] Put mica into a high-pressure hydraulic crusher to crush it into mica flakes. Take mica flakes with a particle size of 10 μm and disperse them in xylene at 70 °C, then add the hydrolysis solution of silane coupling agent KH540, and stir at 100 °C for 120 min. The mass ratio of silane coupling agent KH540 to mica flakes is 0.5:1. After washing and drying, obtain pretreated mica flakes;

[0096] S3. Mix modified epoxy resin E-42, xylene and absolute ethanol according to a mass ratio of 6:2:1, and stir magnetically for 50 min, then add 25 wt% pretreated mica flakes and 0.2 wt% defoamer, and continue to stir magnetically for 60 min to obtain the interface sealant.

[0097] Example 8

[0098] It is different from Example 3 in that:

[0099] In step (2), the preparation method of the interface sealant includes the following steps:

[0100] S1. Heat epoxy resin E-42 to 60 °C, then add 5 wt% 3-isocyanatopropylmethyldimethoxysilane and react for 5 h to obtain modified epoxy resin E-42;

[0101] S2. Disperse nano-SiO2 particles in a mixed solution of absolute ethanol and deionized water (volume ratio 7:3), then add 5 wt% silane coupling agent KH540 and stir for 70 min. After centrifugation and drying, obtain pretreated nano-SiO2 particles;

[0102] S3. Mix modified epoxy resin E-42, xylene, and absolute ethanol in a mass ratio of 6:2:1, and stir magnetically for 50 min. Then add 25 wt% of pretreated nano-SiO₂ particles and 0.2 wt% of defoamer, and continue to stir magnetically for 60 min to obtain the interface sealant.

[0103] Comparative Example 1

[0104] A molding process for the plastic inner liner of a small vehicle-mounted hydrogen storage cylinder includes the following steps:

[0105] (1) Using polyamide as the raw material, injection mold the first head and the second head respectively. The injection temperature is 270 °C, and the injection pressure is 100 MPa.

[0106] (2) Coat the interface sealant with a thickness of 1.2 mm on the corresponding surfaces of the first head and the second head, and then connect the corresponding surfaces of the first head and the second head to form a welding surface.

[0107] (3) Weld and seal the welding surface. The welding pressure is 0.7 MPa, and the welding time is 4 min. Among them, it is heated by an infrared lamp tube with a power of 20 KW. The heating temperature of the workpiece is 300 °C, the heating time is 35 s, and the melting depth is 2 mm.

[0108] (4) Send the welded workpiece to the waiting position, and remove the excess material by cutting to obtain the plastic inner liner of the small vehicle-mounted hydrogen storage cylinder.

[0109] In step (2), the preparation method of the interface sealant includes the following steps:

[0110] S1. Heat epoxy resin E-42 to 60 °C, and then add 5 wt% of 3-isocyanatopropylmethyldimethoxysilane and react for 5 h to obtain modified epoxy resin E-42.

[0111] S2. Add silane coupling agent KH540 to the mixed solution of absolute ethanol and deionized water (volume ratio of 7:3), adjust the pH to 4, and stir for 2 h to obtain the hydrolysis solution of silane coupling agent KH540.

[0112] Put mica into a high-pressure hydraulic crusher to crush it into mica flakes. Take mica flakes with a particle size of 10 μm and disperse them in xylene at 70 °C. Then add the hydrolysis solution of silane coupling agent KH540, and stir at 100 °C for 120 min. The mass ratio of silane coupling agent KH540 to mica flakes is 0.5:1. After washing and drying, obtain the pretreated mica flakes.

[0113] Disperse nano-SiO2 particles in a mixed solution of anhydrous ethanol and deionized water (volume ratio 7:3), then add 5 wt% silane coupling agent KH540 and stir for 70 min. After centrifugation and drying, pretreated nano-SiO2 particles are obtained;

[0114] Disperse the pretreated mica flakes in xylene to obtain a mica flake dispersion. Disperse the pretreated nano-SiO2 particles in deionized water to obtain a nano-SiO2 particle dispersion. Add the nano-SiO2 particle dispersion to the mica flake dispersion and stir and mix for 60 min. The addition amount of the pretreated nano-SiO2 particles is 0.6 wt% of the pretreated mica flakes. After centrifugation, washing and drying, nano-SiO2 modified mica flakes are obtained;

[0115] S3. Mix modified epoxy resin E-42, xylene and anhydrous ethanol according to a mass ratio of 6:2:1, and magnetically stir for 50 min. Then add 25 wt% nano-SiO2 modified mica flakes and 0.2 wt% defoaming agent, and continue to magnetically stir for 60 min to obtain an interface sealant.

[0116] Comparative Example 2

[0117] A forming process for the plastic inner liner of a small vehicle-mounted hydrogen storage cylinder includes the following steps:

[0118] (1) Using polyamide as the raw material, injection mold the first head and the second head respectively. The injection temperature is 270 °C and the injection pressure is 100 MPa. One end of the first head has a first welding structure, and one end of the second head has a second welding structure;

[0119] (2) Connect the surfaces corresponding to the first welding structure and the second welding structure to form a welding surface;

[0120] (3) Weld and seal the welding surface. The welding pressure is 0.7 MPa and the welding time is 4 min. Among them, it is heated by an infrared lamp tube with a power of 20 KW. The heating temperature of the workpiece is 300 °C, the heating time is 35 s, and the melting depth is 2 mm;

[0121] (4) Send the welded workpiece to the waiting position, and remove the excess material by cutting to obtain the plastic inner liner of the small vehicle-mounted hydrogen storage cylinder.

[0122] For the above-mentioned examples and comparative examples, there is no need to specifically limit the heating temperature and heating time of the infrared lamp tube, as long as the workpiece can reach the target temperature and be heated for a specific time;

[0123] Prepare tensile and impact mechanical test specimens circumferentially at the weld. The thickness of the specimens is 2.5 mm, and mechanical property tests are carried out.

[0124] There is no testing institution in China for measuring the hydrogen permeability rate. Since the molecular diameter of helium is only second to that of hydrogen, the gas barrier performance of the specimen is evaluated by measuring the helium permeability rate of the specimen using a differential pressure type gas permeation tester.

[0125] The test results of the specimens at the welds of the plastic inner linings in Examples 1-8 and Comparative Examples 1-2 are shown in Table 1.

[0126] Table 1

[0127]

[0128]

[0129] As mentioned above, only the embodiments of the present application are described. The protection scope 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, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the technical idea and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A molding process for a plastic liner of a small vehicle-mounted hydrogen storage bottle, characterized in that: The following steps are involved: (1) A first end cap and a second end cap are respectively formed by injection molding using thermoplastic plastic as a raw material, wherein one end of the first end cap has a first welding structure, and one end of the second end cap has a second welding structure; (2) coating an interface sealant on the surface corresponding to the first welding structure and the second welding structure, and then connecting the surface corresponding to the first welding structure and the second welding structure to form a welding surface; (3) welding and sealing the welding surface, wherein heating is performed by an infrared lamp tube with a power of 10-30 kW; (4) The welded workpiece is sent to the material waiting position, and the excess material is removed by cutting to obtain the plastic liner of the small vehicle-mounted hydrogen storage bottle.

2. The molding process of the plastic liner of the small vehicle-mounted hydrogen storage bottle according to claim 1 is characterized in that: During the welding process of step (3), the heating temperature of the infrared lamp tube is 200-1000° C. and the heating time is 20-50 seconds.

3. The molding process of the plastic liner of the small vehicle-mounted hydrogen storage bottle according to claim 1 is characterized in that: During the welding process of step (3), the heating temperature of the workpiece is 200-400° C. and the heating time is 20-50 s.

4. The molding process of the plastic liner of the small vehicle-mounted hydrogen storage bottle according to claim 1 is characterized in that: During the welding process of step (3), the melting depth is 1.2-2.5 mm, the welding pressure is 0.3-1 MPa, and the welding time is 2-6 min.

5. The molding process of the plastic liner of the small vehicle-mounted hydrogen storage bottle according to claim 1 is characterized in that: In step (1), the thermoplastic plastic is at least one of polyamide, polyamide 6 and polyamide 12.

6. The molding process of the plastic liner of the small vehicle-mounted hydrogen storage bottle according to claim 1 is characterized in that: During the injection molding process of step (1), the injection molding temperature is 240-300° C. and the injection molding pressure is 80-120 MPa.

7. The molding process of the plastic liner of the small vehicle-mounted hydrogen storage bottle according to claim 1 is characterized in that: In step (2), the method for preparing the interface sealant comprises the following steps: S1, heating the epoxy resin to 50-65°C, adding 4-6wt% of a modifier, and reacting for 3-6h to obtain a modified epoxy resin; S2, the pretreated mica flakes are dispersed in xylene to obtain a mica flake dispersion, the pretreated nano-SiO2 particles are dispersed in deionized water to obtain a nano-SiO2 particle dispersion, the nano-SiO2 particle dispersion is added to the mica flake dispersion, stirred and mixed for 40-80min, centrifuged, washed, and dried to obtain nano-SiO2 modified mica flakes; S3, the modified epoxy resin, xylene and anhydrous ethanol are mixed in a mass ratio of (4-7) : (1-3) : 1, and magnetically stirred for 30-60 minutes, and then 20-30wt% of nano-SiO2 modified mica flakes and 0.1-0.3wt% of defoaming agent are added, and the magnetic stirring is continued for 50-80 minutes to obtain an interface sealant; The added amount of the pre-treated nano-SiO2 particles is 0.3-0.8wt% of the pre-treated mica flakes.

8. The molding process of the plastic liner of the small vehicle-mounted hydrogen storage bottle according to claim 7 is characterized in that: In step S1, the modifier includes one or a combination of 3-isocyanate propyl methyl dimethoxy silane, 3-isocyanate propyl methyl diethoxy silane or 3-isocyanate propyl triisopropoxy silane.

9. The molding process of the plastic liner of the small vehicle-mounted hydrogen storage bottle according to claim 7 is characterized in that: In step S2, the method for preparing the pretreated mica flakes comprises the following steps: Adding a silane coupling agent to a mixed solution of anhydrous ethanol and deionized water, adjusting the pH to 3-5, and stirring for 1.5-3 hours to obtain a hydrolyzate of the silane coupling agent; Putting mica into a high-pressure hydraulic crusher to crush it into mica flakes, taking mica flakes with a particle size of 5-20 μm and dispersing them in xylene at 60-80° C., then adding a hydrolyzate of a silane coupling agent, stirring at 80-120° C. for 60-200 minutes, washing and drying, and obtaining pretreated mica flakes; Wherein, the mass ratio of silane coupling agent to mica flakes is (0.4-0.6):

1.

10. The molding process of the plastic liner of the small vehicle-mounted hydrogen storage bottle according to claim 7 is characterized in that: In step S2, the method for preparing the pretreated nano-SiO2 particles comprises the following steps: The nano-SiO2 particles are dispersed in a mixed solution of anhydrous ethanol and deionized water, and then 3-6 wt% of a silane coupling agent is added and stirred for 50-80 minutes. After centrifugation and drying, the pretreated nano-SiO2 particles are obtained.

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