A process for sealing a heat-generating tube and a composition of silicone oil for use in the process

Abstract

The application relates to the technical field of material surface treatment, and discloses a heating tube sealing process and a silicone oil composition used in the process. The heating tube sealing process of the application is prepared by preparing a silicone oil composition and dropping the silicone oil composition on the end port of a heating tube in a residual heat state, spreading and infiltrating the silicone oil composition into a metal capillary structure by using residual heat, curing to form a silicon-oxygen crosslinked film layer through gradient heating, and completing sealing through post-heating treatment, so that the air tightness, waterproofness, air permeability and aging resistance of the heating tube are effectively improved, and the production efficiency is further improved. Meanwhile, the silicone composition of the heating tube sealing process of the application realizes the multiple functions of water sealing, air permeability and explosion prevention of the film layer through reasonable compounding of polymethylhydrogen siloxane, an additive, a crosslinking agent and a microstructure regulating agent.

Description

Technical Field

[0001] This application relates to the field of material surface treatment technology, and in particular to a heating tube sealing process and a silicone oil composition used in the process. Background Technology

[0002] In the small household appliance manufacturing industry, metal heating elements are crucial as core heating components, widely used in appliances such as electric kettles and rice cookers. As consumers increasingly demand higher safety and longer lifespans for small household appliances, the sealing performance of the metal heating element ports is receiving more and more attention. A good port seal can effectively prevent damage to the internal structure of the heating element from various factors, thereby ensuring the normal operation of the product and playing a significant role in improving the overall product quality of the small household appliance industry.

[0003] To address the sealing issue at the ends of metal heating elements, existing technologies typically employ 704 silicone sealant. During the sealing process, some processes opt for room temperature curing, allowing the silicone to dry naturally and form a seal; others use low-temperature baking to accelerate the curing process. While these conventional methods achieve a seal at the heating element ends, they also have several significant drawbacks. Firstly, although the dense film formed after silicone curing provides a degree of sealing, it cannot expel moisture from inside the heating element. Under high temperatures, the internal pressure of the heating element can surge due to the inability to expel moisture, leading to serious problems such as bulging or bursting. Secondly, the adhesion between silicone and the metal surface is relatively weak. After prolonged exposure to thermal cycles, the silicone is prone to peeling, significantly reducing the sealing effect. Furthermore, the long curing time of silicone, whether 24 hours at room temperature or 4-6 hours of low-temperature baking, is difficult to adapt to the pace of industrial production lines, greatly reducing production efficiency. Summary of the Invention

[0004] To at least overcome one of the problems existing in the prior art, one objective of this application is to provide a heating element sealing process. This process involves preparing a silicone oil composition and dripping it onto the heating element port, which is in a residual heat state. The residual heat allows the silicone oil composition to spread and penetrate into the metal capillary structure. Gradient heating and curing then form a silicone-oxygen cross-linked film layer. Finally, post-heating treatment completes the sealing process. This effectively improves the airtightness, waterproofness, breathability, and aging resistance of the heating element, while also further increasing production efficiency. A second objective of this application is to provide the silicone oil composition for the aforementioned heating element sealing process.

[0005] Therefore, this application adopts the following technical solution: The first aspect of this application provides a heating element sealing process, including the following steps: S1. Preparation of silicone oil composition; S2. Apply the silicone oil composition to the port of the heating element that has just been welded and is still in a residual heat state; S3. Allow the silicone oil composition to stand, allowing it to spread and penetrate the metal surface of the heating element. S4. Gradient heating and curing to form a silicon-oxygen cross-linked film layer at the port of the heating tube; S5. Post-heating treatment to complete the sealing process of the heating element.

[0006] Preferably, in step S1, in order to obtain a uniformly dispersed silicone oil composition, the raw materials of the silicone oil composition are mixed at 30~40°C and stirred for 15~20 minutes.

[0007] Preferably, in step S2, the amount of the dripped silicone oil composition is 0.5~1.0 g / cm², and the temperature of the heating tube port in the residual heat state is 40~50℃. More preferably, in step S2, the amount of the dripped silicone oil composition is 0.8~1.0 g / cm², and the temperature of the heating tube port in the residual heat state is 45~50℃.

[0008] In step S2, the amount of silicone oil composition dripped at 0.5~1.0 g / cm² ensures the formation of a complete covering film, meeting the sealing requirements of the heating element, while avoiding excessive use of the silicone oil composition, which could lead to wastage or an excessively thick film. Controlling the temperature range of 40~50℃ prevents the silicone oil composition from curing prematurely. Within this temperature range, the silicone oil composition exhibits good fluidity and spreads well, avoiding film defects caused by improper temperature.

[0009] Preferably, in step S3, the settling time is 30~70s.

[0010] In step S3, a settling time of 30-70 seconds ensures that the silicone oil composition naturally spreads under surface tension to form a uniform covering layer and fully penetrates into the tiny pores of the metal surface filled in the heating tube. If the settling time is too short, the bonding force between the silicone composition and the metal will decrease due to insufficient penetration, thereby affecting the adhesion and airtightness of the sealing silicone composition. If the settling time is too long, the fluidity of the silicone oil composition may decrease due to the slow cooling caused by residual heat, affecting the integrity of its spread.

[0011] Preferably, in step S4, the gradient heating curing includes pre-curing at 80-100℃, followed by primary curing at a heating rate of 5-10℃ / min to 150-180℃, wherein the pre-curing time is 0.3-0.6 hours and the primary curing time is 1.5-2 hours. More preferably, in step S4, the gradient heating curing includes pre-curing at 85-100℃, followed by primary curing at a heating rate of 5-10℃ / min to 160-180℃, wherein the pre-curing time is 0.3-0.6 hours and the primary curing time is 1.5-2 hours.

[0012] In step S4, pre-curing at 80~100℃ for 0.3~0.6h allows the low-boiling-point components in the silicone oil composition to slowly evaporate and initiate initial cross-linking. This prevents the formation of bubbles due to the rapid evaporation of low-boiling-point components during subsequent high-temperature main curing, ensuring the film's density. The heating rate is controlled within the range of 5~10℃ / min; this slow heating reduces thermal stress caused by temperature differences between the inside and outside of the film, preventing cracking. The main curing process at 150~180℃ for 1.5~2h ensures full cross-linking of the silicone composition, forming a high-strength silicon-oxygen network structure. This imparts excellent high-temperature resistance and impermeability to the film, meeting the requirements for long-term high-temperature operation of the heating element. Furthermore, this step has a short heating and curing time, meeting the industrial production requirements for automation and short processing times.

[0013] Preferably, in step S5, the temperature of the post-heating treatment is 60~80℃, and the time of the post-heating treatment is 2~5 minutes. More preferably, in step S5, the temperature of the post-heating treatment is 65~80℃, and the time of the post-heating treatment is 3~5 minutes.

[0014] In step S5, the low-temperature post-treatment at 60~80℃ gently removes residual trace amounts of low-boiling-point components from the film layer, while the slow shrinkage further enhances the adhesion strength between the film layer and the metal surface. This step is controlled within 2~5 minutes, which effectively removes residual trace amounts of low-boiling-point components from the film layer while avoiding increased film brittleness caused by overheating.

[0015] In the heating element sealing process of this application, step S2 utilizes the residual heat from the heating element processing to promote the initial leveling of the silicone oil composition, reducing bubble generation, eliminating the need for additional preheating, and lowering energy consumption. Step S3's proper settling allows the silicone oil composition to penetrate the metal pores, significantly improving the bonding strength between interfaces compared to traditional surface-only coating methods, and reducing the risk of peeling after long-term use. Step S4's gradient heating and curing avoids the problem of excessive internal stress concentration leading to easy cracking of the film layer caused by curing at a single temperature. Step S5's "post-heating treatment" removes residual low-boiling-point components from the film layer while further stabilizing the film layer structure, ensuring the long-term reliability of the sealing film layer performance. This heating element sealing process, through the synergistic effect of multiple steps, achieves high airtightness, high adhesion, and structural stability of the heating element sealing film layer while saving energy, solving problems such as insufficient bonding strength, easy cracking, and poor aging resistance in traditional sealing processes.

[0016] The second aspect of this application provides a silicone oil composition for the heating element sealing process according to the first aspect of this application, the silicone oil composition comprising polymethylhydrosiloxane, additives, crosslinking agents and microstructure modifiers.

[0017] Preferably, the polymethylhydrosiloxane is selected from at least one of MHX-1107 silicone oil and TSF-484 silicone oil; the viscosity of the polymethylhydrosiloxane is 30~35 cst.

[0018] MHX-1107 silicone oil and TSF-484 silicone oil are highly stable methylhydrosilicone oils with a moderate density of Si-H bonds in their molecular chains. These bonds allow for cross-linking reactions with cross-linking agents, ensuring the cured film exhibits excellent mechanical properties and aging resistance. A viscosity of 30-35 cSt facilitates suitable fluidity of the silicone composition in step S2 at the residual heat temperature at the heating element port, enabling smooth spreading and penetration.

[0019] Preferably, the additive comprises an antioxidant and a surfactant in a weight ratio of (1.2~4.5):(3~5.5); the antioxidant is selected from at least one of antioxidant 168, antioxidant 264, antioxidant 626, and antioxidant 1010; the surfactant is selected from at least one of FC-211, FC-281, and FC-4430. More preferably, the additive comprises an antioxidant and a surfactant in a weight ratio of (2~4.5):(3.5~5.5); the antioxidant is selected from at least one of antioxidant 168, antioxidant 264, antioxidant 626, and antioxidant 1010; the surfactant is selected from at least one of FC-211, FC-281, and FC-4430.

[0020] Preferably, the crosslinking agent is selected from at least one of di-tert-butyl peroxide and 2,5-dimethyl-2,5-di-tert-butylperoxyhexane.

[0021] Preferably, the microstructure regulator is selected from hydrophobic nano-silica, wherein the average particle size of the hydrophobic nano-silica is 50~100nm and the surface is modified by a silane coupling agent.

[0022] In the additives, antioxidants help inhibit the oxidative degradation of polymethylhydrosiloxane during high-temperature curing and long-term use, extending the service life of the film; surfactants reduce the surface tension of the silicone oil composition and enhance its wettability on metal surfaces; at the same time, the weight ratio of antioxidant to surfactant (1.2~4.5):(3~5.5) balances antioxidant and wettability, avoiding performance antagonism caused by excessive amounts of one component.

[0023] Crosslinking agents di-tert-butyl peroxide and 2,5-dimethyl-2,5-di-tert-butylperoxyhexane efficiently initiate the crosslinking reaction of polymethylhydrosiloxane at high temperatures (150~180℃), forming a stable silicon-oxygen bond network structure, thereby improving the strength and high-temperature resistance of the film.

[0024] The hydrophobic nano-silica microstructure regulator with an average particle size of 50~100nm, modified by silane coupling agent, improves the compatibility between the components of the silicone composition. It also enables the heating tube to expel internal moisture through the nanopores when heated, avoiding bulging or bursting, while not affecting the overall waterproof performance of the membrane, thus achieving a two-way function of both sealing water and allowing air to pass through.

[0025] Preferably, in the raw materials of the silicone oil composition, the weight ratio of polymethylhydrosiloxane, additives and crosslinking agents is (80~86):(5~12):(4~7).

[0026] Preferably, in the raw materials of the silicone oil composition, the weight ratio of polymethylhydrosiloxane, additives, crosslinking agents and microstructure regulators is (80~86):(5~12):(4~7):(2~6).

[0027] In the raw materials of the silicone oil composition, through the quantitative synergy between the components and combined with the sealing process of the heating element of this application, the heating element of this application is greatly improved in terms of sealing performance, air permeability, mechanical properties and process performance, thereby ensuring the long-term use requirements of the heating element.

[0028] Compared with the prior art, this application has at least the following beneficial effects: 1) The heating tube sealing process of this application involves preparing a silicone oil composition and dripping it onto the heating tube port which is in a residual heat state. The residual heat is used to spread the silicone oil composition into the metal pores. The silicone oil composition is then cured by gradient heating to form a silicone-oxygen cross-linked film layer. Finally, the sealing is completed by post-heating treatment. The adhesion of the heating tube sealing film layer reaches level 1 in the cross-cut test, which improves the airtightness and aging resistance of the heating tube and further improves the production efficiency.

[0029] 2) In the heating tube sealing process of this application, step S2 utilizes the residual heat of the heating tube itself during processing to promote the initial leveling of the silicone oil composition, without the need for additional preheating, thus reducing energy consumption and production costs.

[0030] 3) The silicone composition of the heating tube sealing process in this application achieves multiple functions of water sealing, air permeability and explosion protection through the rational compounding of polymethylhydrosiloxane, additives, crosslinking agents and microstructure regulators. Detailed Implementation

[0031] The following detailed description of the contents of this application is provided through specific embodiments, comparative examples, and tables, but is not limited to all the arguments and data.

[0032] The polymethylhydrosiloxane used in the embodiments and comparative examples of this application is MHX-1107 silicone oil (Z) 30 viscosity from Dow Chemical (Shanghai) Co., Ltd.; the additives are antioxidant 264 and FC-211 in a weight ratio of 1.2:3.5; the crosslinking agent is di-tert-butyl peroxide; and the microstructure regulator is hydrophobic nano-silica with an average particle size of 50nm modified by KH570 from Hangzhou Jikang New Materials Co., Ltd.

[0033] It is particularly important to emphasize that, unless otherwise specified, the raw materials, reagents or devices used in this application can be obtained from conventional commercial sources.

[0034] This application discloses a heating element sealing process, which specifically includes the following steps: S1. Mix 80-86 parts of polymethylhydrosiloxane, 5-12 parts of additives, 4-7 parts of crosslinking agent, and 2-6 parts of microstructure regulator in a silicone oil composition at 30-40°C and stir for 15-20 minutes to obtain a silicone oil composition.

[0035] Regarding step S1, in some specific embodiments, the polymethylhydrosiloxane can be 80 parts, 82 parts, or 86 parts by weight; the polymethylhydrosiloxane can be one or a combination of MHX-1107 silicone oil and TSF-484 silicone oil; and the viscosity of the polymethylhydrosiloxane can be 30 cst or 35 cst. The additive can be 5 parts, 8 parts, 10 parts, or 12 parts by weight; the additive contains an antioxidant and a surfactant in a weight ratio of (1.2~4.5):(3~5.5); the antioxidant can be one or a combination of antioxidant 168, antioxidant 264, antioxidant 626, and antioxidant 1010; and the surfactant can be one or a combination of FC-211, FC-281, and FC-4430. The crosslinking agent can be 4 parts, 5 parts, or 7 parts by weight; and the crosslinking agent can be one or a combination of di-tert-butyl peroxide and 2,5-dimethyl-2,5-di-tert-butylperoxyhexane. The microstructure regulator can be 2, 4, or 6 parts by weight. The microstructure regulator can be hydrophobic nano-silica with an average particle size of 50-100 nm and a surface modified with a silane coupling agent. The mixing temperature can be 30℃, 32℃, 35℃, or 40℃, and the stirring time can be 15 min, 16 min, 18 min, or 20 min.

[0036] S2. Apply the silicone oil composition to the port of the heating tube that has just been welded and is in a residual heat state of 40~50℃. The amount of silicone oil composition applied is 0.5~1.0g / cm².

[0037] Regarding step S2, in some specific embodiments, the residual heat state can be 40°C, 45°C, or 50°C, and the amount of the silicone oil composition being dripped can be 0.5 g / cm², 0.6 g / cm², 0.8 g / cm², or 1.0 g / cm².

[0038] S3. Let stand for 30~70 seconds to allow the silicone oil composition to spread and penetrate the metal surface of the heating element.

[0039] For step S3, in some specific implementations, the settling time can be 30s, 40s, 50s or 70s.

[0040] S4. Perform gradient heating curing. First, pre-cur at 80~100℃ for 0.3~0.6h, then raise the temperature to 150~180℃ at a heating rate of 5~10℃ / min for main curing. The main curing time is 1.5~2h, so that a silicon-oxygen cross-linked film layer is formed at the heating tube port.

[0041] Regarding step S4, in some specific implementations, the pre-curing temperature can be 80℃, 90℃, 95℃ or 100℃, the pre-curing time can be 0.3h, 0.5h or 0.6h, the heating rate can be 5℃ / min, 6℃ / min, 8℃ / min or 10℃ / min, the main curing temperature can be 150℃, 170℃ or 180℃, and the main curing time can be 1.5h, 1.8h or 2h.

[0042] S5. After heating at 60~80℃ for 2~5 minutes, the heating element sealing process is completed.

[0043] Regarding step S5, in some specific implementations, the temperature of the post-heating treatment can be 60°C, 65°C, 70°C or 80°C, and the time of the post-heating treatment can be 2 min, 4 min or 5 min.

[0044] The process parameters of the heating element sealing process in the following examples and comparative examples, as well as the mass fraction of the silicone oil composition in the process, are shown in Tables 1 and 2, respectively.

[0045]

[0046]

[0047] Based on the heating element sealing process of this application, the following examples and comparative examples are provided: Example 1

[0048] A heating element sealing process specifically includes the following steps: S1. Mix 82 parts of polymethylhydrosiloxane, 5 parts of additives, 4 parts of crosslinking agent and 2 parts of microstructure regulator in a silicone oil composition at 30°C and stir for 18 minutes to obtain a silicone oil composition.

[0049] S2. Apply the silicone oil composition to the port of the heating tube that has just been welded and is in a residual heat state of 45°C. The amount of silicone oil composition applied is 1g / cm².

[0050] S3. Let stand for 50 seconds to allow the silicone oil composition to spread and penetrate the metal surface of the heating element.

[0051] S4. Perform gradient heating curing. First, pre-cur at 80℃ for 0.6h, then increase the temperature to 150℃ at a rate of 6℃ / min for main curing. The main curing time is 2h, so that a silicon-oxygen cross-linked film layer is formed at the heating tube port.

[0052] S5. After heating at 65℃ for 4 minutes, the heating element sealing process is completed. Example 2

[0053] A heating element sealing process is the same as in Example 1, except that the pre-curing temperature in step S4 of Example 2 is 95°C. Example 3

[0054] A heating element sealing process is the same as in Example 1, except that the pre-curing temperature in step S4 of Example 3 is 100°C. Example 4

[0055] A heating element sealing process is the same as in Example 1, except that the heating rate in step S4 of Example 4 is 8°C / min. Example 5

[0056] A heating element sealing process is the same as in Example 1, except that the main curing temperature in step S4 of Example 5 is 160°C. Example 6

[0057] A heating element sealing process is the same as in Example 1, except that the main curing temperature in step S4 of Example 6 is 180°C.

[0058] Comparative Example 1: A heating element sealing process is the same as in Example 1, except that the pre-curing temperature in step S4 of Comparative Example 1 is 60°C.

[0059] Comparative Example 2: A heating element sealing process is the same as in Example 1, except that the heating rate in step S4 of Comparative Example 2 is 15℃ / min.

[0060] Comparative Example 3: A heating element sealing process is the same as in Example 1, except that the main curing temperature in step S4 of Comparative Example 3 is 140°C.

[0061] Comparative Example 4: A heating element sealing process is the same as in Example 1, except that the weight of polymethylhydrosiloxane in Comparative Example 4 is 90 parts.

[0062] Comparative Example 5: A sealing process for a heating element is the same as in Example 1, except that the weight of the microstructure regulator in Comparative Example 5 is 1 part.

[0063] Material performance testing: The sealing film layers of the heating tubes obtained through the sealing processes of Examples 1-6 and Comparative Examples 1-5 were subjected to various performance tests, and the test methods are as follows: Adhesion: Tested according to GB / T 9286-1998 standard. The test results are divided into 6 levels, from 0 to 5, with the smaller the number, the higher the level.

[0064] Water resistance: Place the heating element with the sealing film layer into the pressure testing device, immerse it in water and apply a pressure of 0.3MPa for 30 minutes, release the pressure and check whether water has entered the heating element.

[0065] Air permeability: The air permeability of the sealing film layer was tested under heating conditions of 120℃ according to GB / T 1038-2000 standard.

[0066] Aging resistance: The heating tube with the sealing film layer was placed in a 200℃ oven for 1000 hours. After the test, the sample was taken out, cooled to room temperature, and the sealing area of ​​the tube was observed for cracking, discoloration, powdering, swelling, and insulation resistance before and after the test.

[0067] The test performance of the sealing film layer of the heating tubes obtained by the sealing process of Examples 1-6 and Comparative Examples 1-5 is shown in Table 3 below:

[0068] The heating element sealing process in Examples 1-6 involves preparing a silicone oil composition and dripping it onto the heating element port while it is still under residual heat. The residual heat allows the silicone oil composition to spread and penetrate the metal capillary structure. Gradient heating and curing then form a silicone-oxygen cross-linked film. A subsequent heat treatment completes the sealing process. The resulting sealing film layer exhibits Grade 1 adhesion, and no water ingress was observed after waterproofing testing. Air permeability testing showed a permeability of 0.5-0.9 mL / (cm²). 2 •h) After aging resistance testing, no cracking, discoloration, powdering, or swelling was observed, and the insulation resistance did not decrease.

[0069] Compared with Example 1, the pre-curing temperature in step S4 of Comparative Example 1 was 60°C, while other process conditions were the same as in Example 1. The results showed that the adhesion of the sealing film layer of the heating element in Comparative Example 1 reached level 1. Water ingress was observed after a waterproof performance test, and the air permeability was 0.5 mL / (cm²). 2 •h) After the aging resistance test, swelling was observed, indicating that the pre-curing temperature of step S4 has a significant impact on the performance of the sealing film layer. Although its adhesion did not change, it may be because the pre-curing temperature of S4 in Comparative Example 1 was lower, which affected the curing degree of the subsequent main curing, causing the film layer to swell after the aging resistance test.

[0070] Compared with Example 1, Comparative Example 2 had a heating rate of 15℃ / min in step S4, while other process conditions were the same as in Example 1. The results showed that the adhesion of the sealing film layer of the heating element in Comparative Example 2 was at level 2. Water ingress was observed after a waterproof performance test, and the air permeability was 0.4 mL / (cm²). 2•h) After the aging resistance test, cracking occurred and the insulation resistance decreased significantly. This may be because the heating rate in step S4 of Comparative Example 2 was too fast, which increased the thermal stress caused by the temperature difference between the inside and outside of the film layer, making the sealing film layer easy to crack. It also affected the adhesion, air permeability and other properties.

[0071] Compared with Example 1, the main curing temperature in step S4 of Comparative Example 3 was 140℃, while other process conditions were the same as in Example 1. The results showed that the adhesion of the sealing film layer of the heating element in Comparative Example 3 was at level 2. Water ingress was observed after a waterproof performance test, and the air permeability was 0.6 mL / (cm²). 2 •h) After aging resistance testing, cracking occurred and the insulation resistance decreased slightly. This may be because the main curing temperature of step S4 in Comparative Example 3 was too low, and the cross-linking of the silicone composition was not sufficient, which affected the formed silicon-oxygen network structure and thus reduced the adhesion of the sealing film layer.

[0072] Compared with Example 1, Comparative Example 4 contained 90 parts by weight of polymethylhydrosiloxane, while other process conditions were the same as in Example 1. The results showed that the adhesion of the sealing film layer of the heating element in Comparative Example 4 was at level 1. No water ingress was observed after the waterproof performance test, and the air permeability test showed an air permeability of 0.4 mL / (cm²). 2 •h) Cracking occurred after the aging resistance test, and the insulation resistance decreased significantly. This may be because the weight of polymethylhydrosiloxane in Comparative Example 4 was too high, and the cross-linking of the silicone composition was not sufficient, which affected the formation of the silicon-oxygen network structure. Although the adhesion of the sealing film layer did not decrease, cracking occurred in the aging resistance test.

[0073] Compared with Example 1, Comparative Example 5 had a microstructure regulator weight ratio of 1 part, while other process conditions were the same as in Example 1. The results showed that the adhesion of the sealing film layer of the heating element in Comparative Example 5 was at level 1, and no water entered after a waterproof performance test. The air permeability test showed an air permeability of 0.2 mL / (cm²). 2 •h) No cracking, discoloration, powdering or swelling was observed after aging resistance testing. The insulation resistance decreased slightly, which may be due to the insufficient weight of microstructure regulator in Comparative Example 5, which reduced the compatibility between the components of the silicone composition and thus affected the air permeability of the sealing film layer.

[0074] Obviously, the above embodiments of this application are merely examples for clearly illustrating this application, and are not intended to limit the implementation of this application. For those skilled in the art, other variations or modifications can be made based on the above description. Any obvious variations or modifications derived from the technical solutions of this application are still within the protection scope of this application.

Claims

1. A sealing process for a heating element, characterized in that, Includes the following steps: S1. Preparation of silicone oil composition; S2. Apply the silicone oil composition to the port of the heating element that has just been welded and is still in a residual heat state; S3. Allow the silicone oil composition to stand, allowing it to spread and penetrate the metal surface of the heating element. S4. Gradient heating and curing to form a silicon-oxygen cross-linked film layer at the port of the heating tube; S5. Post-heating treatment to complete the sealing process of the heating element.

2. The heating element sealing process according to claim 1, characterized in that, In step S2, the amount of the dripped silicone oil composition is 0.5~1.0 g / cm², and the temperature of the heating tube port in the residual heat state is 40~50℃.

3. The heating element sealing process according to claim 1, characterized in that, In step S3, the settling time is 30~70s.

4. The heating element sealing process according to claim 1, characterized in that, In step S4, the gradient heating curing includes pre-curing at 80~100℃ and then heating to 150~180℃ at a heating rate of 5~10℃ / min for main curing. The pre-curing time is 0.3~0.6h and the main curing time is 1.5~2h.

5. The heating element sealing process according to claim 1, characterized in that, In step S5, the temperature of the post-heating treatment is 60~80℃, and the time of the post-heating treatment is 2~5 minutes.

6. A silicone oil composition for use in the sealing process of the heating element according to any one of claims 1 to 5, characterized in that, The silicone oil composition includes polymethylhydrosiloxane, additives, crosslinking agents, and microstructure modifiers.

7. The silicone oil composition according to claim 6, characterized in that, The polymethylhydrosiloxane is selected from at least one of MHX-1107 silicone oil and TSF-484 silicone oil; The viscosity of the polymethylhydrosiloxane is 30~35 cst.

8. The silicone oil composition according to claim 6, characterized in that, The additive comprises an antioxidant and a surfactant in a weight ratio of (1.2~4.5):(3~5.5); The antioxidant is selected from at least one of antioxidant 168, antioxidant 264, antioxidant 626 and antioxidant 1010; The surfactant is selected from at least one of FC-211, FC-281 and FC-4430.

9. The silicone oil composition according to claim 6, characterized in that, The crosslinking agent is selected from at least one of di-tert-butyl peroxide and 2,5-dimethyl-2,5-di-tert-butylperoxyhexane; The microstructure regulator is selected from hydrophobic nano-silica, which has an average particle size of 50-100 nm and its surface is modified with a silane coupling agent.

10. The silicone oil composition according to claim 6, characterized in that, Its raw materials include the following components in parts by weight: 80-86 parts of polymethylhydrosiloxane; Additives 5-12 parts; 4-7 parts of crosslinking agent; Microstructure regulator 2-6 parts.

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