Waterproof gasket for mobile phone camera and preparation method

Abstract

The invention relates to the technical field of waterproof gasket processing, in particular to a waterproof gasket for a mobile phone camera and a preparation method of the waterproof gasket for the mobile phone camera. The polytetrafluoroethylene coating is prepared from the following raw materials in parts by weight: polytetrafluoroethylene, polyurethane resin, a dispersing agent, hydroxyl inorganic filler, a silane coupling agent, a curing agent and a solvent, and the rubber layer is prepared from the following raw materials in parts by weight: rubber, a reinforcing agent, an activating agent, an accelerant, a vulcanizing agent, polyamide wax micro powder and a plasticizer. The rubber is composed of polyurethane rubber and ethylene propylene diene monomer, the creep resistance can be effectively improved through the composite structure of the rubber layer and the polytetrafluoroethylene layer, and under continuous pressure, the elastic deformation of the rubber layer can relieve the plastic deformation problem possibly generated by the polytetrafluoroethylene layer due to poor creep resistance. Therefore, the sealing effect is better maintained.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of waterproof gasket processing, in particular to a waterproof gasket for a mobile phone camera and a preparation method. BACKGROUND

[0002] The waterproof gasket for a mobile phone camera effectively blocks water, moisture and dust and other foreign matters from entering the inside of the camera, prevents short circuit, corrosion and lens fogging, dust adhesion and other problems caused by water ingress, and guarantees the clarity of the shooting picture and the normal operation of the camera. At the same time, it can also buffer the impact force caused by collision, falling or vibration, and reduce the risk of damage to the camera.

[0003] At present, polytetrafluoroethylene has become one of the commonly used materials for the waterproof gasket of a mobile phone camera due to its excellent chemical stability and good wear resistance. The chemical stability of polytetrafluoroethylene makes it almost not corroded by any chemical substances, and its wear resistance ensures that the slight friction generated during the camera installation process and the daily use of the mobile phone will not cause wear to the gasket itself and the camera shell, which helps to prolong the service life of the gasket and the camera.

[0004] However, polytetrafluoroethylene also has some shortcomings. The hardness of polytetrafluoroethylene is high and its brittleness is large, and its impact resistance is poor, so it is easy to break when subjected to a large external force impact. At the same time, its anti-creep performance is poor, and it is easy to deform plastically under continuous pressure, which affects the sealing effect. In order to overcome the above technical problems, glass fibers, carbon fibers, graphite and other fillers are added to polytetrafluoroethylene for filling modification, which can significantly improve its mechanical strength and anti-creep performance, so as to better meet the needs of the waterproof gasket of a mobile phone camera.

[0005] However, due to the long molecular chain and high crystallinity of polytetrafluoroethylene, the intermolecular force is strong, and it is difficult to make it melt and flow through the conventional way and fill the mold to form. Generally, sintering process is adopted, which can make polytetrafluoroethylene realize close combination between particles through molecular diffusion and rearrangement at high temperature, so as to form products with specific shape and performance. However, after adding glass fibers, carbon fibers, graphite and other fillers to polytetrafluoroethylene, the melting viscosity of the composite material increases greatly, and the fluidity becomes poor, which not only greatly increases the difficulty of sintering process, but also requires longer sintering time to make the material fully densified, increasing the production cost and energy consumption.

[0006] In addition, due to the difference in thermal expansion coefficient between the filler and polytetrafluoroethylene, internal stress will be generated during sintering and cooling. This internal stress may cause material deformation or cracking, thereby affecting the yield and overall quality of the product. As can be seen, although filling modification can improve some properties of polytetrafluoroethylene, it also introduces a series of new technical problems, which need to be further researched and solved. SUMMARY

[0007] In order to solve the problem that it is difficult to process polytetrafluoroethylene and inorganic fillers to make a waterproof gasket for a mobile phone camera, the application provides a waterproof gasket for a mobile phone camera and a preparation method.

[0008] In a first aspect, the application provides a waterproof gasket for a mobile phone camera, which adopts the following technical solution: A waterproof gasket for a mobile phone camera, comprising a rubber layer and a polytetrafluoroethylene layer formed by coating the rubber layer with polytetrafluoroethylene paint and curing, wherein the polytetrafluoroethylene paint is prepared from the following raw materials in parts by weight: Polytetrafluoroethylene 20-30 parts Polyurethane resin 10-15 parts Dispersant 1-2 parts Hydroxyl inorganic filler 5-10 parts Silane coupling agent 1-2 parts Curing agent 1-2 parts Solvent 90-100 parts The rubber layer is prepared from the following raw materials in parts by weight: Rubber 100 parts Reinforcing agent 10-20 parts Activator 2-4 parts Accelerator 1-2 parts Vulcanizing agent 1-2 parts Polyamide wax micro powder 5-10 parts Plasticizer 3-6 parts The rubber is composed of polyurethane rubber and ternary ethylene-propylene rubber in a weight ratio of 2:(0.5-1).

[0009] By adopting the above technical solution, the problems of high hardness, brittleness, poor impact resistance and poor creep resistance of polytetrafluoroethylene are solved. By adding polyurethane resin and other components to the polytetrafluoroethylene paint, a composite structure of rubber layer and polytetrafluoroethylene layer is formed. The rubber layer has good elasticity and can play a buffering role when subjected to external impact, making up for the defects of high hardness, brittleness and poor impact resistance of polytetrafluoroethylene itself. Moreover, this composite structure can effectively improve the anti-creep performance. Under continuous pressure, the elastic deformation of the rubber layer can alleviate the plastic deformation problem of the polytetrafluoroethylene layer due to poor anti-creep performance, thereby better maintaining the sealing effect.

[0010] At the same time, the process of making polytetrafluoroethylene into paint, coating it on the rubber layer and then curing to form a polytetrafluoroethylene layer is adopted. Compared with the traditional sintering process, this method can more effectively form polytetrafluoroethylene, avoiding the problems of high melt viscosity and poor flowability of the modified composite material, resulting in high difficulty, long sintering time and high energy consumption of the sintering process, and reducing the production cost.

[0011] The polyurethane resin in the polytetrafluoroethylene coating cooperates with the polytetrafluoroethylene, and the polyurethane resin has good adhesion and flexibility, which can improve the coating performance of the polytetrafluoroethylene coating, make it better adhere to the surface of the rubber layer, and also enhance the flexibility of the polytetrafluoroethylene layer, reduce its brittleness, and improve the overall impact resistance. The dispersant helps to uniformly disperse polytetrafluoroethylene and other ingredients in the solvent, ensuring that the coating has good stability and fluidity, making the cured polytetrafluoroethylene layer more uniform and dense, and exhibiting better performance. The hydroxyl inorganic filler can fill into the micro-pores of polytetrafluoroethylene, improve the density and hardness of the polytetrafluoroethylene layer, and further enhance its wear resistance and anti-creep performance.

[0012] During the coating and curing process, the silane coupling agent can form a chemical bond between the polytetrafluoroethylene layer and the rubber layer, making the two layers tightly combined and enhancing the connection strength between the layers. Even under the influence of various external forces and environmental factors during long-term use, there will be no delamination or peeling phenomenon, thereby ensuring the integrity and sealing performance of the entire waterproof gasket.

[0013] In the present application, the rubber is composed of polyurethane rubber and ethylene propylene diene rubber in a specific weight ratio, which combines the high strength and wear resistance of polyurethane rubber with the good elasticity and aging resistance of ethylene propylene diene rubber, providing excellent flexibility and impact resistance for the entire waterproof gasket. As the base support layer, it can relieve external impact force, protect the polytetrafluoroethylene layer, and ensure good sealing between the waterproof gasket and the camera shell and other components.

[0014] The reinforcing agent increases the strength and hardness of the rubber layer, improves the wear resistance and tear resistance of the rubber, and makes the rubber layer better withstand friction and external forces, and cooperates with the polytetrafluoroethylene layer to play a protective and sealing effect.

[0015] The activator, accelerator, and vulcanizing agent play a key role in the rubber vulcanization process. The activator can improve the reactivity of the rubber, the accelerator can speed up the vulcanization reaction, and the vulcanizing agent can cross-link the rubber to form a stable three-dimensional network structure, thereby giving the rubber layer good elasticity and durability, allowing it to effectively play a sealing role for a long time.

[0016] The polyamide wax micro powder forms a lubricating film on the surface of the rubber layer, improves the surface smoothness of the rubber layer, and improves the coating uniformity and adhesion of the polytetrafluoroethylene coating on the surface of the rubber layer. The plasticizer makes the rubber layer have better flexibility and plasticity, facilitates the deformation and fitting of the rubber layer during the camera installation process. The crosslinking agent promotes the crosslinking reaction between the rubber molecules in the rubber layer, further enhances the strength and elasticity of the rubber layer, improves the aging resistance and chemical stability of the rubber layer, prolongs the service life of the rubber layer, and makes it match the service life of the polytetrafluoroethylene layer, together guaranteeing the long-term reliable use of the mobile phone camera waterproof gasket.

[0017] Preferably, the hydroxyl inorganic filler is prepared by the following method: 1) Concentrated sulfuric acid and concentrated nitric acid are configured into a mixed solution in a volume ratio of 3:1; 2) The inorganic filler is added to the mixed solution, heated to 50-60℃, and kept heating for 1-2h, centrifugal filtration, elution, and drying to obtain the hydroxyl inorganic filler.

[0018] Preferably, the inorganic filler includes at least one of silica, multi-walled carbon nanotubes, graphene, titanium dioxide, wollastonite, and mica powder.

[0019] By adopting the above technical solution, the mixed solution of concentrated sulfuric acid and concentrated nitric acid has strong oxidizing property, and under heating conditions, can perform oxidation treatment on the surface of the inorganic filler to generate active groups such as hydroxyl, so that the filler surface is changed from the original inert surface to an active surface, improving the compatibility of the filler with organic matters such as polytetrafluoroethylene, thereby enhancing the interfacial bonding force between the hydroxyl inorganic filler and the polytetrafluoroethylene matrix, helping to improve the comprehensive performance of the gasket such as strength and dimensional stability, and making the polytetrafluoroethylene material better meet the requirements of high-performance materials such as mobile phone camera waterproof gaskets.

[0020] Preferably, the dispersant is composed of fatty alcohol polyoxyethylene ether and fatty acid polyethylene glycol ester in a weight ratio of (1-3):5.

[0021] By adopting the above technical solution, the combination of fatty alcohol polyoxyethylene ether and fatty acid polyethylene glycol ester can effectively reduce the surface tension of the polytetrafluoroethylene coating system, make the filler particles uniformly dispersed in the polytetrafluoroethylene matrix, prevent filler agglomeration, reduce the dispersion instability problem caused by poor compatibility, enhance the stability of the entire coating system, prevent the filler from settling due to too low viscosity. At the same time, the coating has good thixotropy, facilitating construction and ensuring uniform coating layer, thereby improving the quality of the waterproof gasket.

[0022] Preferably, the polyurethane rubber is at least one of polyurethane rubber AU1110, polyurethane rubber EU2710, polyurethane rubber EU2400 and Urepan series polyester mixed polyurethane rubber.

[0023] Preferably, the ethylene content of the ethylene propylene terpolymer is 45-75%, the Mooney viscosity ML(1+4)125℃ is 40-100, and the third monomer content is 4-10%.

[0024] By adopting the above technical solutions, the type of polyurethane rubber and the parameters of ethylene propylene terpolymer are optimized, so that the rubber layer can provide better elasticity and flexibility, cooperate with the polytetrafluoroethylene layer, form a more compact and reliable sealing structure, effectively prevent moisture, dust and other impurities from entering the camera, and improve the sealing performance of the waterproof gasket. At the same time, the excellent aging resistance of the above-mentioned polyurethane rubber and ethylene propylene terpolymer makes the rubber layer not prone to cracking, hardening, wear and tear and other problems during long-term use, thereby prolonging the service life of the waterproof gasket, reducing the frequency of maintenance and replacement, and improving the reliability and stability of the mobile phone camera.

[0025] Preferably, the solvent is composed of butyl acetate, cyclohexanone, xylene and dimethylformamide in a weight ratio of 1:(2-4):(1-4):(4-6).

[0026] By adopting the above technical solutions, the polytetrafluoroethylene and other ingredients show good solubility, ensuring that the ingredients in the polytetrafluoroethylene coating can be uniformly dispersed and mixed to form a stable coating system.

[0027] Preferably, the thickness ratio of the polytetrafluoroethylene layer to the rubber layer is 1:(3-5).

[0028] By adopting the above technical solutions, the thickness ratio of the polytetrafluoroethylene layer and the rubber layer is optimized, which can effectively buffer and absorb external force impact, reduce the impact of impact force on the polytetrafluoroethylene layer, reduce the risk of damage to the polytetrafluoroethylene layer due to large external force, and improve the overall impact resistance of the waterproof gasket. At the same time, the thicker rubber layer can provide support for the polytetrafluoroethylene layer, disperse the pressure, and reduce the continuous pressure on the polytetrafluoroethylene layer, thereby further enhancing the overall anti-cree performance of the waterproof gasket, ensuring its sealing effect in long-term use.

[0029] In addition, the thicker rubber layer makes the overall waterproof gasket have a certain flexibility, which is convenient for proper deformation and adjustment during the camera installation process, and ensures good adhesion. The presence of the polytetrafluoroethylene layer provides the overall gasket with a certain rigidity and stability, so that it is not prone to excessive deformation during use, maintains the stability of the shape, thereby balancing the flexibility and stability, and improving the overall performance and reliability of the waterproof gasket.

[0030] In a second aspect, the application provides a preparation method of a waterproof gasket for a mobile phone camera, which adopts the following technical scheme: A preparation method of a waterproof gasket for a mobile phone camera, comprising the following preparation steps: S1, adding rubber and polyamide wax micro powder into a plastic mixing machine, the plasticizing temperature is 95-100℃, and the plasticizing time is 45-50min, to obtain plasticized rubber; S2, adding the plasticized rubber obtained in step S1, an activating agent, a reinforcing agent, a vulcanizing agent and a plasticizer into a mixing machine, and mixing at 95-100℃ for 50-60min to obtain mixed rubber; S3, continuously adding an accelerator to the mixed rubber obtained in step S2, and placing it in a vulcanizing machine to be pre-vulcanized at 125-130℃ for 10-15min, and then secondarily vulcanized at 170-175℃ for 80-100min to obtain a rubber layer; S4, mixing and stirring a solvent and a polyurethane resin until the polyurethane resin is completely dissolved, and then adding polytetrafluoroethylene, a dispersing agent, a hydroxyl inorganic filler, a silane coupling agent and a curing agent to be stirred to obtain a mixed material; S5, spraying the mixed material on the surface of the rubber layer, and curing to obtain a waterproof gasket for a mobile phone camera.

[0031] By adopting the above technical scheme, the components of the rubber layer are fully mixed through step-by-step plasticizing and mixing, the plasticity and uniformity of the rubber are improved, the strength, elasticity and wear resistance of the rubber layer are improved through the secondary vulcanization process, the aging resistance and chemical stability are also enhanced, and the service life of the rubber layer is prolonged. The solvent and the polyurethane resin are mixed and stirred until the polyurethane resin is completely dissolved, and then the polytetrafluoroethylene, the dispersing agent and the like are added to be stirred to obtain a mixed material, so that the components are fully mixed and uniform, and the performance consistency of the polytetrafluoroethylene coating is ensured. This helps to form a uniform polytetrafluoroethylene layer during the coating process, and improves the sealing performance, impact resistance and creep resistance.

[0032] In summary, the application has the following beneficial effects: 1、The application successfully solves the problems of high hardness, large brittleness, poor impact resistance and poor creep resistance of polytetrafluoroethylene by designing a composite structure waterproof gasket of rubber and polytetrafluoroethylene. The rubber layer has elasticity and can buffer the impact, making up for the defects of polytetrafluoroethylene. At the same time, the addition of polyurethane resin and other components in the polytetrafluoroethylene coating improves the adhesion and flexibility and enhances the impact resistance. The use of dispersants and hydroxyl inorganic fillers further improves the stability of the coating and the density of the polytetrafluoroethylene layer, thereby enhancing the wear resistance and creep resistance. The application of silane coupling agent ensures the close combination between the two layers and improves the integrity and sealing performance. The use of coating and curing process instead of traditional sintering process reduces the production cost. The rubber layer combines the advantages of polyurethane rubber and ethylene propylene diene rubber, improving the flexibility and impact resistance. The addition of reinforcing agents, activators, accelerators, vulcanizing agents and other components further improves the performance of the rubber layer, enabling it to work with the polytetrafluoroethylene layer to provide protection and sealing, prolonging the service life and ensuring the long-term reliable use of the waterproof gasket for mobile phone cameras. DETAILED DESCRIPTION

[0033] Preparation Example Preparation Example 1 A kind of hydroxyl inorganic filler, by the following method is prepared to obtain: 1) concentrated sulfuric acid and concentrated nitric acid are configured into mixed solution according to the proportion of 3:1 by volume ratio; 2) inorganic filler 50g (silicon dioxide) is added to the mixed solution, heated to 50℃, keep heating 1h, centrifugal filtration, elution, dry, obtain hydroxyl inorganic filler.

[0034] Preparation Example 2 A kind of hydroxyl inorganic filler, by the following method is prepared to obtain: 1) concentrated sulfuric acid and concentrated nitric acid are configured into mixed solution according to the proportion of 3:1 by volume ratio; 2) inorganic filler 50g (multi-walled carbon nanotube) is added to the mixed solution, heated to 55℃, keep heating 1.5h, centrifugal filtration, elution, dry, obtain hydroxyl inorganic filler.

[0035] Preparation Example 3 A kind of hydroxyl inorganic filler, by the following method is prepared to obtain: 1) concentrated sulfuric acid and concentrated nitric acid are configured into mixed solution according to the proportion of 3:1 by volume ratio; 2) inorganic filler 50g (titanium dioxide) is added to the mixed solution, heated to 60℃, keep heating 2h, centrifugal filtration, elution, dry, obtain hydroxyl inorganic filler. Example

[0036] The polyurethane resin is purchased from Dongguan Shanjun New Material Co., Ltd., and the model is SR-5585. Polytetrafluoroethylene was purchased from Dongguan Guangye Plastic Raw Material Co., Ltd., with the product number 6C.

[0037] Polyamide wax micro powder was purchased from Dongguan Sanwen Culture Raw Material Trade Co., Ltd., with the model number HW-K.

[0038] Example 1 A mobile phone camera waterproof gasket was prepared by the following method: S1, rubber 1000g and polyamide wax micro powder 50g were mixed and added to the internal mixer, the plasticating temperature was 95℃, and the plasticating time was 45min, to obtain plasticated rubber; S2, the plasticated rubber obtained in step S1, activator 20g (zinc oxide), reinforcing agent 100g (white carbon black), vulcanizing agent 10g (sulfur) and plasticizer 30g (dioctyl sebacate) were mixed and added to the mixing machine, and after mixing at 95℃ for 50min, the mixed rubber was obtained; S3, to the mixed rubber obtained in step S2, accelerator 10g (tetramethyl thiuram disulfide) was continuously added, and placed in the vulcanizing machine for pre-vulcanization at 125℃ for 10min, and then secondary vulcanization at 170℃ for 80min, to obtain the rubber layer; S4, solvent 900g and polyurethane resin 100g were mixed and stirred until the polyurethane resin was completely dissolved, then polytetrafluoroethylene 200g, dispersing agent 10g, hydroxyl inorganic filler 50g, silane coupling agent 10g and curing agent 10g (3,3-dimethyl-4,4-diamino dicyclohexyl methane) were added and stirred to obtain a mixture; S5, the mixture was sprayed on the surface of the rubber layer, and cured to obtain the mobile phone camera waterproof gasket.

[0039] The rubber was composed of polyurethane rubber (polyurethane rubber AU1110) and ethylene-propylene-diene rubber according to a weight ratio of 2:0.5.

[0040] The ethylene content of the ethylene-propylene-diene rubber was 45%, the Mooney viscosity ML(1+4)125℃ was 40, and the third monomer content was 4%, and the third monomer was 5-ethylene-2-norbornene.

[0041] The dispersing agent was composed of fatty alcohol polyoxyethylene ether and fatty acid polyethylene glycol ester according to a weight ratio of 1:5.

[0042] The solvent was composed of butyl acetate, cyclohexanone, xylene and dimethylformamide according to a weight ratio of 1:2:1:4.

[0043] The thickness ratio of the polytetrafluoroethylene layer to the rubber layer was 1:3.

[0044] Example 2-3 differs from Example 1 in that the types and amounts of raw materials used to prepare the waterproof gasket for the camera of a mobile phone and the test parameters are different, and the specific differences are shown in Table 1. Table 1 Types and amounts of raw materials used to prepare the waterproof gasket for the camera of a mobile phone and test parameters in Examples 1-3 In Example 2, the rubber is composed of polyurethane rubber (polyurethane rubber EU2710) and ethylene-propylene-diene rubber in a weight ratio of 2:0.5.

[0045] The ethylene content of the ethylene-propylene-diene rubber is 60%, the Mooney viscosity ML(1+4) 125°C is 80, and the third monomer content is 8%, and the third monomer is ethylidene norbornene.

[0046] In Example 3, the rubber is composed of polyurethane rubber (Urepan 640G) and ethylene-propylene-diene rubber in a weight ratio of 2:0.5.

[0047] The ethylene content of the ethylene-propylene-diene rubber is 75%, the Mooney viscosity ML(1+4) 125°C is 100, and the third monomer content is 10%, and the third monomer is 1,4-hexadiene.

[0048] Example 4 A waterproof gasket for the camera of a mobile phone, this example differs from Example 1 in that the dispersing agent is a fatty acid polyethylene glycol ester.

[0049] Example 5 A waterproof gasket for the camera of a mobile phone, this example differs from Example 1 in that the thickness ratio of the polytetrafluoroethylene layer to the rubber layer is 1:3.

[0050] Comparative Example Comparative Example 1 A waterproof gasket for the camera of a mobile phone, this comparative example differs from Example 1 in that the rubber is polyurethane rubber.

[0051] Comparative Example 2 A waterproof gasket for the camera of a mobile phone, this comparative example differs from Example 1 in that the rubber is ethylene-propylene-diene rubber.

[0052] Comparative Example 3 A waterproof gasket for the camera of a mobile phone, this comparative example differs from Example 1 in that the hydroxyl inorganic filler is replaced with silicon dioxide.

[0053] Comparative Example 4 A mobile phone camera waterproof gasket, the difference between the present comparative example and example 1 is that no polyurethane resin is added.

[0054] Comparative Example 5 A mobile phone camera waterproof gasket, the difference between the present comparative example and example 1 is that no polyurethane resin is added.

[0055] Detection method / test method Impact resistance test: select a pendulum with a mass of 1 kg, and adjust the release height of the pendulum to 0.5 m. Place the mobile phone camera waterproof gasket on the support of the pendulum impact tester, and make sure that the measured part is firmly fixed at the designated position to ensure that it does not shift or loosen during the impact process. Release the pendulum and let it swing freely to impact the fixed mobile phone camera waterproof gasket. Record the impact strength value.

[0056] Creep resistance test: place the mobile phone camera waterproof gasket on the loading platform of the creep test device, and make sure that the stress part is accurately aligned with the loading point. Then apply a constant load of 100 N to make the gasket start to deform. Turn on the measurement system and continuously observe for 24 hours. Record the deformation data, and at the same time, cut off the mobile phone camera waterproof gasket to observe whether the polytetrafluoroethylene layer and the rubber layer are separated.

[0057] Sealing performance test: prepare mobile phone camera modules, and install the mobile phone camera waterproof gaskets of examples 1-5 and comparative examples 1-5 respectively. All camera modules are of the same specification and model, only the type of waterproof gasket is different. Set the initial pressure of the water pressure test to 1 m of water column pressure (about 9.8 kPa), and set the water pressure to increase by 0.5 m of water column pressure as a step, and the pressure holding time of each step is 30 minutes. At the same time, set the test time to 2 hours to simulate the use scenario of the mobile phone under water for a long time. Place the camera module with the installed mobile phone camera waterproof gasket into the test cavity of the water pressure test equipment, make sure that the module is well sealed with the test cavity, and then start the water pressure test. Observe and record whether there is water infiltration into the camera after 30 minutes under 1 m of water column pressure. If there is no water infiltration, continue to increase the water pressure to 1.5 m of water column pressure, and observe and record in the same way, and test according to the set water pressure step and time, until the test period of 2 hours is completed. For example, the test result shows that within 2 hours, the camera module still has no water infiltration under 2 m of water column pressure, the camera interior remains dry, and the imaging function is normal.

[0058] Ageing resistance test: place the mobile phone camera waterproof gasket in the test box, set the temperature to 85℃±2℃, and the humidity to 85%±5%, and let it stand for 1000 hours. Take it out and test the creep resistance again. The experimental data are shown in Table 2. Table 2 Experimental data of examples 1-5 and comparative examples 1-5 The impact resistance of examples 1-5 are all above 0.75J, much higher than the 0.4J-0.6J of the comparative examples. This shows that after using the composite structure of polytetrafluoroethylene and rubber layer and adding polyurethane resin and other ingredients, the impact resistance of the waterproof gasket is significantly improved. The polyurethane resin enhances the flexibility and adhesion of the polytetrafluoroethylene coating, allowing it to better adhere to the surface of the rubber layer, while the good elasticity of the rubber layer can play a buffering role when subjected to external impact, making up for the defects of high hardness, brittleness and poor impact resistance of polytetrafluoroethylene itself, so the waterproof gasket of the examples can withstand greater impact force without damage or rupture in the impact test.

[0059] The anti-creep deformation of examples 1-5 is between 0.13mm-0.17mm, much lower than the 0.25mm-0.35mm of the comparative examples. This shows that the waterproof gasket of the examples is less likely to deform plastically under continuous pressure, and can better maintain the sealing effect. The synergistic effect of polytetrafluoroethylene and rubber layer and the addition of hydroxyl inorganic filler and other ingredients effectively improves the anti-creep performance of the material. The hydroxyl inorganic filler fills the micro-pores of polytetrafluoroethylene, enhancing the density and hardness of the polytetrafluoroethylene layer, making it more difficult to deform under continuous load, while the elastic deformation of the rubber layer can also alleviate the plastic deformation problem of the polytetrafluoroethylene layer due to poor anti-creep performance.

[0060] In the water pressure test, the camera modules of examples 1-5 have no water penetration within 2 hours of test time, while comparative examples 1 and 2 appear to be water penetration under 1.5m water column pressure, and comparative examples 3-4 even appear to be water penetration under 1m water column pressure. This reflects the excellent sealing performance of the waterproof gasket of the examples, which benefits from its unique composite structure and material formula. The polytetrafluoroethylene layer has good chemical stability and wear resistance, which can effectively prevent the penetration of water molecules, and the rubber layer provides good elasticity and sealing performance, and the combination of the two plus the synergistic effect of polyurethane resin and other ingredients makes the waterproof gasket tightly fit with the camera shell, forming an effective sealing barrier to ensure good sealing effect under different water pressure conditions.

[0061] The anti-creep deformation of the examples 1-5 is increased after 1000 hours of the double 85 test, but is still lower than 0.23 mm, while the anti-creep deformation of the comparative examples reaches 0.35 mm-0.45 mm. This shows that the waterproof gasket of the examples has better aging resistance and can maintain stable performance in a high temperature and high humidity environment. Polytetrafluoroethylene itself has excellent chemical stability and aging resistance, and the polyurethane rubber and the ethylene-propylene-diene rubber in the rubber layer also have good aging resistance. The combination of the two and the addition of the silane coupling agent enhance the aging resistance of the material. The silane coupling agent forms a chemical bond between the polytetrafluoroethylene layer and the rubber layer, improving the bonding strength between the layers, so that the material is not easily affected by environmental factors and performance degradation during long-term use.

[0062] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, as long as the modifications are within the scope of the claims of the present application.

Claims

1. A waterproof gasket for a mobile phone camera, characterized in that, It includes a rubber layer and a polytetrafluoroethylene (PTFE) layer formed by coating the rubber layer with a PTFE coating and curing it, wherein the PTFE coating is prepared from the following raw materials in parts by weight: 20-30 parts of polytetrafluoroethylene 10-15 parts of polyurethane resin 1-2 parts of dispersant 5-10 parts of hydroxyl inorganic filler 1-2 parts of silane coupling agent 1-2 parts of curing agent 90-100 parts of solvent The rubber layer is prepared from the following raw materials in parts by weight: 100 parts of rubber 10-20 parts of reinforcing agent Activator 2-4 parts 1-2 parts of accelerator 1-2 parts of vulcanizing agent 5-10 parts of polyamide wax micro powder 3-6 parts plasticizer The rubber is composed of polyurethane rubber and ethylene propylene diene monomer (EPDM) rubber in a weight ratio of 2:(0.5-1).

2. The waterproof gasket for a mobile phone camera according to claim 1, characterized in that, The hydroxyl-containing inorganic filler was prepared by the following method: 1) Prepare a mixed solution by mixing concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1; 2) Add the inorganic filler to the mixed solution, heat to 50-60℃, maintain heating for 1-2 hours, centrifuge, filter, rinse, and dry to obtain the hydroxyl inorganic filler.

3. The waterproof gasket for a mobile phone camera according to claim 2, characterized in that: The inorganic filler includes at least one of silica, multi-walled carbon nanotubes, graphene, titanium dioxide, wollastonite, and mica powder.

4. A waterproof gasket for a mobile phone camera according to claim 1, characterized in that: The dispersant is composed of fatty alcohol polyoxyethylene ether and fatty acid polyethylene glycol ester in a weight ratio of (1-3):

5.

5. A waterproof gasket for a mobile phone camera according to claim 1, characterized in that: The polyurethane rubber is at least one of polyurethane rubber AU1110, polyurethane rubber EU2710, polyurethane rubber EU2400, and Urepan series polyester-blended polyurethane rubber.

6. A waterproof gasket for a mobile phone camera according to claim 1, characterized in that: The EPDM rubber has an ethylene content of 45-75%, a Mooney viscosity (ML(1+4)) of 40-100 at 125°C, and a third monomer content of 4-10%.

7. A waterproof gasket for a mobile phone camera according to claim 1, characterized in that: The solvent is composed of butyl acetate, cyclohexanone, xylene and dimethylformamide in a weight ratio of 1:(2-4):(1-4):(4-6).

8. A waterproof gasket for a mobile phone camera according to claim 1, characterized in that: The thickness ratio of the polytetrafluoroethylene layer to the rubber layer is 1:(3-5).

9. A method for preparing a waterproof gasket for a mobile phone camera as described in any one of claims 1-8, characterized in that, The preparation steps include the following: S1. Mix the rubber and polyamide wax powder and add them to the internal mixer. The plasticizing temperature is 95-100℃ and the plasticizing time is 45-50min to obtain the plasticized rubber. S2. Add the plasticized rubber, activator, reinforcing agent, vulcanizing agent and plasticizer obtained in step S1 to a mixing mill, and mix at 95-100℃ for 50-60 minutes to obtain the compounded rubber. S3. Add accelerator to the compound obtained in step S2, place it on a vulcanizing machine and pre-vulcanize at 125-130℃ for 10-15 minutes, then vulcanize again at 170-175℃ for 80-100 minutes to obtain the rubber layer. S4. Mix the solvent and polyurethane resin until the polyurethane resin is completely dissolved. Then add polytetrafluoroethylene, dispersant, hydroxyl inorganic filler, silane coupling agent and curing agent and stir to obtain a mixture. S5. Spray the mixture onto the surface of the rubber layer and cure it to obtain a waterproof gasket for mobile phone cameras.

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