Insulation protective agent for high-voltage and low-voltage joints of new energy automobile and preparation method of insulation protective agent

Abstract

The invention discloses a new energy automobile high-low voltage joint insulation protective agent and a preparation method thereof, and belongs to the technical field of new energy automobile electrical safety. In order to solve the problems of insufficient interface stability and inconvenience in construction and maintenance of the existing protective material, the invention provides an aerosol type normal-temperature curing protective system. The protective agent comprises the following components in parts by weight: 8-20 parts of main film-forming resin, 0.5-3 parts of an adhesion promoter, 0.5-2.5 parts of a hydrophobic modifier, 0.2-1 part of a stabilizer, 25-45 parts of a solvent system and 35-55 parts of a propellant, wherein the main film-forming resin is modified organopolysiloxane film-forming resin containing a polyether flexible chain segment. Through a special flexible block modified resin structure and cooperation with the synergistic effect of the adhesion promoter and the hydrophobic modifier, an interface self-adaptive protective film with excellent dielectric properties, high resilience and strong adhesion is formed on a joint interface, and long-term reliability of an electrical connection system of a new energy automobile in a complex environment is guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of electrical safety technology for new energy vehicles, specifically relating to an insulating protective agent for high and low voltage joints of new energy vehicles and its preparation method. Background Technology

[0002] With the continuous improvement of the power level and integration of high-voltage (HV) and low-voltage (LV) electrical systems in new energy vehicles, components such as electrical connectors, busbars, battery terminals, and wiring harness terminals are subjected to long-term vibration, shock, frequent thermal expansion and contraction, and complex environments such as humidity and salt spray. Their insulation and protection reliability have become crucial factors affecting the electrical safety and service life of the entire vehicle. Existing insulating and protective coatings or conformal coatings for electrical components are mostly based on rigid or semi-rigid polymer systems, primarily designed for planar circuit board environments. When applied to multi-material heterogeneous interfaces and non-planar structural parts such as high- and low-voltage connectors in new energy vehicles, the following problems easily arise: (1) Under the action of vehicle vibration and thermal cycling, microcracks or local debonding occur at the interface between the coating and the substrate such as metal and plastic; (2) Water vapor and corrosive media penetrate along the interface micro-defects, leading to increased electrochemical corrosion and increased risk of leakage. (3) Some protective coatings have complicated construction processes and require heating or UV curing, making them unsuitable for on-site construction or maintenance after assembly.

[0003] Existing technology CN119039859A discloses an all-solid UV-curable coating for power / energy storage battery insulation, its preparation method, and its application. It primarily uses epoxy acrylate and polyurethane acrylate as film-forming substances. Although this technology improves coating uniformity by adjusting rheology modifiers, its UV curing system necessitates specific curing equipment in practical applications, making it unsuitable for in-situ repairs or on-site touch-ups of vehicle components in confined spaces. Furthermore, acrylate resins exhibit high crosslinking density and internal stress after curing, resulting in a relatively rigid film. Under the high and low temperature impacts and continuous vibrations of new energy vehicles, they cannot effectively dissipate interfacial stress like flexible silicone materials, making them prone to brittleness or detachment, thus affecting the durability of insulation protection.

[0004] Therefore, there is an urgent need to provide an insulation protection technology solution that can adapt to the complex service environment of high and low voltage joints in new energy vehicles, has good interface stability, can be quickly constructed, and also provides long-term protection. Summary of the Invention

[0005] The purpose of this invention is to provide an insulating protective agent for high and low voltage joints of new energy vehicles and its preparation method, so as to overcome the shortcomings of the prior art and solve the problems of insufficient interface stability and inconvenient construction and maintenance of existing protective materials.

[0006] The specific technical solution is as follows: An insulating protective agent for high and low voltage joints in new energy vehicles is an aerosol-type room-temperature curing protective system that forms a continuous insulating protective film after being sprayed at room temperature. The insulating protective agent is composed of a main film-forming resin, an adhesion promoter, a hydrophobic modifier, a stabilizer, a solvent system, and a propellant. The main film-forming resin is a modified organopolysiloxane film-forming resin containing polyether flexible segments. It has a polydimethylsiloxane main chain, side chains containing polyether flexible segments, and micro-crosslinking nodes formed by hydrogen-containing polysiloxane. The residual hydroxyl groups at the ends of the polydimethylsiloxane main chain are end-capped with hexamethyldisilazane.

[0007] Furthermore, the insulating protective agent comprises, by weight, the following components: 8-20 parts of main film-forming resin; 0.5-3 parts of adhesion promoter; 0.5-2.5 parts of hydrophobic modifier; 0.2-1 parts of stabilizer; 25-45 parts of solvent system; and 35-55 parts of propellant.

[0008] Furthermore, the adhesion promoter is an epoxy silane or titanate; the hydrophobic modifier is a silicone oil-based hydrophobic modifier; the stabilizer is a hindered phenol; the solvent system is xylene: butyl acetate: propylene glycol methyl ether acetate = 5:3:2 by weight; and the propellant is one or a combination of dimethyl ether, liquefied petroleum gas, and hydrofluoroolefins.

[0009] Furthermore, the preparation method of the insulating protective agent for high and low voltage joints of new energy vehicles includes the following steps: S1: The preparation of the flexible block modifier includes the following steps: using allyl-terminated polypropylene glycol and dihydro-terminated polydimethylsiloxane to undergo a hydrosilylation reaction to prepare a flexible block modifier with hydrogen-containing siloxane end caps at both ends and flexible polypropylene glycol segments in the middle. S2: Preparation of modified organopolysiloxane film-forming resin, the specific steps include: first synthesizing a vinyl-containing hydroxyl-terminated polydimethylsiloxane backbone, then grafting the flexible block modifier onto the backbone and introducing a micro-crosslinking agent, then capping, and finally obtaining the modified organopolysiloxane film-forming resin. S3: The components of the insulating protective agent are mixed to obtain an aerosol-type room temperature curing insulating protective agent.

[0010] Further, the specific steps of the hydrosilylation reaction in step S1 are as follows: allyl-terminated polypropylene glycol is dissolved in toluene, heated to 80°C, a platinum catalyst is added, and then a toluene solution of dihydro-terminated polydimethylsiloxane is added dropwise for reaction. After the addition is complete, the reaction continues at 80°C until the viscosity of the system stabilizes. After removing the solvent, a flexible block modifier is obtained. The molar ratio of allyl-terminated polypropylene glycol to dihydro-terminated polydimethylsiloxane is controlled at Si-H:allyl = 2.1:2.

[0011] Furthermore, the preparation process of the vinyl-containing hydroxyl-terminated polydimethylsiloxane backbone in step S2 is as follows: vinylcyclotetrasiloxane and dimethylcyclotetrasiloxane are subjected to ring-opening polymerization reaction in the presence of water and an alkaline catalyst. The reaction temperature is controlled at 135±5℃. When the viscosity of the system reaches 2500mPa·s, acetic acid is added as a neutralizing agent to terminate the reaction. Unreacted cyclic monomers are removed under reduced pressure at 140℃ to obtain the vinyl-containing hydroxyl-terminated polydimethylsiloxane backbone.

[0012] Further, the process of grafting onto the main chain and introducing a micro-crosslinking agent in step S2 is as follows: in the presence of a solvent and under the catalysis of a platinum catalyst, the flexible block modifier obtained in step S1 is added dropwise to the vinyl-containing polydimethylsiloxane prepolymer, and a grafting reaction is carried out at 80±5℃; after the grafting reaction is stable, hydrogen-containing polysiloxane is added dropwise as a micro-crosslinking agent, and the reaction continues to form micro-crosslinking nodes between molecular chains; wherein, the amount of hydrogen-containing polysiloxane added is controlled within a range that does not cause the system to gel.

[0013] Furthermore, the end-capping step in step S2 includes: after the micro-crosslinking reaction is completed, adding hexamethyldisilazane to the reaction system and reacting at 90°C for 40 minutes to end the residual hydroxyl groups; after the reaction is completed, distilling under reduced pressure at 120°C to finally obtain the modified organopolysiloxane film-forming resin.

[0014] Furthermore, the specific preparation process of the aerosol-type room-temperature curing insulating protective agent in step S3 includes: adding the solvent system to the reaction vessel, followed by adding the modified organopolysiloxane film-forming resin, heating to 50±10℃ and stirring to dissolve; then, sequentially adding the adhesion promoter, the hydrophobic modifier and the stabilizer, stirring for more than 30 minutes until uniformly mixed to obtain the stock solution; filtering the stock solution through a 10μm pore size filter and then encapsulating it together with the propellant.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) Improve electrical safety and service life: The protective film layer formed by the modified organic polysiloxane film-forming resin has good dielectric properties, hydrophobicity and salt spray corrosion resistance, which helps to delay the aging and failure process of electrical connection parts and improve the safety and reliability of the electrical system of new energy vehicles.

[0016] (2) Improve long-term stability of the interface: Through the synergistic effect of the main film-forming resin, adhesion promoter and hydrophobic modifier, the interface microcracks and debonding phenomenon generated by the high and low pressure joint under vibration and thermal expansion and contraction conditions are significantly suppressed, reducing the risk of water vapor and corrosive media penetrating along the interface.

[0017] (3) Adapting to the complex structure and working conditions of new energy vehicles: The aerosol system can form a continuous and uniform protective film on irregular structures, gaps and hidden parts without disassembling electrical connectors, reducing the blind spots caused by traditional brushing or dot coating methods. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the preparation process of the insulating protective agent of the present invention. Figure 2 This is a schematic diagram illustrating the preparation of the modified organopolysiloxane film-forming resin of this invention; Figure 3 This is a comparison chart of the surface drying time and dielectric strength results of the embodiments and comparative samples of the present invention; Figure 4 This is a comparison chart of the single-coating film thickness results of the embodiments and comparative samples of the present invention; Figure 5 The image shows the infrared spectrum of the modified organopolysiloxane film-forming resin obtained in Example 1 of this invention. Detailed Implementation

[0019] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0020] This invention proposes an insulating protective agent for high and low voltage joints in new energy vehicles and its preparation method, such as... Figure 1 The diagram shows the preparation process of the insulating protective agent of the present invention. The specific preparation steps are as follows: S1. Preparation of flexible block modifiers The purpose of this step is to prepare a key modified intermediate with both ends capped by hydrogen-containing siloxane (H-PDMS) and a flexible polypropylene glycol (PPG) segment in the middle. Its unique rigid-flexible-rigid structure effectively introduces the flexibility and hydrophobicity of the PPG segment into the final organosilicon network, which is fundamental to suppressing interfacial microcracks and improving electrical safety. (See attached image) Figure 2 The diagram shown is a schematic diagram of the preparation of the modified organopolysiloxane film-forming resin of the present invention.

[0021] Raw materials: allyl-terminated polypropylene glycol (Diallyl-PPG), number average molecular weight Mn=500g / mol; dihydro-terminated polydimethylsiloxane (H-PDMS-H), Mn=1000g / mol; platinum catalyst (Pt-cat); toluene.

[0022] Preparation process: In a clean reactor equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel, add 100 parts of Diallyl-PPG and 200 parts of toluene. Initiate nitrogen protection, stir, and heat to 80°C. At 80°C, add 0.02 parts of Pt-CAT and stir for 15 minutes to ensure uniform catalyst dispersion and activation. Dissolve 210 parts of H-PDMS-H in 500 parts of toluene, ensuring a Si-H molar ratio of 2.1:2 (i.e., a slight excess of Si-H). Slowly add the solution dropwise to the reactor over 2 hours using a dropping funnel. During the addition, precisely control the reactor temperature to not exceed 90°C to prevent excessively vigorous reaction. After addition, continue the reaction at 80°C for 4 hours. Monitor the system viscosity using an online viscometer. Stop the reaction when the online viscometer reading fluctuates less than ±2% within 30 minutes and reaches a plateau. After the reaction, cool to room temperature. Under reduced pressure at 70°C, toluene solvent was removed to obtain a colorless to pale yellow transparent viscous liquid, which is the flexible block modifier H-PDMS-PPG-PDMS-H, and it was sealed for later use.

[0023] In the H-PDMS-PPG-PDMS-H, Diallyl-PPG is the central flexible block, providing low-temperature flexibility and stress absorption capability; H-PDMS-H is the end reactive block, providing organosilicon properties and Si-H reaction sites.

[0024] S2. Preparation of modified organopolysiloxane film-forming resin (1) Preparation of vinyl-containing hydroxyl-terminated polydimethylsiloxane (PDMS-OH) backbone: Raw materials: Vinylcyclotetrasiloxane (Vi-D4); Dimethylcyclotetrasiloxane (D4); Water; KOH as an alkaline catalyst; Acetic acid as a neutralizing agent.

[0025] Preparation process: 60 parts Vi-D4 and 517 parts D4 were added to the reactor at a molar ratio of Vi-D4:D4=1:10, with a vinyl content of 9.1 mol%. 2.5 parts water and 0.03 parts KOH were added simultaneously. The mixture was heated to 135±5℃ under nitrogen protection to initiate ring-opening polymerization. The reaction was maintained at this temperature, and the viscosity of the system was monitored by an online viscometer. When the viscosity of the system reached 2500 mPa·s, 0.04 parts acetic acid neutralizer was added to terminate the reaction. Unreacted cyclic monomers and other low-boiling-point substances were removed under reduced pressure at 140℃ to obtain a vinyl-containing PDMS-OH backbone.

[0026] (2) Directional grafting and chain extension of polyether blocks Raw materials: the block copolymer H-PDMS-PPG-PDMS-H obtained above; Pt-cat; xylene.

[0027] Molar ratio: Vinyl in the vinyl-containing PDMS-OH backbone: Si-H from the block copolymer = 1:0.25.

[0028] Preparation process: Add the vinyl-containing PDMS-OH backbone obtained in step (1) to the reactor, add 600 parts of xylene, and heat to 80±5℃ under nitrogen protection and stirring; slowly add 0.01 parts of Pt-cat; prepare 218 parts of H-PDMS-PPG-PDMS-H into a 50% (w / w) H-PDMS-PPG-PDMS-H / xylene solution, and slowly add it dropwise through a drop pump to ensure that the system temperature is stable; maintain the temperature at 80±5℃ and react for 2-4 hours. Monitor the viscosity of the system with an online viscometer. When the online viscometer reading fluctuates less than ±2% within 30 minutes and reaches the plateau period, stop the reaction.

[0029] (3) Introduction of micro-crosslinking points Raw material: polymethylhydrosiloxane (PMHS), Mn=800g / mol, Si-H content 1.6wt%.

[0030] Preparation process: Based on the reaction solution in step (2), without cooling, continue to maintain the system temperature at 80±5℃; prepare a 10% (w / w) PMHS solution with xylene using 1.5 parts of PMHS, and slowly add it dropwise to the reaction solution. Due to the large number of reaction sites, the reaction rate in this step is fast, so it must be added slowly to control the heat of reaction and prevent local overheating that could lead to gelation. Continue the reaction for 1-2 hours to complete the micro-crosslinking process. At this time, the viscosity of the system will increase significantly, but in a controllable manner, and the final state will still be a flowable viscous liquid without forming a gel.

[0031] (4) End sealing and refining Raw material: Hexamethyldisilazane (HMDS) Preparation process: After step (3) is completed, HMDS is added, the temperature is raised to 90℃, and the reaction is carried out for 40 min to ensure that all residual -OH is completely capped. After the reaction is completed, the xylene solvent, excess capping agent and low molecular weight residue in the system are removed under reduced pressure at 120℃ to finally obtain the modified organopolysiloxane film-forming resin.

[0032] S3. Preparation of aerosol-type room-temperature curing insulating protective agent The formulation by weight is as follows: 8-20 parts of main film-forming resin; 0.5-3 parts of adhesion promoter; 0.5-2.5 parts of hydrophobic modifier; 0.2-1 part of stabilizer; 25-45 parts of solvent system; and 35-55 parts of propellant.

[0033] The main film-forming resin is the self-made modified organopolysiloxane film-forming resin, which forms the framework of the entire protective film and provides core insulation, flexibility, weather resistance, and hydrophobic properties.

[0034] The adhesion promoter is an epoxy silane or titanate, one end of which can form a chemical bond with the hydroxyl groups on the surface of the metal or plastic substrate, and the other end can physically entangle or react with the silicone resin, greatly enhancing the adhesion between the film layer and the joint substrate, just like double-sided tape.

[0035] The hydrophobic modifier is a silicone oil-based hydrophobic modifier, used to further reduce the surface energy of the film layer, effectively repelling liquid water and preventing the formation of a conductive water film.

[0036] The stabilizer is a hindered phenol. The solvent system has a weight ratio of xylene: butyl acetate: propylene glycol methyl ether acetate = 5:3:2. The propellant is one or a combination of dimethyl ether (DME), liquefied petroleum gas (LPG), and hydrofluoroolefins (HFO).

[0037] Preparation steps: Add the solvent system to a mixing vessel, start stirring, add the main film-forming resin, and heat the jacket to 50±10℃ to reduce its viscosity and improve its flowability. Add the adhesion promoter, hydrophobic modifier, and stabilizer sequentially, and continue stirring for 30 minutes to ensure all additives are completely dissolved and uniformly dispersed in the resin. Filter the resulting solution through a 10μm filter to remove any minute impurities. Fill the resulting solution into pressure-resistant aerosol cans, immediately press the aerosol valve onto the can opening, and seal it. Inflate the can with propellant through the valve to complete the encapsulation, obtaining an aerosol-formed room-temperature curing insulating protective agent.

[0038] Table 1. Reagents used in the following examples.

[0039] Example 1 1. Preparation of flexible block modifiers In a reaction vessel, 100 parts of Diallyl-PPG and 200 parts of toluene were added under nitrogen protection. The mixture was stirred and heated to 80°C. 0.02 parts of Pt-CAT were then added, and the mixture was stirred at this temperature for 15 minutes. Subsequently, 210 parts of H-PDMS-H were dissolved in 500 parts of toluene and slowly added dropwise to the reaction vessel over 2 hours using a dropping funnel, controlling the temperature during the addition process to not exceed 90°C. After the addition was complete, the reaction was continued at this temperature for 4 hours. At this point, the online viscometer reading fluctuated by less than ±2% within 30 minutes and reached a plateau, at which point the reaction was stopped. After the reaction was complete, the mixture was cooled to room temperature. Under reduced pressure at 70°C, the toluene solvent was removed, yielding a colorless to pale yellow transparent viscous liquid, which is the flexible block modifier H-PDMS-PPG-PDMS-H, and was sealed for later use.

[0040] 2. Preparation of modified organopolysiloxane film-forming resin (1) Preparation of vinyl-containing PDMS backbone: 60 parts Vi-D4 and 517 parts D4 were added to the reactor, along with 2.5 parts water and 0.03 parts KOH. The mixture was heated to 135±5℃ under nitrogen protection and reacted for 5 hours. At this time, the viscosity of the system was monitored by an online viscometer and found to be 2500 mPa·s. 0.04 parts acetic acid neutralizer was added to terminate the reaction. Unreacted cyclic monomers and other low-boiling-point substances were removed under reduced pressure at 140℃ to obtain vinyl-containing PDMS-OH backbone.

[0041] (2) Directional grafting and chain extension of polyether blocks: The vinyl PDMS-OH main chain obtained in step (1) was added to the reactor, 600 parts of xylene were added, and the mixture was heated to 80±5℃ under nitrogen protection and stirring; 0.01 parts of Pt-cat were slowly added; 218 parts of H-PDMS-PPG-PDMS-H were prepared into a 50% (w / w) H-PDMS-PPG-PDMS-H / xylene solution, which was slowly added to the reaction solution by a drop pump, and the temperature was maintained at 80±5℃. The reaction was carried out for 3 hours. When the online viscometer reading fluctuated less than ±2% within 30 minutes and reached the plateau period, the reaction was stopped.

[0042] (3) Introduction of micro-crosslinking points: Based on the reaction solution in step (2), continue to maintain the system temperature at 80±5℃, and slowly add 1.5 parts of PMHS to the reaction solution to prepare a 10% (w / w) PMHS solution with xylene. Continue the reaction for 2 hours to complete the micro-crosslinking process.

[0043] (4) End-capping and purification: After step (3) is completed, HMDS is added, the temperature is raised to 90℃, and the reaction is carried out for 40 min. After the reaction is completed, the xylene solvent, excess end-capping agent, and low molecular weight residues in the system are removed under reduced pressure at 120℃ to finally obtain the self-made modified organopolysiloxane film-forming resin, which is then cooled for later use. (See attached...) Figure 5 The image shows the infrared spectrum of the modified organopolysiloxane film-forming resin obtained in this embodiment: In the spectrum, 2914 cm⁻¹ -1 and 2847cm -1 A strong saturated CH stretching vibration peak appeared at 1047 cm⁻¹. -1 A very broad and deep composite absorption band exists at this point, attributed to the overlapping vibrations of Si-O-Si and COC bonds in the polyether segment, confirming the successful grafting of the flexible polyether segment; 1623 cm⁻¹ -1 The weak absorption peak at 1301 cm⁻¹ corresponds to a small amount of residual vinyl groups, confirming the occurrence and extent of the addition reaction; simultaneously, the absorption peak at 1301 cm⁻¹... -1 and 821cm -1The typical absorption peak at 2160 cm⁻¹ reflects the characteristic structure of the organosilicon framework. Furthermore, the peak at 2160 cm⁻¹... -1 and 3400cm -1 There was no significant absorption in the area, and 682cm -1 The characteristic peak at that point corresponds to the trimethylsilyl group, indicating that the hydrosilylation reaction was complete and the end-capping was thorough.

[0044] 3. Preparation of aerosol-type room-temperature curing insulating protective agent The formulation by weight ratio is as follows: 8 parts modified organopolysiloxane film-forming resin; 0.5 parts epoxy silane adhesion promoter Silquest A-187; 0.5 parts silicone oil-based hydrophobic modifier PMX-200; 0.2 parts stabilizer Irganox 1010; 25 parts solvent system: xylene: butyl acetate: propylene glycol methyl ether acetate = 5:3:2; 35 parts DME.

[0045] Preparation method: Add 25 parts of solvent system to the reactor and start stirring. Slowly add 8 parts of modified organopolysiloxane film-forming resin, heat the jacket to 50±10℃, and continue stirring until completely dissolved. Add 0.5 parts of Silquest A-187, 0.5 parts of PMX-200, and 0.2 parts of Irganox 1010 sequentially, and continue stirring for 30 minutes to obtain the stock solution. Filter the stock solution through a 10μm pore size filter and fill it together with 35 parts of DME into an aerosol pressure vessel to finally obtain an aerosol-type insulating protective agent.

[0046] Example 2 The formulation, by weight ratio, is as follows: 14 parts of the same batch of modified organopolysiloxane film-forming resin as in Example 1; 1.5 parts of epoxy silane adhesion promoter Silquest A-187; 1.5 parts of silicone oil-based hydrophobic modifier AK-1000; 0.5 parts of stabilizer Irganox 1010; 34.5 parts of solvent system: xylene: butyl acetate: propylene glycol methyl ether acetate = 5:3:2 by weight; and 48 parts of propellant LPG. The preparation process is the same as in Example 1, ultimately yielding an aerosol-type insulating protective agent.

[0047] Example 3 The formulation, by weight ratio, is as follows: 20 parts of the same batch of modified organopolysiloxane film-forming resin as in Example 1; 3 parts of titanate adhesion promoter Tyzor TPT; 2.5 parts of silicone oil-based hydrophobic modifier KF-96L; 1 part of stabilizer Irganox 1010; 45 parts of solvent system: xylene: butyl acetate: propylene glycol methyl ether acetate = 5:3:2 by weight; and 55 parts of propellant HFO. The preparation process is the same as in Example 1, ultimately yielding an aerosol-type insulating protective agent.

[0048] Comparative Example 1 Same as Example 1, except that the main film-forming resin is HumiSeal 1A33 polyurethane conformal coating.

[0049] Comparative Example 2 The commercially available aerosol acrylic conformal coating MG Chemicals 419E was used.

[0050] Comparative Example 3 Same as Example 1, except that no adhesion promoter and hydrophobic modifier are added.

[0051] Performance testing: Sample preparation: The test substrates used were 100mm×50mm×2mm copper busbars and 100mm×50mm×2mm PBT-GF30 samples. All substrates were wiped clean with anhydrous ethanol and dried. At 25±2℃ and 50±5% humidity, the aerosol products of the examples and comparative examples were thoroughly shaken and sprayed from a distance of 15-20cm from the substrate. After curing for 24 hours, the samples were tested.

[0052] 1. Surface drying time: The drying time of paint film and putty film shall be determined by the touch test method in GB / T 1728-2020 "Determination of Drying Time of Paint Film and Putty Film". Record the time when the paint film surface is no longer sticky and no fingerprints are left when lightly touched with a finger, in minutes, and retain one decimal place.

[0053] 2. Single spray coating thickness: At room temperature, the cured film layer on the surface of the metal substrate is measured at multiple points using a dry film thickness gauge. The unit is μm, and the measurement is rounded to the nearest integer.

[0054] 3. Dielectric strength: Tested according to GB / T 1408.1-2016 "Test Method for Electrical Strength of Insulating Materials". The protective agent is sprayed onto the copper sheet, and after curing, the breakdown voltage is tested. The dielectric strength (kV / mm) is calculated, and the result is retained to one decimal place.

[0055] 4. Adhesion Evaluation: Refer to GB / T 9286-2021 "Cross-cut Test for Paints and Varnishes". Use a 1mm spacing cross-cut knife to make cuts on both the PBT-GF30 sample and the copper substrate. Apply high-adhesion pressure-sensitive tape and quickly tear it off, observing the degree of peeling. The rating is 0-5, with 0 being the best.

[0056] 5. Neutral Salt Spray Test: Conducted according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test". An "X" shaped scratch is made on the surface of the copper busbar coated with protective agent to break the coating down to the substrate. The busbar is then placed in a salt spray chamber and continuously sprayed for 240 hours. The corrosion spread at the scratched areas and whether blistering or rusting occurs in the non-scratched areas are observed.

[0057] 6. Thermal cycling test: Simulates the high and low temperature environment of new energy vehicles. The temperature cycling range is set from -40℃ to +125℃, with a high and low temperature dwell time of 30 minutes each and a transition time of <5 minutes. After 50 cycles, observe whether the film layer shows signs of cracking, peeling, or detachment.

[0058] 7. Vibration Test: Refer to ISO 16750-3 "Environmental conditions and tests for electrical and electronic equipment of road vehicles – Part 3: Mechanical loads" for environmental conditions of road vehicles. Fix the coated sample on a vibration table and conduct random vibration tests. Set the frequency to 10-1000Hz and the root mean square acceleration to 27.8 m / s². 2 The experiment lasted for 8 hours. The integrity of the membrane was observed after the experiment.

[0059] Table 2. Test results of basic physical and electrical performance of each embodiment and comparative example.

[0060] Table 3. Reliability and environmental adaptability test results for each embodiment and comparative example.

[0061] Analysis of the comparison results between Table 2 and Table 3: (1) The aerosol-type insulating protective agents prepared in Examples 1-3 are superior to those in Comparative Examples 1-3 in terms of surface drying time, single-coat film thickness, and dielectric strength, and meet industry application standards, as shown in the attached figures. Figure 3 , 4 As shown. Furthermore, adhesion testing, salt spray testing, thermal cycling, and vibration testing results demonstrate that the flexible segments introduced by the flexible block modifier in this invention endow the resin with excellent stress dissipation capabilities, enabling it to adapt to the deformation of high and low pressure joints in new energy vehicles under extreme temperature differences and severe vibrations, thus maintaining the continuity and integrity of the film layer.

[0062] (2) The results of Comparative Example 1 show that although the polyurethane conformal coating has acceptable initial adhesion, microcracks appeared at the interface after thermal cycling test. This is because the rigidity of the polyurethane resin increases at low temperatures, resulting in greater internal stress in the film. Comparative Example 2 used commercially available acrylic conformal coating. Although its dielectric strength and surface drying time meet the requirements of conventional electronic protection applications, the integrity of the film decreased significantly after salt spray, thermal cycling, and vibration tests, with blistering, peeling, and brittle fracture occurring. This indicates that the long-term reliability of this type of material under complex automotive conditions is insufficient. In contrast, the organosilicon-modified system of this invention maintains excellent flexibility and strain resistance over a wide temperature range, effectively avoiding cracking caused by stress concentration.

[0063] (3) Comparative Example 3 used the same main film-forming resin as Example 1, but without the addition of adhesion promoter and hydrophobic modifier. The test results showed that the dielectric strength of Comparative Example 3 decreased significantly, the adhesion deteriorated, the film thickness per spray was significantly reduced, and large-area corrosion and peeling occurred in the salt spray test. This strongly proves the necessity of adhesion promoter and hydrophobic modifier in this invention.

[0064] In summary, the insulating protective agent provided by this invention, through specific modified resin structure design and synergistic compounding of functional additives, effectively solves the problems of poor temperature resistance and insufficient interfacial bonding in the prior art, and significantly improves the safety and reliability of the electrical connection system of new energy vehicles.

Claims

1. An insulating protective agent for high and low voltage joints in new energy vehicles, which is an aerosol-type room-temperature curing protective system that forms a continuous insulating protective film layer after being sprayed at room temperature, characterized in that... The insulating protective agent is composed of a main film-forming resin, an adhesion promoter, a hydrophobic modifier, a stabilizer, a solvent system, and a propellant. The main film-forming resin is a modified organopolysiloxane film-forming resin containing polyether flexible segments. It has a polydimethylsiloxane main chain, side chains containing polyether flexible segments, and micro-crosslinking nodes formed by hydrogen-containing polysiloxane. The residual hydroxyl groups at the ends of the polydimethylsiloxane main chain are end-capped with hexamethyldisilazane.

2. The insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 1, characterized in that, The insulating protective agent comprises the following components by weight: 8-20 parts of main film-forming resin; 0.5-3 parts of adhesion promoter; 0.5-2.5 parts of hydrophobic modifier; 0.2-1 parts of stabilizer; 25-45 parts of solvent system; and 35-55 parts of propellant.

3. The insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 2, characterized in that, The adhesion promoter is an epoxy silane or titanate; the hydrophobic modifier is a silicone oil-type hydrophobic modifier; the stabilizer is a hindered phenol; the solvent system is xylene: butyl acetate: propylene glycol methyl ether acetate = 5:3:2 by weight; the propellant is one or a combination of dimethyl ether, liquefied petroleum gas, and hydrofluoroolefins.

4. A method for preparing an insulating protective agent for high and low voltage joints of new energy vehicles according to any one of claims 1-3, characterized in that, Includes the following steps: S1: The preparation of the flexible block modifier includes the following steps: using allyl-terminated polypropylene glycol and dihydro-terminated polydimethylsiloxane to undergo a hydrosilylation reaction to prepare a flexible block modifier with hydrogen-containing siloxane end caps at both ends and flexible polypropylene glycol segments in the middle. S2: Preparation of modified organopolysiloxane film-forming resin, the specific steps include: first synthesizing a vinyl-containing hydroxyl-terminated polydimethylsiloxane backbone, then grafting the flexible block modifier onto the backbone and introducing a micro-crosslinking agent, then capping, and finally obtaining the modified organopolysiloxane film-forming resin. S3: The components of the insulating protective agent are mixed to obtain an aerosol-type room temperature curing insulating protective agent.

5. The preparation method of the insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 4, characterized in that, The specific steps of the hydrosilylation reaction in step S1 are as follows: allyl-terminated polypropylene glycol is dissolved in toluene, heated to 80°C, a platinum catalyst is added, and then a toluene solution of dihydro-terminated polydimethylsiloxane is added dropwise for reaction. After the addition is complete, the reaction continues at 80°C until the viscosity of the system stabilizes. After removing the solvent, a flexible block modifier is obtained. The molar ratio of allyl-terminated polypropylene glycol to dihydro-terminated polydimethylsiloxane is controlled at Si-H:allyl = 2.1:

2.

6. The preparation method of the insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 4, characterized in that, The preparation process of the vinyl-containing hydroxyl-terminated polydimethylsiloxane backbone in step S2 is as follows: vinylcyclotetrasiloxane and dimethylcyclotetrasiloxane are subjected to ring-opening polymerization reaction in the presence of water and an alkaline catalyst. The reaction temperature is controlled at 135±5℃. When the viscosity of the system reaches 2500mPa·s, acetic acid is added as a neutralizing agent to terminate the reaction. Unreacted cyclic monomers are removed under reduced pressure at 140℃ to obtain the vinyl-containing hydroxyl-terminated polydimethylsiloxane backbone.

7. The preparation method of the insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 4, characterized in that, The process of grafting onto the main chain and introducing a micro-crosslinking agent in step S2 is as follows: In the presence of a solvent and under the catalysis of a platinum catalyst, the flexible block modifier obtained in step S1 is added dropwise to the vinyl-containing polydimethylsiloxane prepolymer, and a grafting reaction is carried out at 80±5℃; after the grafting reaction is stable, hydrogen-containing polysiloxane is added dropwise as a micro-crosslinking agent, and the reaction continues to form micro-crosslinking nodes between molecular chains; wherein, the amount of hydrogen-containing polysiloxane added is controlled within a range that does not cause the system to gel.

8. The preparation method of the insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 4, characterized in that, The end-capping step in step S2 includes: after the micro-crosslinking reaction is completed, adding hexamethyldisilazane to the reaction system and reacting at 90°C for 40 minutes to cap the residual hydroxyl groups; after the reaction is completed, distilling under reduced pressure at 120°C to finally obtain the modified organopolysiloxane film-forming resin.

9. The preparation method of the insulating protective agent for high and low voltage joints of new energy vehicles as described in claim 4, characterized in that, The specific preparation process of the aerosol-type room temperature curing insulating protective agent in step S3 includes: adding the solvent system to the reaction vessel, followed by adding the modified organopolysiloxane film-forming resin, heating to 50±10℃ and stirring to dissolve; then, sequentially adding the adhesion promoter, the hydrophobic modifier and the stabilizer, stirring for more than 30 minutes until uniformly mixed to obtain the stock solution; filtering the stock solution through a 10μm pore size filter and then encapsulating it together with the propellant.

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