Processing method of bolt with anti-skid coating
By constructing a coating of PI-PBO matrix and HfB2 microcapsule cross-linked network on the bolt thread surface, the loosening problem of bolts under dynamic working conditions was solved, and the bolt's efficient anti-slip and wear resistance performance was improved.
Patent Information
- Application Number
- CN202511077256.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-01
- Publication Date
- 2025-11-11
AI Technical Summary
Existing bolts suffer from loosening failure due to preload decay caused by micro-slippage of the threads under dynamic conditions such as vibration, impact, alternating load, or temperature cycling. Existing anti-slip coatings also face technical bottlenecks in terms of interfacial bonding strength, environmental adaptability, and process compatibility.
A high-density cross-linked network is constructed using a PI-PBO matrix, HfB2 microcapsules, and THPE-TGE cross-linking agent. This network is then applied to the surface of bolt threads via gradient spraying to form a mechanical-chemical synergistic reinforcement coating of hard microcapsules and polymer network, thereby improving anti-slip performance.
It significantly improves the anti-slip coefficient, wear resistance, and service strength of bolts, and enhances the anti-slip performance of bolts in high-frequency micro-vibration environments.
Smart Images
Figure BDA0005529747840000051
Abstract
Description
Technical Field
[0001] This invention belongs to the field of bolt processing technology, specifically relating to a processing method for bolts with anti-slip coating. Background Technology
[0002] Bolted connections, as the most basic fastening method in mechanical assembly, directly affect the safety and service life of the entire structural system. Under dynamic conditions such as vibration, impact, alternating loads, or temperature cycling, the microscopic slippage between the threads of traditional bolts leads to a decrease in preload, resulting in loosening and failure. According to industrial accident statistics, over 35% of mechanical failures originate from loose fasteners, and this proportion reaches over 60% in high-dynamic-load fields such as aerospace, wind power, and high-speed rail. To address this issue, existing technologies mainly employ mechanical locking (such as double nuts and cotter pins), elastic elements (such as spring washers), or structural modifications (such as wedge threads). However, these methods have significant drawbacks: mechanical locking schemes increase assembly complexity by adding extra parts and are difficult to implement in confined spaces; elastic elements lose their resilience under long-term creep and cannot compensate for wear on the thread surface; and thread structure modifications are limited by machining accuracy and standardization requirements, making it difficult to balance versatility and anti-slip performance. Especially in high-frequency micro-vibration environments, the anti-loosening life of the above methods is generally insufficient, far below the design requirements of heavy equipment.
[0003] In recent years, surface modification technology has been introduced into the field of bolt anti-slip coatings. Existing coating solutions mainly include phosphate conversion films, electroplated zinc layers, and organic coatings. While phosphate films can improve the coefficient of friction, their porous structure makes them prone to brittle fracture under contact stress, and their poor corrosion resistance results in an effective lifespan of less than 6 months. Electroplated zinc layers provide corrosion protection through sacrificial anodes, but their anti-slip performance is insufficient under dry friction conditions, and the addition of chromate sealants faces environmental regulatory restrictions. Organic coatings, such as nylon coatings, can achieve a coefficient of friction μ>0.20, but their glass transition temperature (typically <120℃) leads to intensified polymer chain movement at high temperatures, causing viscoelastic flow and loss of anti-slip function. More importantly, the bonding strength between existing coatings and the metal substrate is generally below 15MPa. During bolt tightening, shear stress causes the coating to peel off, forming abrasive particles that accelerate thread wear. These defects highlight the technical bottlenecks of existing anti-slip coatings in terms of interfacial bonding strength, environmental adaptability, and process compatibility. Summary of the Invention
[0004] To address the shortcomings of existing technologies, the present invention aims to provide a processing method for bolts with anti-slip coatings. In preparing the anti-slip coating, a high-density cross-linked network is formed by using a PI-PBO matrix, HfB2 microcapsules, and THPE-TGE cross-linking agent. This achieves mechanical-chemical synergistic enhancement of the hard microcapsules and the polymer network, which can effectively improve the anti-slip coefficient, wear resistance, and service strength of the coating, thereby improving the anti-slip performance of the bolt.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] A method for processing bolts with anti-slip coating includes the following specific steps:
[0007] S1. Bolt pretreatment: Use 120-150 mesh white corundum sand to spray onto the bolt surface at a pressure of 0.5-0.8MPa to perform sandblasting treatment on the bolt; ultrasonically clean in acetone and ethanol for 15-20 minutes in sequence, and dry at 80±5℃; immerse in 8-12wt% silane coupling agent KH-550 aqueous solution for 1-3 minutes, and cure at 100-120℃ for 15-25 minutes;
[0008] S2. Preparation of anti-slip coating: Hafnium diboride microcapsules were prepared, and a polyimide-benzoxazole copolymer matrix was synthesized. The polyimide-benzoxazole copolymer matrix and the hafnium diboride microcapsules were mixed and reacted to obtain the anti-slip coating.
[0009] S3. Spraying: Apply the anti-slip coating in a gradient to the surface of the bolt threads, and cure at low temperature to obtain the finished product.
[0010] Preferably, in step S2 above, the specific steps for preparing hafnium diboride microcapsules are as follows:
[0011] (1) Preparation of oil phase: Hafnium diboride powder and 2,5-thiophene dicarboxylate chloride were mixed and dissolved in tetrahydrofuran and stirred evenly to obtain an oil phase mixture;
[0012] (2) Aqueous phase preparation: 2,6-diaminopyridine and sodium dodecyl sulfate were mixed and dissolved in deionized water and stirred evenly to obtain an aqueous phase mixture;
[0013] (3) Interfacial polymerization: The oil phase mixture is injected into the aqueous phase mixture, emulsified by high-speed shearing, stirred at constant temperature, and dried by centrifugation to obtain hafnium diboride microcapsules.
[0014] Preferably, the mass ratio of hafnium diboride powder, 2,5-thiophene dicarboxylic acid chloride, and tetrahydrofuran is 15-25:4-6:100, and the particle size of hafnium diboride powder is 200-300 nm; the mass ratio of 2,6-diaminopyridine, sodium dodecyl sulfate, and deionized water is 7-9:0.8-1.2:200.
[0015] Preferably, the mass ratio of the aforementioned oil phase mixture to the water phase mixture is 1:2-3, the shear emulsification speed is 10000-15000 rpm, and the time is 3-8 min; the stirring temperature after emulsification is 40-50℃, and the stirring time is 1.5-2.5 h.
[0016] Preferably, in step S2 above, the method for synthesizing the polyimide-benzoxazole copolymer matrix is as follows:
[0017] (1) Under nitrogen protection, 3,3',4,4'-biphenyltetracarboxylic dianhydride was dissolved in N-methylpyrrolidone;
[0018] (2) Add 4,4'-diaminodiphenyl ether and react;
[0019] (3) Add 2,5-diaminopyrazine chain extender, heat and react;
[0020] (4) Add 9-fluorenemethanol dropwise. After the reaction is complete, cool to room temperature to obtain the polyimide-benzoxazole copolymer matrix.
[0021] Preferably, the mass fractions of the aforementioned 3,3',4,4'-biphenyltetracarboxylic dianhydride, N-methylpyrrolidone, 4,4'-diaminodiphenyl ether, 2,5-diaminopyrazine, and 9-fluorenemethanol are 30-35 parts, 145-150 parts, 15-18 parts, 3.5-4.5 parts, and 2.5-3.0 parts, respectively.
[0022] Preferably, the reaction temperature of step (2) is 25-35℃ and the reaction time is 5-7h; the reaction temperature of step (3) is 190-210℃ and the reaction time is 2-4h.
[0023] Preferably, in step S2 above, the specific steps for mixing the polyimide-benzoxazole copolymer matrix and hafnium diboride microcapsules are as follows:
[0024] (1) Take the polyimide-benzoxazole copolymer matrix, add tris(4-hydroxyphenyl)ethane triglycidyl ether, and stir to mix;
[0025] (2) Hafnium diboride microcapsules and hexagonal aluminum nitride nanowires were added sequentially, ultrasonically dispersed, and iridium acetylacetone catalyst and leveling agent BYK-331 were added. The mixture was then reacted to obtain an anti-slip coating.
[0026] Preferably, the mass parts of the aforementioned polyimide-benzoxazole copolymer matrix, tris(4-hydroxyphenyl)ethane triglycidyl ether, hafnium diboride microcapsules, hexagonal aluminum nitride nanowires, iridium acetylacetone, and BYK-331 are 100 parts, 30-40 parts, 35-45 parts, 12-18 parts, 0.2-0.4 parts, and 0.3-0.7 parts, respectively, and the aspect ratio of the hexagonal aluminum nitride nanowires is 50-60.
[0027] Preferably, in step S3 above, the dry film thickness of the coating on the tip and root of the bolt thread after gradient spraying is 12-18 μm and 7-9 μm, respectively.
[0028] The advantages of this invention are:
[0029] (1) The present invention constructs a hafnium diboride microcapsule-reinforced composite coating on the surface of bolt threads. The microcapsules containing polythiophene amide wall material are oriented and enriched on the threads through a gradient centrifugal coating process. Ultra-hard hafnium diboride is used as the core filler of the microcapsules. The wall thickness of the microcapsules is controlled by the polythiophene amide interfacial polymerization process. By utilizing the cubic crystal form and high hardness of hafnium diboride, the microcapsules continuously expose hard friction points during the coating wear process, thereby improving the anti-slip coefficient and significantly resisting mechanical impact.
[0030] (2) Using high-temperature resistant polyimide-benzoxazole copolymer (PI-PBO) as the coating matrix, a rigid molecular chain containing a diazonium heterocycle is constructed by chain extension of 2,5-diaminopyrazine, which enables the coating to withstand high shear stress and high temperature resistance; the three-dimensional star-shaped epoxy monomer tris(4-hydroxyphenyl)ethane triglycidyl ether (THPE-TGE) is introduced, which forms a high-density cross-linked network during curing with its three epoxy groups, which not only eliminates the risk of UV degradation of traditional epoxy resin, but also effectively improves the coating adhesion by generating strong coordination bonds with the metal plate through densely distributed phenolic hydroxyl groups; hexagonal aluminum nitride nanowires are used as functional fillers, and their axial thermal conductivity is used to construct a fast heat dissipation channel to avoid thermal stress cracking of the coating, while the surface negative charge characteristics are used to achieve long-lasting antistatic function;
[0031] (3) By realizing the mechanical-chemical synergistic enhancement of hard microcapsules and polymer networks, the present invention can effectively improve the anti-slip coefficient, wear resistance and service strength of the coating, thereby improving the anti-slip performance of bolts. Detailed Implementation
[0032] The present invention will be described in detail below with reference to specific embodiments.
[0033] Example 1
[0034] A method for processing bolts with anti-slip coating includes the following specific steps:
[0035] S1. Bolt pretreatment: Use 120-mesh white corundum sand to spray onto the bolt surface at a pressure of 0.5MPa to perform sandblasting treatment on the bolt; ultrasonically clean in acetone and ethanol for 15 minutes in sequence, and dry at 80℃; immerse in 8wt% silane coupling agent KH-550 aqueous solution for 1 minute, and cure at 100℃ for 15 minutes.
[0036] S2. Preparation of anti-slip coating:
[0037] (1) Preparation of hafnium diboride microcapsules: 26.00g hafnium diboride powder and 10.40g 2,5-thiophene dicarboxylic acid chloride were mixed and dissolved in 173.33g tetrahydrofuran and stirred evenly to obtain an oil phase mixture; 21.19g 2,6-diaminopyridine and 2.42g sodium dodecyl sulfate were mixed and dissolved in 605.28g deionized water and stirred evenly to obtain an aqueous phase mixture; the oil phase mixture with a mass ratio of 1:3 was injected into the aqueous phase mixture, emulsified at high speed of 15000rpm for 8min, kept at constant temperature of 50℃, stirred for 2.5h, and centrifuged and dried to obtain hafnium diboride microcapsules.
[0038] (2) Synthesis of polyimide-benzoxazole copolymer matrix: Under nitrogen protection, 30.00 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride was dissolved in 150.00 g of N-methylpyrrolidone; 18.00 g of 4,4'-diaminodiphenyl ether was added, and the reaction was carried out at 25 °C for 7 h; 4.50 g of 2,5-diaminopyrazine chain extender was added, and the temperature was raised to 210 °C for 2 h; 2.50 g of 9-fluorenemethanol was added dropwise; after the reaction was completed, the mixture was cooled to room temperature to obtain polyimide-benzoxazole copolymer matrix.
[0039] (3) Mixing reaction: Take 100.00g of polyimide-benzoxazole copolymer matrix, add 30.00g of tris(4-hydroxyphenyl)ethane triglycidyl ether, and stir to mix; add 45.00g of hafnium diboride microcapsules and 18.00g of hexagonal aluminum nitride nanowires in sequence, disperse by ultrasonication, add 0.20g of iridium acetylacetone catalyst and 0.30g of leveling agent BYK-331, mix and react to obtain anti-slip coating.
[0040] S3. Spraying: The anti-slip coating is sprayed in a gradient onto the surface of the bolt thread. After spraying, the dry film thickness of the coating at the tip and root of the bolt thread is 12μm and 7μm, respectively. It is cured at 75℃ to obtain the finished product.
[0041] Example 2
[0042] The specific processing steps in this embodiment are the same as those in Embodiment 1, the difference being the amount of raw material used: hafnium diboride powder.
[0043] 27.06g, 2,5-thiophene dicarboxylic acid chloride 6.76g, tetrahydrofuran 135.28g; 2,6-diaminopyridine 16.18g, sodium dodecyl sulfate 2.02g, deionized water 404.55g; 3,3',4,4'-biphenyltetracarboxylic dianhydride 32.00g, N-methylpyrrolidone 147.00g, 4,4'-diaminodiphenyl ether 16.00g, 2,5-diaminopyrazine 4.00g, 9-fluorenemethanol 2.70g; hafnium diboride microcapsules 40.00g, THPE-TGE 35.00g, hexagonal aluminum nitride nanowires 15.00g, iridium acetylacetone 0.30g, BYK-331 0.50g.
[0044] Comparative Example 1
[0045] The specific difference between Comparative Example 1 and Example 1 is that 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) was not added during the preparation of the matrix.
[0046] Comparative Example 2
[0047] The specific difference between Comparative Example 2 and Example 1 is that no chain extender 2,5-diaminopyrazine was added during the preparation of the matrix.
[0048] Comparative Example 3
[0049] The specific difference between Comparative Example 3 and Example 1 is that no polyimide-benzoxazole copolymer matrix was added during the preparation of the coating.
[0050] Comparative Example 4
[0051] The specific difference between Comparative Example 4 and Example 1 is that hafnium diboride microcapsules were not added during the preparation of the coating.
[0052] Comparative Example 5
[0053] The specific difference between Comparative Example 5 and Example 1 is that: Hafnium diboride was not prepared into microcapsules during the preparation of the coating, but was directly added to the polyimide-benzoxazole copolymer matrix for mixing.
[0054] Comparative Example 6
[0055] The specific difference between Comparative Example 6 and Example 1 is that the epoxy monomer tris(4-hydroxyphenyl)ethane triglycidyl ether (THPE-TGE) was not added during the preparation of the anti-slip coating.
[0056] Comparative Example 7
[0057] The specific difference between Comparative Example 7 and Example 1 is that hexagonal aluminum nitride nanowires were not added during the preparation of the anti-slip coating.
[0058] Performance testing
[0059] The anti-slip coatings prepared in Examples 1-2 and Comparative Examples 1-7 were subjected to performance tests, and the testing methods are as follows: the coefficient of friction test method was carried out according to GB / T1768-1989; the adhesion test method was carried out according to GB / T9286-1998; the tensile strength test method was carried out according to GB / T528-2009; and the abrasion resistance test method was carried out according to GB / T 1768-2006. Specific results are shown in Table 1.
[0060] Table 1. Effects of antislip coatings prepared with different matrices on bolt performance.
[0061]
[0062] As shown in Table 1, the absence of the core dianhydride monomer BPDA in Comparative Example 1 led to the breakage of the polyimide backbone, causing the coefficient of friction to plummet to 0.12 (only 15% of that in Example 1). This was due to the interruption of the condensation reaction between BPDA and ODA, resulting in the coating losing its rigid aromatic heterocyclic backbone and a 52% decrease in tensile strength caused by molecular weight collapse. The absence of the 2,5-diaminopyrazine chain extender in Comparative Example 2 prevented the molecular chain from extending and failed to form a heat-resistant benzoxazole ring. This resulted in increased chain segment movement at high temperatures, causing the coefficient of friction to drop to 0.16 (a 54% decrease in abrasion resistance) and a tensile strength of only 9.2 MPa. The complete absence of the PI-PBO matrix in Comparative Example 3 caused the continuous phase of the coating to disintegrate, resulting in the loss of the bonding medium between the microcapsules and fillers. The coefficient of friction dropped to 0.11, and the wear loss was only 12.7 mg, confirming the disruption of the "mechanical-chemical synergistic" mechanism.
[0063] Comparative Example 4, without the addition of HfB2 microcapsules, resulted in a lack of hard friction points in the coating, reducing the coefficient of friction to 0.43 and decreasing the tensile strength. Comparative Example 5, where HfB2 powder was directly added to the matrix (without microencapsulation), showed a coefficient of friction of only 0.38 due to particle agglomeration and failure of interfacial stress transfer. This demonstrates the crucial role of the polythiophene amide microcapsule wall in anti-slip performance, and the tensile strength was reduced to the lowest level. This is due to the cubic crystal structure and high hardness of hafnium diboride, which allows the microcapsules to significantly resist mechanical impact during coating wear.
[0064] Comparative Example 6 showed that the absence of THPE-TGE crosslinking agent led to the collapse of the three-dimensional crosslinking network. The lack of coordination bonds between the phenolic hydroxyl groups and the metal matrix reduced the adhesion to level 1, and insufficient cohesion resulted in a 34% decrease in tensile strength. Comparative Example 7, although maintaining a short-term friction coefficient of 0.63 after the absence of h-AlN nanowires, suffered from the interruption of axial heat conduction channels, resulting in the inability to dissipate frictional heat under long-term high-frequency operating conditions. The accumulation of thermal stress led to coating cracking. In summary, the PI-PBO matrix, HfB2 microcapsules, and THPE-TGE crosslinking agent constitute a high-density crosslinking network, achieving a synergistic mechanical-chemical enhancement between the hard microcapsules and the polymer network. This effectively improves the coating's anti-slip coefficient, wear resistance, and service strength, thereby enhancing the anti-slip performance of bolts.
[0065] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.
Claims
1. A method for processing bolts with an anti-slip coating, characterized in that, The specific steps include the following: S1. Bolt pretreatment: The bolts are sandblasted, cleaned, and surface activated. S2. Preparation of anti-slip coating: Hafnium diboride microcapsules were prepared, and a polyimide-benzoxazole copolymer matrix was synthesized. The polyimide-benzoxazole copolymer matrix and the hafnium diboride microcapsules were mixed and reacted to obtain the anti-slip coating. S3. Spraying: Apply the anti-slip coating in a gradient to the surface of the bolt threads, and cure at low temperature to obtain the finished product.
2. The processing method for a bolt with an anti-slip coating according to claim 1, characterized in that, In step S2, the specific steps for preparing hafnium diboride microcapsules are as follows: (1) Preparation of oil phase: Hafnium diboride powder and 2,5-thiophene dicarboxylic acid chloride were mixed and dissolved in tetrahydrofuran and stirred evenly to obtain an oil phase mixture; (2) Aqueous phase preparation: 2,6-diaminopyridine and sodium dodecyl sulfate were mixed and dissolved in deionized water and stirred evenly to obtain an aqueous phase mixture; (3) Interfacial polymerization: The oil phase mixture is injected into the aqueous phase mixture, emulsified by high-speed shearing, stirred at constant temperature, and dried by centrifugation to obtain hafnium diboride microcapsules.
3. The processing method for a bolt with an anti-slip coating according to claim 2, characterized in that, The mass ratio of hafnium diboride powder, 2,5-thiophene dicarboxylic acid chloride, and tetrahydrofuran is 15-25:4-6:100, and the particle size of hafnium diboride powder is 200-300 nm; the mass ratio of 2,6-diaminopyridine, sodium dodecyl sulfate, and deionized water is 7-9:0.8-1.2:
200.
4. The processing method for a bolt with an anti-slip coating according to claim 2, characterized in that, The mass ratio of the oil phase mixture to the water phase mixture is 1:2-3, the shear emulsification speed is 10000-15000 rpm, and the time is 3-8 min; the stirring temperature after emulsification is 40-50 ℃, and the stirring time is 1.5-2.5 h.
5. The processing method for a bolt with an anti-slip coating according to claim 1, characterized in that, In step S2, the method for synthesizing the polyimide-benzoxazole copolymer matrix is as follows: (1) Under nitrogen protection, 3,3',4,4'-biphenyltetracarboxylic dianhydride was dissolved in N-methylpyrrolidone; (2) Add 4,4'-diaminodiphenyl ether and react; (3) Add 2,5-diaminopyrazine chain extender, heat and react; (4) Add 9-fluorenemethanol dropwise. After the reaction is complete, cool to room temperature to obtain polyimide-benzoxazole copolymer matrix.
6. The processing method for a bolt with an anti-slip coating according to claim 5, characterized in that, The mass fractions of 3,3',4,4'-biphenyltetracarboxylic dianhydride, N-methylpyrrolidone, 4,4'-diaminodiphenyl ether, 2,5-diaminopyrazine, and 9-fluorenemethanol are 30-35 parts, 145-150 parts, 15-18 parts, 3.5-4.5 parts, and 2.5-3.0 parts, respectively.
7. A method for processing a bolt with an anti-slip coating according to claim 5, characterized in that, The reaction temperature of step (2) is 25-35 ℃ and the reaction time is 5-7 h; the reaction temperature of step (3) is 190-210 ℃ and the reaction time is 2-4 h.
8. The processing method for a bolt with an anti-slip coating according to claim 1, characterized in that, In step S2, the specific steps for mixing the polyimide-benzoxazole copolymer matrix and hafnium diboride microcapsules are as follows: (1) Take the polyimide-benzoxazole copolymer matrix, add tris(4-hydroxyphenyl)ethane triglycidyl ether, and stir to mix; (2) Hafnium diboride microcapsules and hexagonal aluminum nitride nanowires were added in sequence, ultrasonically dispersed, and iridium acetylacetone catalyst and leveling agent BYK-331 were added. The mixture was then reacted to obtain an anti-slip coating.
9. A method for processing a bolt with an anti-slip coating according to claim 8, characterized in that, The mass fractions of the polyimide-benzoxazole copolymer matrix, tris(4-hydroxyphenyl)ethane triglycidyl ether, hafnium diboride microcapsules, hexagonal aluminum nitride nanowires, iridium acetylacetone, and BYK-331 are 100 parts, 30-40 parts, 35-45 parts, 12-18 parts, 0.2-0.4 parts, and 0.3-0.7 parts, respectively, and the aspect ratio of the hexagonal aluminum nitride nanowires is 50-60.
10. A method for processing a bolt with an anti-slip coating according to claim 1, characterized in that, In step S3, the dry film thickness of the coating on the tip and root of the bolt thread after gradient spraying is 12-18 μm and 7-9 μm, respectively.