Quantitative detection method, spindle and detection set for adhesive force of paint film on surface of tin plate

Abstract

The invention relates to the technical field of metal material surface performance detection, in particular to a quantitative detection method for tin plate surface paint film adhesive force, a spindle and a detection set. According to the quantitative detection method for the adhesive force of the paint film on the surface of the tin-plated plate, low interference and true quantification are taken as the core, and the system error of a traditional drawing method is pressed to be smaller than or equal to 0.1 MPa through a three-step principle design. On the premise that the original corrosion resistance, flexibility and other properties of the paint film are not damaged, system errors and random errors are compressed to be within the first-level precision range, and quantitative, traceable and low-discrete detection of the adhesive force of the paint film on the surface of the tin plate is achieved.

Description

Technical Field

[0001] This invention relates to the field of surface performance testing technology for metallic materials, and in particular to a quantitative testing method, ingot, and testing kit for the adhesion of paint film on the surface of tin-plated plates. Background Technology

[0002] Tinplate, as the main material for food cans, must withstand mechanical friction, thermal expansion and contraction, and chemical corrosion during transportation, filling, sterilization, and long-term storage. Once the tinplate peels off, the risk of can corrosion increases sharply, and the safety of the contents and shelf life decrease accordingly. The current national standard GB / T1720-2020 "Cross-cut Test for Tinplate Film" uses a five-level qualitative rating based on the degree of tinplate peeling after crossing the lines, with the upper limit of the range only reaching "Level 1" corresponding to about 0.3 MPa. This cannot distinguish differences within Level 1, nor does it provide quantitative data to support process optimization. The industry-wide commonly used cross-cut test also relies on visual inspection, is greatly affected by human factors, and the tinplate film deteriorates after being baked at 215℃ for 24 minutes, causing the test results to deviate from the actual service condition. Existing pull-out patents mostly focus on steel plates, walls, or composite films, failing to address the challenges of low-stress sensitivity testing caused by the thinness of tinplate, its susceptibility to warping, and the mere 15μm thickness of the coating. Furthermore, they lack repeatable quantitative judgment rules for structural adhesive curing shrinkage and spindle-adhesive-coating film interface fracture modes, resulting in testing errors often exceeding 0.3MPa. This makes it difficult to meet the urgent needs of high-end food packaging for ≤0.1MPa error, ≤5MPa full-range, traceable quantitative data. Summary of the Invention

[0003] In view of this, embodiments of this application provide a quantitative detection method, spindle and detection kit for the adhesion of tinplate surface coating, in order to solve the following technical problem: how to quantitatively obtain the true adhesion value within level one with an error of ≤0.1MPa without damaging the original performance of the tinplate coating.

[0004] In a first aspect, embodiments of this application provide a method for quantitatively detecting the adhesion of a tin-plated sheet surface coating, comprising: S1. Use a lint-free cloth dampened with anhydrous ethanol to clean the paint film on the surface of the tinplate; S2. Cross-polish the bonding surfaces of the spindle, and then clean the bonding surfaces of the spindle with anhydrous ethanol; S3. Apply structural adhesive evenly to the bonding surface of the spindle, wherein the coating thickness of the structural adhesive is 0.1mm to 1mm; S4. The spindle coated with the structural adhesive is coaxially pressed onto the surface of the paint film to obtain a pressed tin-plated plate; S5. The tin-plated laminate is cured at 40℃~60℃ for 10min~30min to allow the solvent in the structural adhesive to evaporate; S6. Cut the paint film along the outer circumference of the ingot to the substrate of the tin-plated plate to obtain a cured and cut tin-plated plate; S7. Cool the cured and cut tinplate to room temperature, apply axial tension to the ingot at a drawing rate of ≤1MPa / s until the ingot breaks with the tinplate, and record the tension value F at the moment of breakage; S8. Based on the tensile force F and the bonding area A of the spindle, the adhesion force σ of the paint film is obtained; S9. Repeat steps S1 to S8 multiple times, and after removing the maximum and minimum values ​​from the multiple tests, take the arithmetic mean as the final adhesion test result of the paint film, and the absolute value of the difference between a single test value and the average value is ≤0.1MPa.

[0005] Optionally, the structural adhesive has a compressive strength ≥65MPa and a curing shrinkage rate ≤1% under conditions of 40℃~60℃ and 10min~30min.

[0006] Optionally, the surface roughness Ra of the bonding surface of the spindle is 0.8μm to 3.2μm, and the included angle of the cross-polishing texture is 45°±5°.

[0007] Optionally, in step S6, the cutting is performed using a cutter, wherein the difference between the inner diameter of the cutting edge of the cutter and the outer diameter of the spindle is 0 mm to 0.2 mm.

[0008] Optionally, in step S7, the fractured layer is located only at the interface between the paint film and the tin-plated substrate, or it is located inside the paint film and the area of ​​the paint film remaining on the surface of the tin-plated substrate is ≥30%; If the fracture layer is located inside the structural adhesive, at the interface between the structural adhesive and the spindle, or at the interface between the structural adhesive and the paint film, then the tensile force value F is determined to be invalid data and discarded.

[0009] Optionally, the outer diameter of the spindle is 10 mm to 50 mm, and as the outer diameter of the spindle increases, the lower limit of the adhesion force that the method can detect decreases.

[0010] Optionally, the adhesion force σ is obtained by the following expression: σ = F / A.

[0011] In a second aspect, embodiments of this application provide an ingot for use in any of the methods described in the first aspect, characterized in that the ingot is a cylinder made of stainless steel, one end face of the cylinder is cross-polished to form a rough bonding surface, the outer circumference of the cylinder is polished, the diameter of the cylinder is 10mm to 50mm, and the height is 10mm to 30mm.

[0012] Thirdly, embodiments of this application provide a detection kit for the method described in the first aspect, characterized in that the kit comprises: The spindle as claimed in claim 8; Structural adhesive, wherein the compressive strength of the structural adhesive is ≥65MPa, and the curing conditions are 40℃~60℃, 10min~30min; A cutter, wherein the difference between the inner diameter of the cutting edge of the cutter and the outer diameter of the spindle is 0 mm to 0.2 mm; An adhesion tester, wherein the pull-out rate of the adhesion tester is adjustable and the maximum rate is ≤1MPa / s.

[0013] Optionally, the structural adhesive is a two-component epoxy adhesive, the initial viscosity of which at 25°C is 8000 mPa·s to 15000 mPa·s, and the Shore D hardness of which after curing is ≥75.

[0014] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a quantitative detection method for the adhesion of tinplate surface coating. The method is based on "low interference and true quantification" and uses a three-step principle design to reduce the systematic error of the traditional pull-out method to ≤0.1MPa.

[0015] ① Zero interface damage: The tinplate coating is wiped lightly with anhydrous ethanol, without swelling or scratching, maintaining the original cross-linking density and surface energy; the bonding surfaces of the spindles are also wiped clean with ethanol after cross-grinding, which increases the micro-contact area without introducing grease or abrasive residue, so that the strength of the adhesive-coating-tin three-phase interface is dominated by chemical bonds, rather than a weak boundary layer of contaminants.

[0016] ② Stress homogenization: The thickness of the structural adhesive is controlled at 0.1–1 mm, and it is pre-cured at 40–60℃ for 10–30 min to allow the solvent to fully evaporate under low pressure, increase the glass transition temperature of the adhesive layer, and release the curing shrinkage stress in advance; after cooling, the outer periphery of the paint film is cut off to eliminate lateral constraints, so that the axial stress field is ideally circularly distributed during pull-out, avoiding peel-shear mixed failure, ensuring that the fracture occurs at the paint film-substrate interface, and the measured value is the true adhesion force.

[0017] ③ High data fidelity: drawing rate ≤1MPa / s, viscoelastic response negligible, force sensor readings and interface stress instantaneously balanced; 6–10 repetitions and removal of maximum and minimum values, using statistical criteria to limit random error to within ±0.1MPa.

[0018] Therefore, without damaging the original corrosion resistance and flexibility of the paint film, both systematic and random errors are compressed to the first-level accuracy range, realizing quantitative, traceable, and low-discrete detection of the adhesion of the paint film on the tinplate surface. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0021] In a first aspect, embodiments of this application provide a method for quantitatively detecting the adhesion of a tin-plated sheet surface coating, comprising: S1. Use a lint-free cloth dampened with anhydrous ethanol to clean the paint film on the surface of the tinplate; S2. Cross-polish the bonding surfaces of the spindle, and then clean the bonding surfaces of the spindle with anhydrous ethanol; S3. Apply structural adhesive evenly to the bonding surface of the spindle, wherein the coating thickness of the structural adhesive is 0.1mm to 1mm; S4. The spindle coated with the structural adhesive is coaxially pressed onto the surface of the paint film to obtain a pressed tin-plated plate; S5. The tin-plated laminate is cured at 40℃~60℃ for 10min~30min to allow the solvent in the structural adhesive to evaporate; S6. Cut the paint film along the outer circumference of the ingot to the substrate of the tin-plated plate to obtain a cured and cut tin-plated plate; S7. Cool the cured and cut tinplate to room temperature, apply axial tension to the ingot at a drawing rate of ≤1MPa / s until the ingot breaks with the tinplate, and record the tension value F at the moment of breakage; S8. Based on the tensile force F and the bonding area A of the spindle, the adhesion force σ of the paint film is obtained; S9. Repeat steps S1 to S8 multiple times, and after removing the maximum and minimum values ​​from the multiple tests, take the arithmetic mean as the final adhesion test result of the paint film, and the absolute value of the difference between a single test value and the average value is ≤0.1MPa.

[0022] Within Grade 1: Refers to the performance range corresponding to the highest grade "Grade 1" in the adhesion grading system of GB / T1720-2020, which is converted to the quantitative value of this method as ≥0.65MPa. True adhesion: The intrinsic interfacial strength provided by the chemical bonds and mechanical anchoring at the paint film-substrate interface, excluding cohesive failure of the adhesive layer and the paint film itself. Multiple times: Can be 6 to 10 times.

[0023] Working principle: S1 cleaning action targets the "coating film on the tinplate surface". Anhydrous ethanol only dissolves non-polar oil stains and does not swell the cross-linked polyester-melamine coating film, ensuring that the glass transition temperature (Tg) and cross-linking density of the coating film remain unchanged, avoiding "artificial reduction of adhesion due to cleaning". S2 cross-sanding targets the "bonding surface of the spindle". The 45°±5° cross pattern forms "mechanical locking anchor points" within the microscopic valley peak range of 0.8–3.2μmRa, making the subsequent structural adhesive-spindle interface strength greater than the coating film-substrate interface strength, forcing the fracture to occur at the target interface and eliminating the "adhesive-spindle debonding" system error. S3 coating thickness of 0.1mm to 1mm targets the "structural adhesive". The lower limit of 0.1mm ensures that the adhesive layer has sufficient volume to absorb the curing shrinkage stress, and the upper limit of 1mm avoids the shear hysteresis effect caused by excessive adhesive layer thickness; together, both reduce the axial stress error introduced by the curing shrinkage rate to ≤0.01MPa. S4 Coaxial bonding is applied to "spindles coated with structural adhesive". The bonding direction is parallel to the normal of the tinplate, ensuring that the circumferential difference in adhesive layer thickness is ≤5µm and eliminating eccentric bending moment. S5 Curing is applied to "tinplate". Low-temperature short-path curing at 40℃~60℃ for 10min~30min increases the solvent diffusion coefficient D by 2–3 times, but is far below the starting temperature of Tg drop in the coating film of 75℃, ensuring zero degradation of coating film performance; at the same time, the adhesive layer shrinks by more than 98%, and subsequent cooling will not generate additional stress. S6 Cutting is applied to "coating film". It cuts through the outer circumference of the spindle to the substrate at 360°. The cutting action is completed after the adhesive layer has cured and before pulling. It can release lateral constraints and make the pull-out stress field ideally circular, avoiding "edge peeling" that causes a decrease in apparent adhesion. S7 The pulling rate is applied to the "spindle," ≤1MPa / s to ensure sufficient time for the asphaltene-melamine crosslinked network to undergo viscoelastic relaxation, making the peak value of the force-time curve the true static strength and eliminating rate sensitivity errors. S8 The calculation is applied to the "tensile force F and spindle bonding area A," using σ=F / A to directly give a quantitative MPa value, replacing the 0–5 level qualitative description of the circle method. S9 The "S1~S8 steps" are repeated multiple times, and the maximum and minimum values ​​are removed. The average of 4–8 valid data is calculated to ensure that the half-width of the 95% confidence interval is ≤0.1MPa, meeting the "error within level one" requirement.

[0024] For example, thicknesses of 0.1mm to 1mm include, but are not limited to: 0.10, 0.15, 0.20, 0.25, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, and 1.00mm; temperatures of 40℃ to 60℃ include, but are not limited to: 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, and 60℃; times of 10min to 30min include, but are not limited to: 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, and 30min; and drawing rates ≤1MPa / s include, but are not limited to: 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0MPa / s.

[0025] In some embodiments, the structural adhesive has a compressive strength ≥65MPa and a curing shrinkage rate ≤1% under conditions of 40℃~60℃ and 10min~30min.

[0026] Compressive strength ≥65MPa: Axial compressive failure strength of a φ10mm×20mm cylindrical specimen of colloid, tested according to GB / T2567-2008. Curing shrinkage ≤1%: ​​Change rate of adhesive layer length ΔL / L before and after curing.

[0027] The structural adhesive's compressive strength of 65 MPa is significantly higher than the intrinsic strength of the tinplate coating-substrate interface (≤5 MPa), ensuring that "cohesive failure" is impossible. A shrinkage rate of ≤1% results in an axial shrinkage stress of ≤0.65 MPa, which is less than 1 / 5 of the target error of 0.1 MPa and can be ignored. For example, compressive strengths include, but are not limited to: 65, 70, 75, 80, 85, 90, 95, and 100 MPa; shrinkage rates include, but are not limited to: 0.2, 0.4, 0.6, 0.8, and 1.0%.

[0028] In some embodiments, the bonding surface roughness Ra of the spindle is 0.8 μm to 3.2 μm, and the included angle of the cross-polishing texture is 45° ± 5°.

[0029] Ra: Arithmetic mean deviation of the profile, as defined in GB / T3505-2009.

[0030] Ra 0.8–3.2μm and 45°±5° intersecting textures together provide 20–40μm level anchoring grooves. The mechanical locking factor is maximized when the groove opening angle is 90°, increasing the adhesive-spindle interface strength by 2.5 times and ensuring the fracture surface moves down to the target interface. For example, Ra includes, but is not limited to: 0.8, 1.0, 1.2, 1.6, 2.0, 2.4, 2.8, 3.2μm; texture angles include, but are not limited to: 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50°.

[0031] In some embodiments, in step S6, the cutting is performed using a cutter, the difference between the inner diameter of the cutter's blade and the outer diameter of the spindle being 0 mm to 0.2 mm.

[0032] The difference between the inner diameter of the cutting edge and the outer diameter of the spindle: The difference ΔD between the inner diameter Dc of the cutting edge cylinder and the outer diameter Ds of the spindle cylinder is Dc = Dc – Ds. ΔD is 0–0.2 mm to ensure that the cutting gap width is ≤0.1 mm, and the lateral force applied to the adhesive layer during the cutting process is <0.05 MPa, avoiding "pre-damage" that reduces the pull-out value. For example, ΔD includes, but is not limited to: 0.00, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20 mm.

[0033] In some embodiments, in step S7, the fractured layer is located only at the interface between the paint film and the tin-plated substrate, or it is located inside the paint film and the area of ​​the paint film remaining on the surface of the tin-plated substrate is ≥30%; If the fracture layer is located inside the structural adhesive, at the interface between the structural adhesive and the spindle, or at the interface between the structural adhesive and the paint film, then the tensile force value F is determined to be invalid data and discarded.

[0034] Fracture layer: The plane at which damage begins, as observed with the naked eye or under a 10× magnifying glass. Only when the fracture layer is located at the "coating-substrate interface" or "within the coating film and the remaining coating area on the substrate ≥ 30%", is the measured σ equivalent to the true interfacial adhesion. Damage at other locations is considered a system failure and can be discarded to ensure that the true error of the data is ≤ 0.1 MPa.

[0035] In some embodiments, the outer diameter of the spindle is 10 mm to 50 mm, and as the outer diameter of the spindle increases, the lower limit of the adhesion force that the method can detect decreases.

[0036] Detectable adhesion lower limit: For a given paint film system, the minimum σ value that can be pulled to achieve complete failure. As the spindle outer diameter increases sequentially from 10mm to 50mm, the bonding area A increases by a factor of 25 (πr²). Under the same tensile force F, σ decreases inversely, thus the lower limit decreases from 1.0MPa to 0.04MPa, which can cover the low-end requirement of 0.65MPa within "Level 1". For example, the outer diameter of the spindle includes, but is not limited to: 10, 15, 20, 25, 30, 35, 40, 45, and 50mm.

[0037] In some embodiments, the adhesion force σ is obtained by the following expression: σ = F / A.

[0038] Adhesion force σ: Quantitative result, unit MPa. It is calculated directly using σ = F / A, eliminating any empirical correction coefficients and compressing the sources of systematic error to two items: "area measurement ±0.02mm" and "force measurement ±0.5N". The combined uncertainty is ≤0.05MPa, meeting the requirement of ≤0.1MPa.

[0039] In a second aspect, embodiments of this application provide an ingot for use in any of the methods described in the first aspect, characterized in that the ingot is a cylinder made of stainless steel, one end face of the cylinder is cross-polished to form a rough bonding surface, the outer circumference of the cylinder is polished, the diameter of the cylinder is 10mm to 50mm, and the height is 10mm to 30mm.

[0040] Spindle: A cylindrical stainless steel drawing head used to transmit axial tensile force. The stainless steel has an elastic modulus of 200 GPa, which is much higher than the structural adhesive of 3 GPa, ensuring that the deformation of the spindle body is <0.01µm under a tensile stress of ≤5MPa, and the area change caused by deformation is negligible; the polished outer circumference reduces burrs and avoids tearing of the paint film during cutting.

[0041] Thirdly, embodiments of this application provide a detection kit for the method described in the first aspect, characterized in that the kit comprises: The spindle as claimed in claim 8; Structural adhesive, wherein the compressive strength of the structural adhesive is ≥65MPa, and the curing conditions are 40℃~60℃, 10min~30min; A cutter, wherein the difference between the inner diameter of the cutting edge of the cutter and the outer diameter of the spindle is 0 mm to 0.2 mm; An adhesion tester, wherein the pull-out rate of the adhesion tester is adjustable and the maximum rate is ≤1MPa / s.

[0042] Testing kit: refers to the hardware combination required to complete this method. The parameters of each component in the kit are matched in a closed loop: adhesive strength, spindle size, cutting gap, and drawing rate are all designed according to the method in the first aspect. Users can directly obtain an error of ≤0.1MPa without additional calibration, solving the problem of "laboratory-field" result drift.

[0043] In some embodiments, the structural adhesive is a two-component epoxy adhesive, the initial viscosity of which at 25°C is 8000 mPa·s to 15000 mPa·s, and the Shore D hardness of which after curing is ≥75.

[0044] Two-component epoxy adhesive: Component A is epoxy resin + Component B is amine curing agent. Shore D hardness: determined by GB / T2411-2008, using a D-type indenter. Initial viscosity of 8000–15000 mPa·s ensures self-leveling without flow or overflow within a thickness of 0.1–1 mm; after curing, Shore D ≥ 75 ensures an elastic modulus of the adhesive layer ≥ 2.5 GPa, far exceeding the 1.2 GPa of the paint film, ensuring that cohesive failure of the adhesive layer is impossible, further locking the fracture surface at the target interface.

[0045] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards / industry standards / the disclosure herein; if there are no corresponding national standards / industry standards / the disclosure herein, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0046] Example 1 Step S1: Use a lint-free cloth dampened with anhydrous ethanol to clean the paint film on the surface of the tinplate; Step S2: Cross-polish the bonding surface of the spindle, and then clean the bonding surface of the spindle with anhydrous ethanol; Step S3: Apply structural adhesive evenly to the bonding surface of the spindle, wherein the coating thickness of the structural adhesive is 0.10 mm; Step S4: The spindle coated with the structural adhesive is coaxially pressed onto the surface of the paint film to obtain a pressed tin-plated plate; Step S5: Cure the tin-plated laminate at 40 °C for 10 min to allow the solvent in the structural adhesive to evaporate; Step S6: Cut the paint film along the outer circumference of the ingot to the substrate of the tin-plated plate to obtain a cured and cut tin-plated plate; Step S7: Cool the cured and cut tinplate to room temperature, apply an axial tensile force to the ingot at a drawing rate of 0.1 MPa / s until the ingot breaks with the tinplate, and record the tensile force value F at the moment of breakage; Step S8: Obtain the adhesion force σ of the paint film based on the tensile force F and the bonding area A of the spindle; Step S9: Repeat steps S1-S8 6 times, and take the arithmetic mean after removing the maximum and minimum values ​​from the 6 times as the final adhesion test result of the paint film, and the absolute value of the difference between a single test value and the average value is ≤0.1MPa.

[0047] Example 2 Steps S1-S8 are the same as in Example 1, except that the following parameters are replaced: Step S3: Apply structural adhesive to a thickness of 0.25 mm; Step S5: Curing temperature 45 ℃, curing time 15 min; Step S7: Pulling speed 0.3 MPa / s; Step S9: Repeat 7 times.

[0048] Example 3 Steps S1-S8 are the same as in Example 1, except that the following parameters are replaced: Step S3: Apply structural adhesive to a thickness of 0.40 mm; Step S5: Curing temperature 50 ℃, curing time 20 min; Step S7: Pulling speed 0.5 MPa / s; Step S9: Repeat 8 times.

[0049] Example 4 Steps S1-S8 are the same as in Example 1, except that the following parameters are replaced: Step S3: Apply structural adhesive to a thickness of 0.55 mm; Step S5: Curing temperature 55 ℃, curing time 25 min; Step S7: Pulling speed 0.7 MPa / s; Step S9: Repeat 9 times.

[0050] Example 5 Steps S1-S8 are the same as in Example 1, except that the following parameters are replaced: Step S3: Apply structural adhesive to a thickness of 0.70 mm; Step S5: Curing temperature 60 ℃, curing time 30 min; Step S7: Pulling speed 1.0 MPa / s; Step S9: Repeat 10 times.

[0051] Example 6 Steps S1-S8 are the same as in Example 1, except that the following parameters are replaced: Step S3: Apply structural adhesive to a thickness of 0.85 mm; Step S5: Curing temperature 50 ℃, curing time 20 min; Step S7: Pulling speed 0.4 MPa / s; Step S9: Repeat 8 times; spindle outer diameter 35 mm.

[0052] Example 7 Steps S1-S8 are the same as in Example 1, except that the following parameters are replaced: Step S3: Apply structural adhesive to a thickness of 1.00 mm; Step S5: Curing temperature 50 ℃, curing time 20 min; Step S7: Pulling speed 0.6 MPa / s; Step S9: Repeat 8 times; spindle outer diameter 40 mm.

[0053] Example 8 Steps S1-S8 are the same as in Example 1, except that the following parameters are replaced: Step S3: Apply structural adhesive to a thickness of 0.50 mm; Step S5: Curing temperature 50 ℃, curing time 20 min; Step S7: Pulling speed 0.8 MPa / s; Step S9: Repeat 8 times; spindle outer diameter 45 mm.

[0054] Example 9 Steps S1-S8 are the same as in Example 1, except that the following parameters are replaced: Step S3: Apply structural adhesive to a thickness of 0.50 mm; Step S5: Curing temperature 50 ℃, curing time 20 min; Step S7: Pulling speed 0.2 MPa / s; Step S9: Repeat 8 times; spindle outer diameter 50 mm.

[0055] Comparative Example 1 (thickness, temperature, time, and rate are all out of range) Steps S1-S8 are the same as in Example 1, except that the following parameters are replaced: Step S3: Apply structural adhesive to a thickness of 1.2 mm; Step S5: Curing temperature 35 ℃, curing time 5 min; Step S7: Pulling speed 2 MPa / s.

[0056] Comparative Example 2 (thickness, temperature, time, and rate are all out of range) Steps S1-S8 are the same as in Example 1, except that the following parameters are replaced: Step S3: Apply structural adhesive to a thickness of 0.05 mm; Step S5: Curing temperature 70 ℃, curing time 40 min; Step S7: Pulling speed 0.05 MPa / s.

[0057] Comparative Example 3 (Structural adhesive performance does not meet requirements) Steps S1-S8 are the same as in Example 3, except that the structural adhesive used has a compressive strength of 55 MPa and a curing shrinkage rate of 1.5%.

[0058] Comparative Example 4 (Spindle bonding surface roughness and texture angle do not meet requirements) Steps S1-S8 are the same as in Example 3, except that the spindle bonding surface Ra is 0.3 μm and the cross-grinding angle is 30°.

[0059] Comparative Example 5 (Cutter gap not met) Steps S1-S8 are the same as in Example 3, except that the difference between the inner diameter of the cutter blade and the outer diameter of the spindle is 0.3 mm.

[0060] Comparative Example 6 (drawing rate not met) Steps S1-S8 are the same as in Example 3, except that the drawing rate is 5 MPa / s.

[0061] Comparative Example 7 (structural adhesive type not satisfied) Steps S1-S8 are the same as in Example 3, except that the structural adhesive is a commercially available ordinary AB adhesive with an initial viscosity of 3000 mPa·s and a Shore D of 60 after curing.

[0062] Comparative Example 8 (cleaning steps omitted) Step S1: Omitted; Steps S2-S8 are the same as in Example 3.

[0063] Comparative Example 9 (cutting step omitted) Step S6: Omitted; Steps S1-S5 and S7-S8 are the same as in Example 3.

[0064] The above embodiments and comparative examples were tested for effectiveness data using the following methods: 1. Adhesion tester: PosiTest AT-A automatic pull-out adhesion tester, pull-out rate setting value according to the requirements of each scheme.

[0065] 2. Structural adhesive: Two-component epoxy adhesive, compressive strength ≥65 MPa, curing shrinkage ≤1%, initial viscosity 8000–15000 mPa·s.

[0066] 3. Ingot: Stainless steel cylinder, outer diameter as required by each scheme, bonding surface Ra 0.8–3.2 μm, cross-grinding angle 45°±5°.

[0067] 4. Cutter: The difference between the inner diameter of the cutting edge and the outer diameter of the spindle is 0–0.2 mm.

[0068] 5. Coating film Tg test: DSC 200 F3, nitrogen atmosphere, heating rate 10 ℃ / min, midpoint temperature is taken.

[0069] Table 1

[0070] As shown in Table 1, the average measured adhesion of all embodiments was in the range of 0.60–0.68 MPa, with a standard deviation ≤0.04 MPa and a maximum absolute value of dispersion ≤0.08 MPa. The effectiveness of the fracture layer was "effective" in all cases, and the change in film Tg was 0°C, meeting the technical requirement of "true adhesion value within Grade 1 with an error ≤0.1 MPa". The average measured adhesion of all comparative examples was in the range of 0.38–0.46 MPa, with a standard deviation ≥0.08 MPa and a maximum absolute value of dispersion ≥0.16 MPa. The effectiveness of the fracture layer was "ineffective" in all cases, and some comparative examples showed a decrease in film Tg (from -3°C to -4°C), failing to meet the technical requirement of "true adhesion value within Grade 1 with an error ≤0.1 MPa".

[0071] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for quantitatively measuring the adhesion of a surface paint film on a tinplate, characterized by The method comprises the following steps: S1. cleaning the paint film on the surface of the tinplate by using a dust-free cloth to dip anhydrous ethanol; S2. cross-grinding the bonding surface of the ingot, and then cleaning the bonding surface of the ingot by using anhydrous ethanol; S3. uniformly applying structural adhesive to the bonding surface of the ingot, and the application thickness of the structural adhesive is 0.1mm-1mm; S4. coaxially pressing the ingot coated with the structural adhesive to the surface of the paint film to obtain a pressed tinplate; S5. curing the pressed tinplate at 40℃-60℃ for 10min-30min to volatilize the solvent in the structural adhesive; S6. cutting the paint film along the outer circumference of the ingot to the substrate of the tinplate to obtain a cured cut tinplate; S7. cooling the cured cut tinplate to room temperature, applying axial tension to the ingot at a drawing rate of ≤1MPa / s until the ingot is broken with the tinplate, and recording the tension value F at the moment of breaking; S8. obtaining the adhesion σ of the paint film according to the tension value F and the bonding area A of the ingot; S9. repeating the steps S1-S8 for multiple times, removing the maximum value and the minimum value in the multiple times, and taking the arithmetic mean value as the final adhesion detection result of the paint film, and the absolute value of the difference between the single detection value and the average value is ≤0.1MPa.

2. The method of claim 1, wherein, The compressive strength of the structural adhesive is ≥65MPa, and the curing shrinkage of the structural adhesive under the conditions of 40℃-60℃ and 10min-30min is ≤1%.

3. The method of claim 1, wherein, The bonding surface roughness Ra of the ingot is 0.8μm-3.2μm, and the included angle of the cross-grinding pattern is 45°±5°.

4. The method of claim 1, wherein, In step S6, the cutting is performed by using a cutter, and the difference between the inner diameter of the cutting edge of the cutter and the outer diameter of the ingot is 0mm-0.2mm.

5. The method of claim 1, wherein, In step S7, the breaking layer of the breaking is only located at the interface between the paint film and the substrate of the tinplate, or is located inside the paint film and the surface of the substrate of the tinplate retains an area of the paint film ≥30%. If the breaking layer is located inside the structural adhesive, at the interface between the structural adhesive and the ingot, or at the interface between the structural adhesive and the paint film, the tension value F is determined as invalid data and is discarded.

6. The method of claim 1, wherein, The outer diameter of the ingot is 10mm-50mm, and as the outer diameter of the ingot increases, the lower limit of the adhesion that can be detected by the method decreases.

7. The method of claim 1, wherein, The adhesion σ is obtained by the following expression: σ=F / A.

8. A spool for use in the method of any one of claims 1 to 7, characterized in that The ingot is a cylinder, and the material is stainless steel. One end surface of the cylinder is cross-ground to form a rough bonding surface. The outer circumference of the cylinder is polished. The diameter of the cylinder is 10mm-50mm, and the height is 10mm-30mm.

9. A test kit for use in the method of any one of claims 1 to 7, characterized in that The kit comprises: The ingot of claim 8; The structural adhesive, and the compressive strength of the structural adhesive is ≥65MPa, and the curing conditions are 40℃-60℃ and 10min-30min; The cutter, and the difference between the inner diameter of the cutting edge of the cutter and the outer diameter of the ingot is 0mm-0.2mm; The adhesion tester, and the drawing rate of the adhesion tester is adjustable, and the maximum rate is ≤1MPa / s.

10. The test kit of claim 9, wherein The structural adhesive is a two-component epoxy adhesive, the initial viscosity of the two-component epoxy adhesive at 25 DEG C is 8000 mPa s-15000 mPa s, and the Shore D hardness of the cured two-component epoxy adhesive is greater than or equal to 75.

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