A method for rapidly predicting and evaluating the risk of shoulder abnormal wear of a tire tread compound in a wet ground handling working condition

Abstract

The present application relates to the field of tire manufacturing technology, and more particularly to a method for quickly predicting and evaluating the risk of shoulder abnormal wear of tire tread rubber in wet land operation conditions. After in-situ vulcanization of the rubber sample by a rubber processing analyzer (RPA), the method successively carries out medium temperature constant temperature shearing and high temperature shearing tests, records the change of storage modulus with time, calculates the storage modulus retention rate η, and judges the abnormal wear risk of the rubber in the actual working condition according to the value of η. The results show that when η≥85%, the rubber performance is stable and is not prone to failure such as flattening, flanging or tearing, and when η<85%, there is a higher risk. The test process of the present application is simple, the result criterion is clear, the rapid screening and optimization of the tread formula can be realized, and the research and development efficiency and product reliability are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of tire manufacturing technology, and in particular to a method for rapidly predicting and assessing the risk of abnormal shoulder wear of tire tread compounds in wet handling conditions. Background Technology

[0002] During typical wet braking or high lateral acceleration maneuvers, the outer shoulder of the tire is subjected to a coupled load of high-frequency, low-amplitude shear strain (>15Hz) and rapid thermal shock. If the tread compound softens or reverts to its original state under dynamic high temperatures, abnormal wear such as "chunking / tearing"—including flattening, flanging, and tearing of continuous strip-shaped tread blocks—is highly likely to occur, reducing driving safety and affecting the overall tire's NVH and lifespan. However, current industry testing systems still primarily rely on whole-tire road tests or real-vehicle track tests, which have long development cycles, high costs, and difficulty in providing timely guidance for formula optimization.

[0003] EU UNECER 117 and its 2024 revision R117-04 stipulate a speed limit of 80-20 km / h. -1 The wet braking method and PBFC / MFDD evaluation index have been developed, and the wet grip limit of worn tires is being explored. Although this regulation effectively constrains overall tire safety, the test must be completed on a closed track and wetted surface with a standard reference tire, which is costly and cannot directly quantify the microscopic failure mechanism of the rubber compound. Commonly used methods in the industry, such as wet handling circle test, ISO fixed circle, and J-turn, also have the same time and site limitations.

[0004] Traditional laboratory-level instruments such as DIN abrasion, LAT100 lateral abrasion, and Blade-Type Cut & Chip primarily target dry-road abrasive wear or off-road cutting failure. Typical examples include the MonTech CC3000 and Coesfeld-Endurica ICCA, which can reproduce "chip-and-cut" damage through high-speed blade impact or controlled impact wheels. These tests focus more on the large-volume spalling caused by impact cutting and are not sensitive to the microscopic tearing caused by dynamic thermal fatigue in wet shoulders.

[0005] Commercialized in 1992, the RPA (Regenerative Polarizing Agent) enables programmable oscillatory shearing within a closed cavity, achieving frequencies from 0.001 to 50 Hz, strains from 0.005 to 360°, and temperatures from room temperature to 230°C. It is considered a key tool for bridging the processing and performance of rubber compounds. Nine standards, including ASTM D6204, D6601, and D7050, have been subsequently published for routine evaluations such as isothermal curing profiles and low-frequency two-point or high-strain scans. However, current standards mostly employ single-stage, isothermal testing, focusing on Mooney viscosity substitution, vulcanization kinetics, or the Payne effect, without providing evaluations of fatigue / modulus retention under continuous high-frequency shear-heating coupling.

[0006] While ASTM D6204-C's VTA (Variable Temperature Analysis) allows for linear temperature increases from 100-180℃, its strain is fixed at ±7% or ±100% (non-linear region), primarily prioritizing scorch safety. Test durations are typically <30 minutes, insufficient to reveal the energy storage modulus decay caused by the "thermal reversion" of the vulcanization network under low-strain, high-frequency, long-term shear. Publicly available industry data indicates that under continuous loading at 50Hz and >1% strain, the stiffness and thermal stability of RPA devices become limiting factors. Furthermore, the academic community lacks a two-stage loading process specifically designed for abnormal wear scenarios in wetlands.

[0007] In recent years, studies have emerged that use optical contact pressure distribution and principal component regression to establish statistical models for wet grip index (G) and outer shoulder contact ratio. MDPI researchers have also found that variations in outer shoulder contact width caused by different wear conditions significantly alter lateral stiffness. While these methods can correlate contact geometry and performance at the whole tire level, they still require a real tire testing platform (optical platform, rollers, or high-speed test bench) and have not yet focused on rapid screening based on the intrinsic properties of the rubber compound.

[0008] Road tests and finite element simulations generally indicate that during high-speed cornering in wet conditions, the outer shoulder experiences a cyclical increase in frictional heat due to alternating cooling from the wheel and water, causing the rubber compound temperature to rise from 110°C to over 150°C within tens of seconds. If the formulation contains a high proportion of polysulfide bonds, insufficient anti-reversion agents, or poor thermal stability at the resin-filler interface, the storage modulus G' will decrease sharply, the crack initiation rate will increase exponentially, leading to shoulder shearing and block tearing. Existing Cut & Chip methods cannot simulate this coupled condition of medium-temperature long-term shearing and high-temperature short-term impact, while R117 wet braking only focuses on the longitudinal μ value. Summary of the Invention

[0009] To address the aforementioned pain points, the purpose of this invention is to provide a method for rapidly predicting and assessing the risk of abnormal shoulder wear in tire tread compounds under wet handling conditions. This method combines the closed-cavity dynamic shear advantage of RPA with a two-stage coupled procedure, and uses the storage modulus retention rate to determine the threshold, enabling the prediction of abnormal shoulder wear risk in wet conditions from small-scale test samples. Compared with existing ASTM D6601 single-stage strain scanning or ICCA impact cutting tests, the invention offers significant improvements in condition reproducibility, data quantifiability, and industrial decision-making efficiency, filling the gap in rapid laboratory screening of tread compounds.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A method for rapidly predicting and assessing the risk of abnormal shoulder wear in tire tread compounds during wet handling conditions includes the following steps: 1) Sample preparation: Cut rubber material circumferentially from the shoulder area on the outer side of the target tire tread to prepare a circular sample with a thickness of 1.5-2.5 mm and a diameter of φ20-φ25 mm; 2) In-situ vulcanization: Place the sample in the sealed test chamber of the rubber processing analyzer (RPA) and vulcanize it at 140-160℃, 0.5-2Hz, and 0.1-1% dynamic shear strain until the torque reaches 90% of the maximum torque, and then keep it at the temperature for 1-5 minutes. 3) Temperature drop: Keep the test chamber sealed and reduce the chamber temperature to 110-130℃ within 1-10 minutes; 4) First-stage dynamic holding test: At the aforementioned 110-130℃, continuously load at 15-25Hz and 1-3% dynamic shear strain for 90-150 min, and record the initial storage modulus G'0 and the storage modulus G' at the end of the stage. t ; 5) Heating-Second Stage Dynamic Holding Test: Maintain the same shear conditions, and increase the temperature of the test chamber by 1-10℃·min. -1 The heating rate was increased to 140-150℃ and held at that temperature for 30-60 minutes, and the initial storage modulus G' of the second stage was recorded. 20 With the end-stage energy storage modulus G' 2t ; 6) Calculation of index: The energy storage modulus retention rate η is calculated using the following formula. ; 7) Risk assessment: When η≥85%, the tread compound is deemed to have the ability to resist abnormal shoulder wear in wet conditions; when η<85%, it is deemed to have a high risk of abnormal shoulder wear.

[0011] Preferably, the width of the shoulder sampling area in step 1) is 10-30mm and the length is 20-50mm.

[0012] Preferably, the in-situ vulcanization conditions in step 2) are 150°C, 1 Hz, 0.5% dynamic shear strain, and t 90 Continue vulcanization for 2 minutes.

[0013] Preferably, in step 3), the temperature of the test chamber is reduced to 120°C, and the time taken is 3-5 minutes.

[0014] Preferably, the test conditions for step 4) are 20Hz, 2% dynamic shear strain, and 120min.

[0015] Preferably, the heating rate in step 5) is 5°C·min. -1 The target temperature is 145℃, and the temperature is maintained for 40 minutes.

[0016] Preferably, the abnormal wear of the shoulder is manifested as flattening, flanging, and tearing failure of continuous band-shaped patterned blocks.

[0017] Furthermore, the present invention also provides a tire tread compound wet abnormal wear risk prediction system based on a rubber processing analyzer, the system implementing the method comprising: A sample loading assembly is used to clamp the circular sample and apply an oscillating torque. The temperature-frequency-strain coupling control module can achieve continuous temperature control of 110-150℃, frequency of 0.5-25Hz, and dynamic shear strain output of 0.1-3% in a single test. The real-time modulus acquisition module is used to record the curve of G' changing over time; The data processing unit has a built-in algorithm based on η=G' 2t / G'0×100% automatically calculates the energy storage modulus retention rate and outputs the risk assessment result.

[0018] Furthermore, the present invention also provides a computer-readable storage medium having a computer program or instructions stored thereon, which, when executed by a processor, implement the method.

[0019] Furthermore, the present invention also provides a computer program product, including a computer program or instructions that, when executed by a processor, implement the method.

[0020] By employing the above-mentioned technical solution, this invention achieves the following significant technical effects by designing a continuous high-frequency small-strain shear sequence of medium-temperature isothermal-high-temperature heating within a rubber processing analyzer (RPA) and using the storage modulus retention rate η as a quantitative criterion: 1. Rapid and quantitative prediction: The risk of abnormal shoulder wear, which traditionally requires hundreds of kilometers of wetland road testing to become apparent, can be reduced to a laboratory testing cycle of as little as 3 hours; a single indicator η can provide a "safe / high-risk" result in percentage form, simplifying the judgment process and significantly improving R&D efficiency.

[0021] 2. Realistic working condition reproduction: The dual-stage program simultaneously simulates the temperature-shear coupled load trajectory of "water film cooling-friction heat surge" in wetland operation, overcoming the limitation of existing RPA isothermal tests that only reflect single scenarios of medium or high temperature, and can reveal the thermal fatigue instability mechanism of vulcanization network under temperature-frequency coupled conditions.

[0022] 3. High correlation verification: Numerous examples show that the η obtained by the present invention is highly consistent with the abnormal wear results of the outer shoulder of the actual vehicle in wet conditions: when η≥85% (preferably ≥90%), no continuous strip-shaped flattening or tearing occurs in the actual vehicle; when η<85%, abnormal wear generally occurs. The correlation coefficient between the two is R²≥0.93, which can directly guide the screening of tread compound.

[0023] 4. Improved sensitivity and resolution: Compared with DIN / LAT abrasion or Cut & Chip impact which only rely on mass loss, this method monitors the rate of decrease in energy storage modulus in real time. It is more sensitive to early failures such as minor cross-linking bond cleavage and resin-filler interface debonding, and can clearly distinguish pseudo-durable formulations that are "stable at medium temperature but rapidly decay at high temperature".

[0024] In summary, this invention, through laboratory-level controllable high-throughput testing, has for the first time achieved rapid, accurate, and quantitative prediction of abnormal wear risk on wet shoulder at the material formulation level, significantly improving tire R&D efficiency and product safety and reliability, and has outstanding industrial promotion value and significant technological advancement. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0026] I. Description of Common Test Conditions Sample preparation: All samples were cut circumferentially from the outer shoulder of a 235 / 45R18 ultra-high performance tire (UHP), with a diameter of approximately 22 mm and a thickness of 2 mm.

[0027] RPA instrument parameters: In-situ vulcanization stage: 150℃, 1Hz, 0.5% dynamic shear strain, vulcanized to t 90 Then continue to keep warm for 2 minutes; Cooling phase: Temperature drops to 120℃ within 4 minutes; First stage dynamic holding: 120℃, 20Hz, 2% strain, continuously for 120min; Heating phase: 5℃·min -1 The rate rises to 145°C; Second stage dynamic holding: 145℃, 20Hz, 2% strain, continuously for 40min; Energy storage modulus retention rate η=G′ 2t / G′0×100%.

[0028] Real-world wetland testing method: A modified Volkswagen Golf GTI was tested on a water-sprinkled concrete track, achieving a speed range of 80 to 20 km / h. -1 ABS wet braking and ISO fixed circle control, cumulative 50km; after the test, observe the flattening, flanging or tearing of the outer shoulder tread block and score it from 0 to 5 (0 is no abnormality, 5 is severe continuous flattening).

[0029] II. Examples and Comparative Examples Example 1 Formulation overview: The polymer is SSBR 80 phr / high cis-BR 20 phr; the resin system is hydrogenated DCPD 45 phr, α-methylstyrene resin 5 phr; anti-reversion agent HVA-20.6 phr; carbon black N234 35 phr; other rubber processing raw materials and auxiliaries are all conventional raw materials and added in conventional amounts.

[0030] Example 2 Formulation overview: SSBR 75 phr / high cis-BR 15 phr / liquid BR 10 phr; resin system hydrogenated DCPD 50 phr + α-methylstyrene 10 phr; HVA-20.7 phr; other rubber processing raw materials and auxiliaries are conventional raw materials, as in the conventional addition amount of Example 1.

[0031] Example 3 Formulation overview: SSBR 70 phr / natural rubber 30 phr; resin system hydrogenated DCPD 40 phr + aromatic modified resin 8 phr; anti-reversion agent ETU-U 0.5 phr; other rubber processing raw materials and auxiliaries are conventional raw materials, as in the conventional addition amount of Example 1.

[0032] Example 4 Formulation overview: Functionalized SSBR 85 phr / high cis-BR 15 phr; Resin system: bisphenol-A phenolic resin 35 phr + α-methylstyrene 5 phr; Anti-reversion agent PER-320 0.4 phr; Other rubber processing raw materials and auxiliaries are conventional raw materials, as in the conventional addition amount of Example 1.

[0033] Comparative Example 1 The formula is the same as in Example 1, but the heating to 145°C and the second stage of 40 min shearing are omitted in the test procedure, and only the temperature is held at 120°C for 160 min.

[0034] Comparative Example 2 The formulation was the same as in Example 1, but HVA-2 was removed. A complete two-stage test was performed.

[0035] Comparative Example 3 The formula was the same as in Example 1, and the temperature was maintained at 120°C throughout the test without any increase.

[0036] Comparative Example 4 The formulation is the same as in Example 1, but the shear strain in both stages is changed to 0.5%.

[0037] III. The experimental results are summarized as follows: serial number η (Storage Modulus Retention Rate, %) Wetland Real-World Vehicle Rating* Result determination Example 1 92 0 No abnormal wear Example 2 95 0 No abnormal wear Example 3 90 1 Slight edge wear Example 4 91 0 No abnormal wear Comparative Example 1 88 2 Scattered burrs Comparative Example 2 78 4 Continuous flattening Comparative Example 3 84 3 Patterned block edging Comparative Example 4 80 4 Block tearing *Wetland Real-World Vehicle Rating: 0 = No abnormalities; 5 = Severe continuous shearing / tearing. See the Common Test Conditions description for real-world test conditions.

[0038] IV. Conclusion In Examples 1-4, under the dual-stage high-frequency shear-heating program with η≥90%, the actual vehicle only showed slight or no abnormal wear at level 0-1, verifying the reliability of the threshold η≥85% (preferably ≥90%).

[0039] Comparative Examples 1 and 3, even after removing the heating shock or achieving complete isothermal conditions, still showed significant wear despite η being close to the threshold, demonstrating that the two-stage procedure is crucial for revealing thermo-mechanical coupling fatigue.

[0040] Comparative Example 2, which removed the anti-reversion agent, and Comparative Example 4, which reduced the shear strain, both showed η≤80% and exhibited a level 4 severe anomaly in wetland testing. This indicates that the method can sensitively capture the failure risks caused by crosslinking network reversion and insufficient strain.

[0041] The foregoing description of embodiments of the present invention, through which those skilled in the art are able to implement or use the present invention, will be readily apparent to those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art. 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 novelty disclosed herein.

Claims

1. A method for rapidly predicting and assessing the risk of abnormal shoulder wear in tire tread compounds during wet handling conditions, characterized in that, Includes the following steps: 1) Sample preparation: Cut rubber material circumferentially from the shoulder area on the outer side of the target tire tread to prepare a circular sample with a thickness of 1.5-2.5 mm and a diameter of φ20-φ25 mm; 2) In-situ vulcanization: Place the sample in the sealed test chamber of the rubber processing analyzer (RPA) and vulcanize it at 140-160℃, 0.5-2Hz, and 0.1-1% dynamic shear strain until the torque reaches 90% of the maximum torque, and then keep it at the temperature for 1-5 minutes. 3) Temperature drop: Keep the test chamber sealed and reduce the chamber temperature to 110-130℃ within 1-10 minutes; 4) First-stage dynamic holding test: At the aforementioned 110-130℃, continuously load at 15-25Hz and 1-3% dynamic shear strain for 90-150 min, and record the initial storage modulus G'0 and the storage modulus G' at the end of the stage. t ; 5) Heating-Second Stage Dynamic Holding Test: Maintaining the same shear conditions, the temperature of the test chamber is increased to 140-150℃ at a heating rate of 1-10℃·min⁻¹ and held at that temperature for 30-60 min. The initial storage modulus G' of the second stage is recorded. 20 With the end-stage energy storage modulus G' 2t ; 6) Calculation of index: The energy storage modulus retention rate η is calculated using the following formula. ； 7) Risk assessment: When η≥85%, the tread compound is deemed to have the ability to resist abnormal shoulder wear in wet conditions; when η<85%, it is deemed to have a high risk of abnormal shoulder wear.

2. The method according to claim 1, characterized in that: In step 1), the width of the shoulder sampling area is 10-30mm and the length is 20-50mm.

3. The method according to claim 1, characterized in that: The in-situ vulcanization conditions in step 2) are 150℃, 1Hz, 0.5% dynamic shear strain, and t. 90 Continue vulcanization for 2 minutes.

4. The method according to claim 1, characterized in that: In step 3), the temperature of the test chamber is reduced to 120℃, which takes 3-5 minutes.

5. The method according to claim 1, characterized in that: The test conditions for step 4) are 20Hz, 2% dynamic shear strain, and 120min.

6. The method according to claim 1, characterized in that: The heating rate in step 5) is 5℃·min⁻¹, the target temperature is 145℃, and the temperature is held constant for 40min.

7. The method according to claim 1, characterized in that: The abnormal wear on the shoulder area manifests as flattening, flanging, and tearing failure of continuous band-shaped patterned blocks.

8. A system for predicting the risk of abnormal wet wear of tire tread rubber compounds based on a rubber processing analyzer, characterized in that, The system implements the method according to any one of claims 1-7, comprising: A sample loading assembly is used to clamp the circular sample and apply an oscillating torque. The temperature-frequency-strain coupling control module can achieve continuous temperature control of 110-150 ℃, frequency of 0.5-25 Hz, and dynamic shear strain output of 0.1-3% in a single test. The real-time modulus acquisition module is used to record the curve of G' changing over time; The data processing unit has a built-in algorithm based on η=G' 2t / G'0×100 % Automatically calculates the energy storage modulus retention rate and outputs the risk assessment result.

9. A computer-readable storage medium having a computer program or instructions stored thereon, characterized in that, When the computer program or instructions are executed by a processor, they implement the method of any one of claims 1-7.

10. A computer program product, comprising a computer program or instructions, characterized in that, When the computer program or instructions are executed by a processor, they implement the method of any one of claims 1-7.

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