Method for testing demolding force value between rubber composition and metal mold

Abstract

The invention relates to the field of rubber performance detection methods, and discloses a method for testing a demolding force value between a rubber composition and a metal mold, which adopts a rheometer for testing, is convenient and fast, and can accurately determine the demolding force value between the rubber composition and the metal mold. And the development of a formula of the rubber composition and the optimization of a processing technology can be guided and optimized, and smooth demolding of the rubber composition is ensured.

Description

Technical Field

[0001] The invention relates to the field of rubber performance testing methods, in particular to a testing method for the demoulding force value between a rubber composition and a metal mold. Background Art

[0002] During driving, tires face severe challenges of high friction, high temperature and high pressure. If only pure rubber materials are used, they are easily damaged in such an environment. Therefore, in order to improve the mechanical properties of rubber and enhance the strength and durability of tires, we usually add reinforcing fillers such as carbon black to rubber. Since Michelin launched the "Green Tire Concept" in 1992, white carbon black, as an environmentally friendly filler, has become more and more widely used in tire tread rubber.

[0003] With the introduction of tire labeling laws in various countries and the increasingly stringent requirements of automobile companies for the performance of matching tires, tire companies are committed to developing tires with better performance, and the filling ratio of silica is gradually increasing. Since silica contains a large number of polar silanol groups on the surface, the interaction between silica is very strong, resulting in poor dispersion of silica in rubber. Although many studies have reported that functional modification of polymers can be used to improve the dispersibility of silica itself. However, it is still necessary to use silane coupling agents to overcome the polarity difference between silica and rubber. Silane coupling agents can strongly affect the interaction between silica and silica, and silica and rubber, and can significantly improve the physical properties and processing properties of silica reinforced rubber. However, due to the high affinity of silica for metal molds, rubber compositions filled with a high proportion of silica are prone to stick to the extruder roller during processing and to stick to the mold during vulcanization. At the same time, the silane coupling agent and white carbon black require a certain temperature and silanization reaction time for the silanization reaction. If the silanization reaction is not sufficient, the white carbon black will be poorly dispersed and more likely to stick to metal. However, there is a lack of a fast and accurate test method for evaluating the affinity between the rubber composition and the metal mold.

[0004] The Chinese invention patent (publication number: CN107246927B, publication date: 2020.01.31) discloses a plastic demoulding force test mold and method thereof, which solves the problem of a mold that can perform a complete and comprehensive test on plastic particles, and causes certain difficulties in evaluating the demoulding properties of plastic particles. The key points of its technical solution are that the ejection device includes an ejection plate and an ejector pin, and an ejector pin groove for the ejector pin to penetrate is provided on the bottom plate of the fixed mold. The two opposite side plates of the fixed mold are pivoted with the bottom plate so that they can be turned outward by 0.2°~5° to form their corresponding demoulding angles, and are fixed by corresponding fixing devices. The bottom plate and side wall inside the fixed mold are provided with pressure sensors, and also include a pressure terminal, and the detection signal of the pressure sensor is processed by a processing unit. It is achieved that two opposite side plates of the fixed mold can be pivoted outward to achieve different demoulding slopes, and the angle change is fast and convenient, which greatly saves the cycle of adjusting the demoulding angle for comprehensive detection, and can obtain comprehensive and accurate data. Summary of the invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a method for testing the demoulding force value between a rubber composition and a metal mold. The method can quickly and accurately test the demoulding force value between the rubber composition and the metal mold.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions: A method for testing the demoulding force between a rubber composition and a metal mold, the method using a rheometer for testing, the testing method comprising the following steps: 1) Preparation before the test: clean the rubber composition with a thickness of D, clean and install the metal fixture, and then preheat the metal fixture to reach the first vulcanization temperature T1; the rubber composition is a sheet product of an open mill, and the surface is flat; the metal fixture includes an upper fixture and a lower fixture, and the surfaces of the upper fixture and the lower fixture are provided with grid needle tips; 2) Rubber vulcanization: install the rubber composition between the upper fixture and the lower fixture, control the sinking amount of the upper fixture to be H, wherein H<D; keep the rubber composition at a first vulcanization temperature T1 for 5 min; then continue to heat the sample at a temperature rise rate T to heat the sample to a second vulcanization temperature T2, and keep the temperature at the second vulcanization temperature T2 for 10 min; 3) Demolding force measurement: At the second vulcanization temperature T2, lift the upper fixture at a constant speed V, set the lifting time S, and measure the force.

[0007] Preferably, the rheometer is ARES-G2.

[0008] Preferably, H=0.5mm±0.02mm, D=2mm±0.2mm, V=0.04-0.06mm / s, S=20s; preferably, H=0.5mm, D=2mm, V=0.05mm / s.

[0009] Preferably, the rubber composition is washed with acetone.

[0010] Preferably, the metal fixture is cleaned with acetone.

[0011] Preferably, the metal clamp is made of steel or aluminum.

[0012] Preferably, the metal clamp is a disc; preferably, the diameter of the disc is 8 mm.

[0013] Preferably, T1=95-105°C, T2=170-180°C, and T=45-55°C / min.

[0014] Preferably, T1=100°C, T2=174°C, and T=50°C / min.

[0015] Preferably, the test method further includes performing a frequency scan on the sample under the first vulcanization temperature T1, with a scanning range of 200rad / s-0.2rad / s and a strain setting of 0.2%; and performing a frequency scan on the sample under the second vulcanization temperature T2, with a scanning frequency of 62.8rad / s and a strain setting of 0.2%.

[0016] The testing method provided by the present invention is convenient and quick, can accurately measure the demoulding force value between the rubber composition and the metal mold, is helpful to guide the development of the formula and processing technology of the rubber composition, and ensures smooth demoulding of the rubber composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The demolding force curves of different tread rubber compositions (a: sample 1, b: sample 2, c: sample 3, d: sample 4). DETAILED DESCRIPTION

[0018] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Example 1 The demoulding force values ​​of four tread rubber compositions were tested by the method provided by the present invention.

[0020] Sample 1: 70 phr white carbon black filled high-performance tread rubber composition, silanization reaction time controlled at 240 s; Sample 2: 50phr white carbon black filled extreme cold snow tire tread rubber composition, silanization reaction time controlled at 240s; Sample 3: 130phr white carbon black filled high-performance tread rubber composition, silanization reaction time controlled at 240s; Sample 4: The rubber composition formula is the same as that of Sample 3, and the silanization reaction time is controlled at 100s.

[0021] The above samples are all products produced by an open mixing mill, with a flat surface, a thickness of D=2mm, and are cut into square films with a side length of 10mm.

[0022] ARES-G2 equipment is used for testing. The test steps are as follows: 1) Preparation before testing: Use acetone to clean the sample and metal fixture, then install the metal fixture, and then preheat the metal fixture to 100°C; 2) Rubber vulcanization: Install the sample between the upper fixture and the lower fixture, and control the sinking amount of the upper fixture to be 0.5mm; keep the sample at a constant temperature of 100℃ for 5 minutes, and then perform a frequency scan on the sample at 100℃, with a scanning range of 200rad / s-0.2rad / s and a strain setting of 0.2%; then continue to heat the sample at a temperature rise rate of 50℃ / min, heat the sample to 174℃ and keep the temperature constant for 10 minutes, and then perform a frequency scan on the sample at 174℃, with a scanning frequency of 62.8rad / s and a strain setting of 0.2%; 3) Demolding force measurement: At 174°C, lift the upper fixture at a constant speed of 0.05 mm / s, set the lifting time to 20 seconds, and measure the force.

[0023] The results are as follows Figure 1 As shown, sample 1 (curve a) is a high-performance tire tread with a medium filling ratio, and its demolding force value with the mold is lower than that of the other three samples, and its demolding time is in the middle; sample 2 (curve b) is a tread for extreme cold snow tires, showing a low demolding force value, but a longer demolding time and more difficult to detach, which is consistent with its low hardness and high elongation characteristics; sample 3 (curve c) is a high-performance tire tread with a high filling ratio, and its demolding force value with the mold is greatly increased; sample 4 (curve d) has a greater demolding force value with the mold than sample 3 due to the less sufficient silanization reaction. In view of the above results being consistent with the actual demolding conditions of the samples, this method can effectively evaluate the demolding force value between the rubber composition and the metal mold.

[0024] The above is a description of the embodiments of the present invention. Through the above description of the disclosed embodiments, professionals and technicians in the field can implement or use the present invention. Various modifications to these embodiments will be apparent to professionals and technicians in the field. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown in this article, but will conform to the widest range consistent with the principles and novelties disclosed herein.

Claims

1. A method for testing the demoulding force between a rubber composition and a metal mold, characterized in that: The method uses a rheometer for testing, and the testing method includes the following steps: 1) Preparation before the test: clean the rubber composition with a thickness of D, clean and install the metal fixture, and then preheat the metal fixture to reach the first vulcanization temperature T1; the rubber composition is a sheet product of an open mill, and the surface is flat; the metal fixture includes an upper fixture and a lower fixture, and the surfaces of the upper fixture and the lower fixture are provided with grid needle tips; 2) Rubber vulcanization: install the rubber composition between the upper fixture and the lower fixture, control the sinking amount of the upper fixture to be H, wherein H<D; keep the rubber composition at a first vulcanization temperature T1 for 5 min; then continue to heat the sample at a temperature rise rate T to heat the sample to a second vulcanization temperature T2, and keep the temperature at the second vulcanization temperature T2 for 10 min; 3) Demolding force measurement: At the second vulcanization temperature T2, lift the upper fixture at a constant speed V, set the lifting time S, and measure the force.

2. The testing method according to claim 1, characterized in that: The rheometer is ARES-G2.

3. The testing method according to claim 1, characterized in that: The H=0.5mm±0.02mm, D=2mm±0.2mm, V=0.04-0.06mm / s, S=20s; preferably, H=0.5mm, D=2mm, V=0.05mm / s.

4. The testing method according to claim 1, characterized in that: The rubber composition was cleaned with acetone.

5. The testing method according to claim 1, characterized in that: The metal fixtures were cleaned with acetone.

6. The testing method according to claim 1, characterized in that: The material of the metal clamp is steel or aluminum.

7. The testing method according to claim 1, characterized in that: The metal fixture is in the form of a disc; preferably, the diameter of the disc is 8 mm.

8. The testing method according to claim 1, characterized in that: The T1=95-105°C, T2=170-180°C, and T=45-55°C / min.

9. The testing method according to claim 1, characterized in that: The T1=100°C, T2=174°C, and T=50°C / min.

10. The testing method according to claim 1, characterized in that: The test method also includes performing a frequency scan on the sample under a first vulcanization temperature T1, with a scanning range of 200 rad / s-0.2 rad / s and a strain setting of 0.2%; and performing a frequency scan on the sample under a second vulcanization temperature T2, with a scanning frequency of 62.8 rad / s and a strain setting of 0.2%.

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