A method for determining the vulcanization time of thick rubber products based on the vulcanization effect method

Abstract

This invention belongs to the technical field of rubber product vulcanization molding process, specifically relating to a method for determining the vulcanization time of thick rubber products based on the vulcanization effect method, including the following steps: S1, calculating the vulcanization effect E at the center of the thick rubber product. 厚 S2, Calculate the vulcanization effect E of the rubber specimen. 片 Select the vulcanization time T so that E 厚 =E 片 The vulcanization time for the determined thick rubber product is obtained; where Δτ is the time interval for temperature measurement, and I... i Let t be the i-th interval time and temperature. i vulcanization strength, P i E is the correction factor for the degree of vulcanization. 片 =Iτ, where t is the temperature at which the temperature rise curve at the center of the thick rubber product stabilizes, K is the vulcanization temperature coefficient at the stable temperature, and τ is the positive vulcanization time t90 of the rubber sample at the stable temperature. This invention is simple and eliminates the defects of traditional vulcanization effect methods in theoretically calculating the vulcanization time of thick products.

Description

Technical Field

[0001] This invention belongs to the technical field of rubber product vulcanization molding process, specifically relating to a method for determining the vulcanization time of thick rubber products based on the vulcanization effect method. Background Technology

[0002] Vulcanization time, vulcanization temperature, and vulcanization pressure are the three most important process parameters in the vulcanization process of rubber products. For a given vulcanization temperature and pressure, the rationality of the vulcanization time is one of the most important factors affecting the performance of the rubber product. Excessive time leads to over-vulcanization, while insufficient time leads to under-vulcanization, both of which degrade product performance. For rubber products thicker than 6mm, the vulcanization time can be set using engineering experience, vulcanization effect methods, and vulcanization simulation methods. Among these, the vulcanization effect method is a relatively accurate way to determine the vulcanization time for thick rubber products. For the vulcanization time of thick rubber products, the time-temperature rise curve at the center layer of the thick product is usually tested using the pre-embedded thermocouple method. Then, based on the theoretical calculation of the temperature rise curve, it is determined that the vulcanization effect at the center layer is within the vulcanization plateau region of the rubber sample.

[0003] The traditional vulcanization effect method assumes that the degree of vulcanization of rubber is equal under different vulcanization conditions. However, in reality, the final degree of crosslinking of various rubbers, such as silicone rubber (SIR), chloroprene rubber (CR), and natural rubber (NR), varies with temperature. This difference lies in… Figure 3-5 The research data and Fang Yuesheng's "Research on the Vulcanization Effect of Thick Rubber Products after Vulcanization" from South China University of Technology both reflect this. This leads to certain defects in the traditional vulcanization effect method. In particular, for large marine vibration isolators, sound-absorbing plates, bearing strips, and engineering vehicle tires, the longer the vulcanization time, the greater the deviation between the vulcanization time calculated according to the vulcanization effect method and the optimal vulcanization time. Summary of the Invention

[0004] To reduce the deviation caused by the difference in crosslinking degree of various rubbers due to vulcanization temperature, which leads to the deviation of the traditional vulcanization effect method in calculating the optimal vulcanization time for thick rubber products, this invention provides a method for determining the vulcanization time of thick rubber products based on the vulcanization effect method. This invention introduces a vulcanization correction coefficient, which eliminates the error of the vulcanization effect method caused by the different vulcanization degree at different temperatures, resulting in higher accuracy and helping to improve the vulcanization process level of thick rubber products.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0006] A method for determining the vulcanization time of thick rubber products based on the vulcanization effect includes the following steps:

[0007] S1. Calculate the vulcanization effect E at the center of a thick rubber product. 厚 ,

[0008] S2. Calculate the vulcanization effect E of the rubber specimen. 片 Select the vulcanization time T so that E 厚 =E 片 This allows us to determine the vulcanization time for thick rubber products.

[0009]

[0010] Where Δτ is the time interval for temperature measurement, ranging from 1 to 5 minutes; I i Let t be the i-th interval time and temperature. i The sulfidation intensity, i∈[1,n-1], K i For temperature point t i The vulcanization temperature coefficient is given by I0, where I0 is the vulcanization intensity at the start of vulcanization at temperature t0, and I1 is the vulcanization intensity at the first interval time and temperature t1. n The last interval time and temperature is t. n vulcanization strength; P i Let t be the i-th interval time and temperature. i The sulfidation degree correction factor is given, where P0 is the sulfidation degree correction factor at the start of sulfidation and temperature t0, and P1 is the sulfidation degree correction factor at the first interval and temperature t1. n The last interval time and temperature is t. n The correction factor for the degree of sulfidation;

[0011] E 片 =Iτ

[0012] Where I represents the vulcanization strength, The vulcanization effect E of rubber test pieces 片 The calculation is based on the temperature at which the temperature rise curve at the center of the rubber thick product stabilizes, using the thermocouple method as the reference. t is the temperature (°C) corresponding to the temperature rise curve stabilizing, K is the vulcanization temperature coefficient at the stable temperature, and τ is the positive vulcanization time t90 (min) of the rubber sample at the stable temperature.

[0013] Compared with the traditional vulcanization effect method, this invention introduces a vulcanization correction coefficient P, which eliminates the error in calculating vulcanization time caused by vulcanization temperature in the vulcanization effect method.

[0014] The temperature at which the temperature stabilizes during the thermocouple heating curve is chosen as the benchmark. This is because the theoretical vulcanization effect differs at different temperatures. Furthermore, when the vulcanization time of a thick product is too short, the vulcanization effect at the center layer of the thick product is lower than that of the rubber sample at the stable temperature, resulting in a certain amount of vulcanizing agent remaining in the product and causing under-vulcanization.

[0015] Furthermore, a vulcanizing instrument was used to test the vulcanization curves of thick rubber products at different vulcanization temperature points between 100 and 170°C. The vulcanization temperature points were set in a gradient of 2 to 5°C, and the temperature t at each temperature point was recorded. i The corresponding theoretical positive vulcanization time t90 and maximum torque MH i and minimum torque ML i .

[0016] Furthermore, according to van der Hoff's law, t is calculated for each test temperature point. i vulcanization temperature coefficient K i And perform vulcanization temperature coefficient K i Multiple fittings were performed, simultaneously satisfying the coefficient of determination R. 2 ≥85%;

[0017]

[0018] Where, τ i The temperature is t i The positive vulcanization time t90, min; τ i+1 The temperature is t i+1 The normal vulcanization time is t90 min.

[0019] The higher the fitting order, the better R. 2 The closer the value is to 1, the better the correlation of the parameters and the lower the calculation error. Of course, test points above the temperature at which the center layer of the thick product stabilizes can also be omitted, resulting in a smaller deviation when fitting the vulcanization coefficient K.

[0020] Furthermore, calculate t at each test temperature point. i Degree of sulfidation △M i And perform vulcanization to a degree ΔM i Multiple fittings were performed, simultaneously satisfying the coefficient of determination R. 2 ≥85%, the degree of vulcanization ΔM at the temperature at which the temperature rise curve of the center layer of the thick rubber product stabilizes. 稳定 As a benchmark, with As a correction factor for the degree of sulfidation, P i ;

[0021] ΔM i =MH i -ML i

[0022] Among them, MH i The temperature is t i The highest torque in the vulcanization curve, Nm; ML i The temperature is t i The lowest torque in the vulcanization curve, Nm.

[0023] The higher the fitting order for the degree of vulcanization, the higher the R value. 2 The closer the value is to 1, the better the correlation of the parameters and the lower the calculation error. Of course, test points above the temperature at which the center layer of the thick product stabilizes can also be omitted, so that the deviation is smaller when fitting the degree of crosslinking ΔM.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] When using the traditional vulcanization effect method to calculate the vulcanization time of thick rubber products, it is usually necessary to test different vulcanization temperature curves of rubber samples in order to fit and calculate the vulcanization temperature coefficient K of the rubber material at different temperatures. This invention directly uses the difference between MH and ML values ​​in the vulcanization curve to characterize the degree of vulcanization ΔM of the material. Taking the temperature of the thick rubber product under stable temperature as the benchmark, a vulcanization degree correction coefficient P is added. The method is simple and eliminates the defects of the traditional vulcanization effect method in theoretically calculating the vulcanization time of thick products. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is the temperature rise curve of the rubber in the center layer of the NR / BR thick product in Application Example 1;

[0028] Figure 2 Example 2 shows the temperature rise curve of the rubber in the center layer of a thick silicone rubber product.

[0029] Figure 3 These are graphs showing the vulcanization characteristics of silicone rubber at different vulcanization temperatures;

[0030] Figure 4 These are graphs showing the vulcanization characteristics of chloroprene rubber at different vulcanization temperatures;

[0031] Figure 5 This is a diagram showing the vulcanization characteristics of natural rubber at different vulcanization temperatures. Detailed Implementation

[0032] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0033] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0034] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0035] Example 1:

[0036] A method for determining the vulcanization time of thick rubber products based on the vulcanization effect includes the following steps:

[0037] S1. Calculate the vulcanization effect E at the center of a thick rubber product. 厚 ,

[0038] S2. Calculate the vulcanization effect E of the rubber specimen. 片 Select the vulcanization time T so that E 厚 =E 片 This allows us to determine the vulcanization time for thick rubber products.

[0039]

[0040] Where Δτ is the time interval for temperature measurement, ranging from 1 to 5 minutes; I i Let t be the i-th interval time and temperature. i The sulfidation intensity, i∈[1,n-1], K i For temperature point t i The vulcanization temperature coefficient is given by I0, where I0 is the vulcanization intensity at the start of vulcanization at temperature t0, and I1 is the vulcanization intensity at the first interval time and temperature t1. n The last interval time and temperature is t. n vulcanization strength; P i Let t be the i-th interval time and temperature. i The sulfidation degree correction factor is given, where P0 is the sulfidation degree correction factor at the start of sulfidation and temperature t0, and P1 is the sulfidation degree correction factor at the first interval and temperature t1. n The last interval time and temperature is t. n The correction factor for the degree of sulfidation;

[0041] E 片 =Iτ

[0042] Where I represents the vulcanization strength, The vulcanization effect E of rubber test pieces 片The calculation is based on the temperature at which the temperature rise curve at the center of the rubber thick product stabilizes, using the thermocouple method as the reference. t is the temperature (°C) corresponding to the temperature rise curve stabilizing, K is the vulcanization temperature coefficient at the stable temperature, and τ is the positive vulcanization time t90 (min) of the rubber sample at the stable temperature.

[0043] Specifically, a vulcanizing instrument was used to test the vulcanization curves of thick rubber products at different vulcanization temperature points between 100 and 170°C. The vulcanization temperature points were set in a gradient of 2 to 5°C, and the temperature t at each temperature point was recorded. i The corresponding theoretical positive vulcanization time t90 and maximum torque MH i and minimum torque ML i .

[0044] Furthermore, according to van der Hoff's law, t is calculated for each test temperature point. i vulcanization temperature coefficient K i And perform vulcanization temperature coefficient K i Multiple fittings were performed, simultaneously satisfying the coefficient of determination R. 2 ≥85%;

[0045]

[0046] Where, τ i The temperature is t i The positive vulcanization time t90, min; τ i+1 The temperature is t i+1 The normal vulcanization time is t90 min.

[0047] Furthermore, calculate t at each test temperature point. i Degree of sulfidation △M i And perform vulcanization to a degree ΔM i Multiple fittings were performed, simultaneously satisfying the coefficient of determination R. 2 ≥85%, the degree of vulcanization ΔM at the temperature at which the temperature rise curve of the center layer of the thick rubber product stabilizes. 稳定 As a benchmark, with As a correction factor for the degree of sulfidation, P i ;

[0048] ΔM i =MH i -ML i

[0049] Among them, MH i The temperature is t i The highest torque in the vulcanization curve, Nm; ML i The temperature is t i The lowest torque in the vulcanization curve, Nm.

[0050] In the above method, In P n K n The calculation methods all refer to I i P i K i The calculation method.

[0051] This invention uses the thermocouple method to test the time T and temperature t of thick rubber products. i t at each temperature point i The corresponding vulcanization temperature coefficient K i and vulcanization temperature correction factor P i The corrected vulcanization effect E value at each temperature point was calculated using software such as Excel and MATLAB. A suitable vulcanization time T was then selected to maximize E. 厚 =E 片 .

[0052] The above method for determining the vulcanization time of thick rubber products based on the vulcanization effect is specifically applied to thick natural rubber products and thick silicone rubber products.

[0053] Application Example 1:

[0054] A thick natural rubber product was vulcanized and molded at temperatures ranging from 100℃ to 170℃ in 5℃ increments. The vulcanization curves of this rubber formulation at different temperature points were tested, as shown in Table 1. Based on ML and MH in Table 1, the degree of crosslinking at different temperatures was calculated and fitted to satisfy the following quartic equation, where R... 2 =92.67%

[0055] y = 2.64933931 * 10 -6 x 4 -0.0014155x 3 +0.27701314x 2 -23.50031343x+744.2613

[0056] Based on the t90 positive vulcanization time in Table 1, the vulcanization coefficient K at different temperatures is calculated and fitted to satisfy the following fourth-order equation, where R... 2 =85.91%

[0057] y = -6.77313429 * 10 -7 x 4 +3.67586007*10 -4 x 3 -0.07421592x 2 +6.59032317x-214.3127

[0058] The temperature rise curve of the rubber in the center layer of thick natural rubber products was tested using the thermocouple method, as shown below. Figure 1 As shown, the time interval Δτ = 2 min. The vulcanization effect E of the rubber specimen was theoretically calculated using the formula. 片 Equals 581.58; In an Excel spreadsheet, display the time T, temperature t, and degree of sulfidation ΔM at each temperature point in the heating curve. i , correction factor P for degree of sulfidation i Vulcanization temperature coefficient K i Vulcanization strength I i Sulfidation effect E 厚 Calculate separately when E 厚 =E 片 When the vulcanization time is calculated, the vulcanization time for the thick product is 380.79 minutes; if the vulcanization correction factor P is not considered... i That is, when using the traditional sulfur effect method for calculation, when E 厚 =E 片 When the vulcanization time of the thick product was 369.86 minutes, the difference between the two was approximately 11 minutes. Vulcanization times of 380.79 minutes and 369.86 minutes were used for the thick products of the high-damping seismic isolation bearings for bridges. The swelling indices of the rubber at the center layer and the rubber specimens were then tested. The results were 3.352, 3.379, and 3.256, respectively. The swelling indices of the traditional vulcanization effect method, the modified vulcanization effect method, and the standard specimen differed by 0.81% and -2.86%, respectively. The HG / T 3870-2008 standard allows a relative error within ±1.5%, so the swelling index of the modified vulcanization effect method is within the allowable deviation range and is more reasonable. However, the cross-linking degree of the rubber in the thick products vulcanized using the traditional vulcanization effect method did not reach the optimal vulcanization state.

[0059] Table 1. Vulcanization curves of NR / BR thick product formulations

[0060] vulcanization temperature ML MH t90 / min 100 3.22 17.07 770.58 105 3.12 17.33 483.26 110 3.07 17.8 295.65 115 2.98 19.04 178.78 120 2.91 19.16 111.37 125 2.6 19.49 68.84 130 2.3 20.68 45.00 135 2.2 20.04 31.10 140 2.18 19.13 21.01 145 2.05 18.59 14.25 150 1.83 17.21 9.60 155 1.85 17.29 6.50 160 1.87 15.92 4.70 165 1.77 15.56 3.54 170 1.63 14.68 2.70

[0061] Application Example 2:

[0062] Thick silicone rubber products were vulcanized at temperatures ranging from 100℃ to 170℃ in 5℃ increments, and the vulcanization curves of the rubber formulation at different temperature points were tested, as shown in Table 2 below. Based on ML and MH in Table 2, the degree of crosslinking at different temperatures was calculated and fitted to satisfy the following fourth-order equation, where R... 2 =98.80%

[0063] y = -4.78634163 * 10 -7 x 4 +2.93154755*10 -4 x 3 -0.06750356x 2 +6.91510739x-256.8962

[0064] Based on the t90 positive vulcanization time in Table 2, the vulcanization coefficient K at different temperatures is calculated and fitted to satisfy the following quartic equation, with R² = 92.13%:

[0065] y = 2.58208170 * 10 -6 x 4 -0.00143038x 3 +0.29359168x 2 -26.43220813x+882.2358

[0066] The temperature rise curve of the rubber in the center layer of thick silicone rubber products was tested using the thermocouple method, as shown below. Figure 2 As shown, the time interval Δτ = 2 min. The vulcanization effect E of the rubber specimen was theoretically calculated using the formula. 片 Equals 6754.88; In the Excel spreadsheet, display the temperature T and t in the heating curve, along with the degree of sulfidation ΔM at each temperature point. i , correction factor P for degree of sulfidation i Vulcanization temperature coefficient K i Vulcanization strength I i Sulfidation effect at different temperatures E 厚 List or calculate respectively when E 厚 =E 片 At that time, the vulcanization time for thick products is 183.52 minutes. If the vulcanization correction factor P is not considered... i When using the traditional sulfurization effect method for calculation, when E 厚 =E 片 The vulcanization time for the thick product was 179.51 minutes, a difference of approximately 4 minutes. A thick silicone product was vulcanized using both the traditional vulcanization effect method and the modified vulcanization effect method. The swelling index of the rubber at the center layer and the rubber sample were measured. The results were 3.155, 3.220, and 3.207, respectively. The swelling indexes of the traditional vulcanization effect method, the modified vulcanization effect method, and the standard sample differed by -1.62% and 0.41%, respectively. According to the HG / T3870-2008 standard, the swelling index of the modified vulcanization effect method is within the allowable deviation range, indicating that it is more reasonable.

[0067] Table 2. Vulcanization curves of silicone rubber thick products formulation

[0068] vulcanization temperature ML MH T90 100 1.135 6.005 1140.46 105 1.085 7.172 779.15 110 1.063 8.259 665.6 115 1.054 8.758 561.55 120 1.042 9.255 419.84 125 0.998 9.586 293.55 130 0.987 9.328 197.68 135 0.752 9.42 118.51 140 0.942 9.696 66.36 145 0.933 9.668 38.50 150 0.904 9.663 21.6 155 0.886 9.419 12.93 160 0.845 9.254 8.60 165 0.855 9.269 5.65 170 0.89 9.265 3.58

Claims

1. A method for determining the vulcanization time of thick rubber products based on the vulcanization effect method, characterized in that, Includes the following steps: S1, calculating the vulcanization effect E at the center of the thick rubber article 厚 , S2. Calculate the vulcanization effect E of the rubber specimen. 片 Select the vulcanization time T so that E 厚 =E 片 This allows us to determine the vulcanization time for thick rubber products. ； in, The time interval for temperature measurement ranges from 1 to 5 minutes; i Let t be the i-th interval time and temperature. i vulcanization strength, , K i For temperature point t i The vulcanization temperature coefficient is given by I0, where I0 is the vulcanization intensity at the start of vulcanization at temperature t0, and I1 is the vulcanization intensity at the first interval time and temperature t1. n The last interval time and temperature is t. n vulcanization strength; P i Let t be the i-th interval time and temperature. i The sulfidation degree correction factor is given, where P0 is the sulfidation degree correction factor at the start of sulfidation and temperature t0, and P1 is the sulfidation degree correction factor at the first interval and temperature t1. n The last interval time and temperature is t. n The correction factor for the degree of sulfidation; ； Where I represents the vulcanization strength, The vulcanization effect E of rubber test pieces 片 The calculation is based on the temperature at which the temperature rise curve at the center of a thick rubber product stabilizes, determined by the thermocouple method. t is taken as the temperature corresponding to the stable temperature of the temperature rise curve, and K is taken as the vulcanization temperature coefficient at the stable temperature. The normal vulcanization time t90 of rubber specimens at a constant temperature; The vulcanization curves of thick rubber products at different vulcanization temperatures between 100 and 170°C were tested using a vulcanizer. The vulcanization temperatures were set in a gradient of 2 to 5°C, and the temperature t at each temperature point was recorded. i The corresponding theoretical positive vulcanization time t90 and maximum torque MH i and minimum torque ML i ; Calculate t at each test temperature point i Degree of sulfidation △M i And perform vulcanization to a degree ΔM i Multiple fittings were performed, simultaneously satisfying the coefficient of determination R. 2 ≥85%, the degree of vulcanization at the temperature at which the temperature rise curve of the center layer of a thick rubber product stabilizes. As a benchmark, with As a correction factor for the degree of sulfidation, P i ; ； Among them, MH i The temperature is t i The highest torque in the vulcanization curve, ML i The temperature is t i The lowest torque in the vulcanization curve.

2. The method for determining the vulcanization time of thick rubber products based on the vulcanization effect method according to claim 1, characterized in that, Calculate t at each test temperature point according to van der Hoff's law. i vulcanization temperature coefficient K i And perform vulcanization temperature coefficient K i Multiple fittings were performed, simultaneously satisfying the coefficient of determination R. 2 ≥85%; ； in, The degree is t i The positive vulcanization time is t90. Temperature t i+1 The positive vulcanization time is t90.

Images