Fuzhou University Journal (Natural Science Edition) Study on Vulcanization Crosslinking Temperature and Mechanical Properties of Low Elastic Shock Absorbing Foam Materials Liu Canpei (College of Chemistry and Materials, Fujian Normal University, Fuzhou 350007, China) Blend (SIBC/BR). Under certain temperature and pressure, foaming with dicumyl peroxide (DCP) and foaming agent (AD) foaming to obtain a low elastic closed-cell foaming material with elasticity less than 12%. The blending ratio was studied. The effect of temperature on mechanical properties was studied by a torque vulcanizer. The preferred vulcanization temperature is 433~443K, and the optimum temperature of 438K vulcanization index (Cri) can be used as an indicator to determine the vulcanization temperature. Scanning electron microscopy (EM) was used to characterize the morphology of the pores in the material profile.
The elasticity of the closed-cell foamed elastomer material can reach more than 45%, and the foaming material has a strong rebound effect on the external force. Wu et al. 3 obtained a crosslinked foamed material by melt blending a styrene-based resin and a crosslinked polyolefin in the presence of a phase compatibilizer and a foaming agent.
Vulcanization cross-linking and foaming mold specifications (length X width X thickness) is 1 250mmX650mmX25mm. Vulcanization cross-linking and foaming temperature range is 433~ 458IK pressure is 17.6MPa, when the temperature is 438K, vulcanization cross-linking and foaming The time is 40min. 1.3 The mechanical property test is 438K, the pressure is 6.86MPa, the heating time is 9min, the cooling is 20C7 water, the cooling time is 9min. The test of vulcanization cross-linking curve, using EKT-2000 type rotorless torque vulcanizer (Taiwan æ™”China Science and Technology Co., Ltd.) Analytical characterization of the pore structure of the high cavity foam material in the cavity. After the sample was subjected to gold spray on the surface, it was scanned with an XL30ESEM type (PHILIP) electron scanning microscope.
The mechanical properties were tested according to the method specified in the paper.
In order to overcome the influence of different materials in the process, the mechanical properties of the materials are different, and the samples are sampled and tested in 6 different positions and in different directions. The average value is taken as the mechanical properties. result.
The hardness (H) was measured by a Durometer C type hardness meter (Japan Polymer Co., Ltd.). The elastic (E) test was performed using a Frank type elastic meter (Loss Corporation). Tensile strength (p-stretch), tear strength (Y tear), peel strength (7 peel), and elongation at break (t) were tested using a GT-7010-A2 microcomputer tension machine (High Speed ​​Rail). Density (P) was tested using a 125A microcomputer densitometer (Song Sho).
Compression deformation (c-set) test, using GT-7017M constant temperature oven and GT-7490 5mm interval compression plate compression deformation instrument (high-speed rail company). The sample is a cylinder (2.54 cm in diameter, thickness h0 is 10.00±0.20 mm), the compression ratio is 50%, placed in an oven at 50±2 ° C, taken out after 6 h and placed at 23±2 ° C for 30 min. , measure its thickness h, accurate to 0.01mm, calculated by the following formula: 2 Results and discussion 2.1 Mechanical properties of the material SIBC and BR are arranged according to different mass ratios, vulcanization cross-linking and foaming at 438K. The material formulation and its mechanical properties are listed in Table 1. The mechanical properties of the low-elastic shock-absorbing foaming materials of different formulations are shown in Table 1. The L-house tensile zMPa from the data in Table 1 shows that compared with the standard values, when the SIBC and BR quality When the ratio is 70/30, the obtained low elastic shock absorbing foam material has the best mechanical properties. When the mass ratio of SIBC to BR is as low as 60/40 or less, it is too soft, the shrinkage rate is increased, the elasticity is increased, and the shock absorbing effect is deteriorated; when it is more than 80/20 or more, the peeling strength is deteriorated and becomes stiff. When the hardness at 5 ° C exceeds 75 Asker C, the shock absorbing effect is deteriorated. Therefore, the mass ratio of SIBC to BR was determined to be 70/30. The effect of vulcanization cross-linking temperature (T) on the mechanical properties of the material was investigated at this mass ratio.
2.2 Vulcanization cross-linking curve is a vulcanization cross-linking curve of vulcanization cross-linking torque (M) with time at different vulcanization cross-linking temperatures. The vulcanization cross-linking parameter can be directly measured by the torque vulcanizer, that is, the process positive vulcanization time (C90)16. It can be seen that the torque at the late stage of the vulcanization cross-linking curve below 443K does not decrease substantially; The latent torque of the vulcanization cross-linking curve has decreased, showing over-vulcanization.
2.3 Vulcanization index (Cri) and temperature relationship 100 / that is, the torque rising in the process of the curing time is divided into 100 parts, Cri is the vulcanization cross-linking process in the process of the vulcanization cross-linking process The number of vulcanized cross-linking curves. The larger the Cri, the greater the rate of vulcanization crosslinking. According to the measurement of Fig 1 Cg obtained tC90 and the calculated Cri are listed in Table 2. Table 2 process positive curing time tC90 and calculation result CriTab. As shown, Cri increases with the vulcanization crosslinking temperature increase, when it exceeds 443K Cri is rising very fast. Within 433~ 458K, according to. The results show that as the vulcanization cross-linking temperature increases, the foaming effect is also strengthened and the hardness gradually softens. This is because the gas decomposed by the blowing agent swells more at high temperatures and shrinks after cold cooling. As a result, the pores inside the foamed material become larger, the volume increases, the hardness decreases, and the density also decreases (see Table 3). 2.4.2 Effect of vulcanization cross-linking temperature on elongation at break 2.4.3 Effect of vulcanization cross-linking temperature on compressive deformation, tensile, tearing and peeling strength Compressive deformation gradually decreases with increasing vulcanization cross-linking temperature, but the temperature After more than 448K, the compression deformation increases with the increase of vulcanization crosslinking temperature. Between 438 and 448K, the lowest point of compression deformation occurs, ie 29%. As shown, the peel strength increases almost linearly with temperature. When the tear strength increases with temperature, it drops gently between 433 and 443K, but after 448K, it drops rapidly, and the tensile strength shows a maximum at 438K, and then decreases almost linearly. . Therefore, from the three mechanical properties, the suitable vulcanization crosslinking temperature is between 433 and 443K.
2.4.4 Effect of vulcanization cross-linking temperature on elasticity As the vulcanization cross-linking temperature increases, the elasticity tends to rise as shown. Throughout, the heat shrinkage rate is extremely low in the range of 438 ~ 448K, and the heat shrinkage rate below 438K rises sharply with the decrease of the vulcanization crosslinking temperature, which is caused by insufficient vulcanization crosslinking; After 448K, the heat shrinkage rate gradually increases, which indicates that as the vulcanization crosslinking temperature increases, the degree of crosslinking increases and the foaming effect also increases, resulting in a decrease in the heat resistance of the material.
At the same time as the rising, the foaming effect is also strengthening. When the temperature is higher than 448K, the vulcanization crosslinking reaction is different from the vulcanization crosslinking reaction lower than 443K. In the high-temperature vulcanization cross-linking curve, such as 448 ~ 458K, the late torque has a downward trend, showing over-vulcanization. Since AD ​​is mainly composed of azodicarbonamide and contains a certain amount of N,N-dinitrosopentamethylenetetramine, its decomposition temperature is 132~138 ° C. When heated, it is based on The first phase of the gas generated by the decomposition of free radicals is 60 s. When the temperature exceeds 448 K, the half-life is about 20 s or even shorter. In this system, the free radicals generated by DCP and AD act simultaneously to initiate the vulcanization cross-linking reaction, causing the vulcanization cross-linking reaction to deepen. When the temperature exceeds 448K, the gas generated by AD causes the material to foam rapidly and even locally expands rapidly. The result of these two effects leads to over-vulcanization, and cracked pores appear locally in the material, resulting in poor mechanical properties.
In summary, the mechanical properties of the low-elastic shock-absorbing foamed material at the sulfation cross-linking temperature of 438 K are the best. When the vulcanization cross-linking temperature exceeds 448K, since there is still a certain amount of C=C double bond in the molecule of SIBC, the vulcanization cross-linking rate is increased at high temperature, which leads to an increase in vulcanization cross-linking density, or other factors such as degradation, resulting in materials. There are cracked pores inside, and there is 1101 vulcanization, which shows tear, peeling, tensile strength and elongation at break. When the temperature is 433K, the rate of vulcanization crosslinking reaction of SIBC/BR at a lower temperature is too slow, showing insufficient vulcanization, and the compression deformation and shrinkage are too large. Therefore, the suitable vulcanization temperature range is 433 ~ 443K, and the optimum vulcanization temperature is 438K. 2.5 Material profile Pore morphology The SEM image of the stomatal morphology of the low elastic shock absorbing foam material is shown. It can be seen that the pore diameter (25~40/%!) and the wall thickness (2~3/%i) of the low elastic shock absorbing foam material are uniform and fine. The thermodynamic compatibility between SIBC and BR is still relatively good. It also shows that because the polarity of BR is larger than that of SIBC, the polarity of SIBC/BR obtained after blending SIBC and BR is larger than that of SIBC, which is beneficial to The dispersion of AD in the blend results in a foamed material with finer uniform pores, which is also beneficial to the improvement of mechanical properties.
3 Conclusion The mass ratio of SIBC to BR is the best at 70/30, the suitable vulcanization crosslinking temperature is 433 ~ 443K, and the optimum temperature is 438K. The low elastic shock absorbing foam material prepared by it has excellent mechanical properties. And better shock absorption capacity, in line with adidas shoe material standards.
Cri increases with the increase of vulcanization cross-linking temperature. When the temperature exceeds a certain range, Cri rises extremely fast and an inflection point appears, which can be used as the boundary of over-vulcanization crosslinking temperature. Therefore, the vulcanization index Cri is suitable from 0.26 to 0.30, and can be used as a technical index for determining the correct vulcanization crosslinking temperature.
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