Effect of bisphenol vulcanization system on the properties of fluorine rubber

Thread Content

Effect of bisphenol vulcanization system on the performance of fluorine rubber. Fluorine rubber contains fluorine atoms on the main chain or side chain carbon atoms, which makes it resistant to high temperatures, chemical media and aging. It is widely used in aviation, aerospace, automobiles, ships, petroleum and other fields. The traditional diamine vulcanizing agent of fluorine rubber (such as No. 3 vulcanizing agent) has a slow vulcanization speed, good adhesion to metal, high hot tensile strength, and large high-temperature compression permanent deformation. ； Dihydroxy compounds (such as bisphenol AF) developed to improve high-temperature compression permanent deformation not only reduce high-temperature compression permanent deformation, but also have a fast vulcanization speed. It has good scorch safety. This work studies the influence of variable test of vulcanizing agent bisphenol AF and accelerator BPP vulcanizing system on the vulcanization characteristics and physical properties of fluorine rubber. 1 Test 1.1 Raw material fluorine rubber 2603 vinylidene fluoride, hexafluoropropylene copolymer, broad molecular weight distribution, product of Shanghai Sanaifu New Materials Co., Ltd. ； Activated magnesium oxide, product of Shanghai Dunhuang Chemical Factory ； Spray carbon black, product of Fushun Chemical Factory ； Calcium hydroxide, product of Shanghai Jinshan Caojing Chemical Factory, bisphenol AF (hexafluoroisopropylidene-bis(4-hydroxybenzene)), product of Shanghai Sanaifu New Materials Co., Ltd. ； BPP (benzyltriphenylphosphonium chloride), product of Dalian Institute of Chemical Physics. 1.2 Formula The test formula is shown in Table 1. basic recipe: Fluorine rubber 2603, 100 ； Activated magnesium oxide, 4 ； Spray carbon black, 15 ； Calcium hydroxide, 6. 1.3 Test instrument XK-160 open mill (Shanghai Rubber Machinery Factory) ； 50 t flat plate vulcanizing machine (Qingdao Machine Tool Factory) ； MDR2000 rheometer (Monsanto Company, USA) ； Tensile testing machine (Shimadzu Co., Ltd., Japan) ； Aging box (Suzuki Manufacturing Co., Ltd., Japan). 1.4 Sample preparation and rubber mixing are all carried out on the XK-160 open mill. ； The vulcanization characteristics of the rubber compound were tested on the MDR200O rheometer ； The sample was molded and vulcanized in one stage at 180℃x10 min, and in the second stage vulcanized at 200℃x24 min. 1.5 Performance test physical properties according to the corresponding * * Tested by standard test methods. The test temperature is 170℃. 2 Discussion of results 2.1 Vulcanization performance of the rubber compound 2.1.1 Effect of the dosage of bisphenol AF on the vulcanization characteristics The dosage and ratio of bisphenol AF and BPP are the key to the vulcanization system. It not only affects the vulcanization speed and scorch safety of the rubber compound, but also affects the tensile properties, heat resistance, and compression permanent deformation properties of the rubber compound. Therefore, this test adopts a two-factor and three-level orthogonal test plan. It can be seen from Figure 1 that when the amount of BPP is the same, as the amount of bisphenol AF increases, the vulcanization curve moves parallel to the right, prolonging the scorch time and increasing the scorch safety. ； The torque of the vulcanization curve increases one by one, indicating that the vulcanization cross-linking density increases with the amount of bisphenol AF. ； At the same time, when the amount of BPP is the same, the scorch time increases with the amount of bisphenol AF, indicating that the scorch time not only shortens with the increase in the amount of accelerator, but is also related to the amount of vulcanizing agent. The scorch time increases with the increase in the amount of vulcanizing agent. 2.1.2 The influence of the dosage of BPP on the vulcanization characteristics. It can be seen from Figure 2 that when the dosage of bisphenol AF is the same, the dosage of BPP increases and the vulcanization curve moves parallel to the left, indicating that the scorch time and positive vulcanization time are shortened, and the vulcanization speed is accelerated. ； When the amount of bisphenol AF is the same, as the amount of BPP increases, the torque of the vulcanization curve does not increase or decrease, indicating that increasing the amount of BPP does not affect the torque of the rubber compound. 2.2 Effect of the vulcanization system on the physical properties of fluorine rubber 2.2.1 Effect of the dosage of bisphenol AF on the physical properties Taking formulas No. 4, 5, and 6 as an example, the dosage of BPP is 0.6 parts. It can be seen from Figure 3 that when the dosage of accelerator is constant, as the dosage of bisphenol AF increases from 1.5 parts to 3.5 parts, the hardness of the rubber increases from 67 to 74 ； Rubber elongation reduced from 340% to 180% ； The tensile strength increased slightly from 13.9 MPa to 14.3 MPa. ； The tear strength decreased from 23.2 kN·m to 18.3 kN·m. This fully demonstrates that the degree of chemical cross-linking between bisphenol AF and fluororubber molecules is increasing, that is, the cross-linking density or degree of vulcanization is increasing. 2.2.2 The effect of BPP amount on the physical properties of fluororubber. Taking formulas No. 2, 5, and 8 as an example, the amount of bisphenol AF is 2.5 parts. As can be seen from Figure 4, when the amount of bisphenol AF is constant, as the amount of BPP increases from 0.4 parts to 0.8 parts, the hardness of the rubber increases by 2 to 3 parts. ； The increase or decrease in rubber elongation is not obvious ； There is a slight increase in tensile strength and tear strength. This shows that the function of BPP is only to shorten the vulcanization scorch time and speed up the vulcanization reaction. It does not conduct substantial chemical cross-linking with fluororubber. It is a veritable vulcanization accelerator. 2.2.3 The influence of bisphenol AF dosage on thermal aging performance. The dosage of accelerator BPP in formulas 1-3, 4-6, and 7-9 is fixed respectively. It can be seen from Figure 5 to Figure 7 that as the dosage of bisphenol AF increases, the hardness change after thermal aging will increase, and the tensile strength will increase by 10% to 30%. ； However, within the dosage range of bisphenol AF, the change trend of tensile strength is not obvious, which shows that as the dosage of bisphenol AF increases, the thermal aging process is the continued cross-linking of bisphenol AF and fluororubber molecules, the hardness increases, and the tensile strength increases. ； The elongation change rate decreases with the increase in the amount of bisphenol AF. This is because as the amount of bisphenol AF increases, the elongation before heat aging decreases, and the elongation change rate after heat aging decreases relatively. 2.2.4 Effect of BPP dosage on thermal aging performance When the dosage of bisphenol AF is constant, it can be seen from Figure 9-Figure 1 that as the dosage of accelerator BPP increases, the hardness after thermal aging increases with the increase in BPP dosage. The elongation change rate fluctuates within 20%, and the tensile strength change rate fluctuates within 30%, and is less affected by BPP variables. 2.2.5 Effect of bisphenol AF dosage on compression permanent deformation Taking formulas 4, 5, and 6 as examples, it can be seen from Figure 8 that when the BPP dosage is constant, as the bisphenol AF dosage increases, the compression permanent deformation decreases, which is due to the increase in the degree of cross-linking. 2.2.6 The effect of the amount of BPP on the compression permanent deformation. Taking formulas 2, 5, and 8 as examples, it can be seen from Figure 12 that when the amount of bisphenol AF is constant, the compression permanent deformation increases with the increase in the amount of BPP, which is worth noting. 3 Conclusion a. When the dosage of vulcanizing agent bisphenol AF is constant, the dosage of BPP increases, the scorch time shortens, the torque remains unchanged, and the positive vulcanization time shortens. b. When the dosage of accelerator BPP is constant, the dosage of bisphenol AF increases, the scorch time increases, the torque increases, and the positive vulcanization time increases. c. When the dosage of vulcanizing agent bisphenol AF increases, the hardness and tensile strength of the rubber compound increase, while the tear strength and elongation at break decrease. On the contrary, when the amount of bisphenol AF decreases, the hardness and tensile strength of the rubber material decrease, and the tear strength and elongation at break increase. d. When the amount of accelerator BPP increases, the hardness of the rubber increases, the elongation of the rubber does not increase or decrease significantly, and the tensile strength and tear strength increase slightly. e. As the dosage of vulcanizing agent bisphenol AF increases, the hardness and tensile strength after thermal aging will increase, while the change rate of elongation and compression permanent deformation will decrease. When the amount of accelerator BPP increases, the hardness and tensile strength after thermal aging will increase, as will the change rate of elongation and compression permanent deformation. f. By adjusting the dosage and ratio of the vulcanizing agent bisphenol AF and the accelerator BPP, the scorch time, normal vulcanization time of the rubber compound, as well as the elongation, tensile strength, tear strength, compression permanent deformation and thermal aging performance of the vulcanized rubber can be effectively adjusted to meet the required expectations. This post was last edited by eastchen on 2009-4-7 10:07 ]