| Nitrile-buladiene rubber (NBR), which has excellent characters of oil, heat and corrosion resistance, is a very important kind of industrial materials and has large dosage. NBR seals are widely used in machinery, electronics, transportation, petrochemical, metallurgical, aviation, and so on. With the improving of the properties of mechatronic equipments, the properties of rubber seals are increasingly stringent required under bad conditions of high speed, high-low temperature, deep-etching, and so on. In order to improve the working abilities of seals, the necessary properties of the rubber seals, such as mechanical properties, spring and oil resistance, should be considered, the wear-resistant and antifriction properties of materials must be improved farthest, the storage life and working life of the rubber seals should be mastered, and the evaluating indicators of the rubber materials for sealing should be understood, which could compare the development level of each property in different materials or different properties in same material, so that the most suitable rubber material for working conditions is finally chosen.Based on the summary of early study on Fe3O4 magnetic nitrile-buladiene rubber of which the mass percent of Fe3O4 particles is controlled at 0%16%, and the investigation of the actual and new progress about oversea and domestic rubber seals, in this research topics, application of nanometer technique in nitrile-buladiene rubber was put forward, because the nano-particles possess some unique advantages, such as small size, big specific surface area, different shape between the surface and the inside particle, defective coordination of surface atoms, strong surface active. Then nano-SrOˇ6Fe2O3 magnetic nitrile-buladiene rubber (nano-SrOˇ6Fe2O3 MNBR) was prepared through dry process.The test results show that the friction coefficient of the NBR added a few unmodified nano-SrOˇ6Fe2O3 particles would have certain reduction, and reached the minimum at 10%. After that, the friction coefficient of the samples would be evidently lager than the NBR by increasing the mass percent of nano-SrOˇ6Fe2O3 particles. And because the mass percent of nano-SrOˇ6Fe2O3 was different, the wearied forms of the rubber materials were different. The wear forms of materials were changed from the ploughing and adhesive wear to the adhesive and fatigue flake. When the mass percent of nano-SrOˇ6Fe2O3 exceeded 15%, the wear-resistant and antifriction effect was unconspicuous because a large number of magnetic particles was in the reunion. The abrasion loss had the same variation. However, the friction coefficient and abrasion loss of the NBR added modified nano-SrOˇ6Fe2O3 particles would be reduced by a large margin, and the friction coefficient reached the minimum 0.2069 at 10%. Why did this phenomena appear? First, the modified nano-SrOˇ6Fe2O3 particles not only existed in individual steadily, but also had a strong affinity with NBR, which uniformly scattered themselves on the NBR; secondly, each particle could still remain strong surface energy and surface active; thirdly, such magnetic particles was propitious to strengthen NBR, and then the compounded rubber could form a physisorption film on the surface of rubbing pair that had self-repairing capability, which played a role in wear-resistant and antifriction effect.This research topics did accelerated thermal-oxygen aging test for nano-SrOˇ6Fe2O3 MNBR. Through theoretical derivation and mathematical computation of the Arrhenius equation and the relational expression between performance changes and aging time of polymer materials, two kinds of evolution were obtained. One was the relational expression among the three factors which are elongation retention, period of storage and storage temperature in the storage temperature for magnetic rubber sealing materials; the other was the relational expression among the three factors which are compression set, period of storage and storage temperature in the storage temperature for magnetic rubber seals. Then the predictive equation between performance and time in the storage temperature was established, and the storage life and working life of the sealing materials was forecasted. Compare these two forecast results of life, it can be found that dynamic seals of nano-SrOˇ6Fe2O3 MNBR had lower friction coefficient, and static seals of nano-SrOˇ6Fe2O3 MNBR had longer life. From discussion, it can be known that the aging of rubber materials played a pivotal role in the working life of static seals, and the friction coefficient between rubber materials and metal surfaces played a pivotal role in the working life of dynamic seals.In this research topics, according to the characteristics of use and evaluation of rubber materials for sealing, the construction flow of evaluation index system was established, the purposes of evaluation were defined, and the contents of evaluation, such as constitution, basic performance status, friction and wear, aging, special features, and use economy, was analysed. Based on the principles of scientific, simple and effective, universal, qualitative and quantitative, and continuity, and considering the functions of evaluation, monitoring, guidance, and decision-making, the evaluation index system was established. Through the case study, it can be known that the evaluation index system could compare the development level of each property in different materials or different properties in same material, so that the purpose of evaluation making rubber materials for sealing achieve scientific and reasonable development could be realized.A kind of shaft seal composite structure adopting nano-SrOˇ6Fe2O3 MNBR was designed in this research topics. This structure had not only lower friction coefficient and abrasion loss, but also better self-repairing and self-sealing capability, which enhanced the sealing capability effectively. The simulation and experimental results showed that the posterior lib angle played an important role for the stability of oil seal. The value of the posterior lib angle should be smaller as the pressure of system was higher. The value of the posterior lib angle should be larger as the pressure of system was lower. At last, the applications and classified information of nano-SrOˇ6Fe2O3 MNBR in sealing structure was simply discussed. |
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