The rubber seal is an indispensable basic element in various sealing devices. The sealing effect is directly related to the compression set of the rubber used. The smaller the compression set, the better the sealing effect; among them, nitrile rubber or butyl Nitrile reclaimed rubber is the main raw material processed seals with excellent oil resistance and excellent sealing effect in oil medium for a long time; then what are the factors related to the compression set of nitrile rubber, and how to reduce its compression Permanent deformation to improve the sealing effect of nitrile seals?
1. Choose nitrile rubber/recycled rubber with suitable acrylonitrile content
It is well known that the higher the acrylonitrile content of nitrile rubber or nitrile reclaimed rubber, the greater the oil resistance coefficient and the better the oil resistance, but the high acrylonitrile content of the nitrile rubber main chain tends to be more thermoplastic acrylonitrile blocks, resulting in more The elasticity of the nitrile rubber decreases and the compression set increases, that is, the higher the acrylonitrile content, the greater the compression set of the nitrile rubber/recycled rubber; therefore, the rubber product manufacturer must select the rubber used for the oil-resistant seal. Comprehensive consideration, do not blindly choose high acrylonitrile nitrile rubber.
2. Use peroxide curing
When using a nitrile rubber/recycled rubber to produce a rubber seal, the compression set of the nitrile rubber is directly related to the vulcanization crosslink bond, the crosslink bond energy is high, and the rubber compression set is small; the peroxide vulcanization system and the nitrile When the rubber is co-heated to form an alkoxy radical, the alkoxy radical addition reaction is taken to take the α-methylene active hydrogen on the polymer chain for cross-linking reaction, and a CC cross-linking bond is formed during the reaction. The bond energy is high, and the vulcanized nitrile rubber has a small compression set; if the sulfur vulcanization system must be used, it is necessary to appropriately reduce the amount of sulfur, and the control is between 0.3 and 0.5 parts.
3. Select the appropriate accelerator according to the type of vulcanizing agent
The vulcanized rubber after peroxide vulcanization has good compressive deformation at high temperature, good heat resistance and good extraction resistance, but its mechanical strength is not high, so more manufacturers of nitrile seals are willing to DCP and sulfur. Used together, but sulfur will cause the compression set of the nitrile rubber/recycled rubber seal to rise. At this time, the accelerator is needed. The use of the accelerator TMTD and the accelerator DPG can significantly reduce the compression set of the nitrile rubber. The effect of adding a small amount of accelerator DTDM during use can further reduce the compression set of the nitrile rubber/recycled vulcanizate and improve the sealing performance of the nitrile seal.
In addition, when using nitrile rubber/recycled rubber to produce oil-resistant seals, the type and amount of reinforcing filler, anti-aging agent and plasticizer will also affect the compression set of nitrile rubber, but the effect is not great. The characteristics of various compounding agents are selected according to the characteristics, and the compression permanent deformation of the nitrile rubber/recycled rubber seal is reduced, the sealing effect is improved, and the service life is prolonged.