EPDM reclaimed rubber has excellent resistance to high and low temperatures, ozone resistance, and weather resistance, and is widely used in the production of various rubber O-rings, effectively reducing raw material costs. When producing O-ring rubber seals using EPDM reclaimed rubber, the permanent compression deformation of the O-ring directly determines the seal's lifespan; Rationally designing the rubber O-ring formula not only meets the low-pressure variation requirements of the sealing ring but also reduces raw material costs, making it suitable for sealing in more mid- to high-end operating conditions.
1. Tips for selecting EPDM base rubber and recycled rubber for low-pressure deformable O-rings
When producing low-compression permanent deformation O-rings using reclaimed EPDM rubber or raw rubber, it is recommended to choose high-mony, low-ethylene EPDM rubber, which offers better heat resistance and resilience; EPDM reclaimed rubber with high EPDM content, < ash content of 10%, and Mooney viscosity of 45-65 ML (1+4) at 100°C was selected, and each batch of reclaimed rubber was sampled for tensile strength, elongation at break, hardness, and Mooney resin. The ratio of reclaimed rubber to raw rubber is determined according to the specific requirements of the rubber O-ring.
2. Key design points for the vulcanization system of low-pressure transformer rubber O-rings for producing EPDM reclaimed rubber
When producing low-compression deformation rubber O-rings using EPDM reclaimed rubber as the main raw material, a peroxide vulcanization system is often chosen, commonly DCP/BIPB at dosages of 1.5-2.5 parts, generally slightly less than pure EPDM raw rubber formulations by 0.1-0.3 parts; co-crosslinking agents TAIC/TAC are used in 1-2 parts, which promote the formation of more stable C–C crosslinking bonds in peroxides and significantly reduce permanent compression deformation.
3. Key design points for the low-pressure transformer rubber O-ring reinforcement system for producing EPDM reclaimed rubber
When producing low-pressure modified rubber O-rings with EPDM reclaimed rubber, general-purpose carbon black such as N660 can be used for reinforcement, which has good dispersibility and improves the elasticity of the rubber compound, with a dosage of 30-50 parts. Combined with a small amount of fast-pressed black E6LYY16, it has good dispersibility, strong elasticity of the compound, and a smooth surface, with a dosage of 8-10 parts. Reasonably control the amount of reinforcing agent in the O-ring of EPDM reclaimed rubber. Too much reinforcing agent can cause the compound to harden, while too little can loosen the colloid structure and make it difficult to meet low-pressure variation standards.
4. Key design points for the low-pressure transformer rubber O-ring softening system for producing EPDM reclaimed rubber
Rubber softener is a key factor affecting the compression permanent deformation of EPDM reclaimed rubber, and the amount of softener used is positively correlated with compression deformation. When producing rubber O-rings with EPDM reclaimed rubber, it is best to avoid using softeners as much as possible; If softeners must be used, it is recommended to choose paraffin oil with a high flash point and low volatility, and keep the dosage below 5 parts; For the strictly required low-voltage variable EPDM reclaimed rubber O-rings, it is recommended to control the amount among 0-3 parts.
5. Key design points for the anti-aging system of low-pressure transformer rubber O-rings in the production of EPDM reclaimed rubber
Proper use of antioxidants can further improve the aging resistance of low-pressure O-rings produced by EPDM reclaimed rubber. Common anti-aging agents RD or 2246 are used in 1.0-1.5 parts; adding 0.3-0.5 parts of heat-resistant stabilizer helps suppress volatilization and migration, ensuring long-term stability and relaxation of vulcanization networks.
When producing low-pressure variable rubber O-rings with different hardness using EPDM reclaimed rubber, the formulation needs to be appropriately adjusted. It is recommended to first adjust the packing system, then adjust the co-linking agent, and finally determine the peroxide dosage. Peroxide is recommended to be added last during the low-temperature remixing stage to prevent early cross-linking that could cause local scorching or uneven networking; If necessary, two-stage vulcanization can be performed to further improve the compound's compression permanent deformation, volatile components, and odors.
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