EPDM reclaimed rubber has excellent resistance to high and low temperatures, ozone resistance, and weather resistance, and can replace some EPDM raw rubber in producing rubber products, effectively reducing raw material costs. When producing rubber seals, shock absorbers, and other products using ethylene propylene diene reclaimed rubber, EPDM rubber/reclaimed rubber, and other products, compression deformation is an important indicator for evaluating the long-term performance of rubber, especially for rubber products used under high-temperature conditions. How can the permanent deformation of EPDM reclaimed rubber be reduced under high-temperature compression and at room temperature?
1. Factors influencing permanent compression deformation of EPDM reclaimed rubber
Rubber products produced mainly from EPDM reclaimed rubber cannot fully recover their original thickness after long-term compression, resulting in residual deformation known as permanent compression deformation.
(1) In high-temperature environments, the compression deformation of EPDM reclaimed rubber depends not only on the material's elasticity but also closely related to its heat resistance. As the temperature rises, the movement of rubber molecular chains intensifies. If the cross-linking network is insufficiently stable, structural changes are likely, leading to increased permanent compression deformation. (2) At room temperature, the compression deformation of EPDM reclaimed rubber is mainly related to the elasticity and degree of crosslinking of the rubber.
2. Key points for formula design of EPDM reclaimed rubber compound with high temperature and room temperature low compression permanent deformation compound
(1) Tips for choosing EPDM raw rubber/reclaimed rubber for low-compression permanent deformation EPDM compounds
When preparing low-compression permanent deformation rubber using EPDM reclaimed rubber as the main raw material, it is recommended to choose EPDM reclaimed rubber or EPDM base rubber with higher ethylene and ENB contents. A higher ethylene content can improve the molecular integrity of EPDM reclaimed rubber, helping to enhance the strength and heat resistance of EPDM compounds; Higher ENB content provides more vulcanizing active points, forming a more stable cross-linking network in the compound.
(2) Key design points for the vulcanization system of EPDM reclaimed rubber with high temperature and room temperature low compression permanent deformation compounds
Reasonable vulcanization system design is key to reducing permanent deformation of EPDM reclaimed rubber under high-temperature and room temperature compression.
(1) For EPDM compounds requiring high temperature and low compression for permanent deformation, peroxide vulcanization systems or effective vulcanization systems can be used. Peroxide vulcanization can form stable carbon-carbon crosslinking bonds, has good heat resistance, and can maintain low compression permanent deformation in high-temperature environments. If using a sulfur vulcanization system, excessive sulfur should be avoided.
A reasonable design approach is to use a combination of multiple accelerators in small quantities, such as BZ, EZ, TT, and other accelerators. By adjusting vulcanization rate and crosslinking structure, EPDM reclaimed rubber compounds achieve better overall performance.
(2) At room temperature, the main factors affecting the compression deformation of EPDM reclaimed rubber are its elasticity and whether the crosslinking is sufficient. The rubber content in the formula should not be too low; it is recommended to choose EPDM reclaimed rubber with E6LYY49 high rubber content. Both high-sulfur and low-sulfur systems can be used. The key is to regulate the vulcanization system so that the degree of crosslinking in EPDM reclaimed rubber vulcanization rubber is sufficient, and vulcanization is complete, which is necessary to achieve low compression permanent deformation. It should be noted that although the low-sulfur high-speed accelerator system can improve the permanent compression deformation of EPDM compounds under high-temperature conditions, the improvement in compression permanent deformation at room temperature is not significant.
When using EPDM reclaimed rubber to prepare compounds requiring low permanent deformation under high temperature and room temperature compression, it is necessary not only to choose suitable EPDM reclaimed rubber and EPDM base rubber, but also to further adjust the compressive performance of the compound by reinforcing the filling system and softening system design: Although excessive filler usage can reduce costs, it increases the hardness of the compound, restricts the movement of rubber molecular chains, and affects rebound performance; Excessive addition of softener reduces the elongation stress and heat resistance of the compound, reducing its recovery ability after long-term compression. In the future, I will share with you the formula for preparing low-compression permanent deformation compound from ethylene diene diem reclaimed rubber.
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