Heat-resistant rubber gaskets are mainly used for equipment and pipelines working in high-temperature environments, and play a good role in sealing and buffering. EPDM rubber has excellent high temperature resistance, ozone resistance, weather resistance, electrical insulation, etc., and is an ideal raw material for the production of heat-resistant rubber gaskets. In actual production, due to the high price of EPDM rubber, many heat-resistant rubber gasket manufacturers began to use EPDM reclaimed rubber.
1. Performance requirements for heat-resistant rubber gaskets
(1) Mechanical properties
Heat-resistant rubber gaskets require the rubber compound to have a certain tensile strength, and it will not break easily when pulled by external force; The hardness of the rubber material is required to be appropriate, and the gasket can better fill the gap when sealing to prevent the leakage of the medium; The rubber material is required to have high tear strength, and the gasket with low tear strength is easy to crack at the sharp corners when the plate is assembled and disassembled or under pressure, especially the non-adhesive gasket; The lower the compression set rate of the compound, the better the elastic recovery ability, and the more beneficial it is to the sealing performance and service life of the heat-resistant rubber gasket.
(2) Aging performance
The rubber compound used for the production of heat-resistant rubber gaskets needs to have good heat resistance, and the chemical structure and properties should remain stable in a high-temperature environment, and the performance will not be greatly reduced due to decomposition, excessive cross-linking or other chemical reactions caused by heating; Good medium resistance to prevent the gasket from expanding, dissolving, aging and other effects on sealing performance caused by medium erosion. Under the combined action of high temperature and other environmental factors, the rubber compound should have good aging resistance, slow down the aging rate, and prolong the service life of the gasket.
2. The advantages of using EPDM reclaimed rubber for heat-resistant rubber gaskets
EPDM reclaimed rubber is made of EPDM head glue, unvulcanized EPDM rubber and waste EPDM rubber products as raw materials, which retains the basic performance characteristics of EPDM rubber, excellent high temperature E4LYY1211 resistance and aging resistance, and the price is much lower than EPDM original rubber, which can be used alone or combined with EPDM rubber to produce heat-resistant rubber sealing gaskets, effectively reducing the cost of raw materials; Compared with pure EPDM rubber, the heat-resistant rubber gasket mixed with EPDM reclaimed rubber is more stable in size and shape.
3. EPDM rubber/EPDM reclaimed rubber produces heat-resistant rubber gasket vulcanization formula
70 parts of EPDM rubber, 30 parts of EPDM reclaimed rubber, 1 part of antioxidant MB, 35 parts of carbon black N330, 20 parts of mixed carbon black, 10 parts of reinforcing silica, 7 parts of cumene peroxide, 2 parts of crosslinking additive HVA-2; 175 copies.
4. EPDM rubber/EPDM reclaimed rubber production of heat-resistant rubber gasket formula design
(1) Vulcanization system: effective vulcanization system or peroxide system (such as cumene peroxide DCP) is used for vulcanization with low sulfur dosage, and EPDM rubber/reclaimed rubber vulcanized rubber has better heat resistance.
(2) Reinforcing filling system: When high wear-resistant carbon black is used for reinforcing with high wear resistance, an appropriate amount of semi-reinforcing carbon black, fast-pressing furnace black, gas-mixed carbon black and inorganic fillers (such as silica, zinc oxide, magnesium oxide) balance the relationship among the mechanical strength and aging resistance of EPDM. Excessive reinforcing properties of carbon black will lead to a decrease in the elongation of EPDM reclaimed rubber vulcanized rubber during aging, which will affect the thermal and oxidative aging resistance.
(3) Softening system: The selection and dosage of softener have an important impact on the heat resistance of EPDM rubber/EPDM reclaimed rubber. Softeners with low molecular weight or poor compatibility with rubber will reduce heat resistance, and it is recommended to use softeners with high flash point paraffin oil, liquid ethylene propylene rubber or polybutylene that are resistant to high temperature aging; Avoid using softeners that are easy to migrate and volatile at high temperatures.
(4) Anti-aging system: use heat-resistant anti-aging dosage form antioxidant to inhibit thermal and oxidative aging, such as RD, BLE, 264 and other free radical scavengers, and a small amount of MB combined with the effect is better.
When using EPDM reclaimed rubber to reduce the production cost of heat-resistant rubber gaskets, it is not only necessary to select the appropriate EPDM reclaimed rubber and reasonably design the heat-resistant rubber sealing gasket formula containing reclaimed rubber, but also to strictly control the production process, especially the mixing and vulcanization process.
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