EPDM reclaimed rubber has excellent high and low temperature resistance, aging resistance, ozone resistance, and weather resistance, and is widely used in the production of various rubber sealing products, such as automobile door and window seals, building door and window seals, radiator seals, etc. In order to ensure the reliability of EPDM rubber sealing products for long-term sealing, strict requirements are put forward for the compression set performance of EPDM reclaimed rubber compounds. Today, Xiaobian will share with you the key points of the formula design of EPDM reclaimed rubber for the preparation of low-compression permanent shape rubber.
1. Design of vulcanization system of EPDM reclaimed rubber
(1) Key points of EPDM reclaimed rubber with low compression set rubber peroxide vulcanization system
When using EPDM reclaimed rubber to prepare rubber with low compression set, the vulcanization system used needs to form a stable cross-linking network, and the carbon-carbon cross-linking bond formed by the peroxide vulcanization system is more stable, and the compression permanent deformation of the obtained rubber material is the smallest. Appropriately increasing the amount of peroxide in the EPDM reclaimed rubber vulcanization system or combining with appropriate cross-linking additives (such as TAC, TAIC, HVA-2, etc.) can further improve the density of cross-linking and further reduce the compression set.
When peroxide vulcanization, when the filling amount of EPDM reclaimed rubber compound is large (the glue content is low), the degree of cross-linking of the rubber compound is generally low, the resilience is poor, and the compression set is generally large, so it must be compensated by increasing the amount of peroxide. It should be noted that when the peroxide is cross-linked at a relatively deep level, attention should be paid to the influence on the tear strength of the rubber compound, especially the poor thermal tear strength makes the product easy to tear when demolding, and will affect the performance of the product at high temperature.
Therefore, in order to obtain a low compression set, it is necessary to maintain a high glue content of the rubber as much as possible.
(2) Key points of sulfur vulcanization system of EPDM reclaimed rubber with low compression set
When EPDM reclaimed rubber selects sulfur vulcanization system, it is necessary to use an effective vulcanization system or sulfur delivery system with a low sulfur dosage (about 0.5 parts), and a large number of accelerators and accelerators that can release active sulfur (such as DTDM, TRA, TT, etc.) to form more stable monosulfur or disulfide bonds, which can effectively avoid the shortcomings of easy slippage and poor heat resistance and stability of polysulfur cross-linked bonds, and the compression and permanent deformation of EPDM reclaimed rubber vulcanized rubber is lower.
2. Design of EPDM reclaimed rubber filling system
When using EPDM reclaimed rubber as the main raw material to prepare low-compression set rubber compounds, it is recommended to use medium-reinforcing or low-reinforcing carbon black in the reinforcing filling system, such as fast-pressed carbon black, semi-reinforcing carbon black, medium particle thermal cracking carbon black, etc.; Reasonably control the amount of carbon black, improve the resilience of EPDM reclaimed rubber compound, and reduce the compression and permanent deformation of rubber compound. When EPDM reclaimed rubber 2SLYY1127 is used to prepare black rubber compound, some inorganic fillers, such as calcium carbonate, talcum powder, etc., will not affect the compression and permanent deformation of the rubber material; The use of silica or hard clay as a reinforcing filler will affect the vulcanization of the rubber compound, and the impact on the compression set is often greater.
3. Design of EPDM reclaimed rubber softening system
When EPDM reclaimed rubber is prepared with low compression set rubber, it is recommended to use high boiling point and low volatile paraffin oil as the main softening system, and appropriately reduce the amount of softener. In actual production, the softener will affect the vulcanization of peroxide and reduce the efficiency of cross-linking of reclaimed rubber; At the same time, the softener enters the macromolecular gap, which affects the formation of cross-linking bonds and reduces the cross-linking density of the cross-linking network, so that the compression set of the rubber compound increases. In addition, the volatilization of the softener at high temperatures also increases the shrinkage of the product, resulting in an increased compression set.
4. EPDM reclaimed rubber anti-aging system design
The low compression set rubber of EPDM reclaimed rubber needs to be combined with paraffin heat-resistant antioxidant to improve the heat resistance of the rubber without affecting the vulcanization of the rubber compound, and then improve the low compression set performance of the rubber compound.
When using EPDM reclaimed rubber to produce rubber products with strict requirements for compression set, rubber products enterprises also need to select EPDM reclaimed rubber with appropriate indicators, reasonably determine the mixing ratio of reclaimed rubber, and use it with a small amount of butyl rubber and butyl reclaimed rubber if necessary. The editor will continue to discuss related issues with you in the future.
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