EPDM recycled rubber retains the basic performance characteristics of EPDM rubber, with excellent high and low temperature resistance, weather resistance and ozone resistance, and is widely used in the production of automotive seals, building waterproof membranes, shock absorbing materials and outdoor equipment seals. These rubber products are subject to mechanical stress, environmental aging, and frequent deformation during use, so there are strict requirements for the tear resistance of EPDM recycled adhesives. How to improve the tear strength of EPDM recycled adhesive?
1. EPDM compound choose skills for EPDM recycled rubber products with high tear strength
When using EPDM recycled rubber to produce rubber products with high tear strength, it is recommended to choose EPDM recycled rubber with high glue content, and vulcanized rubber has better tear strength. If necessary, it can be used with a small amount of EPDM rubber with high Mooney viscosity E5LYY1113 and high ethylene content to appropriately increase the glue content and improve the tear strength of EPDM recycled rubber.
2. Design skills of vulcanization system of EPDM recycled rubber products with high tear strength
The cross-linking bond type and cross-linking density of EPDM recycled vulcanized adhesive directly affect the tear strength.
(1) The cross-linked bonds generated by the effective vulcanization system or the high-promotion and low-sulfur system are mainly single and disulfide bonds, the cross-linking network structure is stable, and the tear strength of EPDM recycled adhesive vulcanized adhesive is high. The amount of sulfur should be controlled at 0.5-1.5 parts, and the autumn rams and thiazoles should be used together.
(2) The carbon-carbon cross-linked bond generated by the peroxide vulcanization system has high bond energy and good thermal stability, and the EPDM recycled adhesive vulcanized adhesive has excellent heat resistance and tear strength. The mixed vulcanization system of peroxide and less than 0.3 parts of sulfur can take into account the tear strength and heat resistance, and is suitable for EPDM recycled rubber products under medium and low temperature working conditions with high tear strength requirements.
To improve the tear strength of EPDM recycled adhesive, it is also necessary to reasonably control the degree of vulcanization. Insufficient vulcanization degree of EPDM recycled adhesive will lead to low cross-linking density and poor tear strength. If the degree of vulcanization is too high, the molecular chain will be over-crosslinked, the network rigidity will increase, and the tearing performance will be reduced. In actual production, EPDM recycled rubber products need to determine the optimal vulcanization time according to the thickness and formula composition of the product to avoid undersulfur or persulfurization.
3. Design skills of EPDM recycled rubber products with high tear strength
Reasonable choose of reinforcing agents and fillers is an effective way to improve the tear strength of EPDM recycled adhesives.
(1) High structure carbon black forms a reinforcing network in EPDM recycled adhesive, which effectively hinders crack propagation and improves the tear strength of recycled rubber, and high wear resistance carbon black N330 is commonly used. The processing performance of high-structure carbon black is slightly poor, and the thinning time needs to be appropriately extended during compounding.
(2) Add an appropriate amount of silica or hard terracotta to improve the tear strength and hardness of EPDM recycled adhesive vulcanized adhesive; It is recommended to control the amount of silica below 30 parts, as excessive dosage will not only increase the cost, but also affect the processing process of the compound.
(3) An appropriate amount of ultra-fine PTFE powder is added to the formula of EPDM recycled adhesive to effectively improve the tear strength and wear resistance of recycled vulcanized adhesive. Ultrafine PTFE powder has excellent self-lubrication and chemical stability, and it is recommended to use ultrafine PTFE powder when using EPDM recycled rubber to produce seals and shock absorbing parts.
(4) The directional arrangement of staple fibers in EPDM recycled adhesive can effectively hinder the direction of crack propagation, so the reasonable use of staple fiber can significantly improve the tear strength of EPDM recycled adhesive, and attention should be paid to the dispersion uniformity of the fiber and the impact on processing performance during use.
4. Design skills of EPDM recycled rubber products with high tear strength
When using EPDM recycled rubber to produce rubber products with high tear strength, it is recommended to use paraffin oil, which has good compatibility with EPDM recycled rubber, is not easy to extract and volatile, and has little impact on the performance of vulcanized rubber. The choice of high-cleanliness paraffin oil can also reduce the adverse effects of impurities on the tearing properties of EPDM recycled adhesives; Strictly control the amount of softener, generally controlled within 20 parts, too much will dilute the rubber molecules, reduce the cross-linking density, and reduce the tear strength of EPDM recycled rubber.
When using EPDM recycled rubber to produce rubber products with high tear strength requirements, it is also necessary to reasonably set the mixing process parameters, such as the mixing temperature: the temperature of the front roller is controlled at 50-60 °C when mixing in the open machine, the temperature of the rear roller is controlled at 45-55 °C, and the discharging temperature of the mixer is controlled below 130 °C; Too high the mixing temperature will lead to scorching of the compound and degradation of molecular chains, which will affect the tear strength of EPDM vulcanized rubber. Do you have any other ways to improve the tear strength of EPDM recycled adhesives?
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