How to design the formula of recycled rubber products with high tear strength The tearing of rubber is caused by the rapid expansion and cracking of cracks and cracks in the material when stressed, which is an important indicator to measure the performance of rubber products. When using reclaimed rubber to produce rubber products with high requirements for tear strength, it is necessary to reasonably design the rubber product formula, especially the vulcanization system and reinforcing system.
1. Design of vulcanization system for recycled rubber products with high tear strength
When producing rubber products with high tear strength, it is necessary to design a reasonable vulcanization system, and the appropriate cross-linking density and cross-linking bond type can give the reclaimed rubber a high tear strength. The tear strength increases with the increase of cross-linking density, and after reaching the maximum, the tear strength of reclaimed rubber decreases with the continuous increase of cross-linking density. In general, the vulcanization time (degree of vulcanization) should be less than the correct vulcanization time of the process, and the tear strength will be reduced by pervulcanization, and the effective vulcanization system will be much less than that of the conventional vulcanization system.
(1) The sulfur-containing cross-linked bond has high tear strength. When peroxide vulcanization is used in reclaimed rubber products, a small amount of sulfur (0.1-0.5 parts) can be combined to improve the tear strength of reclaimed rubber vulcanized rubber. In actual production, the tear strength of the sulfur vulcanization system of styrene-butadiene rubber/reclaimed rubber is 2-3 times that of the peroxide vulcanization system; For EPDM/reclaimed rubber, the tear strength of the DCP/sulfur/accelerator combination system is better than that of the sulfur/accelerator combination system.
(2) Polysulfide bonds have high tear strength. When using reclaimed rubber to produce rubber products with high requirements for tear strength, try to choose the traditional sulfur/accelerator system; The dosage of sulfur is controlled among 2-3 parts, and the medium activity and high flatness of the promoter DM and accelerator CZ are used to combine sulfur. When natural rubber/reclaimed rubber is used to produce rubber products, the effective sulfur system is used to replace the ordinary sulfur vulcanization system, and the tear strength is significantly reduced. When using a common sulfur vulcanization system, persulfur will cause a significant reduction in the tear strength of the vulcanized rubber.
2. Design of reinforcing filling system for recycled rubber products with high tear strength
The rational use of reinforcing agents and fillers can effectively improve the tear strength of reclaimed rubber. The use of carbon black in reclaimed rubber can not only improve tear strength, but also dilute the effect of the reclaimed rubber vulcanization system on the E4LYY1127 of tear strength, and reduce the degree of tear strength decline with increasing temperature. The particle, structure, oxidation degree and other properties of carbon black affect the tear strength of reclaimed rubber; With the decrease of carbon black particle size, the tear strength of reclaimed rubber vulcanized rubber increased. In the case of the same particle size, carbon black with lower structure is beneficial for the improvement of tear strength.
The amount of carbon black required when the tear strength of reclaimed rubber reaches the optimal value is more than the amount of carbon black required for the tensile strength to reach the optimal value; Anisotropic fillers, such as clay and calcium carbonate, are difficult to impart high tear strength to the rubber compound; The reclaimed rubber vulcanized rubber with new fumed silica after surface treatment has better tensile strength and tear strength.
3. Design of softening system for recycled rubber products with high tear strength
The addition of softening plasticizer will reduce the tear strength of the reclaimed rubber vulcanized rubber, especially the paraffin oil is extremely unfavorable to the tear strength of styrene-butadiene vulcanizate, and the aromatic oil can ensure that the styrene-butadiene vulcanizate rubber has high tear strength. When using petroleum-based softening plasticizers as softening plasticizers for nitrile rubber and neoprene, high aromatic oil with aromatic content higher than 50%-60% should be used, and paraffin oil and naphthenic oil are not recommended.
To improve the tear strength of reclaimed rubber products, rubber product manufacturers can also use rubber with large molecular weight and high crystallinity, such as natural rubber; With the increase of molecular weight, the intermolecular force increases and the tear strength increases. When the molecular weight increases to a certain extent, the strength no longer increases, and gradually tends to equilibrium. What other good suggestions do you have for designing recycled rubber products with high tear strength? We look forward to discussing this with you.
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