When producing rubber products mainly from reclaimed rubber, the vulcanization speed directly determines how long the reclaimed rubber remains in the mold—the earlier the demolding, the faster the mold turnover, and the lower the energy consumption and labor costs. E6LYY71. Many reclaimed rubber product manufacturers have encountered this dilemma: the formula seems fine, but vulcanization time is always insufficient, production capacity is stuck in the vulcanization process, and vulcanizing agents can be considered from vulcanizing agents, accelerators, and vulcanizing aids. However, in actual production, vulcanization of reclaimed rubber is not always better the fastest; it requires comprehensive consideration of the compound type, activity, scorke safety, modulus, processing conditions, and physical and mechanical property requirements.
1. Common vulcanization speed of reclaimed rubber accelerators
In actual production, different types of accelerators have significant differences in their impact on the vulcanization speed and scorching safety of rubber compounds. Aldehyde amine accelerators have slower vulcanization rates, guanidines are usually at a moderate level, thiazoles have moderate to rapid promoting effects, sulfanimides balance rapid vulcanization with delayed scorching, and thiolamine and dithiocarbamate compounds have strong promoting effects. Dithiophosphates can be used in rapid vulcanization systems, with specific effects depending on product structure and formulation combinations.
When producing rubber products with reclaimed rubber, the vulcanization characteristics of the compound are also influenced by the source of raw materials, desulfurization process, residual vulcanization system, and the raw rubber used.
2. Measures to increase the vulcanization speed of the reclaimed rubber sulfur vulcanization system
Sulfur is the most commonly used vulcanizing agent for reclaimed rubber products. Reclaimed rubber products using sulfur vulcanization can improve the vulcanization efficiency of the compound by adjusting the combination of the main accelerator and auxiliary accelerator. The accelerator TBBS belongs to the sulfinamide accelerator. When TBBS is the main accelerator, small amounts of TMTM, TMTD, TETD, DPG, etc., can be combined as accelerators to observe whether vulcanization time is shortened, while also checking whether scorching time and vulcanized rubber properties have changed significantly; In some reclaimed rubber formulations, appropriately reducing the amount of TBBS and adding a small amount of TMTM may increase vulcanization speed when modulus changes are minimal.
Most reclaimed rubber products using sulfur as the vulcanizing agent use an activation system composed of zinc oxide and stearic acid; When the promoter dosage and stearic acid ratio are reasonable, appropriately increasing zinc oxide may accelerate the vulcanization reaction, but adding more is not necessarily more effective; When using thiazole-type accelerators in the vulcanization system of reclaimed rubber, it is also necessary to consider the adverse effects of organic acids such as salicylic acid and benzoic acid on vulcanization speed in the formulation.
3. Measures to increase the vulcanization speed of reclaimed rubber peroxide vulcanization systems
When producing rubber products with EPDM reclaimed rubber, peroxide vulcanization is commonly used. Generally, larger amounts of DCP can be used faster than BPIB, which can accelerate the vulcanization of the compound.
Ketone peroxide vulcanization is faster than that of dialkyl peroxides. In peroxide vulcanization systems, choosing trimethylethane triacrylate (TMPTA), TMPTMA, and N,N'-iso-phenylene maleimide (HVA-2) can effectively increase the vulcanization rate. 1,2 Polybutyrene (PB), adienephthalate (DAP), triallyl isocyanourerate (TAIC), and triallyl cyanourerate (TAC) have less effect on vulcanization rate.
When producing rubber products using reclaimed rubber, different reclaimed rubbers have different molecular structures and residual blending systems, and their roles differ from vulcanizing agents, accelerators, and activators. Therefore, vulcanization characteristics need to be adjusted according to the type of reclaimed rubber and vulcanization system; For example, nitrile reclaimed rubber needs to be distinguished among sulfur vulcanization and peroxide vulcanization systems: the acrylonitrile content may affect the two systems in different directions and should not be confused. It is recommended to use a vulcanization instrument to measure scorch time, normal vulcanization time, and vulcanization curve, then verify based on the actual dimensions, hardness, and mechanical properties of the molded product.
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