Accelerated-sulfur system recipes

Curing-System Recipes for Accelerated-Sulfur Vulcanization. Recipes for only the curing-system part of formulations are given in Table 4.6. 

TABLE 7.4 Recipes for Accelerated-Sulfur Vulcanization Systems ... 

Mathai et al. examined blends of NR with NBR of 34% ACN eontent at various weight ratios under a conventional sulfur curing system containing CBS accelerator. The cure characteristics evaluated at 150 °C showed that the scorch time and the optimum cure time decreased as the weight ratio of NR increased in the blend. A more or less similar trend was presented by Ismail et al. for a sulfur-cured recipe containing TBBS accelerator at 150 °C. The scorch and optimum cure time decrease was more pronounced when the blend involved NR having 50 mol% of epoxidation (ENR-50). 

Typically a recipe for the vulcanization system for one of these elastomers contains 2-10 phr of zinc oxide, l phr of fatty acid (e.g., stearic), 0.5-4 phr of sulfur, and 0.5-2 phr of accelerator. Zinc oxide and the fatty acid are vulcanization-system activators. The fatty acid with zinc oxide forms a salt, which can form complexes with accelerators and reaction products, formed between accelerators and sulfur. Accelerators are classified and illustrated in Table 7.1. 

Aircraft tread requires a high modulus, better abrasion resistance and low heat generation. The above requirements could be satisfied by using a CV/SEV cure system with DCBS as accelerator and insoluble sulfur (IS) as crosslinker. For achieving high modulus, HMT and a resorcinol system is used. In order to reduce the heat generation, the use of Perkalink 900 has been suggested. A typical formulation for an aircraft tyre tread recipe is shown in Table 40. 

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