Silica‐filled NR compounds are prepared by mixing rubber with organic‐networked silica and additives such as curatives, processing and coupling agents, and stabilizer in a dried state (dry‐mixed NR, DNR) and mixing a silica‐NR wet masterbatch prepared in liquid phase with the additives (wet‐mixed NR, WNR). The effects of mixing method and time of DNR and WNR compounds on their cure, process, tensile, and dynamic properties are investigated. The mixing of DNR crushes silica aggregates to smaller ones, but also forms occasionally large ones, while the mixing of WNR produces small aggregates without forming larger ones because silica aggregates are already covered with rubber. The high silica dispersion, suppressed silica aggregation, low Payne effect, and low‐loss modulus of the WNR compounds prepared by mixing for a sufficient time result in their low viscosity, high scorch safety, and low rolling resistance without sacrificing other rubber properties.
The roles of curatives such as sulfur (S), N-cyclohexylbenzothiazole sulfenamide (CBS), and diphenylguanidine (DPG) in the vulcanization of SBR compounds were deduced from a quantitative discussion of their contribution to the induction period (tind) of cure and the rate constant (kc) for crosslinking reaction. tind and kc of the SBR compounds with different S, CBS, and DPG were determined in the simulation of their rheocurves using a simple kinetic model with these two parameters. The increase of S content caused an appreciable increase of delta torque (Δτ) with negligible influences on tind and kc. By contrast, the increase of the CBS content increased both kc and Δτ while slightly extending tind. DPG significantly shortened tind by accelerating the generation rate of the active sulfurizing species. The regression analysis of tind, kc, and Δτ provided not only a quantitative comparison of the effect of the curatives on rheocurves but also the optimization of the compositions of the SBR compounds in terms of the rate and extent of cure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.