On the various roles of 1,3-DIPHENYL Guanidine in silica/silane reinforced sbr/br blends.

The aim of this study was to evaluate the various roles of 1,3-DiPhenyl Guanidine (DPG) in silica-reinforced rubber compounds. Two roles of DPG are well known to be: adsorption onto silica surface to reduce the acidic sites and second to boost the silanization reaction as secondary accelerator. However, these two roles are in a way conflicting. When DPG molecules occupy the reactive silanol sites on silica by adsorption, then the access of silane molecules needed for silica-rubber coupling is blocked. Therefore, it may be assumed that there is another role DPG plays in silica filled rubber compounds. In order to evaluate another role which can reconcile these contradictory functions of DPG, a series of rubber compound mixings was performed with different DPG concentrations in the masterbatch and final stages. Additionally, a series of model reaction experiments has been done in combination with other ingredients, such as zinc oxide and stearic acid. According to the results a new role of DPG is observed: DPG possibly reacts with the silane coupling agent bis-(triethoxysilylpropyl)tetrasulfide (TESPT) and releases sulfur during the mixing process, which enhances filler-polymer coupling, but reduces cure rate and crosslink density. Image 1 • Roles of DPG in silica/silane reinforced SBR /BR blends: adsorption onto the silica surface and boosting the silanization. • However, these roles are in a way conflicting. • Another functionality of DPG: it reacts directly with bis-(triethoxysilylpropyl)tetrasulfide (TESPT). • This induces faster filler-polymer coupling, more bound rubber but slower vulcanization and lower crosslink density. • DPG and TESPT are partly consumed during mixing and alter the network structure. [ABSTRACT FROM AUTHOR]