The Action of Binary Accelerator Systems of Vulcanization

Abstract

1. It was established that in the joint use of vulcanization accelerators there takes place mutual activation of the accelerators, activation of one accelerator or additive action depending on the chemical structure of the accelerators. 2. Of the studied combinations of vulcanization accelerators the systems showing mutual activation are disulfides or mercaptans with nitrogen containing organic bases, and disulfides with sulfenamides. Sulfenamides with nitrogen containing organic bases result in activation of one of the accelerators. Examples of systems of accelerators with additive action are combinations of sulfenamides or disulfides with TMTM. 3. It was established that in the case of systems with mutual activation, such as MBTS with DPG or with CHBTS, the reaction between the accelerators produces MBT. For such systems, greater yields of MBT were observed under vulcanization conditions than were obtained by action of the accelerators alone. This indicates that the principal result of the chemical reaction of the accelerators is the formation of free radicals which are capable of splitting hydrogen from the rubber molecule with the formation of rubber high polymer radicals. 4. There is presented a tentative scheme for a radical mechanism of the joint action of vulcanization accelerators for the case where mutual activation of accelerators exists.

Synergism of novel thiuram disulfide and dibenzothiazyl disulfide in the vulcanization of natural rubber: curing, mechanical and aging resistance properties

“…Frequently, the use of two or more accelerators simultaneously, instead of a single one, has been found to be more advantageous for technological applications, since these mixed systems generally exhibit higher vulcanization activity (synergism) than the individual accelerators separately. Significant contribution with respect to mutual activity of the binary systems of accelerators during the vulcanization of NR has been made by Dogadkin and co-workers [3], Skinner and Watson [2], Kempermann [1] and Krymowski and Taylor [4]. Debnath et al [5,6] have also made some studies in this regards in the recent past.…”

Safe amine based zinc dithiocarbamates for the vulcanization of carbon black reinforced natural rubber

“…The physical and chemical properties of the vulcanizates depend on the type of the accelerators used and also on the condition of vulcanization. Frequently, the use of two or more accelerators simultaneously, instead of a single one, are found to be more advantageous for technological applications, as these mixed systems generally show higher vulcanization activity (synergism) than the individual accelerators separately . Mixed accelerator systems have, therefore, gathered much attention both from scientific and technical points of view.…”

“…It is suggested that in a binary accelerator system, the interaction between the accelerators produce reactive compounds, which decompose into free radicals or ions, capable of initiating a reaction between sulfur, rubber and crosslinking process of the latter . Significant contribution with respect to synergistic activity of the binary systems of accelerators during vulcanization of natural rubber (NR) are revealed by Dogadkin et al, Skinner and Watson, Kempermann and Redetzky, and Krymowsky and Taylor. Debnath and Basu also have made some investigations in this regard.…”

Effect of the cure system on aging resistance of natural rubber compounds

“…These observations are in accordance with the work by Dogadkin et al, who established that the combined action of accelerators as disulfides (TMTD) or mercaptans (MBT) with nitrogen containing organic bases (Sulfads) takes place by mutual activation of the accelerators. 25 The results may be credited to a large amount of cross-links ( Figure 2) which provide a network strong enough to stand the applied deformations.…”