Quantum-chemical modeling of reactions initiating sulfuric vulcanization of isoprene rubber

The quantum-chemical method of the density functional DFT B3LYP / 6-311G ** have been used for calculation of thermodynamic functions and changes in the total electronic energy during the initiation of sulfur vulcanization of isoprene rubber using the N - cyclohexyl - 2 benzthiazolyl sulfenamide accelerator in the presence of atmospheric oxygen. Since sulfur, in the process of vulcanization of rubber compounds, is in a larger amount in a dissolved state, unlike oxygen, it is concluded that in the presence of sulfur, the formation of a valid vulcanization agent (DAV) will occur, and oxidation will occur to a lesser extent. When comparing the values of the reaction energy with the addition of the S8 molecule, it was found that sulfur in the accelerator radical acceptance reactions is a more active acceptor than oxygen in similar reactions. The effect of the number of sulfur atoms on the activity of the radicals of the sulfidating complex arising upon the acceptance of sulfur by the radicals formed during the decay of the accelerator is analyzed. It was found that the cyclohexyl radicals of the accelerator are the most active, however, in subsequent reactions of DAV with rubber, the radicals of DAV obtained with the participation of benzthiazolyl fragments are more active. The study of the effect of the number of atoms on the energies of the reactions of the formation of persulfhydryl suspensions shows that the primary suspensions are most likely to contain 8 sulfur atoms formed in reactions involving biradicals formed during the decay of the eight-membered ring of a sulfur molecule