DEPENDENCE OF THE PROPERTIES OF SULFUR AND PEROXIDE VOLCANISES BASED ON A MIXTURE OF ISOPRENE WITH POLYVINYL ACETATE ON THE STRUCTURE OF THE VOLCANIZATION NETWORK
Authors: Sabina Rahimova Sabina Rahimova 
Published: January 2022

The effect on the crosslinking process of modified isoprene rubber (SKI-3-PVA) with the participation of sulfur and dicumyl peroxide (PD) in the presence of hexachloroparaxylene (HCPA) and 2,4-dichloro-6-dimethyl-amino sym triazine was studied. It was found that, depending on the length of time, the number of crosslinks in these systems (SKN-3-PVA + sulfur + GHPK + ZnO; SKI-3-PVA + PD + GHPK) is 2.5x105 and 1.9x105 mol / cm³, respectively, per Based on the observed changes in the parameter of the spatial grid of the crosslinked samples, the yield of effective crosslinks was calculated. It was shown that in the presence of dicumyl peroxide in filled systems, the number of crosslinks decreases, and a decrease in crosslinks is also observed. Comparative tests of elastomeric materials based on SKI-3 - PVA copolymers in liquid aggressive media were carried out. Sol-gel analysis found that with an increase in the content of the copolymer in isoprene, the concentration of the number of cross-linked molecules in the copolymer increases. It is shown that the physical and mechanical properties of filled vulcanizates are inferior to sulfuric ones in strength properties, but surpass peroxide ones in thermal aging and the action of solvents. It was found that an increase in aging with an increase in the heating time of the samples indicates the formation of additional cross-links. The role of zinc oxide in the peroxide crosslinking of the SKI-3 - PVA copolymer has been studied. It was found that the introduction of zinc oxide has a noticeable effect on the rate of sulfur and peroxide crosslinking of mixtures based on SKI-3 - PVA copolymers, an increase in the structuring time of mixtures, destructive processes are observed, and the number of crosslinks and crosslinks decreases.
It was found that the physical and mechanical properties of peroxide vulcanizates are inferior to sulfuric ones in strength properties, but they are superior to peroxide ones in thermal aging. It is shown that an increase in the resistance to aging with an increase in the heating time of the samples indicates the formation of additional cross-links. As a result of the reaction with oxygen and the accumulation of interacting polar groups. A decrease in the degree of swelling is associated with the formation of C-C chemical bonds in elastomers, it effectively participates in the formation of cross-links during peroxide vulcanization.
The nature of the interaction of sulfur PD, HCPC, and DCDEAST with elastomers was judged by the change in the conditional number of crosslinks (n´c) and the number of crosslinked molecules (1 \ Ms) in unfilled sulfur and peroxide vulcanizates. It is shown that in sulfur peroxide mixtures based on SKI-3-PVA with the proposed agents at room temperature it causes the formation of effective crosslinks, and with an increase in the duration of heating in systems 1, 2, the number of crosslinked molecules increases.
An increase in resistance to aging with an increase in the heating time of the samples indicates the formation of additional cross-links as a result of the reaction with oxygen and the accumulation of interacting polar groups. A decrease in the degree of swelling is associated with the formation of C - C chemical bonds in elastomers, effectively participating in the formation of a network of crosslinks during peroxide vulcanization.
Thus, the analysis of the results of the studies performed allows us to conclude that elastomers based on the isoprene copolymer SKI-3-PVA obtained with the participation of vulcanizing agents of sulfur and peroxide (PD) in the presence of hexachloroparaxylene (HCP) and triazine compounds are superior to those known in terms of thermal stability. aging in strength and accumulation of permanent deformation in aggressive environments.
Keywords: isoprene, polyvinyl acetate, hexachloroparaxylene, peroxide dicumil, vulcanization, modification