Modification of ethylene-propylene-diene elastomers to improve the ozone resistance of their covulcanizates with butadiene-nitrile rubbers

Influence of Propylene Units Stereoregularity in Modified Ethylene-Propylene-Diene Elastomers on the Ozone Resistance of Covulcanizates with Acrylonitrile-butadiene Rubbers

“…The heat treatment of EPDM-40 during its modification with the dissociation of propylene supramolecular structures (the maximum dissociation temperature is 443 K [19]) and their formation during cooling leads to the concentration of chemical reagents in relatively small (by volume) disordered regions. As was shown in [11], with an increase in the modification temperature, the molecular dynamics of the EPDM-40 phase in the covulcanizates slows down. This behavior attests the intra phase crosslinking of EPDM, which is confirmed by a marked decrease in the content of the sol fraction in the covulcanizates with an increase in the temperature of heating with the accelerating agent and sulfur (Table 3).…”

“…The composition of sulfur-containing crosslinking systems for NBR and EPDM includes stearic acid, zinc oxide, mercaptobenzothiazole, tetramethylthiuram disulfide, and sulfur [11]. Each of the rubbers was mixed with its crosslinking system on rolls at 313-333 K for 15 min.…”

“…For Elastokam 6305 with a high content of diene, which is compatible only with the fragments of chains containing cis-1,4-and 1,2-units of butadiene [4,11], there is an increase in the fraction of the crosslinks in the interfacial layer with an increase in the content of the above elastomers (Fig. 4b).…”

“…In [11] the specific features of the structure of the interphase interaction region and its volume are related to the efficiency of inhibition of ozone degradation of the diene elastomer in cured heterophasic blends of BNKS-28 and domestic EPDMs with different compositions and stereoregularities of propylene sequences, and the effect of their modification by means of heating with an accelerating agent and sulfur on the characteristics of covulcanizates.…”

“…When the heating temperature increases from 433-443 K for the mixtures of BNKS-28 with the accelerating agent and sulfur, the ozone resistance decreases. In [11], this effect has been explained in terms of EPR spectroscopic data. It was shown that EPDM-40 with a high degree of isotacticity of propylene units contains ordered regions formed by propylene sequences and regions with a mixed composition that contain ethylene and propylene chain fragments.…”