*2.1. Processing of Plasticized Compounds*

NBR with 34% ACN and 18% ACN were named NBR-34 and NBR-18 accordingly. The formulation of the materials, which is reported in Table 1, di ffers mainly in the NBR type, plasticizer types, and contents, whereas the other mixing ingredients were kept almost unchanged.


**Table 1.** Composition and time of addition during mixing.

1 6PPD, N-(1,3–dimethylbutyl)–N'–phenyl–p–phenylenediamine; 2 CBS, N–cyclohexyl–benzothiazole–2–sulfonamide

The compounds were prepared with a two-stage mixing procedure in a lab kneader with a fill factor of 0.7. The starting temperature in the kneader was 50 ◦C, and a rotation speed of 50 rpm was used. The polymer was introduced first in the chamber, and the CB, plasticizer, stearic acid, ZnO, and 6PPD were added after 1 min. After 5 min, the sulfur and CBS were added. The compounded stock was discharged after 10 min, and as a final step, it was homogenized on a two-roll mill before curing.

Further, cure characteristics at a temperature of 160 ◦C were determined by using a vulcameter (type GÖTTFERT elastograph, GÖTTFERT Werksto ff-Prüfmaschinen GmbH, Buchen, Germany). According to the results of the vulcameter tests, the time *t90* was fixed as the vulcanization time for the necessary plates. For each material (formulation), plates with a size of 120 mm× 120 mm × 2 mm were vulcanized. From these plates, specimens of the desired form for the tests were cut using a metal cutter.
