Investigation of novel carbasulphane crosslinks to diene-NR-vulcanisates

Investigation of the crosslink structure by using 2,3-dimethylbutene-2 (DMB ) as a model showed that 1,6-bis(N,N-dibenzylthiocarbamoyldithio)hexan (Vul curen(R) VP KA 9188 of Bayer AG) forms novel carba-sulphane crosslinks. The thiol-amine swelling technique for determination of crosslink density a nd sulphur crosslink structure was used to show that Vulcuren results in sh ort sulphur bridges in comparison with a semi-ev vulcanisation system. The alteration of the crosslink structure and the crosslink density after overc uring is less for the compound with Vulcuren. The performance of the bifunctional crosslinker has been investigated in te rms of static and dynamic properties in a carbon black-filled NR compound i n comparison with a conventional and semi-ev vulcanisation system and also in a silica-filled S-SBR/BR compound. The outstanding performance of the Vulcuren-containing system can be seen b y comparing the rheometer curves. The reversion tendency is almost nit whil e the rheometer torque of the other reference compounds decreased considera bly. By adjusting the sulphur level, the physical properties (tensile stren gth, hardness, modulus, etc.) of all vulcanisates are very similar after op timum cure. However, if the same compounds are overcured, a significant imp rovement in the retention of physical and dynamic properties can be seen fo r the compound containing Vulcuren. The improved compression set values ind icate that the network alterations (S-x rupture and formation of shorter cr osslinks or cyclisation) at high temperature are considerably less when Vul curen is used.