The Influence of the Rubber Crosslink Structure on the Activation Energy Calculated UNDER Thermo-Oxidative Conditions

Apart from the base elastomer and its chemical structure, the thermo-oxidative resistance of rubber is known to be influenced by a variety of factors (i.e. antioxidant, filler, plasticizers, cure system, …etc.) depending on their type and level.  This investigation will examine the effect of the type of cure system (i.e. crosslink structure) on the thermo-oxidative resistance in a series of bromo-butyl based compounds.  Due to its inherent reactivity, bromo-butyl is unique in its ability to be cured using a wide variety of cure systems.  In this investigation, a series of seven simple carbon black reinforced compounds have been devised varying in cure system: zinc oxide, sulfur, sulfur donor, peroxide, peroxide coagent, phenolic resin and ionic.  These compounds have been aged from room temperature up to 115°C for varying aging times.  Hardness, mechanical properties and network chain density have been measured on the thermo-oxidized samples.  Time-temperature superposition has been used to derive shift factors which allowed for the calculation of the activation energy for the process through the Arrhenius equation.