CURE MAPPING IN RUBBER VULCANIZATION: PEROXIDE CURES OF EPDM

“Cure mapping” takes the complementary viscous and elastic outputs of cure rheometry and plots them against each other, so that the resultant plot is no longer in the time domain. Such outputs are routinely available for rubber vulcanization, and in this paper we explore the cure maps for a series of peroxide cures on EPDM. The cure map from moving die rheometer outputs is a plot of viscous torque against elastic torque, and the variables explored herein include the levels of peroxide and coagent. The plot follows the conversion of viscous to elastic character, and its slope can be considered to reflect the balance of reactions that promote or impede this conversion. By this approach, the effect of the above-mentioned cure variables on the competitive reactions of cure is explored. The dominant reactions can be revealed, to provide a fresh perspective on the changes occurring during an industrial rubber vulcanization. But the value of cure mapping extends beyond mechanistic insights: this study has shown the vulcanization cure maps to be particularly sensitive to batch effects. A coherent picture emerges to reveal how routine cure data can be productively exploited to characterize process history and cure.