Influence of Accelerator Content on Cure Kinetics of Sulfur-vulcanized Natural Rubber

Abstract

Based on the cure characteristics of the NR/S/TBBS system, a kinetic model with induction, curing, and post-cure periods was chosen to simulate the cure reaction of this system. Cure curves reflecting the evolution of crosslink density were recorded as a function of curing time for NR compounds using a rubber processing analyzer (RPA). The cure curves were then non-linear fitted and the kinetic parameters were determined. The results showed that the simulated curves fit well with the experimental curves. As the concentration of activated sulfurating agents, A o , increased, the activity of crosslink precursors increased (K 2 increased), while the activity for crosslinks to degrade decreased (K 6 decreased) due to shortening of the sulfur chain both in crosslink precursors and in crosslinks, leading to the improved thermal stability of NR vulcanizate at elevated temperatures. Increased accelerator amount also increased the competition of the reaction to form crosslinks over the reaction to form dead by-products, which improved the efficiency of sulfur. Reaction activation energy E 2 and E 6 , calculated from K 2 and K 6 through the Arrhenius equation, showed that E 6 is higher than E 2 . The increase of accelerator dosage led to the decrease of E 2 and increase of E 6 , which explained the phenomenon of improved anti-reversion.

Vulcanization Kinetics of Starch Xanthate /Natural Rubber Composite

“…The main techniques used to study the kinetics of rubber vulcanization include differential scanning calorimetry (DSC), oscillating disk rheometry (ODR), moving die rheometry (MDR) and RPA. The RPA is a new, condition-controlled shear cone-and-cone dynamic mechanical rheological tester specifically designed to measure the dynamic properties in a certain range of time, temperature, frequency and strain for polymers before and after curing [5,6]. In this paper, the vulcanization kinetic of SX/NR composite in range of induction period and curing period was analyzed with use of a RPA(MFR, Prescott UK).…”