Characterization of blends of virgin nitrile rubber and compounded nitrile rubber latex waste reclaimed with urea. Part 1: Cure characteristics

The objectives of this study were to develop a cost-effective, environmental-friendly, mechanochemical reclaiming process for compounded nitrile rubber (NBR) latex waste generated from the dipping and treatment plants of the glove manufacturing process and evaluate properties of reclaimed NBR and virgin NBR/reclaimed NBR blend compounds. Initially, compounded NBR latex waste containing NBR latex mixed with compounding ingredients was dried and reclaimed mechanically by varying the milling time from 0 min to 12.5 min at 2.5-min time interval. Properties such as initial plasticity, Mooney viscosity, swelling, and cross-link density of the mechanically reclaimed NBR samples were evaluated. Also, a series of mechanochemically reclaimed NBR samples were produced using urea and varying its amount from 0 phr to10 phr at 2 phr intervals and milling according to the selected milling time. The mechanochemically reclaimed NBR samples were also tested for the above properties. Finally, a reclaimed NBR sample was prepared by applying the best urea loading and the optimum milling time. Further, a series of virgin NBR/reclaimed NBR blend compounds was prepared by varying the reclaimed NBR from 0% to 70% at 10% interval. Cure characteristics of the above blend compounds were evaluated and compared with those of the 100% virgin NBR (control) compound. Initial plasticity and Mooney viscosity of mechanochemically reclaimed NBR revealed that urea is effective as a reclaiming agent for dried compounded NBR latex waste. Results in overall indicated that 5 min is the optimum milling time and 6 phr is the optimum loading of urea required to produce the best reclaimed NBR in terms of properties and energy consumption. Minimum torque and cure time of the 50:50 virgin NBR/reclaimed rubber blend compound were higher compared to the control, whereas scorch time, maximum torque, and cure rate index of the former were lower compared to the latter.