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

Abstract

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.

Characterization of Blends of Virgin Nitrile Rubber and Compounded Nitrile Rubber Latex Waste Reclaimed with Urea: Part II - Physico-Mechanical Properties

“…This figure indicates that the vulcanizates containing the reclaimed material (except the vulcanizates containing 10% and 70% reclaimed rubber) possess higher hardness than the control, which does not contain any reclaimed rubber. Lower hardness shown by the vulcanizates containing 10% and 70% reclaimed rubber can be attributed to lower state of crosslinking and crosslink density as indicated by the maximum torque and (maximum-minimum) torque, respectively of virgin NBR/reclaimed rubber blend compounds [4] . It is known that modulus at 100% elongation is a measure of stiffness or hardness of a vulcanizate.…”

“…All the above-mentioned raw materials and rubber compounding ingredients were used in the preparation of the NBR blend compounds mentioned in Part-I of this study [4]. These blend compounds were subsequently vulcanized as described below for evaluation of physicomechanical properties.…”

“…Seven virgin NBR / reclaimed NBR blend compounds were prepared by varying the reclaimed NBR content from 10-70% (%w/w) at 10% (%w/w) intervals, namely W10 (90:10 virgin NBR/reclaimed NBR), W20 (80:20 virgin NBR/reclaimed NBR), W30 (70:30 virgin NBR/reclaimed NBR), W40 (60:40 virgin NBR/reclaimed NBR), W50 (50:50 virgin NBR/reclaimed NBR), W60 (40:60 virgin NBR/reclaimed NBR), W70 (30:70 virgin NBR/reclaimed NBR) and the control compound, namely control NBR (100% virgin NBR) was also prepared in Part-I [4] of this study. These compounds were placed in test piece moulds and pressed between the platens of a hydraulic press (Yeji Corporation, Taiwan).…”

“…Therefore, modification of waste rubber has been carried out in the past with the aim of enhancing adhesion between the two phases, waste rubber and polymer matrix [3]. The different modification processes carried out in the past were reviewed and reported in Part-I of this study [4].…”

“…This work compared the physico-mechanical properties of vulcanizates with those of the control vulcanizate. The first part paper [4] reported reclaiming compounded NBR latex waste with urea, which is a readily available, low-cost, environmentally friendly amino compound. The reclaimed compounded NBR latex waste thus produced was initially characterized for its properties.…”