Effect of Glycerol as Processing Oil in Natural Rubber/Carbon Black Composites: Processing, Mechanical, and Thermal Aging Properties

The present work aims to study the effect of glycerol as a replacement for mineral oils in natural rubber (NR) composites to obtain suitable properties via cure characteristics, mechanical properties, and thermal stability. Glycerol was used at a 5 phr rate in the compound with carbon black as a reinforcing filler and was compared to mineral processing oils such as aromatic oil, treated distillate aromatic extracted oil, and paraffinic oil. Compared to the other oils, glycerol exhibits better maximum torque and torque differences. Also, a shorter scorch time, cure time, and a higher cure rate index of the compounds were observed. However, although the received mechanical properties, including tensile strength, elongation at break, and compression set of the vulcanized rubber using glycerol showed slightly lower values than the others, the 100% and 300% moduli, as well as the hardness of the composites filled with glycerol, exhibit better values relative to the other commercial oils. These findings demonstrate that glycerol overall presents a good balance of properties, making it beneficial to use glycerol as a substitute for mineral oil in tire, shoe sole, and rubber stopper applications.

Automated summary

This study found that glycerol can effectively replace mineral oil in natural rubber composites, providing suitable properties in terms of cure characteristics, mechanical properties, and thermal stability. Compared to other oils, glycerol exhibited superior maximum torque and torque differences, as well as shorter scorch time, cure time, and a higher cure rate index. Although the mechanical properties of the vulcanized rubber using glycerol showed slightly lower values than the others, the composites filled with glycerol had better values for 100% and 300% moduli, as well as hardness. This suggests that glycerol presents a good balance of properties, making it a beneficial substitute for mineral oil in tire, shoe sole, and rubber stopper applications.