Waste walnut shell as an alternative bio-based filler for the EPDM: mechanical, thermal, and kinetic studies

In recent years, bio-based polymers and fillers are attracting the attention of researchers due to strong concerns on environmental friendly production of rubbers. In this study, the waste walnut shell was used as an alternative filler for ethylene–propylene–diene monomer rubber (EPDM). The surface of the waste walnut shell was modified with bis[3-(triethoxysilyl)propyl] tetrasulfide to achieve a better interfacial interaction with EPDM matrix. Effect of different parameters on mechanical, thermal, and rheological properties of EPDM/waste walnut shell filler composite was investigated. It was seen that the increase of walnut shell content led the increase in tensile strength. Moving die rheometer tests have shown that the addition of walnut shell improved the torque value. In addition, the thermal tests were shown that using the waste walnut shell as filler results with no considerable difference in the thermal properties. Swelling test and cross-link density analyses showed that walnut shell addition has no negative effect on cross-link density. It was concluded that the waste walnut shell could be an effective filler with its advantages of bio-based and biodegradable.