Influence of Component Ratio on Thermal and Mechanical Properties of Terpenoid-Sulfur Composites

Terpenoids are potentially sustainable replacements for petrochemical olefins. Sulfur is a waste product produced in large quantities from fossil fuel refining. Several composites with attractive properties have recently been made from terpenoids and sulfur. This report details the extent to which the ratio of sulfur to terpenoid and the terpenoid olefin content influences the thermal and mechanical properties of such terpenoid-sulfur composites. The terpenoids selected were diunsaturated geraniol and triunsaturated farnesol that, upon their inverse vulcanization with elemental sulfur, yield composites GerS(x) and FarS(x), respectively (x = wt % sulfur). The wt % sulfur in the monomer feed was varied from 30-95 for this study, providing twelve materials. Mechanical analysis of these materials was undertaken by compressive and tensile strength techniques. Differential scanning calorimetric analysis revealed both polymeric and orthorhombic sulfur present in the materials with glass transition temperatures (T-g) of -37 degrees C to -13 degrees C and melt temperatures (T-m) of 119 to 104 degrees C. The crystallinity of composites decreases as the weight fraction of sulfur decreases and composites having the highest olefin content exhibit no detectable crystalline microstructures. The compressive strength of the materials showed increasing strength for higher olefin-content materials for both GerS(x) (with compressive strength of up to 32 MPa) and FarS(x) (with compressive strength of up to 43 MPa). The improved strength with increasing olefin content levels off at around 80-85% of terpenoid, after which point both tensile and compressive strength diminish.

Automated summary

Terpenoids are potentially sustainable replacements for petrochemical olefins and composites with attractive properties have been made from terpenoids and sulfur. The ratio of sulfur to terpenoid and the terpenoid olefin content significantly influence the thermal and mechanical properties of the composites, with compressive strength reaching up to 43 MPa for FarS(x) materials.