Inverse vulcanized sulfur-styrene polymers as effective plasticizers for polystyrene

Inverse vulcanized polymers have demonstrated significant potential as alternatives to conventional petrochemical polymers in various applications, including environmental remediation, where they are used to absorb heavy metals and pollutants from water and soil, and energy devices, such as in the development of high-capacity lithium-sulfur batteries. Despite their promise in these areas, the full application scope of these sulfur-based polymers remains unexplored. There is substantial potential for their use in other fields, such as advanced material coatings, medical devices, and as additives to improve the properties of existing polymers, yet these possibilities have not been thoroughly investigated. This study presents a sulfur-based polymer, synthesized via the inverse vulcanization of sulfur and styrene and partially crosslinked with divinylbenzene, as a novel plasticizer for polystyrene (PS). This polymer blend was prepared using an internal mixer to replace conventional organic-based plasticizers. The selected system was designed to maximize miscibility. Both virgin and plasticized PS were injection molded for comprehensive characterization. Differential Scanning Calorimetry (DSC) confirmed the complete consumption of sulfur, revealing a significant reduction in the glass transition temperature of PS upon the addition of the sulfur-based plasticizer. Morphological analysis showed a homogeneous surface with uniform single-phase morphology, indicating full miscibility of the blend. Tensile tests demonstrated enhanced ductility and reduced stiffness in plasticized PS, with strain at maximum tensile strength and elongation at break increasing by 22.0 % and 28.1 %, respectively. The plasticizer also improved the toughness of PS by 25.2 %. Rheological assessments corroborated the plasticization effect and confirmed the blend's full miscibility. Contact angle measurements indicated increased hydrophilicity of the plasticized PS samples. This newly developed sulfur-based plasticizer proved to be highly effective for PS, showcasing competitive efficiency comparable to commercial plasticizers. This advancement paves the way for new applications in the expanding field of sulfur-based polymers.