Melt processed elemental sulfur reinforced polyethylene composites

摘要

Elemental sulfur represents a largely unutilized resource for high performance materials development. In this context, elemental sulfur was investigated as reinforcing agent for high density polyethylene (HDPE) composites via extrusion. We were able to produce homogenous composites with sulfur content up to 30 wt %. Compounding was done at 190 degrees C well above the polymerization temperature of elemental sulfur. Infrared and Raman spectroscopy showed that sulfur did not undergo chemical reaction with HDPE. Additionally, Raman spectroscopy showed that sulfur exists in its most stable allotrope, cyclooctasulfur (S-8). Differential scanning calorimetry (DSC) showed that sulfur is present in non-orthorhombic crystal and X-ray diffraction confirms the same. Results suggest that sulfur is predominantly in its cyclooctasulfur allotrope and occupies the amorphous region of HDPE. According to TEM and SEM microscopy, the composites were of high quality, smooth and without distinguishable defects. Quality and smoothness of composites depend on the experimental parameters and sulfur loading. The addition of elemental sulfur significantly improved the elongation at break of the composites from 835 to 1202% (43% increases with 15 wt % sulfur) despite the obvious fact that HDPE possess an already impressive elongation at break quality. Such phenomena have not been reported in the literature. The improved composites would be suitable for a variety of engineering applications. (C) 2015 Wiley Periodicals, Inc.