Surface modification of sulfur by vacuum plasma polymerization with acetylene was applied in order to modify its surface properties without losing reactivity for vulcanization. A nm-thin layer of crosslinked polyacetylene was deposited on the surface of the sulfur powder. Its surface energy was decreased as monitored by wetting in liquids of various polarities. A delay in the onset of weight loss by sublimation in thermal gravimetric analysis was shown by the plasma-modified sulfur. Scanning electron microscopy showed a core/shell structure of the coated sulfur. In 50:50 blends of styrene-butadiene rubber and ethylene-propylene-diene rubber, the encapsulated sulfur samples resulted in pronounced improvements in the mechanical properties relative to the use of unmodified sulfur.
- Plasma polymerization