Dark Sulfur: Quantifying Unpolymerized Sulfur in Inverse Vulcanized Polymers

Inverse vulcanization allows polymeric materials to be formed from excess elemental sulfur, promoting polysulfide chains to be stabilized between organic comonomers, rather than reforming as crystalline S8, resulting in high sulfur content materials with interesting properties. The techniques used to determine if free unreacted sulfur remains in the polymers only detect the crystalline and not the amorphous form. A detailed study is presented on the quantification of free amorphous sulfur within inverse vulcanized polymers, in which free sulfur is shown to increase over a period of aging. Postaging regeneration by stimulating homolytic S–S cleavage in the polymer is investigated.