Crosslinking reaction mechanism of diisopropyl xanthogen polysulfide accelerator in bromobutyl elastomer for medical device applications

The use of an accelerator based on diisopropyl xanthogen polysulfide (DIXP) to formulate bromobutyl elastomer (BIIR‐DIXP) compositions for sealing medical devices was published in the Journal of Applied Polymer Science (Ohbi, D. S.; Pureval, T. S.; Shah, T.; Siores, E. 2007, 106, 526). In this publication, a reaction scheme for the DIXP accelerator in situ with BIIR is proposed. It is based on the evolved volatile chemical species determined during the curing reaction of BIIR‐DIXP composition, and is formulated in the light of generally accepted mechanism of crosslinking elastomers using sulfur‐based accelerators. The volatile chemical species were determined using coupled thermogravimetric infrared analysis ( TGA‐IR) and head space gas chromatography mass spectroscopy (GC‐MS) analysis. The main volatiles evolved during the curing reaction were carbonyl sulfide, carbon disulfide, and isopropyl bromide. These are considered to be associated with the formation of the active rubber‐bound DIXP sulfurating species required for the crosslinking reaction. Analysis of the acetone extract of cured BIIR‐DIXP also showed that the DIXP is totally consumed during the cure reaction, and the formulation is largely free of cure reaction byproducts.