Determination of p-Phenylenediamine Antiozonant in Polychloroprene Rubber

Elastomers susceptible to ozone cracking can be protected by the addition of antiozonants. For polychloroprene (CR) rubber, a mixture of diaryl-p-phenyl-enediamines, Wingstay 100 (WS 100), is one of the most effective antiozonants. Preliminary studies in our laboratory have shown that the effectiveness of WS 100 can be improved even further by the use of an organobentonite clay. To provide more insight into the way in which this antiozonant provides resistance to ozone cracking, a technique for its analysis was required. High performance liquid chromatography (HPLC) is an attractive technique for analyzing WS 100, as well as for a wide variety of additives in polymers. This study describes a newly developed method for the determination of WS 100 in CR. The method is based on acetonitrile extraction of the antiozonant from the rubber, followed by quantitative analysis using HPLC. With this method, subtle differences in concentrations of WS 100 in CR, caused by changes in compounding, mixing sequence, curing conditions, and grease extraction, have been measured.