Quantitative ToF-SIMS analysis of monomers, oxidation and trace elements in EPDM gels

During the production, processing and use of ethylene-propylene-diene monomer terpolymers (EPDMs), small (0.1-2 mm) visible inclusions are occasionally encountered in the polymer matrix. These inclusions are commonly called gels and result in degraded polymer performance. In this work, new cross-sectional time-of-night (ToF) SIMS methods were developed for quantitative ethylene, ethylidene-norbornene (ENB), oxidation and trace element analysis of EPDM gels. The ethylene calibrations were obtained by plotting C5H9+/C2H3+ and C8H13+/C2H3+ versus wt.% ethylene. The ENB calibration was obtained by plotting (C7H8+ + C7H10+)/2(C2H3+) versus wt.% ENB. Oxidation calibrations were obtained by plotting C2H3P+/C2H3+ versus wt.% oxygen from oxidation for both high- and low-ENB EPDMs. Relative sensitivity factors were also determined for semiquantitative trace metals (V, Al, Cl, Ti, Si, S, Fe, Ni, Ca and Zn) analysis in polypropylene, EPDM and polyethylene polymers. The relative sensitivity factors determined in the different polymers were very similar, indicating the absence of substantial matrix effects. The detection limits for these trace element analyses varied from 2 to 50 ppm. The analyses of well-characterized EPDMs (treated as unknowns) were used to verified the accuracy of these calibrations. These ToF-SIMS methods then were used to examine the composition of a variety of EPDM gels found in industry. Copyright (C) 2001 John Wiley & Sons, Ltd.