Surface Characterization of Rubber by Secondary Ion Mass Spectrometry

It has been demonstrated that static SIMS is potentially a very useful technique for the characterization of rubber surfaces. Its major capability is to provide molecular structural information of the polymer in addition to elemental analysis, which would also be possible with other surface techniques such as XPS or AES. The SIMS spectra are in many cases highly characteristic, and they can be used to identify the type and structure of the hydrocarbon polymer. In addition, structural changes in the rubber surface can be detected, and very useful information on the types and amounts of sulfur crosslinks can be obtained as well, as has been published elsewhere. Therefore, the technique shows great promise as a tool for the study of surface-related rubber phenomena, such as oxidation, wear, tack, antiozonant and antioxidant performance and mechanisms, and also for the study of the adhesion between dissimilar rubbers or between rubbers and other materials, such as metals. Before SIMS can be routinely used in rubber laboratories, a considerable amount of basic and fundamental work will have to be done because the spectra of many materials are not known, and they cannot always be predicted either. Therefore, a rubber-related data base will have to be built up with well-characterized polymers but also using clean films of various rubber additives. Crosslinking studies will have to be confirmed with compounds of known crosslink structures, e.g., by using different polymers, different types of accelerators, and a series of model compounds of organic sulfides.