Antimony compounds play a major role in commercial polyester catalysis. Antimony complexes are used in ppm quantities, not only to catalyze melt-phase reactions in which oligomers are converted to high molecular weight polymers, such as poly(ethyleneterephthalate) (PET), but to further increase chain length through a high temperature solidphase polymerization process. During the course of the melt-phase reaction the initial, clear and colorless, Sb+3 compounds are transformed to a gray product that has been linked with the reduction of Sb+3 complexes to metallic antimony (Sb°). The presence of oxygen during the solid-phase process also increases clarity and reduces color of gray polymers. to further our understanding of antimony catalysis, a field emission-based scanning electron microscope (FEGSEM) was used to study antimony transformations during melt-phase polymerization and after treatments at high temperature in oxidizing and reducing environments.

Antimony metal powder from Fisher Scientific was used in redox studies.