This project seeks to examine how impurities affect the polymerization kinetics of recycled polyester monomers. The textile industry used over 50 million tons of polyester fibers made from polyethylene terephthalate (PET) annually.1 Because polyester fibers are slow to degrade, waste textiles have accumulated in landfill and natural environments, causing near-permanent land contamination.2 The ability to recycle polyester fibers is, therefore, essential to the responsible use of textiles and environment stewardship. While the technology for turning the polyesters back to the starting monomers is well documented, it is unclear whether the impurities formed during the recycling affects the polyester’s re-usability, i.e., whether the monomers are re-polymerizable. This project aims to address this open question—can the chemically recycled polyester monomers be polymerized in the same way as the petroleum-derived polyester monomers. To address this knowledge gap, we will examine how the presence of dyes and related additives affect the polymerization. We will quantify the polymerization kinetics using the viscosity analysis and gel-permeation chromatography (GPC). Then, we will characterize the side products to understand how the dyes and additives interfere with polymerization using nuclear magnetic resonance (NMR).