Plasticizer Identification and Characterization Across Multiple Poly(Vinyl) Chloride (PVC) Blends

Abstract

Poly(vinyl) Chloride (PVC) is extensively utilized as a thermoplastic due to its exceptional properties and diverse applications. However, PVC presents various recycling challenges compared to other polymer plastics. The characteristic halogen group (chlorine) is released as HCl during vigorous recycling processes, which deters researchers and recyclers. Formulations of PVC consist of multiple additives, such as plasticizers, which provide the material with flexibility but complicate recycling. Industrial plasticizers are typically phthalate-based, which are toxic and migrate from the material over time. In our research, we developed a methodology for the removal, identification, and quantification of a known phthalate di-isononyl phthalate (DINP)) and PVC blend. The extraction process, comprised of a solvent/anti-solvent system (THF: MeOH), coupled with multiple analytical methods, effectively removes multiple plasticizers from PVC blends. The process produces two products: the plasticizers in solution and the recycled PVC (rPVC) resin. Our findings indicated that the plasticizers were successfully removed and were below the limit of detection (LOD) with Fourier Transform Infrared - Attenuated Total Reflectance (FTIR-ATR) and Nuclear Magnetic Resonance (NMR) analysis. Through NMR analysis, we identified multiple plasticizers utilized in the sample rPVC blends, highlighting the importance of understanding the composition of our blend. All rPVC blends contained the toxic phthalate plasticizer, di(2-ethylhexyl) phthalate (DEHP), with one blend relying on it as the sole plasticizer. DEHP is known for its strong plasticizing properties, which explains the flexibility of this blend. Another blend used in extrusion applications contained di-(2-ethylhexyl) terephthalate (DEHT) (primary plasticizer), tri-octyl trimellitate (TOTM), and DEHP. A custom blend produced by the recycler, made from 50% industrial and 50% post-consumer reprocessed PVC, contained a dual-plasticizer system of DEHT and DEHP. These results emphasize the need to identify and quantify phthalates in applications in PVC to control quality and mitigate the environmental and health impacts of toxic plasticizers.