Solvent-based recycling of flexible PVC for DEHP removal: extraction optimization and material characterization

Flexible polyvinyl chloride (PVC) contains high loadings of di-(2-ethylhexyl) phthalate (DEHP), a plasticizer restricted under REACH. In this study, flexible PVC with 30 wt.% DEHP—representative of medical waste streams—was subjected to solvent-based recycling (SBR) via dissolution–precipitation using cyclohexanone and ethanol. The process aimed to selectively extract DEHP while preserving the PVC backbone. The recovered polymers were characterized by FTIR and GC–MS for DEHP removal, K-value analysis for molecular weight, DSC and TGA for thermal behavior, and SEM/EDS for morphology. After three SBR cycles, DEHP content decreased from 29.86 wt.% to 0.064 wt.% (>99.7% removal), below the REACH threshold of 0.1 wt.%. The K-value of the recycled resin (69 ± 2) matched virgin K70 (70 ± 1), indicating negligible degradation. DSC confirmed recovery of the glass transition temperature (~82–83 °C), while TGA showed elimination of low-temperature plasticizer volatilization. SEM revealed smaller, denser particles compared to virgin PVC. Re-plasticization with dioctyl terephthalate (DOTP) restored flexibility. Mechanical testing showed properties close to virgin DOTP–PVC: a slightly higher modulus, but modestly lower yield stress and elongation. Shore A hardness increased marginally, while DMA and TGA confirmed comparable viscoelastic and thermal profiles. These results demonstrate that SBR efficiently removes DEHP from flexible PVC while preserving polymer integrity, producing a resin that can be re-formulated with non-phthalate plasticizers to achieve near-virgin performance. This establishes SBR as a promising route for compliant, high-quality recyclates from flexible PVC, relevant to future medical waste valorization.