Upcycling waste PET into advanced plasticizers for enhanced NBR/PVC blend performance

Abstract This manuscript focused on breaking down waste polyethylene terephthalate (WPET) into useful products using glycolysis techniques and then analyzing the resulting glycolyzed PET (GPET) with Fourier transform infrared and proton nuclear magnetic resonance spectroscopy. The hydroxyl values were measured to evaluate the quality of the glycolyzed product. The potential application of GPET as a plasticizer for acrylonitrile butadiene rubber (NBR)/polyvinyl chloride (PVC) blends was investigated at various contents, and its results were compared with the traditional dioctyl phthalate (DOP) plasticizer. The rheological and mechanical characteristics such as tensile strength, elongation at break, and shore A hardness, as well as electrical properties, were assessed to determine the efficacy of GPET as an alternative plasticizer. Unlike conventional plasticizers, the reactive hydroxyl (OH) and carboxyl (COO) groups in GPET participate in the vulcanization process, increasing crosslinking density and torque values. Consequently, GPET improved the rheological, mechanical, and thermal properties of NBR/PVC blends more effectively than DOP. Notably, GPET increased crosslinking density, with torque differences rising to 18.61 d.Nm at 10 phr compared to 16 d.Nm with DOP, indicating superior reinforcement capability. GPET significantly enhanced curing performance by reducing scorch and curing times and increasing the cure rate index by 82.7% compared to DOP. Mechanical testing revealed that blends plasticized with GPET achieved higher tensile strength (up to 16.1 MPa) and elongation at break (482%) compared to DOP, aligning with the requirements of flexible and durable materials. Furthermore, GPET demonstrated better thermal oxidative aging resistance, retaining 91.15% tensile strength and 90.35% elongation at break after aging, outperforming both DOP and unplasticized blends. Dielectric results revealed that GPET contributed to higher permittivity and dielectric loss values compared to DOP, suggesting its suitability for applications requiring antistatic or dielectric properties. Additionally, morphological analysis via scanning electron microscope (SEM) demonstrated enhanced dispersion and phase compatibility in GPET-plasticized blends, confirming GPET has a multifunctional role as a plasticizer, compatibilizer, and reinforcing agent. Overall, these results highlight GPET as a promising sustainable alternative to traditional plasticizers in NBR/PVC blends, offering enhanced mechanical, thermal, rheological, and electrical performance. Graphical abstract