Abstract Summary (Max 250 words)
Dissolution-based chemical recycling can recover high-quality polymers, but scaling remains challenging. Under specific operating conditions, polymer dissolution can be described as externally mass-transfer-controlled, neglecting internal solvent diffusion and polymer swelling (1). For instance, this study (2) focuses on mixing miscible systems with strong physical properties differences, using concentrated glucose syrup as model fluid dissolving in water. This system behaves analogously to a polymer-solvent and hydrodynamic mixing regimes are identified, highlighting limitations of classical correlations and extending applicability. This study investigates how hydrodynamics governs polymer dissolution. Rheological measurements, including frequency and time sweeps within the linear viscoelastic regime, assess whether polypropylene dissolution is controlled by internal polymer dynamics or external mass transfer. Measurements are performed at temperatures around 160 °C and polymer mass fractions between 40 and 70 wt%, representatives of industrial conditions. Assuming rheological equivalence between non-homogeneous systems and homogeneous mixtures at the same average polymer concentration, an effective diffusion coefficient is identified and used to construct Deborah and Sherwood numbers. In this way, rheological insight provides the basis for subsequent hydrodynamic analysis, with relevant mixing conditions explored through dimensionless groups such as Re* and Ri* and mass-transfer coefficients estimated to support dissolution optimization and scale-up. References 1) Martini, R. E., Brignole, E. A., & Barbosa, S. E. (2009). Dissolution mechanism of polymers in high pressure–high temperature n‐alkanes—Application to blends separation. Polymer Engineering & Science, 49(3), 602-612. 2) Mirfasihi et al., Chemical Engineering Journal 486, 149712 (2024).
