Rheological Characterization and Multi‐Regime Viscosity Modeling of Diluted Polyethylene Mixtures

ABSTRACT Solvent‐assisted recycling processes, such as the CreaSolv‐technology, represent a critical pathway for closing the loop on complex polyolefin waste streams. However, the optimization of unit operations, from dissolution to devolatilization, is frequently impeded by the lack of constitutive models capable of describing the rheological behavior of recycled polymers across the entire concentration regime. This study investigates the viscoelastic properties of low‐density polyethylene (PE‐LD), a branched and multimodal polymer, dissolved in a specialty solvent specific to the recycling process. Systematic steady‐shear and oscillatory measurements were conducted to map the flow behavior from the dilute solution to the entangled melt (0 to 100 m% polymer content). To bridge the gap between theoretical fidelity and industrial applicability, a semiempirical modeling framework based on a combination of time–concentration superposition (TCS) and time–temperature superposition (TTS) was developed. The derived model unifies the dependencies of temperature, shear rate, and diluent concentration, capturing the transition from Newtonian plateaus to pronounced shear‐thinning regions. Despite the complexity of the polymer‐diluent mixture, the model predicts the viscosity over nine decades with a mean relative error (MRE) of less than 12%. These findings provide a robust, computation‐efficient tool for the design and scale‐up of solvent‐assisted recycling equipment.