State‐Of‐The‐Art Quantification of Polymer Solution Viscosity for Plastic Waste Recycling

Abstract

Solvent-based recycling is a promising approach for closed-loop recovery of plastic-containing waste. It avoids the energy cost to depolymerize the plastic but still allows to clean the polymer of contaminants and additives. However, viscosity plays an important role in handling the polymer solutions at high concentrations and in the cleaning steps. This Review addresses the viscosity behavior of polymer solutions, available data, and (mostly algebraic) models developed. The non-Newtonian viscosity models, such as the Carreau and Yasuda-Cohen-Armstrong models, pragmatically describe the viscosity of polymer solutions at different concentrations and shear rate ranges. This Review also describes how viscosity influences filtration and centrifugation processes, which are crucial steps in the cleaning of the polymer and includes a polystyrene/ styrene case study.

Toward More Universal Prediction of Polymer Solution Viscosity for Solvent-Based Recycling

“…A more detailed analysis of these models can be found in Kol et al 4 The segment-based Eyring-NRTL, Eyring-Wilson, Eyring-NRF, and modified-NRF are based on Eyring's theory and local composition models, 4 whereas the polymer mixture viscosity model is based on the ideal linear mixing rule for polymer solutions and the nonideal mixing effect is described by a symmetric and anti-symmetric binary parameter. 1,4 The Newtonian viscosity models require the viscosity of the pure components as input. This study is based on binary mixtures, the pure components being the solvent and the polymer.…”

“…For example, for the PS/ geranyl acetate case at 25 °C (Supporting Information, Figure S25), the viscosity of the 15 wt % is approximately four times the viscosity of the 10 wt % solution. It has been shown in a previous work by Kol et al 4 that for the dissolution− precipitation technique during the first cleaning steps, i.e., filtration of the polymer solution for removal of additives, an increase in polymer solution viscosity leads to a significant increase of the necessary pressure drop (to obtain the same flow rate). It can be also observed in Table 2 that o-xylene and anisole lead to the highest entanglement concentration, meaning that it is possible to dissolve a higher amount of polymer before entering the entangled region.…”

“…Polymer solutions can also be characterized by three main regimes: a dilute, semi-dilute, and concentrated regime. 4 In diluted solutions, the polymer chains behave as isolated hard spheres. 10 It has been reported that typically polymer solutions are in this regime for (mass) concentrations lower than 5 wt %.…”

“…The (simplified) Newtonian models are a combination of Eyring's theory and local composition models to account for nonlinearity. 4 The non-Newtonian models are empirical models proposed to describe the influence of shear rate on viscosity. 12 A frequently applied non-Newtonian model is the Ostwald−de Waele power-law model, which is able to describe the shear-thinning region.…”

Electroconductive and photoactive poly(phenylenediamine)s with antioxidant and antimicrobial activities for potential photothermal therapy

“…As a result, an increase in viscosity would affect (decrease) the dissolution rate. 43 In addition, the [Z inh ] values of the doped and undoped poly(phenylenediamine)s increase in the following order: PpPDA 4 PoPDA 4 PmPDA. This shows that the molecular weight of the synthesized PmPDA is lower than those of PoPDA and PpPDA.…”