Table 3.
Information about five common types of polymers and possible separation salt solutions (PE: polyethylene, PP: polypropylene, PS: polystyrene, PVC: polyvinyl chloride, PET: polyethylene terephthalate).
| Polymer type | Chemical structure | Polymer density (g/cm3) | Commonly used saturated salt solution for density separation | Shaking time | Settling time | Recovery rate | References |
|---|---|---|---|---|---|---|---|
| PE |  |
0.92-0.97 | NaCl (1.2 g/cm) | 3 min | 10 min | > 85.0% | Quinn et al. (2016) |
| PP |  |
0.90-0.91 | ZnCl2 (1.5 g/cm) | 10 min | 15 min | > 95.0% | Rodrigues et al. (2020) |
| PS |  |
1.04-1.10 | ZnCl2 (1.5 g/cm) | 5 min stirring + 5 min rest + 3 short stirring bursts | overnight | 96.3% | Vermeiren et al. (2020) |
| PVC |  |
1.16-1.58 | ZnCl2 (1.5 g/cm) | 5 min stirring + 5 min rest + 3 short stirring bursts | overnight | 82.8% | Vermeiren et al. (2020) |
| PET |  |
1.37-1.45 | ZnBr2 (1.7 g/cm3) | 3 min | 10 min | > 95.0% | Quinn et al. (2016) |