DENSITY-BASED SEPARATION OF THERMOPLASTICS FOUND IN THE POSTCONSUMER WASTE STREAM

Separation of thermoplastics from each other and from contaminants fac ilitates their recycling and improves the properties of the reprocesse d material. Clean, dry, shredded thermoplastics obtained from post-con sumer, plastic waste were separated using pure CO2 and mixtures of CO2 and SF6 in a lab-scale, density-based separator. The separator was de signed to operate at the pressures and temperatures required to attain the appropriate densities for the separations using these near-critic al fluids. Separation efficiency, factors affecting separation purity, and favorable operating conditions and procedures were determined. Se veral thermoplastic mixtures were separated, including HDPE/LDPE/PP an d PVC/PET. The purity of the separated homopolymers ranged from 100%-7 7% by weight, with most runs yielding 96%-100% purity.