Blend structure of commingled plastic from recycled polyethylene and polystyrene

Abstract

AbstractThe hierarchical morphology of commingled plastic waste in the form of thick beams prepared by the ET‐1 process has been examined. Blends of recycled high‐density polyethylene (RHDPE, New Jersey Curbside Tailings) with 25 and 35 wt % expanded polystyrene (EPS) were compared with blends of a virgin high‐denisty polyethylene resin (VHDPE). At the macroscale, observed with the optical microscope, the beams consisted of a solid skin that extended about one‐third of the distance to the center of the beam and a voided core with about half the density of the skin. The phase morphology of the skin at the microscale was characterized by examining etched cryogenic fracture surfaces in a scanning electron microscope. The blends of RHDPE and VHDPE exhibited a gradient morphology with highly elongated EPS domains near the edge and spherical or co‐continuous EPS domains closer to the core. The morphology gradient was created by the competition between the relaxation rate of the melt‐flow morphology and the cooling rate in the mod. In addition to high‐density polyethylene, a variety of other components were identified in RHDPE by photoacoustic infrared and thermal analysis. These included polypropylene, polystyrene, poly(ethylene terephthalate), and chunks of nonpolymeric material. As a result of the heterogeneous composition, the crystallinity of RHDPE was significantly lower than that of VHDPE. © 1994 John Wiley & Sons, Inc.