ABSTRACT:A dissolution/reprecipitation route was followed for the recycling of poly-(ethylene terephthalate) (PET). Model experiments on virgin material, either in the form of pellets or blow-molded bottles, are presented. The process proposed comprises dissolution of the plastic in an appropriate solvent, reprecipitation by using a nonsolvent, thorough washing of the material obtained, and drying. The solvent mixtures involved are separated by fractional distillation for further reuse. N-Methyl-2-pyrrolidone (NMP)/n-octane ϩ n-hexane proved to be a particularly effective solvent/nonsolvent system. Further investigation was focused on the effect of the sample history through successive recycling cycles. The recycled material was evaluated in terms of molecular weight, crystallinity, and grain-size analysis, resulting in an excellent quality, competing with the virgin grade.

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A model dissolution/reprecipitation process is studied for the recycling of high‐density polyethylene (HDPE). The process proposed basically comprises dissolution of the plastic in an appropriate solvent, reprecipitation by using a nonsolvent, thorough washing of the material obtained, and drying. The solvent mixtures involved are separated by distillation for further reuse. Toluene/acetone was tried as a potential solvent/nonsolvent pair and proved to be very satisfactory, similarly to the case of recycling low‐density polyethylene. Further investigation was focused on the effect of sample history through successive recycling cycles. The recycled grades were evaluated in terms of the following properties: melt flow index (MFI), molecular weight, crystallinity, mechanical performance in tensile mode, and grain size analysis. In all cases the recycled polymer exhibited excellent retention of its properties. © 1995 John Wiley & Sons, Inc.

The potential of recycling polypropylene‐based composites by means of a dissolution process was investigated. The composites were dissolved in an appropriate solvent, and subsequently the polymer solution, containing the fibers in suspension, was filtrated for recovery of the reinforcing agent and of the polymer matrix. Different amounts of hot solvent were employed for washing during filtration, to vary the polymer content remaining on the fibers. The recycled fibers were incorporated in the same polymer matrix, but of virgin quality. The results on the tensile and impact performance of these second generation composites were compared to those of the base material containing unused fibers. It becomes evident that a significant increase of the tensile modulus and strength occurs as the polymer phase deposited on the fibers increases. However, it appears that this interphase alteration has a negative effect on the Izod impact strength. The overall behavior is discussed in terms of fiber dispersion aspects and fiber/matrix adhesion. © 1997 John Wiley & Sons, Inc. Adv in Polym Techn 16; 313–322, 1997