An efficient method of material recycling of municipal plastic waste

The recycling of municipal plastic waste after separation of poly(ethylene terephthalate) (PET) bottles, containing various grades of polyethylene (PE), polypropylene (PP), polystyrene (PS) and a small amount of PET, was studied. It was found that a mixture of ethylene-propylene elastomer EP(D)M with styrene-butadiene (SB) block copolymer is a very efficient compatibiliser for PE/PP/PS blends. Surprisingly, EP(D)M/SB is also a more efficient compatibiliser than neat SB for some binary polyolefin/PS blends, probably due to correlation between locations of SB and EP(D)M in the blend. For achievement of acceptable mechanical properties, blends containing an admixture of PET must be mixed at a high temperature. A strong synergism between the effects of SB/EP(D)M compatibilisers and substituted diamine stabilisers on toughness of recyclates of municipal plastic waste was observed and the recyclate with mechanical properties comparable with virgin polyolefins was prepared. Experiments on model systems led to the conclusion that the synergism is a consequence of the grafting of pre-aged polyolefins to SB copolymers. (C) 2004 Elsevier Ltd. All rights reserved.