Simple in situ synthesis of copolymer compatibilizers for plastics recycling

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Post-consumer plastics recycling is strongly hampered by the fact that heterogeneous polymer feeds areintrinsically immiscible, which leads to phase separation within the mixture and typically very poor mechanicalproperties for the recycled products. A well-established method to improve the degree of dispersion in polymerblends and to improve the mechanical properties is through the use of block and graft copolymer additives ascompatibilizers. Unfortunately these materials are generally very expensive to synthesize, and therefore notamenable to large scale plastics recycling. We now suggest a methodology to generate graft copolymercompatibilizers in situ, based on a new cryogenic process developed by KWI Solutions Polymères to turnmixed plastic feeds into fine (1-5 micrometer) powders by mechanical fracturing in an extrusion process. Thisgenerates a large number of radical species at the surface of the particles, due to the polymer chain-breakingprocesses taking place in fracturation of the materials. We will investigate the use of mixed microstructurepolyisoprene (PIP) as a post-fracturation additive to react with the free radical species present, to generatecompatibilizing graft copolymers in situ during the extrusion process. The project will be concerned withgenerating PIP samples of different molecular weights, that can be used to optimize the extrusion conditionsand generate suitable compatibilizing agents. The performance of the additives will be evaluated in terms oftheir ability to improve the tensile and impact properties of the blends obtained by that approach.