This article is a review on the thermodynamic and chemical aspects for the recycling of thermoplastics in blends as well as on the way this type of recycling is approached at the industrial level. In the general case, although the techniques of sorting of materials are increasingly elaborated, it can be advantageous to process blends of polymers. Most of polymers are not miscible and many scientific studies showed the interest of chemical compatibilisers for non-miscible blends. Whereas the potential of the mixtures is largely exploited for the ‘first life’ of materials, the concept of mixture seems to become a problem when it comes to recycling. The chemistry of compatibilisers (largely studied in many scientific publications) seems to be far from being sufficiently exploited to improve the properties and to largely diversify the applications of recycled materials.