Common Additives used in Recycling of Polymers

Managing Plastic Waste─Sorting, Recycling, Disposal, and Product Redesign

“…The nature and purpose of the various additives has been summarized in the literature. , The literature provides also valuable information on barrier additives for food packaging, namely polymeric, metallic or metal oxide films and additives…”

“…So far, plastic recycling consists mainly of mechanical recycling and is focused on the three dominant packaging polymers PE, PP, and PET. The recycling processes rely on cautious sorting of the clean and pure monostream fraction, compounding it to granules, and blending them with a virgin polymer of the same family, together with compatibilizers and additives to mitigate the shortcomings of recycled material. ,,, …”

“…These shortcomings can be mitigated by addition of small amounts of compatibilizers, e.g. short block copolymers with chain segments of the same nature as two polymers of the blend (e.g., PP–PE block compatibilizers). ,,, Alternatively, the compatibilizers contain a main chain that resembles the target matrix and a reactive end group that can react with the functional group of the polymer impurity, for instance, one that can react with an alcohol group of PET or EVOH (ethylene-vinyl alcohol) polymers.…”

“…Fourth, recycled polymer chains may be partly degraded, e.g., through oxidation or UV radiation upon use, or through thermal degradation upon repeated hot processing. ,,, Indeed, hydrocarbon polymers and PVC are reprocessed at 160–260 °C, and performance polymers such as PA and PET are reprocessed at 220–320 °C . Such processing temperatures are not benign, particularly when the polymer chains has been damaged during use.…”

“…But recycled polymers may also exhibit an increased Mw and higher viscosity. The resulting shortcomings can be mitigated by means of various additives. ,,, …”