Chemical recycling of polyesters

Abstract

In the presented paper, two basic strategies that can be used in the processes of chemical recycling of polyester material were described. The first of them involves increasing the molar mass of recycled materials in the solid-state polycondensation (SSP) process and/or joining their chains with various types of substances easily reacting with the end groups of polyesters (so-called extending agents). The essence of the second strategy is the degradation of the material under the influence of various protogenic agents (such as water, alcohols, glycols and amines) to obtain low-molecular products or oligomers that can be used as raw materials in the synthesis of many classes of polymers. The methods that are already used in PET [poly(ethylene terephthalate)] recycling and the possibility of their extension to other types of polyesters are both shown.

Electrochemical methods for materials recycling

“…71 Strategies have been identified to improve the outcomes from these methods, such as solid phase polycondensation, in which a polymer sample is heated under vacuum or inert gas flow to increase molecular weight and improve mechanical properties of the recycled material. 73 Despite such techniques being applied industrially in some capacity, the typical number of mechanical processing cycles a plastic can undergo is still severely limited and varies by polymer type. 71 Both primary and secondary recycling methods result in an energy savings of 50% of the energy that would have been necessary to make the recycled product outputs from virgin materials.…”

Polietilen Tereftalatoaren (PET) birziklapen kimikoa hidrolisiaren bidez

“…Gehien erabiltzen diren ur-amina primarioen disoluzioak metilamina, etilamina, etanolamina eta n-butilamina anhidroa dira. Hala ere, aminolisi partziala baliatzen da PET propietateak hobetzeko (adibidez, zuntzen kolorazioa) prozesatzeko propietate zehaztuak dituzten zuntzen fabrikazioan [21,23].…”

“…Hidrolisia despolimerizazio-metodo alternatiboa da, baldintza moderatuetan lan egiten duena, eta hidrolisi neutroan, azidoan eta alkalinoan sailkatzen da. Glikolisiak ez bezala, oso kutsatuta dauden elikagaiak ahalbidetzen ditu, batez ere bere metodo alkalino eta azidoan, azidoen erabilerari esker kolorea kentzea lortzen baita [21]. Elikaduran, PETak beste plastiko mota batzuen ezpurutasunak aurkeztu ditzake, hala nola, PVC eta PU.…”

“…EKAIA (2022), artikulua prentsan/article in press https://doi.org/10.1387/ekaia.23769Asier Barredo eta lankideak BehinSolbolisi teknologia bakoitzerako planta pilotu eta komertzialen adibideak[21,22,[24][25][26][27][28][29][30][31][32][33][34][35][36].…”

Recent Studies on Recycled PET Fibers: Production and Applications: a Review

“…Generally, there are two methods for PET recycling: mechanical and chemical. In general, in the chemical method (16% of recycling), the reverse of the polymerization reaction, i.e., depolymerization, occurs and the primary monomers are obtained (Al-Sabagh et al 2016;Scremin et al 2019;Dębowski et al 2019). Chemical recycling is less used because it causes destructive changes in properties such as mechanical, thermal, and electrical conductivity (El Essawy et al 2017).…”