Current developments in chemical recycling of post-consumer polyethylene terephthalate wastes for new materials production: A review

Abstract: Plastic recycling is gaining traction to reduce the demand for fossil resources for plastic production. Poly(ethylene terephthalate) (PET), mainly used in the packaging and textile sectors, is often isolated in the sinking fraction during the density-based separation of mixed plastic waste streams. The heterogeneity of the sinking fraction makes direct mechanical recycling of PET impossible. Therefore, neutral hydrolysis of PET was investigated in the presence of other polymer contaminants to study their impact on the neutral hydrolysis of PET. PA6, PC, POM, and PVC were found to decompose during hydrolysis, whereas ABS, PMMA and a mixture of PE, PP and PS was chemically inert during the hydrolysis treatment. The subsequent BHET synthesis with excess ethylene glycol was performed directly on a mix of the polymer contaminated hydrolysis products or a hydrolyzed post-consumer plastic waste fraction. BHET was successfully formed in the plethora of decomposition products in the synthesis, and a subsequent recrystallization recovered the BHET in high purity with only water being used as solvent. This demonstrated a robust method to handle PET fractions in mixed plastic waste that can be applied without purification prior to BHET synthesis - enabling chemical recycling of PET. Abbreviations: ABS, Poly(acetonitrile-butadiene-styrene); ATR-FTIR, Attenuated Total Reflectance Fourier Transformed Infrared Spectroscopy; BC, Bis(2-Hydroxyethyl) terephthalate crystals; BHET, Bis(2-Hydroxyethyl) terephthalate; DMSO, Deuterated dimethyl sulfoxide; DSC, Differential Scanning Calorimetry; EG, Ethylene glycol; 1H NMR, Proton Nuclear Magnetic Resonance; Hm, Melting enthalpy; Oligo, Oligomers; PA6, Polyamide 6; PC, Polycarbonate; PE, Polyethylene; PET, Poly(ethylene terephthalate); PMMA, Poly(methyl methacrylate); POM, Polyoxymethylene; PP, Polypropylene; PS, Polystyrene; P, Purity; PVC, Poly(vinyl chloride); rpm, Revolutions per minute; SPHP, Solid Phase Hydrolysis Product; Ti(IV)OBu, Titanium(IV) butoxide; Tm, Melting temperature; TPA, Terephthalic acid; Wt, Weight; Y, Solid Phase Hydrolysis Product yield; Yt, Bis(2-Hydroxyethyl) terephthalate yield; ν, IR stretching mode; δ, IR bending mode; ω, IR wagging mode.

TL;DR: In this article , a taguchi orthogonal array (L 9 , 3 4 ) was applied to study the main interactions between these factors to optimise the yield, which results in a good yield (79-88%) to the monomer bis (2-hydroxyethyl) terephthalate (BHET), with optimum conditions.

TL;DR: A vasta aplicação do polietileno de alta densidade (PEAD), principalmente no setor de embalagens, confere ao PEAD o lugar entre os plásticos mais produzidos e consumidos no mercado worldial as mentioned in this paper.

TL;DR: Advances in technologies and systems for the collection, sorting and reprocessing of recyclable plastics are creating new opportunities for recycling, and with the combined actions of the public, industry and governments it may be possible to divert the majority of plastic waste from landfills to recycling over the next decades.

TL;DR: This review presents a comprehensive description of the current pathways for recycling of polymers, via both mechanical and chemical recycling, and discusses the main challenges and some potential remedies to these recycling strategies, thus providing an academic angle as well as an applied one.

TL;DR: Although primary and secondary recycling schemes are well established and widely applied, it is concluded that many of the PSW tertiary and quaternary treatment schemes appear to be robust and worthy of additional investigation.

TL;DR: The effect of recycled and waste plastic on bulk density, air content, workability, compressive strength, splitting tensile strength, modulus of elasticity, impact resistance, permeability, and abrasion resistance is discussed in this paper.