Bio-Based Upcycling of Poly(ethylene terephthalate) Waste for the Preparation of High-Performance Thermoplastic Copolyesters

Abstract

Thermoplastic copolyesters occupy an important segment in the materials market, finding use in a wide range of engineering plastic applications. This fact owes itself to the versatility underlying the synthetic preparation. However, the industry relies nearly exclusively on virgin feedstocks that are derived from fossil-based resources. With a keen interest in improving the deleterious environmental impact of this material class, we combine postconsumer recycled PET (rPET) with a bioderived dimer fatty acid (DFA) building block for the synthesis of segmented thermoplastic copolyesters (TPCs) via solvent-free melt polycondensation. The influence of (i) catalyst type, (ii) hard block (i.e., PET) precursor, and (iii) soft block (i.e., DFA) content on the microstructure and mechanical properties of TPCs was assessed. Samples that exhibit equivalent mechanical strength and segment distribution are accessible using either pristine bis-hydroxy ethylene terephthalate (BHET) or rPET as starting materials. Screening of reaction conditions and composition space within this context was performed with small-scale (2 g) reactions. Further optimization of reaction conditions in terms of catalyst concentration and ethylene glycol deconstruction agent content allowed for the upscaled synthesis (100 g) of engineering-grade TPCs in a custom-built reactor. We believe that our results contribute to a new paradigm in the efforts for more responsible manufacturing practices for TPCs and provide an additional outlet for the efficient handling of end-of-life, recyclable plastics.

Utility of Chemical Upcycling in Transforming Postconsumer PET to PBT-Based Thermoplastic Copolyesters Containing a Renewable Fatty-Acid-Derived Soft Block

“…However, the PET samples with increasing FADD content first undergo crystallization during heating, with T c around 100 °C. This is consistent with our earlier work on PET-based copolyesters and suggests prohibitively slow crystallization kinetics that hinders crystallization during cooling before all molecular motion is frozen in place below the T g . Only after sufficient molecular mobility is regained at relatively high temperatures (i.e., above the T g ; > 70 °C) can the short PET segments arrange onto a lattice, which is accompanied by an exotherm.…”

“…Alternatively, rPET has been reacted directly with various functional building blocks to form diverse copolyesters, plasticizers, or resins. − This has been done with several biobased bifunctional comonomers such as isosorbide , or fatty acid derivatives, , but this approach routinely leads to oligomers lacking mechanical integrity. Our interest lies in generating high molar mass segmented copolymers, generically called thermoplastic copolyesters (TPCs) possessing high-performance mechanical properties, using a direct, one-pot reaction pathway from rPET …”

“…The different copolymers are interrogated thoroughly to uncover contrasting thermal and mechanical properties, which are connected to the detailed molecular makeup as confirmed with various analytical tools. This work builds on our previous publication in two important ways . First, a functional fatty acid diol is used in place of a diacid.…”

“…Our interest lies in generating high molar mass segmented copolymers, generically called thermoplastic copolyesters (TPCs) possessing highperformance mechanical properties, using a direct, one-pot reaction pathway from rPET. 25 TPCs are multiblock copolymers comprising alternating rigid and flexible segments. 26,27 They are found in an enormous array of engineering plastic applications, owing to the broad range of accessible properties.…”

Plastic Waste Valorization by Leveraging Multidisciplinary Catalytic Technologies

“…Cradle-to-gate LCA of the resultant rPET-FRPs predicted a 57% savings of total supply chain energy and a 40% reduction of greenhouse gas (GHG) emissions relative to standard petroleum-based FRPs. In addition, Pitet and colleagues prepared high-performance segmented thermoplastic copolyesters from depolymerized PET and bioderived dimer fatty acid via solvent-free melt polycondensation . These cases show a good paradigm for economical and sustainable plastic reclamation by depolymerization and subsequent copolymerization with bioderived monomers to fabricate improved polymers.…”