Dynamic covalent chemistry (DCC) allows the development of thermally (re)processable and recyclable polymer networks, which is a highly attractive feature for new generations of thermoset materials and composite materials.

However, despite a huge surge in academic interest where soon almost any imaginable DCC platform may have been applied in a thermoset formulation, dynamic or reversible covalent polymer networks have so far found only few industrial applications. This lecture will provide a perspective on the main strategies for the application of DCC in the design and development of bulk thermoset materials and presents some of the key hurdles for their industrial implementation.

The polymer design strategies and associated chemistries will be placed into the perspective of how ‘close to market’ their development pathway is, thus providing a roadmap to achieve high-volume breakthrough applications.

Besides a general outline, this presentation will highlight a number of our actual research efforts to overcome remaining limitations for the industrial implementation of this new generation of reprocessable thermoset materials, mainly based on smart chemical design.

Polyurethane (PU) and polyisocyanurate (PIR) foams have gained increasing interest as insulation materials due their superior thermal resistance compared to alternatives. However, increasing environmental concerns necessitate sustainable end-of-life solutions for these materials, as traditional disposal methods like landfilling and incineration contribute to waste buildup and release of toxic chemicals. The current state of the art in chemical recycling of PU materials mainly focusses on the recovery of polyols, while little effort is put into the recovery of the isocyanate part. As most of the economical value of rigid PUR and PIR foams is contained in the isocyanate, these materials call for a different strategy. This work investigates the depolymerization of rigid PU and PIR foams through hydrolysis, glycolysis, and aminolysis to recover both polyols and isocyanate-derived amines. Virgin and end-of-life foams are treated, and the efficiency of these methods in recovering original building blocks is compared. The findings provide insights into more comprehensive recycling strategies, potentially reducing environmental impact and enhancing resource efficiency.

The recent interest for covalent dynamic bonds applied to polymer science has opened the door to recyclable thermosets. In addition to the synthesis of covalent adaptive networks, dynamic chemistry can also enable the valorisation of end-of-life thermosets by promoting or introducing bond exchanges within these materials. In the case of polyurethanes (PU), the constitutive urethane groups are naturally subjected to exchange mechanisms.1 This has led researchers to promote this phenomenon by mixing catalysts, typically tin-based organometallic or organic acids and bases in the polymer.2,3 Despite the demonstrated efficiency of such molecules for PU reprocessing, addressing the issues of PU stability, leaching of potentially hazardous compounds, and performance loss over time is important.
In our work, we investigated the possibility of grafting an amino-alcohol urethane exchange catalyst, namely tetrahydroxyethylethylenediamine (THEED), to a rigid PU foam used for window frame manufacturing. Taking advantage of the naturally occurring urethane exchange, THEED was covalently integrated to the PU via its alcohol functions, while the tertiary amine promoted urethane exchange. Soxhlet solvent extractions of modified PU showed no catalyst release, confirming its grafting. Tensile testing, dynamic mechanical analysis, creep and relaxation measurements helped assessing the grafting effect on the thermo-mechanical properties of the reprocessed PU material. The Tg reduction from 118 to 108 °C enabled to reprocess PU at 200 °C for 30 minutes by compression-molding, yielding a modulus of about 2 GPa. Finally, extrusion tests were performed, demonstrating the potential of this simple process for the revalorisation of rigid end-of-life polyurethanes.

The increasing interest in disposable electronics such as wearable patches, e-textiles, and smart packaging, warns emergence of another man-made disaster. We propose a paradigm shift towards a more sustainable future through development of soft material architectures that are robust and durable, but also degradable by external stimuli.
Hydrogels, a class of soft polymers with exceptional properties, and high water content are rarely used as substrate, mainly due to lack of ink-adhesion and rapid dehydration. Here, we tailor-made photodegradable hydrogels that are non-drying, robust, adhesive to ink, and permit triggerable degradation, making them a suitable substrate for sustainable electronics. These hydrogels are prepared by reversible ionic crosslinking between sodium alginate and divalent cations (Ca2+) and light-responsive crosslinking of poly(acrylamide) (PAAm) chains through synthesized ortho-nitrobenzyl (ONB)-based crosslinkers [1]. By displacing the water molecules in the hydrogels by immersion in glycerol, we addressed the drying problem, and printability of conductive ink. We demonstrate digital printing of a liquid metal (LM) based stretchable ink over the developed substrate, show several body-worn printed wearable sensors, and demonstrate their degradation and recycling of the expensive metals. This work lays the foundation for the use of hydrogels as promising substrates for the next generation of environmentally friendly electronics.

The recovery of high value reinforcing fibers is of particular interest in the field of composites, and opens the way for the use of vitrimers as matrix materials in carbon-fiber reinforced polymers (CFRPs)[1]. However, the vitrimer matrix itself is often downcycled or disposed of. The degradation of the matrix induced by the temperatures, pressures and reagents associated with the recycling process can irreversibly impact its chemical structure [2]. Despite this, the parameters governing the efficiency and mechanisms of this process remain largely unexplored.
In this context, this presentation focuses on the chemical recycling of the vitrimer matrix with an emphasis on understanding the degradation mechanisms and characterizing the recyclates of polybenzoxazine (PBz) vitrimers [3,4]. This process was conducted under mild acidic conditions, with recyclates characterized via liquid and solid-state nuclear magnetic resonance (NMR) spectroscopy. Thermogravimetric analysis (TGA) coupled with Fourier transform infrared (FT-IR) spectroscopy was used to monitor the removal of the recycling medium throughout the recycling process. Post-recycling thermal and vitrimeric properties were assessed using TGA, stress relaxation measurements and FT-IR. Efforts to move nearer to closed-loop recycling were made via physical reconsolidation of the samples, with efficacy assessed via micro-computed x-ray tomography (μ-CT) measurements.
This presentation summarizes the findings to date, highlighting the lessons learned and discussing the broader implications for the chemical recycling of vitrimers. The insights gained should facilitate more effective recovery and reuse of vitrimers and their composites.

Trinseo, as a specialty material solutions provider, has been integrating recycled content into commercial products for over a decade, aiming to reduce the environmental impact of plastics by minimizing reliance on fossil-based raw materials.
Beyond mechanical and chemical recycling, Trinseo has developed DiRecT, a dissolution-based recycling technology designed to return end-of-life plastics to the value chain, particularly those currently destined for incineration or landfill.
DiRecT selectively extracts target polymers from post-consumer and end-of-life waste, removing additives and contaminants through purification steps. This process enables high-quality material recovery while maintaining polymer integrity and reducing energy demand compared to alternative recycling methods.
This presentation will explore Trinseo’s strategy for leveraging dissolution-based recycling to close the loop on plastics, discussing its benefits, challenges, and the role of waste as a renewable feedstock. Additionally, we will compare the product carbon footprint of dissolution-recycled materials versus fossil-based virgin alternatives.