From Waste Stream to Value Chain: Chemistry Strategies for Plastics Recycling Processes

It is well understood that mechanical recycling of PET leads to degradation and development of color bodies. A recent study in Sweden showed a significant increase in L* and b* with a shift to 100% mechanical rPET bottles in the deposit return system, resulting in decreased quality across the whole system and limiting the applicability of the material. While mechanical recycling remains an important and needed technology in material circularity, the complimentary technology of chemical recycling can address these impacts/gaps to further increase the amount of material that is recycled and kept in circulation by creating virgin-quality material.

Focusing on the complementary nature of chemical recycling, Eastman has started up a 110 kmt methanolysis facility designed to process hard-to-recycle PET, including colored and opaque materials. This facility produces high-purity DMT with yields greater than 87%, along with polymer-grade EG monomers, both of which are used to manufacture food-and medical-grade polyesters and copolyesters. This talk will discuss this start-up journey, including development of feedstock qualification, mechanical pre-processing, quality control measures, testing for food contact and medical compliance, and ultimately demonstrating 105% of nameplate production capacity within two years of start-up. Enabling high-quality copolyesters has allowed recycled content to be incorporated into demanding applications where mechanically recycled material cannot perform today, while also enabling up to 100% recycled content products through mass balance that can improve the quality of the mechanical recycle stream.

Transitioning to a circular economy is vital to preserving and protecting material resources. Demand for post-consumer recycled (PCR) polyolefins is expected to rise over the coming decades, driven by society’s push for low-carbon solutions, regulatory mandates for recycled content, and brand-owner commitments. However, variability in feedstock, recycling processes, and contaminant profiles create challenges for product safety and application suitability.

This work introduces a PCR Recycling Stewardship program designed to establish product safety principles for mechanical and dissolution recycling through a structured, risk-based framework. The approach considers intrinsic hazards of PCR materials and exposure potential for specific end-use applications, prioritizing risk management measures toward higher-risk scenarios. PCR feedstocks and compounded materials were evaluated using targeted and non-targeted analytical methods, including heavy metals and volatile/semi-volatile organic analyses. Risk characterization combined hazard identification with application-specific exposure potential, enabling tiered toxicological assessments and defining acceptable use conditions.

To date, more than 1,200 PCR samples representing over 140 waste streams across multiple regions have been analyzed. Supplier engagement focused on feedstock selection, bale specifications, plastic management protocols, and improvements in sorting, washing, and extrusion processes. Data revealed a strong correlation between feedstock cleanliness and contaminant profiles, confirming cleaner inputs yield cleaner PCR. Cross-polymer impurities, notably PVC in polyethylene and polypropylene streams, were key contributors to certain contaminants. Targeted process improvements at recycling facilities reduced these contaminants measurably. New recycling processes such as dissolution may also be useful in reducing polymeric and non-polymeric contaminants resulting in increased performance by a reduction of color and odor, and improved contamination profile, which allows for broader waste inputs and more options for recycled plastics.

This program demonstrates that combining large-scale analytical datasets with a science-based, application-driven approach enables responsible, scalable PCR use. Continued advancement in analytical methods and sorting technologies will be critical to improving PCR quality and supporting broader proliferation of recycled content adoption.

The landscape of chemical compounds that impact package appearance/performance and raise safety concerns is continually evolving, making it essential to evaluate their presence in post-consumer recycled plastics. Understanding the levels of these chemicals and their removal during dissolution recycling processes is critical for assessing and communicating the benefits of this technology. In this study, we compare polypropylene (PP) feedstock entering the dissolution recycling process with purified PP resin using a broad range of analytical measures, including evaluations of physical properties, a non-targeted migration screening method (CosPaTox), and selective extraction of target compounds across four organic chemical classes: pesticides, PAHs, alkylphenols/bisphenols, and phthalates, along with an assessment of total elemental composition. This analysis aims to evaluate the effectiveness of the dissolution recycling process to remove impurities. The results show that purified PP exhibits improved physical properties, including better color and polymer purity compared to the mixed and waste material feedstock. Additionally, the non-targeted analysis revealed a significant reduction in various migratable organic compounds in the purified PP resin, with complete removal of phthalates and pesticides and a substantial decrease in total elemental contaminants, PAHs, and alkylphenols/bisphenols. This comprehensive assessment provides stakeholders with valuable insights into the suitability of dissolution-recycled PP, facilitating effective communication about its purity safety and promoting the advantages of using dissolution-recycled material in sensitive applications.

Plastics are a cornerstone of modern life, with annual production now exceeding 450 million tons. Driven by global population growth and rapid urbanization, our reliance on synthetic packaging has skyrocketed. Polyethylene terephthalate (PET) alone accounts for approximately 50 million tons of this volume, the majority of which is end up into landfills and oceans. Through weathering and biological degradation, plastics break down into microplastics and nanoplastics, and release persistent bio-accumulative toxins that disrupt marine ecosystems and infiltrate the global food chain.

RiKarbon, Inc. has developed a proprietary RiPurpose® technology to upcycle post-consumer PET, collected from oceans and the environment, into sustainable adhesives for packaging and beyond. This one-step energy-efficient technology is uniquely designed to deliver 1) stronger cohesive strength, 2) environmentally flexible applications, 3) customizable setting time, 4) recyclability, and other value propositions. This presentation will provide a technology summary and key features and specifications of the GEN-1 RiPurpose® adhesive product.

A wide array of chemicals is added to plastics to enhance their properties and aid in manufacture. Additives give polymers seemingly limitless versatility, for example, by softening or stiffening (plasticizers, fillers), aesthetic options (pigments and dyes), improving safety (flame retardants, antimicrobials), durability (ultraviolet stabilizers) and processability (slip agents, antioxidants). However, the accumulated chemical composition of these materials is essentially unknown even to those within the supply chain, let alone to consumers or recyclers. The drive to increase recycled content in plastic products highlights the issues presented by these chemical mixtures, amid growing public concern about the impacts of plastic-associated chemicals on environmental and human health.
At the same time, microplastic pollution is an emerging problem that is gaining attention worldwide due to harmful effects on ecosystems and biota. Significant uncertainty and concern exist regarding the potential for additives release from plastics during photoaging. Although attempts have been made to quantify additive leaching or additive release into the environment, there is less information about the complex interplay between the composition of plastic products and environmental aging that produces microplastics.
This talk will discuss the broad classes of additives used in plastics, and a case study will be shared regarding the influence of antioxidants on aging and fragmentation behaviors of PET and PE in simulated environments. Guidelines for manufacturers and regulators on types of additives and disclosure of compositional information are provided that would improve recycling prospects for that wide array of plastics waste generated today. Improved understanding of the use and fate of additives could aid in developing formulation guidelines to improve the environmental sustainability of plastic products through better recycling outcomes and by reducing microplastic shedding in outdoor applications.

Additive manufacturing generates substantial plastic waste from failed prints, support structures, and end-of-life parts. Polylactic acid (PLA) is widely used because it is bio-based and industrially compostable under specific conditions, yet current recycling routes for printed PLA are often limited by thermal degradation, additive contamination, and loss of mechanical properties after repeated melt-processing. This work targets a dissolution-based recycling route that enables selective PLA recovery and additive/co-polymer separation using lower-hazard solvent systems.
A combined computational-experimental workflow was developed to identify effective solvents and reduce trial-and-error screening. Hansen solubility parameters and COSMO-RS (infinite-dilution activity coefficient–based screening) were used to rank conventional and emerging solvents, including ionic liquids and bio-derived candidates. Ranked solvents were then validated experimentally through PLA dissolution tests conducted under mild thermal conditions and across temperatures above and below the polymer glass transition to map dissolution kinetics and handling windows. The resulting labeled dataset (good/poor solvents; dissolution performance descriptors) was used to train machine-learning classifiers to predict solvent suitability and propose additional candidates for validation.
Multiple screened solvents achieved complete PLA dissolution under mild conditions, and the ML models consistently differentiated effective and ineffective solvents, enabling rapid identification of new candidates for solvent-based recycling. By integrating molecular thermodynamic screening, experimental validation, and AI-driven selection, this approach supports scalable process design for polymer recycling with reduced reliance on high-volatility or hazardous solvents, advancing circular materials infrastructure relevant to SDG 9.

Polypropylene (PP) represents one of the largest fractions of global polymer production, yet it suffers from low recycling rates at end-of-life, with most of the waste ultimately landfilled. Mechanical recycling of PP is limited by its propensity for chain scission during reprocessing. Chemical recycling remains challenging due to the inert nature of the hydrocarbon PP backbone and the reliance on solvents, catalysts, or complex separation steps. While mechanical recycling remains critical, chemical recycling strategies are needed to enable value recovery from degraded, mixed or otherwise non-mechanically recyclable PP waste streams. Improving end-of-life outcomes for PP therefore requires scalable chemical strategies that generate value-added feedstocks using minimal additional inputs and infrastructure. Here, we investigate the melt oxidation of isotactic PP during reactive extrusion as a solvent-free, industrially relevant route to introduce reactive functionality, such as ketones and alcohols, while retaining polymer integrity. PP was melt-extruded under controlled oxygen atmospheres at a range of temperatures, with and without exogenous organic peroxide initiation. The resulting materials were analyzed using solution-state high-temperature nuclear magnetic resonance spectroscopy to identify and quantify oxygen-containing functionalities introduced along the polymer backbone. Complementary high-temperature gel permeation chromatography was used to track molecular weight during processing. By correlating functional group formation with molecular weight changes, we identify temperature- and peroxide-dependent conditions in which oxidative functionalization outpaces backbone degradation. These results delineate processing conditions that enable the controlled introduction of chemically useful functional groups onto commercial PP while limiting excessive scission. This work demonstrates how oxidative extrusion – requiring only heat, oxygen, and existing extrusion infrastructure – can serve as a scalable, solvent-free and green upcycling strategy for polypropylene.