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Plastic waste is an ever-growing problem; with less than 9% of plastic goods being recycled, NREL estimates landfilled plastics represent the loss of over $7.2 billion and 3.4 EJ of embodied energy. The plastics industry accounts for roughly 7% of global CO₂ emissions related to energy and is projected to account for 15% of the carbon budget by 2050. To remain within a safe operating space for our planetary boundaries, we must implement a drastic increase in recycling rates by 2030.

Unfortunately, improved plastics recycling faces many challenges. Mechanical recycling, the current standard, is ineffective for most plastics as it often results in irreversible molecular weight loss which in turn degrades mechanical properties. Additionally, unknown additive composition limits the re-use of mechanical recyclate in many applications. Thus, chemical depolymerization or additive separation methods are needed for highly contaminated, colored, and mixed-plastic resins. While chemical recycling methods can often address multiple waste streams, it is often energy intensive to produce small molecules of inherently lower value than the plastic feed. Solvent purification technologies, while promising, use high loadings of toxic solvents to dissolve polymers and remove contaminants. To achieve our sustainability goals, robust new technologies are needed that is responsive both to plastic mixtures and their additives while maintaining molecular integrity.

Research Interests

Since my first research experience as an undergraduate in the plastics engineering department at UMass Lowell, I have been interested in applications of green and sustainable chemistry relating to polymer science. Specifically, I am interested in pursuing research related to sustainable polymer synthesis and improved end-of-life processes, green solvents at near and supercritical conditions and their interactions with polymers, separation processes for intimately mixed plastic waste streams, developing greener alternatives to harmful coatings and finishes, and generating new composite materials using lower carbon techniques and reduced cost.

Green solvents for polymer purification: Solvent purification technologies dissolve plastic waste, filtering additives from the mixture, before using an anti-solvent to reform a high-molecular weight plastic. While it can provide a virgin-like resin, due to many plastics’ inherent chemical resistance, solvent selection is limited and often toxic. During my first year, I hypothesized that complete dissolution was not necessary to remove most additives and that at elevated temperatures, polymers would swell in green solvents leading to additive migration. Initially aiming to target multi-layer films, I generated a model of Hansen Solubility Parameters (HSPs) to show the reaction conditions in which green solvents can swell commercially available polymers. The solvents selected included water, acetone, isopropanol, ethanol and more; all of which are known to not cause significant changes to most polymers at room temperatures. However, using a Parr reactor at temperatures higher than what is seen in extrusion, increases the solubility enabling swelling effects without causing significant chain degradation for many polymers. These models were used as a guide for experimental work in which swelling was confirmed. To expand upon this study in the future, I have begun setting up a view-cell reactor that can be used for in-situ swelling quantification using Raman spectroscopy.

Sustainable plastics recycling: Room temperature water is a non-solvent for nearly all engineering plastics, meaning that it is useless for polymer recycling. However, near and supercritical water is always thought of as a destructive solvent for polymers. This drastic change in water’s behavior is accounted for by the nearly linear reduction in dielectric constant with increasing temperature. Near the SC point, the dielectric constant of water decreases to the extent that hydrocarbons are miscible at these temperatures and salts become immiscible in it. Using temperature conditions below those used in pyrolysis but above those used in extrusion, I have been able to use water to blend immiscible waste streams of PE and PP while preserving molecular weights. This process, termed chemi-mechanical recycling, produces a compatibilized blend that is able to undergo at least three treatments without losing molecular weight. By controlling temperature and shear, chain scission is minimized at our operating conditions as water and HDPE effectively dilute the more reactive PP radicals. Deliberately controlling the temperature profile across heat-up and quench, we are able to capture water’s tunable solvation parameters leading to PE/PP compatibilization and 96% VOC extraction. Water is also able to extract some pigments from real waste streams. For dark colored mixed waste, the color was significantly improved after treatments, with lightness values increasing two-fold. Light color sorted waste streams were able to achieve a near-virgin quality in terms of color post-treatment. This process is able to significantly change our approach to recycling and is both cost and carbon competitive from preliminary TEA and LCA models.

Separation of textile blends: In tandem with my PhD studies, I have been completing an internship at US Army DEVCOM Soldier Center with the Emerging Materials Team. Combining my knowledge of textiles and solvent tunability, I am developing a process to separate nylon and cotton textile blends to strengthen the domestic supply chain. As textile manufacturers continue to move overseas, this is an area of great concern for the DoD to maintain domestic manufacturing and security. In this work I have generated solubility models to map solvents and temperatures to selectively swell or solubilize one component of the blend to aid separation. By exploiting the distinct melting behaviors of nylon and cotton combined with selective solubilization, initial experiments have enabled partial separation.

Sustainable coatings and functionality: While not a main component of my thesis, an area of personal interest has always been creating alternative coatings to replace environmentally harmful finishes as well as finding sustainable ways to incorporate functionality into polymers and textiles. Beginning in undergrad, I worked on several projects to develop a sustainable flame retardant and insect repellant coating. Through my work at Soldier Center, I have had the opportunity to contribute to their work in finding a replacement for PFAS finishes. Additionally, I am developing a more sustainable and cost-efficient process at WPI in which enhanced strength and conductivity is imparted to polyolefins, thus reducing the carbon footprint of common engineering plastics.