Dissolution creates new path to recycling flexible plastics
Flexible plastics are affordable and commonly used. Their flexibility makes them resilient to traditional recycling processes.
By Peter Murphy
Published March 2, 2026
Polypropylene and polyethylene are two durable and affordable plastics commonly used as packaging materials, snack wrappers, microwave containers, and other, usually flexible, plastic films. Their flexibility, however, makes them resilient to recycling processes, and these plastics often end up in landfills or leak into the environment.
University at Buffalo researchers are leading efforts on a new, innovative way to recycle these plastics through solvent-based recycling, or solvent purification. Their work has the potential to unlock for recycling millions of tons of plastics that are discarded or burned after use.
Polyethylene (PE) and polypropylene (PP) are polyolefins, some of the most common plastics used worldwide. Over 359 million tons of plastic were produced worldwide in 2024 alone, and polyolefins account for over 50% in weight of produced polymers, according to research in the journals Polymers and Cleaner Materials. Polyolefins are used in packaging to protect contents from external elements. Few solvents can dissolve polyolefins, making them one of the most efficient choices for protecting food, liquids and other materials. According to Paschalis Alexandridis, UB Distinguished Professor, there is momentum in discovering ways to dissolve these plastics.
“There is interest in dissolving polyolefins, for example, during their processing and, more recently, for the purpose of plastics recycling,” Alexandridis says. “To separate or isolate polyolefins from their mixtures or blends or multi-material films, and to purify recycled polyolefins from additives, which are typically harmful to health.”
Paschalis Alexandridis
Alexandridis, Marina Tsianou, professor, and Ali Ghasemi, PhD student, all in the Department of Chemical and Biological Engineering; and Luis Velarde, associate professor in the Department of Chemistry, have co-authored recent papers describing ways to dissolve polyolefins and the potential benefits this method could have on alleviating plastic waste. In each paper, they introduce experimental and modelling framework to address dissolution of different forms of polyolefins.
“Solvent-based recycling of polyolefins presents an opportunity to manage plastic waste and recover useful materials,” Alexandridis says. “Our study facilitates the design and optimization of an energy efficient and environment-friendly, large-scale dissolution-precipitation recycling process for plastics that are currently being landfilled or incinerated following their use.”
Scientists need to understand how PE and PP dissolve at microscopic levels in order to dissolve these plastics efficiently. Alexandridis, Tsianou and Ghasemi’s work combines experiments with computer models to better understand the plastics’ behavior throughout the dissolution process. Despite being one of the most widely produced and used polymers, there have been just four articles published on PP dissolution since the 1970s. Their study, “Polypropylene Dissolution Kinetics: Effects of Solvent, Temperature, and Particle Size,” describes their experimental findings as well as the new model they developed that is validated by the experimental findings. The researchers dissolved PP pellets — spheres of the polymers, also known as nurdles — across multiple solvents. They found that the pellets fully decrystallize before dissolving completely.
In their most recent study, “Dissolution of Semicrystalline Polyethylene: Contributions of Decrystallization and Disentanglement to Kinetics Revealed by Integrated Experiments and Modeling,” they also developed a model to provide detailed information on the PE’s crystalline and amorphous domains and solvent diffusivity in different solvents and temperatures, information that is impossible or difficult to observe from experimentation.
The researchers also compared the behavior of PE both under dissolution and while it melts in their study, “Real-Time Quantification of Polyethlene Crystallinity via In Situ Mid- and Near-Infrared Correlation Spectroscopy: Melting and Dissolution.” They developed a temperature-controlled liquid flow-cell experimental setup, which allowed them to monitor mid-infrared and near-infrared spectra in real time. These spectroscopic results allowed researchers to examine when PE decrystallizes and when its long polymer chains disentangle.
Solvent purification is a form of chemical recycling, and one of the more effective ways to complement mechanical recycling, which is the current preferred method for recycling plastics. This solvent-based method offers greater advantages over another chemical recycling method, pyrolysis, according to Alexandridis. Pyrolysis is a controlled thermal breakdown that breaks plastic chains into smaller molecules such as oils and gasses, whereas solvent purification preserves the plastics and allows for their reuse.
“Chemical recycling presents a useful complement to mechanical. Mechanical recycling is rather limited in the objects and types of plastics it can handle efficiently; less than 10% of plastics are recycled currently,” Alexandridis says. “Pyrolysis is promoted as a method that can process much more waste plastics but generates concerns. The solvent-based recycling highlighted in this set of articles has many benefits over pyrolysis.”
The impact of this work could expand beyond plastics recycling as well, and into other fields, according to Alexandridis. “This work also has implications in drug delivery and biomedical applications by enabling controlled release rates through tailored dissolution profiles, and in plastics processing by informing solvent selection and fabrication conditions for efficient manufacturing,” Alexandridis says.
These studies were made possible by the the NSF award # 2029375 EFRI E3P: Valorization of Plastic Waste via Advanced Separation and Processing.
