Bio-based Film Recycling via Solvent-Targeted Recovery and Precipitation (STRAP) Process

Overview

The Solvent-Targeted Recovery and Precipitation (STRAP) process is a dissolution-based recycling technology that selectively recovers polymer resins from multicomponent plastic waste, including multilayer packaging films. Unlike traditional mechanical recycling, STRAP preserves the chemical integrity of the polymer, avoiding depolymerization and enabling recovery of resins pure enough for food-grade applications. This project extends STRAP to bio-based multilayer films containing aliphatic polyesters such as polylactic acid (PLA) and polyhydroxyalkanoate (PHA), which are increasingly used in sustainable packaging. The goal is to demonstrate that STRAP can recover these bio-based resins in chemically pure form while removing common post-consumer contaminants, including phthalates and PFAS compounds.

Technical specifications

• Selective dissolution: STRAP exploits physicochemical differences between polymers, using carefully chosen solvent systems in which a target polymer dissolves while other polymers and contaminants remain insoluble.
• Filtration and precipitation: The dissolved target polymer is separated from undissolved solids by filtration, then cooled to precipitate as a dry, pure solid resin.
• Solvent reuse: Solvents are recovered and reused, and the process can be sequentially repeated to recover multiple polymer types from a single waste stream.
• Molecular modeling-guided solvent selection: A computational approach predicts temperature-dependent polymer solubilities across over one thousand solvents, enabling rapid identification of optimal solvent systems for new waste streams.
• Validated resin purity: Recovered resins have been characterized by FTIR and headspace GC-FID and confirmed as chemically pure polymers.
• Process modeling: Existing models indicate STRAP can recover resins at lower cost and with 60–70% lower greenhouse gas emissions compared to petroleum-derived virgin resins.
• Bio-based extension: New work targets 99% pure PLA and PHA resins from bio-based films, incorporating safety screening to exclude hazardous solvents.

Technology readiness level

STRAP has been demonstrated in laboratory settings for a range of waste plastics, including flexible and rigid multilayer films, face masks, and mixed plastic waste. Near-quantitative recovery of pure resins has been achieved experimentally, and resins produced by STRAP have been validated for use in food-grade applications. The current project represents the first application of STRAP to bio-based polymers. Planned validation includes laboratory demonstration of the STRAP process for PLA and PHA films, complete material balances, resin characterization via FTIR, DSC, and TGA, and collaboration for independent resin characterization and process modeling at multiple scales.