Upcycling of polyesters through acid hydrolysis and polysaccharide grafting for antibacterial packaging films

Overview

This research proposes a novel chemical upcycling method for mixed polyester packaging waste, including PLA and PHAs, that combines simultaneous acid hydrolysis with polysaccharide grafting to produce high-performance copolymer films. The process targets FDA-compliant polysaccharides such as chitosan and cellulose acetate, leveraging amidation or transesterification reactions with exposed polyester end groups. A key advantage is the ability to process mixed-material packaging directly, without the need for preliminary isolation or separation of individual polymer components, simplifying recycling workflows and reducing costs. The resulting films exhibit antibacterial properties, improved barrier performance, and enhanced mechanical characteristics while retaining biodegradability. By improving thermal stability, the approach enables multiple thermal processing cycles before end-of-life biodegradation, addressing a critical limitation that has hindered broader adoption of biodegradable polyesters in commodity packaging.

Technical specifications

Key features:

• Simultaneous acid hydrolysis and polysaccharide grafting on mixed polyester packaging feedstock
• Compatibility with FDA-compliant polysaccharides including chitosan and cellulose acetate
• Direct processing of mixed-material packaging, including materials containing metallic aluminum films
• Multi-component grafting that exploits varying thermal and mechanical properties of different polyester components
• Production of copolymer films with tailorable thermal, mechanical, and barrier properties
• Use of green solvent alternatives and potential low-cost catalysts to reduce reaction time
• Tunable macromolecular structure through variation of polysaccharide side chain functionality
• Preservation of biodegradability in final copolymer products

Planned characterization methods:

• Differential scanning calorimetry to quantify glass transition temperature
• Tensile testing to assess Young's modulus
• ASTM E96 to measure water vapor permeability
• Biodegradability assessment of resulting copolymer films

Technology readiness level

This technology is at an early-to-mid stage of development. Simultaneous acid hydrolysis and grafting of aliphatic polyesters with polysaccharides has been demonstrated in prior literature but remains time-intensive with poorly understood final copolymer properties. The proposed research aims to advance the technology through three phases: developing scalable acid hydrolysis-grafting pathways using green solvents and catalysts, comprehensively characterizing how polyester chain length and polysaccharide content affect film performance, and demonstrating scalability through pilot-scale reactor design with energy footprint and cost analysis. The work is currently in the research planning and validation phase, with future steps including pilot-scale demonstration and preliminary techno-economic analysis.