Water-borne barrier coating for PLA film to reduce vapor transmission and enable compostable, recyclable packaging
A low-cost, compostable, FDA-approved water-borne barrier coating using barrier pigments (e.g., kaolin) applied to PLA film reduces water vapor transmission rates from ~400 to ~2 g/m²·day. Double-layer wet-on-dry application heals coating defects for even lower permeability, supporting recyclable and industrially compostable food-contact packaging.
Overview
This solution is a water-borne barrier coating technology designed to be applied to PLA (polylactic acid) film to dramatically reduce water vapor transmission rate (WVTR) while remaining recyclable and compostable. The formulation uses commercially available, low-cost, certified compostable, FDA-approved materials combined with barrier pigments such as kaolin. In preliminary testing on paper substrates with cellulose nanofiber (CNF) layers, the coating reduced WVTR from approximately 400 to around 4 g/m²·day; when barrier pigments were added, transmission dropped further to roughly 2 g/m²·day. Applied to PLA film—which already offers meaningful moisture resistance—the coating is expected to achieve near-target barrier performance suitable for food-contact packaging applications.
Technical specifications
Core technology:
- Water-borne polymer coating system modified with barrier pigments (e.g., kaolin)
- Applied to PLA film substrates, including both metalized and standard PLA variants
- Double-layer wet-on-dry application enables the second coat to heal defects in the first, driving WVTR even lower
Key features:
- Reduces WVTR from baseline ~400 g/m²·day to ~2 g/m²·day on paper-CNF substrates; expected to be lower on PLA
- Uses commercially available, low-cost raw materials
- All components are certified compostable and FDA approved for food contact
- Designed to be recyclable through melt processing
- Compatible with a range of coat weights and polymer types
- Oxygen permeability will also be characterized as part of performance validation
Validation approach:
- Screening of approximately 16 different formulations at varying coat weights
- Variation of barrier pigment type, amount, and polymer type
- Viscosity-modifying additives may be incorporated to improve substrate wetting
- Side-by-side comparison with paper-CNF substrates
- Recyclability assessed by melting coating material, characterizing rheology, and reforming films
- Economic analysis to assess commercial viability
Technology readiness level
This technology is at an early-to-mid stage of development. Preliminary proof-of-concept work has demonstrated the barrier mechanism on paper-CNF substrates, achieving significant WVTR reductions. Future validation will extend the approach to PLA film substrates—both metalized and standard—across multiple formulations and coat weights, while also characterizing oxygen permeability, recyclability, and economics. The work is being conducted at the University of Maine, which offers pilot-scale prototyping facilities and industry-oriented research support. The technology is not yet commercially deployed but is advancing toward formulation optimization and application validation suitable for packaging industry partners.
About University of Maine
The University of Maine is a comprehensive public research university and the state’s flagship, coupling broad academic depth with an applied, industry‑oriented culture. On campus, companies access large‑scale prototyping facilities, pilot‑scale lines, and specialized test tanks that move concepts toward deployable systems. A statewide Cooperative Extension and field sites connect R&D teams to real‑world conditions across Maine’s coastal, forested, and cold‑weather settings, while industry liaisons streamline sponsored research. Funding comes from competitive federal sources such as the National Science Foundation, Department of Energy, U.S. Department of Agriculture, and the National Oceanic and Atmospheric Administration, while a centralized tech transfer office supports IP, licensing, SBIR/STTR, and startup formation.
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