Bio-Based Aqueous Dispersions Based on Unsaturated PLA Polymers for Barrier Packaging Applications

Area of Science:

• Polymer Chemistry
• Materials Science
• Sustainable Packaging

Background:

• Growing demand for sustainable packaging necessitates bio-based alternatives to fossil-derived polymers.
• Poly(lactic acid) (PLA) offers renewable origin and biodegradability but its use in aqueous dispersion coatings is limited.
• Barrier applications require materials with reduced environmental impact and enhanced recyclability.

Purpose of the Study:

• To synthesize PLA-based copolymers for aqueous dispersions.
• To optimize copolymer composition and dispersion processing for small, uniform particle sizes.
• To assess the scalability of producing these sustainable barrier coatings.

Main Methods:

• Copolymer synthesis via polycondensation of L-(+)-lactic acid, itaconic acid, and butanediol.
• Solvent-free thermomechanical method for preparing aqueous dispersions.
• Evaluation of particle size, distribution, and water vapor barrier properties.

Main Results:

• Optimal copolymer molecular weight (M_n ≈ 10,180 g mol^-1) and low glass transition temperature (T_g = -1.4 °C) yielded the smallest, most uniform dispersion particles.
• Dispersion stabilizer grade and dosage critically affected particle size and distribution.
• Successful pilot-scale polymer production and bench-scale dispersion preparation were achieved.

Conclusions:

• Aqueous PLA-based dispersions show potential as sustainable barrier coatings.
• The developed process is scalable from laboratory to pilot production.
• Achieved water vapor barrier properties (<10 g/m² at 23 °C/50% RH) are promising for packaging applications.