Modified PLA Plastic Breaks Down in Weeks, Not Months
A team of researchers at the University of Minnesota has developed a new version of polylactic acid (PLA) plastic that degrades significantly faster under composting conditions.
The modified PLA completely degraded within 21 days under industrial composting conditions, compared to unmodified PLA which only reached 83% biodegradation after 90 days.
Led by Marc Hillmyer and Christopher Ellison, the team published their findings in a new paper. PLA, a bioplastic derived from renewable resources like corn starch, is widely used in food packaging, textiles, and biomedical devices. It accounts for roughly two-thirds of global bio-based and biodegradable plastics production.
The Problem with Standard PLA
Standard PLA has a significant limitation: it degrades efficiently only in industrial composting facilities, which maintain high temperatures and humidity over several months. It does not readily break down in home composts or natural environments.
The Innovation: "Masked Acids"
The researchers solved this by blending PLA with small amounts of organic anhydrides—specifically phthalic anhydride or 2-sulfobenzoic acid cyclic anhydride. These compounds act as "masked acids" that activate upon exposure to water, catalyzing the breakdown of polymer chains.
The key achievement is that this modified PLA retains the mechanical properties—strength and transparency—of unmodified PLA, making it a practical drop-in replacement.
Key Results
- At 0.1% (100 ppm) of 2-sulfobenzoic acid cyclic anhydride, the modified PLA degraded completely within 21 days at 58°C (136°F)—industrial composting conditions.
- Unmodified PLA under the same conditions needed 90 days to reach just 83% biodegradation.
- The modified PLA also showed improved biodegradability at 45°C (113°F), a temperature achievable in healthy home compost bins.
Implications
According to the authors, this approach could enable PLA to degrade not only in industrial composting facilities but also in home composting systems. "This approach could enable PLA to degrade not only in industrial composting facilities but also in home composting bins," the authors note.
Further testing is needed to understand the material's behavior in various environmental conditions.
Funding
The research was supported by the U.S. Army Corps of Engineers' Engineer Research and Development Center's Construction Engineering Research Laboratory, a National Science Foundation Graduate Research Fellowship, and a University of Minnesota Doctoral Dissertation Fellowship.