Process for Improved Barrier PLA Film

Executive Summary

Consumers, companies, and governments are increasingly favoring compostable materials over fossil-based alternatives, as waste from traditional materials has escalated significantly in recent decades. However, a key challenge with compostable materials is their inferior oxygen and moisture barrier properties compared to non-compostable options. For instance, compostable films used in flexible food packaging often lack the moisture resistance needed to maintain sufficient shelf life. Current compostable film technologies typically rely on metallization or non-fully compostable layers to achieve these properties. In response to this, researchers at Michigan State University and California Polytechnic University have developed a new process to extrude bio-sourced stereocomplex polylactic acid (sc-PLA) films without the need for masterbatches, creating compostable films with medium to high water transmission rates.

Description of the Technology

The technology utilizes cast extrusion of two enantiomeric forms of PLA, specifically L-PLA (PLLA) and D-PLA (PDLA), to produce stereocomplex PLA (SC-PLA) as a monolayer film, which is then annealed as a substitute for biaxial orientation. The moisture vapor transmission rate (MVTR) at 38°C and 90% relative humidity was as low as 0.433 × 10−14 ((kg m)/(m² s Pa)), with the best samples showing a transmission rate of 180 g/(m²day) for films normalized to 25.4 µm at 37.8°C and 90% relative humidity. This performance was approximately twice as effective as films made from either L-PLA or D-PLA alone. Achieving a low water vapor transmission rate (WVTR) remains one of the key challenges in developing compostable films with high water barrier properties.

Benefits