Polylactic acid: A potential sustainable bio-based controlled release packaging polymer

Polylactic acid (PLA), a bio-based polymer produced from fermentation of starch into lactic acid followed by polymerization process, is considered to be a sustainable packaging material. Stereochemical isomers, P-LLA and P-DLA, affect polymer final properties and can be used in controlled release packaging (CRP) to provide a wide range of release profile. CRP is a new generation of functional packaging materials in which the package acts as a delivery system for antimicrobials or antioxidants. The delivery occurs in a timely manner to increase shelf life and maintain safety and quality of the food.;This study is divided into two parts. The first part aimed at investigating the effects of stereochemical isomers and processing conditions (drying and annealing) on release profile of tocopherol and film properties. The second part investigated the effect of two processing methods, solvent and extrusion casting, on tocopherol release kinetics and film properties.;PLA containing different ratios of stereochemical isomers was impregnated with 3000ppm tocopherol using solvent casting and commercial scale extrusion casting methods to produce the films. The solution casting films were first dried at room temperature for 24 hours and further dried at 40°C. The films from both methods were annealed at 120°C for 4 hours. Then release study was conducted to monitor the release of tocopherol over time on the annealed and unannealed films.;Results of the first part showed varied tocopherol release profiles and diffusivities (2.42X10-19 to 8.68X10-16m 2/s) with three orders of magnitude. Annealing process increased film crystallinity, which led to lower diffusivity and slower tocopherol release. It also decreased water vapor and oxygen transmission rates of the films. Results of the second part showed that solvent casting and extruded films had different tocopherol release profiles but shared similar trend. Scanning electron microscopy performed on films from two methods revealed different topographies. The films from both methods were only comparable in terms of mechanical properties such as tensile strength.;Overall, results suggest that while a wide range of tocopherol release profile using solvent casting method is achievable; data from solvent casting cannot extrapolate directly to extrusion casting in terms of tocopherol release profile.