Development of improved materials from poly(lactic acid) with the aid of plasticizers and crystallization-promoting gelators

M. Colaers1, W. Thielemans2, and B. Goderis1

1Polymer Chemistry and Materials, KU Leuven, 3001 Heverlee, Belgium
2Chemical Engineering, Campus Kulak Kortrijk, 8500 Kortrijk, Belgium

Polylactic acid (PLA) is a bio-based polymer which might become an alternative for petroleum-based plastics such as polypropylene and polystyrene. However, at present, the properties of PLA do not meet the requirements for a number of applications. The challenge to be addressed is to develop transparent PLA with an increased heat distortion temperature, balanced stiffness and toughness and increased barrier properties. The method explored to reach this multi-dimensional goal is to blend PLA with combinations of plasticizers (for reducing the brittleness) and crystallization-promoting gelators (to increase the crystallinity). Upon cooling, the gelator forms a fine fibrillary network, which nucleates the PLA crystallization. The resulting, small-sized crystal aggregates limit the scattering of visible light and enhance transparency, which is desired for packaging purposes. An increased crystallinity is required to enhance the barrier properties and increase the heat distortion temperature.

The semicrystalline morphology and efficiency of the gelator fibrillary network depends on the cooling conditions and the addition of plasticizers. Both aspects are addressed using Differential Scanning Calorimetry, optical microscopy and time-resolved synchrotron SAXS/WAXD.