Temperature-Dependent Mechanical Behaviour of Polylactic Acid Plasticised with a Bio-Based Chitin–Lecithin System

Polymers, vol. 18, pp. 2257

Abstract

Polylactic acid (PLA) is a bio-based thermoplastic whose inherent brittleness limits mechanically demanding applications. This study investigates how a bio-based chitin-lecithin plasticiser system affects the mechanical behaviour of injection-moulded PLA as a function of additive composition, testing temperature, and annealing-induced crystallisation. Tensile and notched Charpy impact tests were performed under ambient conditions, complemented by dynamical mechanical characterisation, tensile testing at 40 and 50 °C, and DSC analysis after annealing at 130 °C for 2 h. Chitin alone increased Young's modulus from 0.95 ± 0.08 to 1.26 ± 0.02 GPa but reduced ductility and impact strength. In contrast, ternary formulations showed increased deformability at low-to-intermediate additive contents, with fracture strain increasing from 6.87 ± 0.61% for neat PLA to 27.38 ± 3.73%. Dynamical mechanical characterisation showed only a small shift in the glass-transition temperature, while tensile deformability increased strongly as the testing temperature approached the glass-transition range. Annealing lead to crystallinities of approximately 43-45% in the ternary formulations and reduced fracture strain by 86-93%. These results indicate that the chitin-lecithin system promotes deformation of the amorphous PLA phase without a pronounced reduction in bulk glass-transition temperature, while crystallisation largely suppresses this effect.

Authors 2

1. Paul Marten Aachen Institute for Building Materials Research (ibac)

   RWTH Aachen University

   Affiliation as printed

   Institute for Building Materials Research, RWTH Aachen University, Schinkelstraße 3, 52062 Aachen, Germany

2. Oliver Weichold corresponding Aachen Institute for Building Materials Research (ibac)

   RWTH Aachen University

   Affiliation as printed

   Institute for Building Materials Research, RWTH Aachen University, Schinkelstraße 3, 52062 Aachen, Germany