Morgan Deroiné, Antoine Le Duigou, Yves-Marie Corre, Pierre-Yves Le Gac,
Peter Davies, Guy César, Stéphane Bruzaud, Accelerated ageing of
polylactide in aqueous environments: Comparative study between distilled
water and seawater, Polymer Degradation and Stability, Available online
23 January 2014, ISSN 0141-3910,
http://dx.doi.org/10.1016/j.polymdegradstab.2014.01.020.
(http://www.sciencedirect.com/science/article/pii/S0141391014000226)
Abstract: Pollution of nature by plastics is a major environmental
problem and the challenge for the future is to manage the lifetime of
polymers better. The aim of this study is to establish a baseline on
degradation mechanism and degradation kinetics for lifetime prediction
of polylactide (PLA) in a marine environment. The ageing of PLA was
accelerated by raising temperature in distilled water, filtered and
renewed seawater and natural seawater. Samples were immersed in
distilled water for six months at different temperatures (25, 30, 40 and
50 °C) in order to evaluate the influence of temperature on PLA
degradation kinetics and to predict lifetime. Then, samples were
immersed in seawater both in the laboratory and at sea, in order to
compare the effects of environment, marine organisms and salt, on
degradation. The different degradation steps were followed by
gravimetry, tensile tests, scanning electron microscopy (SEM), steric
exclusion chromatography (SEC) and differential scanning calorimetry
(DSC). In distilled water, accelerated ageing of PLA is complex with
deviation from Fickian behaviour at higher temperature. Moreover,
immersion in distilled water induces morphological changes, in
particular holes, which are absent in seawater at 40 °C for the same
immersion time. Indeed, seawater has little impact on the diffusion
kinetics but affects M∞ values, which are slightly lower compared to the
distilled water uptake.
Keywords: PLA; Accelerated ageing; Hydrothermal ageing; Degradation