Behaviour of 3D printed PLA and PLA-PHA in marine environments

Abstract

Abstract The accumulation of marine debris in the oceans has been escalating. There is an urgent need to develop new technologies that efficiently record and transmit ocean data without contributing to ocean pollution. In this study, the behaviour of Polylactic Acid (PLA) and Polylactic Acid-Polyhydroxyalkanoate (PLA-PHA) in marine environments was analysed in order to assess biodegradability in marine applications. 3D Printed samples were submerged completely in seawater and cyclically in a salt spray chamber. Their change in mechanical properties was evaluated by conducting uniaxial tension tests after submersion periods of up to 45 days and failure regions were observed in microscope. Contrarily to PLA’s behaviour, PLA-PHA’s samples suffered embrittlement and registered losses in elongation at break of around 10-18%. The alignment of salt crystals and other impurities in the failure regions suggests that embrittlement could be related with environmental stress cracking resulting from the penetration of those impurities into the polymer. Such inclusions originate residual stresses which lead to a faster and more brittle failure. Embrittlement could also be related to an increase in crystallinity caused by chain scission of amorphous regions by means of chemical degradation. Further evaluation of changes in molecular weight should be conducted to confirm the latter.