α-costic acid, a plant sesquiterpenoid from Dittrichia viscosa, as modifier of Poly (lactic acid) properties: a novel exploitation of the autochthone biomass metabolite for a wholly biodegradable system

Abstract

In this work, α−costic acid (α-CA), a metabolite coming from a perennial autochthon shrub Dittrichia viscose, was used as natural additive of polylactic acid (PLA), a biodegradable thermoplastic polymer, in order to modulate its chemico-physical properties, for the achievement of a wholly biobased packaging system. It’s the first time that α−costic acid is exploited for this appealing and novel application. The investigations performed on PLA/α-CA films, evidenced strong physical interaction occurring between the polymer and α-CA, as confirmed by NMR and FTIR-ATR analyses; SEM micrographs showed a good embedding of α-CA particles inside PLA polymer matrix; GPC analysis highlighted a slight hydrolysis of polymer matrix clearly evidenced in mechanical properties. DSC analysis underlined the significant decreasing of Tg, associated with the increase of PLA chain mobility. TGA thermograms evidenced one broad degradation profile of PLA/α-CA system, accounting for the weighty physical interaction occurring between the polar groups of both polymer and plasticizer. Finally, PLA surface wettability notably enhanced by the inclusion of α-CA polar groups. In conclusion, α-CA can be considered as a promising plasticizer of PLA and a worthy modifier of its overall properties.