Photo-stabilization of biopolymers-based nanocomposites with UV-modified layered silicates

Eco-friendly in-situ stabilised biopolymer nanocomposites based on polyamide 11 (PA11) and polylactic acid (PLA) were prepared by melt mixing in the presence of a modified organo-montmorillonite clay containing a chemically-bound hindered amine UV-stabilising function, [(UV)OM-MMt]. Characterisation of the newly synthesised organo-modifier containing the reactive hindered amine (HAS) UV-stabilising function [(UV)OM] has confirmed a successful synthesis. The (UV)OM was then introduced into NaMMt through ion exchange reaction to prepare the UV stabiliser-bound organo-modified-MMt, [(UV)OM-MMt]. The in-situ stabilised PA11- and PLA- nanocomposites (PA11-(UV)OM-MMt and PLA-(UV)OM-MMt) were characterised and their photoxidative stabilities (under accelerated weathering conditions) were compared with their nanocomposite analogues containing either the organo-modified MMt (OM-MMt) alone (i.e. without UV-stabiliser) or the OM-MMT containing conventionally added commercial hindered amine HAS-UV-stabiliser (Cyasorb® UV-3853). It was found that both of the newly prepared in-situ stabilised PA11- and PLA- nanocomposites gave good clay dispersion and have demonstrated a much higher, especially in PLA-nanocomposites, photo-oxidative stability compared to the corresponding nanocomposites but in the absence, or the presence, of the conventionally added HAS-UV-stabiliser.