Hybrid clay mineral-carbon nanotube-PLA nanocomposite films. Preparation and photodegradation effect on their mechanical, thermal and electrical properties

Novel hybrid materials, obtained by direct Catalytic Chemical Vapour Deposition (CCVD) growth of carbon nanotubes (CNT) over a clay mineral catalyst, were incorporated into Polylactic acid (PLA) through melt mixing. Nanocomposites in the form of films were exposed to UV irradiation at constant temperature (30 °C) and relative humidity (50%). Young's Modulus measurements show a strong mechanical degradation with the UV irradiation time. The decrease was higher in neat PLA compared with nanocomposites and was attributed to the extensive macromolecular chain scission due to the UV irradiation. From thermogravimetric characterization it was found that the degradation temperature decreases with the photoageing. The addition of the hybrid filler causes an initial decrease of this temperature (up to 3%) and a slight increase thereafter. A similar behaviour was found for the enthalpy relaxation during the morphological rearrangement which occurred in the glass transition process. Indeed, the electrical conductivity of the nanocomposites was found to monotonically increase with the UV irradiation time.

Graphical abstractElastic moduli for PLA and hybrid nanocomposites, as function of irradiation time (h).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Hybrid fillers Clay-CNTs were incorporated into a PLA matrix at up to 5 wt.%. ► Films were subjected to prolonged photoageing times, up to 300 h. ► The filler prevents the loss of mechanical consistence of PLA. ► DSC analysis showed that at 300 h of ageing it is evident an increase of the Tg. ► Electrical conductivity showed an increment as function of irradiation time.