Control of halloysite nanotubes localization into a LLDPE/EVA (70/30) blend through specific chemical modifications and sequence of mixing during extrusion

Abstract

Surface modification of halloysite nanotubes (HNT) with different organosilanes (3aminopropyltriethoxysilane (APTS), dodecyltricholosilane (DTCS) and triacontyltrichlorosilane (C30)) was investigated to modulate its localization in a linear lowdensity polyethylene/ethylene-vinyl acetate copolymer (LLDPE/EVA) blend. The amount of the grafted silanes onto the HNT surface was evaluated qualitatively by infrared spectroscopy and quantitatively by thermogravimetric analysis. Grafting amount about 0.10 mmol/g were obtained whatever the nature of the organosilane. After the introduction of unmodified and modified HNT into the blend using a microextruder, scanning electron microscopy (SEM) allowed to study the localization of the fillers. These observations were discussed regarding the determination of the wettability coefficient. It was observed that both the neat HNT and modified HNT were localized in the EVA phase while the addition of polyethylene-graftedmaleic anhydride (PE-g-MA) into the blend containing HNT modified with APTS permitted to transfer them in the LLDPE phase. Finally, through a scale-up step carried out with a twinscrew extruder, the impact of the sequence mixing of the different components was evaluated and successfully used to localize the modified HNT into the LLDPE phase.