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

The control of the localization of halloysite nanotubes (HNT) in a linear low-density polyethylene/ethylene-vinyl acetate copolymer (LLDPE/EVA, 70/30) blend was studied through three approaches: i) Functionalization of the filler, ii) Addition of a compatibilizer and iii) Modification of the processing sequence. First, the HNT surface modification was carried out with three different organosilanes (3-aminopropyltriethoxysilane (APTES), dodecyltricholosilane (DTCS) and triacontyltrichlorosilane (C30)). Grafting amounts about 0.10 mmol/g were reached whatever the nature of the organosilane. Then, the unmodified and modified HNT were mixed with a LLDPE/EVA (70/30) polymer blend using a microextruder and the localization of the fillers were scrutinized by scanning electron microscopy (SEM) analysis. It was observed that both the neat HNT and modified HNT were mostly localized in the EVA phase. These observations were also discussed according to the wettability coefficient determined for neat HNT and modified HNT thanks to contact angle measurements. The addition of PE-g-MA as a compatibilizer to the blend containing the HNT-APTES allowed to localize the HNT in the LLDPE phase. Finally, the influence of the mixing sequence of the different components was evaluated by using a twin-screw extruder, and it was successfully used to localize the modified HNT into the LLDPE phase.