Tuning the interphase adhesion in high-density polyethylene-silica nanocomposites with ionic liquids

This work addresses the use of ionic liquids (ILs) as multifunctional additives in the formation of high-density polyethylene (HDPE)/sol-gel silica nanocomposites via the melt-mixing process. Different approaches for nanocomposite formation were studied and compared, including (1) silica modification with ILs during the sol-gel process and further addition into the polymer matrix, (2) reactive mixing in which silica-IL filler was formed in situ, and (3) direct IL application in the melt-mixing chamber with nonmodified silica xerogel and HDPE. The nanocomposites were characterized by thermogravimetric analyses, differential scanning calorimetry, scanning electron microscopy, dynamic thermomechanical analyses, transmission electron microscopy, and contact angle analyses. To improve the silica compatibilization with HDPE, we investigated imidazolium ILs that presented at least one nonpolar ionic counterpart. This permitted control of the silica structure, morphology, dispersion, and interfacial interactions, providing enhancements in thermomechanical properties. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47366.