Confined Crystallization Behaviors in Polyethylene/Silica Nanocomposites: Synergetic Effects of Interfacial Interactions and Filler Network

The confinement effects introduced by nanoparticles have been reported to influence the phase behaviors thus the properties of polymer nanocomposites. In this study, molecular dynamics and crystallization behaviors of polyethylene (PE) composited with three types of silica (SiO2) nanoparticles, namely unmodified SiO2, hydrophobically modified SiO2, SiO2-APTES (3-aminopropyltriethoxysilane) and SiO2-PTES (n-propyltriethoxysilane), were systematically investigated via a combination of DSC, XRD and H-1 solid-state NMR measurements. The suppressions in crystallization and chain mobilities of PE rank in the order of unmodified SiO2< SiO2-APTES< SiO2-PTES due to the increasing interfacial interactions between PE and SiO2 nanoparticles. Additionally, independent of polymer-nanoparticle interactions, a silica network forms for all three kinds of nanocomposites when SiO2 content reaches 83 wt %. The mobilities of polymer chains are severely restricted by such a percolated network structure, leading to a turning point in the crystallization ability of nanocomposites and a new crystallization peak at 45 degrees C lower than that of pure PE. The synergetic effects of interfacial interactions and filler network on polymer crystallization have been thoroughly studied in this work, which will provide guidance on modifying and designing nanocomposites with controlled properties. (C) 2017 Wiley Periodicals, Inc.