Preparation of well-dispersed graphene oxide-silica nanohybrids/ poly(lactic acid) composites by melt mixing

Abstract

Graphene oxide has a strong tendency to agglomerate in polymers that are only hydrogen bonded acceptors due to the strong hydrogen bonding and van der Waals forces between its lamellae, which greatly limits its application. In this work, Silica (SiO2) was introduced on the surface of graphene oxide (GO) by hydrolysis of tetraethoxysilane (TEOS). Graphene oxide-silica/polylactic acid (PLA) composites with different grafting ratios were prepared by melt blending. The results by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectrometry (XPS) show that the silica is grafted on the GO surface in the form of covalent bonds. Other test results show that regulating the amount of TEOS addition could effectively control the grafting rate. The performance test shows that grafting SiO2 on the GO surface can increase the layer spacing of graphene oxide flakes and thus improve its melt dispersion. It also slows down or improves the performance degradation caused by the severe agglomeration of graphene oxide. At the grafting rate of 45.65%, GO is well exfoliated and well dispersed in PLA in the form of monolayers resulting in a substantial improvement in crystalline properties, mechanical properties, and barrier properties. This work solves the problem of severe agglomeration of GO in polymers that are only hydrogen bond acceptors by modifying GO, and provides guidance for the melt processing of graphene oxide and polymers that are only hydrogen bond acceptors.