The effect of surface hydroxylation of Nano-SiO2 on the insulating paper cellulose/Nano-SiO2 interface

Abstract

It has become an important method to modify cellulose insulating paper by doping nano-SiO2 particles to improve its thermal stability. But in the doping process, the pure nano-SiO2 surface can easily react with oxygen and produce hydroxyl groups. The influence of interface hydroxylation is difficult to be explained in macroscopic experiments. Therefore, in this paper, the surface hydroxylated nano-SiO2/cellulose bilayer model and the unhydroxylated nano-SiO2/cellulose bilayer model were established by means of molecular simulation. The interface change before and after hydroxylation was analyzed from the microscopic parameters such as model interface interaction energy, interface relative concentration, cellulose chain mean square displacement and interface hydrogen bond. The result of research shows: compared with the N–C (unhydroxylated) bilayer model, the interaction energy and interaction energy density of the SNH–C (hydroxylated) bilayer model were increased to 2.3 times and 2.2 times respectively. Furthermore, the overlapping area and peak value of interfacial relative concentration increased to 1.62 times and 1.24 times respectively, the mean square displacement (MSD) jumping temperature of cellulose decreased by 20 K, and a hydrogen bond network with a density of 4.18 nm−2 was formed between the interfaces. Obviously, the surface hydroxylation of nano-SiO2 helps to promote the interaction between the interfaces, so that the nano-SiO2 and cellulose bond becomes more closely, which helps to strengthen the constraint of cellulose chain, and delays the process of transition from glassy state to high elastic state.