ULTRADRAWING OF NANODIAMOND REINFORCED POLY (VINYL ALCOHOL) NANOCOMPOSITE FIBER

As a new member of nanocarbons, nanodiamond (ND) has recently been exploited in the fields of nanotechnology. ND consists of core shell structure; the core of diamond primary particles and the shell of graphite like layer with oxygen containing functional groups. The core provides high performances derived from diamond, such as high bulk modulus, high thermal conductivity, hardness, wear resistance and so on. Unlike the conventional nanocarbons, ND can be nano-dispersed in water due to the oxygen containing functional groups on the surface. Previously, we reported that ND was highly dispersed in poly (vinyl alcohol) (PVA) matrix by using water as a processing medium. As a result, ND was found to show excellent reinforcement effects on the nanocomposite performances. In this study, ND reinforced PVA nanocomposite fibers were prepared through gel process. The structure and the properties of the nanocomposite fibers were investigated. The orientation degree of PVA crystallites increased with increasing of DR and achieved around 97 % for both PVA fibers and PVA/ND nanocomposite fibers. Since PVA crystallites were highly oriented, the mechanical properties of the fibers increased by ultradrawing. As for the nanocomposite fibers, remarkable increase in the Young's modulus and the tensile tensile strength were observed. For example, the PVA/ND nanocomposite fiber with 1 wt % ND loading showed the increase in the tensile strength from 0.05 MPa (DR=1) to 1.89 GPa (DR=50). Surprisingly, the Young's modulus was revealed to be 67 GPa at DR of 50, which approaches to the value of glass fiber (similar to 70 GPa). It was suggested that the excellent reinforcement effect of ND was exploited in the nanocomposite fibers.