Enhancing mechanical strength and breakdown behavior of insulating presspaper by introduction of nanofibrillated cellulose

This study explores the possibility of enhancing both mechanical and breakdown properties of insulating presspaper by introduction of an organic nano additive. Two different concentrations of nanofibrillated cellulose (NFC) were taken into account, namely 0.5 wt. % and 10 wt. %. Presspaper containing no NFC was also prepared as a reference. Obtained samples were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Mechanical properties and breakdown behaviors were also measured. Results show that the addition of 10 wt. % NFC to softwood fibers can achieve better performance. Tensile strength of reference presspaper is 109 MPa, whereas that of presspaper modified by 10 wt. % NFC is 136 MPa, resulting in a 25% increase. The improved tensile strength can be attributed to the increased density and inter fiber bond strength. More importantly, presspaper reinforced by 10 wt. % NFC can also achieve increased AC and DC breakdown strengths, which are 19% and 21% higher than those of the reference presspaper. It is concluded that NFC is probably a promising nano additive for cellulose insulation.