Nanofibrillated cellulose for enhancement of strength in high-density paper structures

In order to enhance dry and wet strength properties of paper, handsheets were made of wood pulp fibers and nanofibrillated cellulose (NFC). 10% NFC was mixed with wood pulp fibers (90%) subjected to different number of beating revolutions. Effects from xyloglucan (XG) hemicellulose addition were also studied. High density paper handsheets from these mixtures were prepared using a laboratory handsheet former. Strength properties were measured and densities of the materials estimated. Scanning electron microscopy was used to observe paper sheet surfaces. NFC significantly enhances strength for the paper handsheets both at 50% relative humidity and in the wet state so that NFC addition may be an alternative to mechanical beating. The main reason for property improvements is increased density of the final material. Tensile energy absorption improved strongly through favorable fiber-fiber interaction. NFC or NFC/XG addition combined with some mechanical beating may decrease energy needs compared with beating only.