The influence of fibrillation on the oxygen barrier properties of films from microfibrillated cellulose

The potential of microfibrillated cellulose (MFC) films as oxygen barrier has been investigated in several studies before. However, no study clearly shows the minimum degree of fibrillation, which is required to reach this barrier property. In the case where a range of different fibrillation grades of the same material has been evaluated, it was seen that increased fibrillation brought no significant observed changes in oxygen barrier properties. Since MFC production is a highly energy intensive process, determining a minimum fibrillation required to develop oxygen barrier properties has the potential for significant savings. In this study, a series of fibrillation levels was evaluated in respect to oxygen barrier film formation in order to identify such a minimum MFC quality derived from a given fibre feed. A combination of various analytical methods was used in order to characterise the MFC fibrillation grades produced. The tested oxygen transmission rate shows a sudden rather than a gradual development of the oxygen barrier as a function of increasing fibrillation. Measurements with a fibre image analyser revealed that beyond a certain amount of detectable fines and small fibre fraction there is no disturbance of the oxygen barrier performance.