Facilitating the selection of raw materials: evaluation of the effects of TCF and ECF bleaching sequences on different wood and non-wood pulps

Abstract

Properties of cellulosic raw materials are known to vary widely among different sources. The interest in the usage of non-conventional fibers makes necessary a better knowledge of the peculiarities of each source and their behavior under different bleaching processes. ECF and TCF bleached pulps (ISO brightness= 82%) from eucalyptus, flax and sisal as well as cotton linters were analyzed. Eucalyptus showed the highest zero-span tensile strength (1.1-1.2 N.m/g), higher than that of sisal (0.85-0.95 N.m/g) and flax (0.7-0.8 N.m/g) which were also found to be linearly correlated to their viscosity regardless of the cellulose source. Sisal and eucalyptus showed the largest hemicelluloses content (˜13-16 %) while cotton linters appeared as a high-cellulose content (97.7 %)source for high-quality fibers. ECF and TCF bleaching processes produced different effects on fibers, as the latter showed a slightly lower quality than the former, difference that may not be significant if the great environmental benefit of TCF bleaching is considered. Finally, fiber surface was examined using SEM microscopy for a more complete assessment of raw materials