Influence of Fiber Morphology on Paper Properties

Investigations have been made on the influence of fibre length on paper strength, the experiments being designed to isolate the effect of fibre length from that of other morphological and chemical factors. Araucania klinkii chips were delignified by treatment with sodium chlorite solution and cut into lengths ranging from 1 to 7 mm. These cut lengths were separated into "fibres" by treatment with dilute sodium hydroxide solution. Both the unbeaten and beaten pulps showed a linear relationship between "fibre" length and tearing resistance; properties associated with fibre bonding had very low values for the unbeaten pulp but for the beaten pulp, these values tended to increase with increasing fibre length. Sulphate pulps made from Araucairia chips cut to different lengths in the longitudinal direction showed the same general trend in strength properties. Handsheets made from Pinus radiata sulphate pulp were cut into 2 mm. strips and re-formed into handsheets. All strength properties were reduced by the consequent fibre shortening, tearing strength being most affected. The effect of fibre length was also studied by comparing pulps made from the innermost and outermost growth rings of P. radiata and Eucalyptus regnans. Although the fibres from the inner and outer portions of the tree differed both chemically and morphologically, it was clear that fibre length was the most important variable and that once again, its influence was mainly on tearing strength.