RELATIONSHIP BETWEEN FIBRE CHARACTERISTICS AND TENSILE STRENGTH OF HARDWOOD AND SOFTWOOD KRAFT PULPS

Fibre characteristics of kraft softwood and hardwood unbleached and bleached pulps, namely FS number – indicating fibre strength, L number – indicating fibre length and B number – indicating fibre bonding ability, were determined by the PULMAC zero-span tester. A higher tensile index of softwood pulp and unbleached pulps is related to a higher FS and L number and, consequently, to higher strength and length of fibres. On the contrary, hardwood pulps have, at an equal tensile index, a higher B number than softwood pulps. At an equal tensile index, the B number of bleached pulp is higher than that of unbleached pulp.