FIBER SURFACE CHARACTERISTICS OF HARDWOOD REFINER PULPS

A fundamental study into the breakdown of aspen and bitch fibres was u ndertaken to provide a better understanding of the peeling and fibrill ation processes that occur during chip refining of hardwoods. Fibres o f TMI: CTMP and CMP pulps were analyzed in cross-section. The degrees to which the compound middle lamella and outer secondary wall (S-1 lay er) were retained, and the S-2 layer exposed were recorded Higher prop ortions of S-2 layers were exposed in TMP fibres compared with CTMP an d CMP fibres. Alkaline sulphite pretreatment of chips did not improve the degree of S-2 layer exposure of the extent of fibrillation of the fibres. These treated fibres retained most of their compound middle la mellae. Pulp strength was,rot related to the degree of exposure of the S-2 layer but rather closely followed fibre flexibility (as measured by sheet density). Thus, despite the apparently superior bonding poten tial of TMP fibres (large exposure of S-2 layer), the fibres remained stiff and produced sheets with low density and strength.