The kraft pulping properties of Canadian red and sugar maple.

Application: Variability in pulping Canadian hardwoods can be controlled by managing the furnish on the basis of researched differences between the wood species and the ages of the trees.

Many kraft pulping operations have to contend with variability in pulping and in pulp and paper properties. During our investigations into the sources of variability in mixed northern hardwood kraft pulps, we evaluated regional and species differences between red and sugar maples.

We found a significant difference between the wood density of red maple and that of sugar maples, which will affect digester throughput. Red maple was easier to pulp than sugar maples, and juvenile wood required longer cooking times than mature wood. Sugar maple produced a higher pulp yield at a given kappa number by approximately 1%, although blockages affected juvenile sugar maple pulp yield as a result of the harsh cooking required to achieve delignification. Blockages in maples are generally associated with wound response (e. g., insect attack) and can be difficult to detect in standing trees.

Fibers properties determine product performance. In ongoing research at PAPRICAN, fiber property differences are measured and quantified through conventional and confocal microscopy. We observed that red maple fibers the longer and coarser than sugar maple fibers but that sugar maple fibers have thicker wails and a smaller fiber center-line perimeter. Consequently, red maple pulps exhibit higher sheet density and tensile index.

By contrast, the sugar maples have better values than the red maples have for bulk, porosity, wet web stretch, and optical properties. Any differences observed between juvenile and mature wood pulp samples were marginal at best. Microfibril angles for both red and sugar maples were found to be 22[degrees] in the juvenile wood and 16[degrees] in the mature wood, corresponding to the transition point of 40 years observed for fiber length and coarseness. S!

Watson, Hussein, Reath, Gee, and Drummond are with the Pulp and Paper Research Institute of Canada, 3800 Wesbrook Mall, Vancouver, BC, Canada V6S 2L9. Hatton is with John Hatton & Associates, 3337 Quesnel Drive, Vancouver, BC V6S 1Z7. Email Watson at [e-mail].