COMPARISON OF 2 METHODS FOR ESTIMATING THE VARIABILITY OF THE KRAFT PULPING PROPERTIES OF POPLAR CLONES

Two different methods are applied to evaluate the variability of wood ability for Kraft pulping of 25 poplar clones (1-year-old trees). The first one consists in pulping almost all of the wood of each analyzed tree (''macro-pulpings''). The second one is based on pulping very small wood samples, entire cross sections close to 1 g, taken at 50-cm height (micropulpings and paper microtests). This paper presents the results found separately with the two methods for the following parameters: pulp yield, Kappa (kappa) index or permanganate index, and average fiber length. We observed that the evaluations of these parameters deduced by microtests are always well correlated with those obtained from pulping of the whole trees. Moreover, the two methods reveal that the suitability of poplar wood for Kraft pulping is under genetic control at age 1. But for each parameter (especially the ratio (kappa index)/(pulping yield)2 and the average weighted fiber length), the differentiation of the clones is never exactly the same. Therefore, it is necessary to slightly modify the micropulping and microtests methodology to evaluate with better accuracy the pulp and paper properties of the whole trees.