Results of regression analysis of factorial test of experiment (according to Yates), as interrelation between output variables (mechanical characteristics of pulp) and input variables of sulphate process are presented.
As input variables were determined: maximum pulping temperature, time at maximum temperature, wood to liquor ratio and species (clone) of the wood examined.
Mechanical properties of pulp: breaking length, bursting and tearing strength were output variables in type 24 factorial test. Pulping of chips from three poplar clones: P. euramericana cl. I-214, and cv. Robusta, P. deltoides cl. 618, was done in a rotation digester according to the previously defined plan.
On the basis of analysis of factorial tests, significant negative influence of temperature was observed on all examined mechanical characteristics. Most important double interaction (temperature with wood to liquor ratio) was also obtained. Species (clone) of poplar wood, as an independent factor, or in interactions, was present in almost all equations which connect mechanical properties and input variables. Differences of chemical composition of some clones were eliminated with increasing of degree of beating of pulp.
On the basis of the obtained results the hypothesis that sulphate pulping of poplar wood needs not to be done at temperature above 170°C was confirmed.
Key words: poplars, sulphate pulping, main process parameters, mechanical properties of pulp.
Correspondence: Bojana Klasnja, Poplar Research Institute, Antona Cehova 13, P.O.Box 117, 21000 Novi Sad, Yugoslavia
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