Effect of bark content on physical and mechanical properties of the kraft pulp from chips Populus deltoids

This study was done to investigate the effect of bark content on the physical and mechanical properties of kraft pulp from chips Ppopulous deltoids. Three tree of the populous deltoids from the same age were randomly selected cut from Shastkalate research forest Gorgan. A disc was taken from each tree. The discs were completely debarked and wet weight of wood and bark from each disc was determined. Then weight ratio of wood/bark was determined in each disc. Kraft pulp was prepared under following pulping condition: sulfidity 25%، AA: 20%، temp: 170 0c، l/w: 6/1 and bark content as 0، 6، 12، 18 and 24%، by weight. Pulp with kappa number around 20 was prepared from each treatment، which were separately beaten to reach freeness value around 350 ml،CSF. To determined the effect bark content on yield and kappa number of the pulp and their physical and mechanical properties، F test was used in completely randomized، and for comparison of the means، Dunkan test was used. Yield and kappa number of the pulps were as 50/32 - 52/03% and 20/37 - 21/17، respectively. With increasing، of the bark content، density of paper was decreased and the lowest value of which was 0/477 g/cm2for bark – contained pulp. Also، with increasing of the bark content to 18%، strength properties of the related pulp was improved.