Comparison of Soda and Kraft Pulp Properties of Populus deltoides Sapwood and Heartwood

This study was conducted to compare the yield and strength properties of soda and kraft pulp produced from Populus deltoeides sapwood and heartwood. Initially fiber length, lignin content in both sapwood and heartwood were measured. Then from either sapwood or heartwood pulps were prepared with using soda and kraft processes, Handsheets were made from this pulp and mechanical properties were measured. The results showed that fiber length in heartwood is shorter than sapwood. For both sapwood and heartwood pulps residual lignin content and kappa number of the pulps made by kraft process were higher than those for soda process. Also kappa number in the kraft and soda processes from heartwood was less than sapwood. The yield of soda and kraft processes from heartwood was lower than sapwood. This study also showed that tensile, tear and burst strength of the pulps made by kraft process were higher than relevant strength for soda process and the sapwood pulps were stronger than heartwood.