Papermaking Properties of Carpinus betulus with kraft, Soda and Soda-Urea Pulping Processes

This research was carried out in order to comparatively investigate the hornbeam kraft، soda and soda-urea papermaking properties. The selected treatment in kraft process had an average yield of 44. 43% and kappa number of 23. 75. In soda process the selected treatment had an average yield of 38. 75% and kappa number of 19. 28. In soda-urea process، the selected treatments had an average yield of 39. 85، 40. 1، 40. 5، 39. 8 and 40. 61 and kappa number of 21. 21، 22. 33، 22. 66، 25. 28 and 26. 85. After refining the selected pulp to reach the freeness of 400±25 ml CSF، 60 g/m2 handsheets were made and physical، mechanical and optical properties were measured. Results showed that kraft pulps had higher yield and better refinability than soda and soda-urea pulps. Papers made from kraft process had higher strength properties than those made of soda and soda-urea process. With addition of urea، yield and kappa number of pulps increased. The highest improvement in tensile index، breaking length and tear index was achieved with addition of 3% urea and the highest improvement in burst index was achieved with adding 4% urea. Results of brightness measurements showed that papers from kraft and soda processes had the lowest and highest brightness degree respectively. With the addition of urea، brightness of papers decreased.