EFFECTS OF TREE AGES AND CHIP PRETREATMENTS ON CHEMITHERMOMECHANICAL PULP PROPERTIES FROM Alstonia scholaris (L) R.Br.

Abstract

The effects of tree ages, chip pretreatments, and concentrations of utilized chemicals on unbleached CTMP properties were investigated in this study. Alstonia scholaris (L) R. Br. with three ages of 5, 7 and 9 years old were processed to make wood chips separately and each of them was subjected to caustic soda and alkaline sulfite pretreatments before subjecting to mechanical pulping process. Each of the pretreatments was utilized by using two levels of chemical concentration, i.e., 10 and 20%. The results indicated that pulp yield, tensile index, tear index, and brightness were ranged from 56.72-67.74%, 4.99-23.14 Nm/g, 1.01-3.85 mN.m²/g, and 22.72-38.62% ISO, respectively. Wood chips pretreated with alkaline sulfite yielded higher pulp with better beatability, higher brightness, and lower strength comparing to those of wood chips pretreated with caustic soda. The increase in chemical concentration utilized in caustic soda pretreatment reduced pulp yield and increased pulp strength and brightness while that in alkaline sulfite pretreatment decreased pulp strength and brightness. A. scholaris (L) R. Br. with the age of 9 years old yielded the highest pulp while that with the age of 5 years old offered pulp with higher strength and brightness and inferior beatability comparing to those of the trees with the age of 7 and 9 years old.