Five C. Africana trees with average age six years, were randomly selected according to TAPPI standards 2002 [22], from Jelhag natural forest (Upper Nile state, South Sudan). The trees were felled and branches were removed, transported to Khartoum capital of Sudan by bus, stored in National Centre for Research NCR). Leaves, flowers fruits and seeds were collected for identification with taxonomists of Medicinal and Aromatic Plants Research Institute National Center for Research, Sudan [18].
Five logs of 100 cm long were exposed to air dry under sun, prepared according to TAPPI standard (T 257-cm- 02 [22], chipped with hands and packed in plastic bags for further analysis. The average basic density was determined using wood specimens according to the British standards [23]. Wood fibers were macerated using a mixture of 30% hydrogen peroxide and acetic acid (1:1). Fiber dimensions were determined microscopically at X100 and X 300 magnifications according to (TAPPI-232cm-01) after staining with aqueous safranin [24]. Standard deviation and arithmetical mean were used to determine fiber properties Morphological indices. The heat value of C. Africana wood was carried out using a Krocher oxygen bomb calorimeter [25].
About one Kg of chips was grinded for chemical Analysis of wood sample was carried out using 40 to 60 mesh wood meal in accordance with (TAPPI-264-cm-97). Sampling and testing for moisture (TAPPI-210cm-93), cellulose Kurshner and Hoffer [26] lignin (TAPPI-222), Pentosans (TAPPI-223-cm-01), ash (TAPPI-212) hot water soluble (TAPPI-T- 207) and solvent extraction of wood (TAPPI-204).
After negotiations and suggestions with other coauthors the pulping conditions and cooking parameters were decided according to physical properties Cordia africana wood and mainly on its chemical components. The Soda and soda-anthraquinone conditions were 12-15% as Na2O on oven dry weight of wood, the maximum temperature was kept constant at 1700C. Time to maximum temperature was 60 minutes for all cooking trials, the time at maximum temperature was 120 minutes kept constant for all trials under study.
The pulps were subjected to beating in Valley beater according to TAPPI 200-sp-01, evaluated at 25 and 40 degree Schopper Reegler (0SR) freeness of pulp (Canadian standard method TAPPI 227om-99), Kappa number (TAPPI-236 om-99), physical testing of pulp sheets (TAPPI-220-sp-01). Conditioning of testing atmosphere (TAPPI-402-sp-98), folding endurance (TAPPI423cm-98) Burst strength (TAPPI403om-97), tearing resistance (TAPPI-414 om-98), and Tensile (TAPP-404-cm-92).Hand sheets were prepared using a rapid- Kothen sheet forming machine and tested using TAPPI standards.
Physical properties of C. africana wood were shown in (Table 1 supplementary materials). The average basic density was (410kg m-1) and bark-to- wood ratio were in the medium range for tropical hardwoods [28]. This will not cause wear on chipper knives in pulp mills with normal liquor-to wood ratio (usually 4:1), impregnation will be easy as yield of pulp per unit volume is related to basic density. The heat value was 18187 K j Kg-1 indicating their suitability in coal firewood production and indicated a high lignocellulosic materials could be expected.
The fiber length for C. Africana (1.31 mm) as presented in Table 1 was considered as medium fibred species, therefore it does not need to be mixed with other long fibered wood pulp to obtain good paper properties very good tear resistance could be expected from this raw material. The comparatively wide lumen and fiber diameter indicated that to collapse easily and produce good surface contact between adjacent fibers of C. africana, this supported further with morphological indices (Table 1).
The chemical constituents of C. africana wood were reflected in Table 2, the inorganic components (ash and silica) were high (5.84% and 2.65% respectively) may cause an increase in alkali consumption and negatively affect the black liquor recovery. The average cellulose content (48.7%) was in normal range for tropical hardwoods and good pulp yields could be expected from C. Africana wood, it is well known that Kurschner- Hoffer cellulose gave less percentage when compared to alpha cellulose thus may results of high yield of this raw material if appropriate cooking conditions used. The lignin content was medium (23.9%) which indicated normal delignification of wood chips. However 1% NaOH soluble (20.2%) reflected normal cooking parameters should be applied.
The cooking conditions and yield for C. africana wood were given in Table 3. At same pulping conditions C. africana chips have shown lower screened yield (41.5 and 44.7%) when cooked with soda process, whereas the screened yield was increased with addition of 0.13% AQ to 47.7% and 53.6%. The bleachable pulps resulted when soda-AQ cooking were used [29-32]. These results indicated clearly the superiority of soda cooking when anthraquinone applied as catalyst, thus improve yield, and reduce rejects with bleachable Kappa numbers although the initial ISO brightness more or less similar during soda pulping with or without anthraquinone.
The unbleached pulps evaluation was given in (Table 2 supplementary materials), indicated that when hand sheets of C. africana tested at both 25 and 40 0SR gave high tensile index, tear index, burst index and folding endurance( Figure 1 and 2 supplementary materials), all the mechanical strength properties were increasing with increase of beating degree showed that still fibers were strong enough even at high degrees of beating and pulps of this raw material can be used for wrapping paper and paperboard.