Date of Award


Degree Name

Bachelor of Science


Paper Science and Engineering


Paper made from TMP fibers offers good opacity and stiffness, but its use is limited because of its low strength. Chemical post-treatment of TMP offers possibilities of improving strength. Sulphonation of lignin appears to be the most economically feasible treatment. This thesis was oriented toward finding out if sulphonation of TMP fibers would improve the strength properties of TMP handsheets. Southern pine TMP fibers were treated with sodium sulfite (Na2SO3). The chemical concentration to be used was between 3-27% in alkali solution between pH 7-9. The temperature was between 90°-150°C. Pulp was consistency was 10%. Handsheets were made using the Noble and Wood mold. The target grammage was 60gr/m2. Sheets were tested for density, tensile, brightness and opacity. The control variable was the nontreated pulp. This information helps to identify the relationship between, pH, temperature, yield and chemical concentration and the strength properties of modified TMP. The best strength properties were obtained at a temperature of 150°C. Increasing the cooking time has some impairment on the optical properties but the opposite is seen on the strength properties. The optimum pH range for strength development was 7-8. The concentration of Na2SO3 should be high for the sulphonation to take place fast. It should be around 3%. Also, it could be proved that different treatment of pulp with Na2SO3 may be performed to obtain fiber with wanted properties by controlling temperature, time, and liquor concentration.

Keywords: Thermomechanical pulp, sodium sulphite, strength properties, optical properties, cooking