Ph.D. Tezi Görüntüleme

      In this study, agricultural waste of wheat straw has been used as raw material which is not dependent on forest resources. Five different pulping methods such as Soda-Oxygen (SO), Soda (S), Soda-AQ (S-AQ), Alkaline-Sulfite (AS) and Alkaline-Sulfite-AQ (AS-AQ) has been chosen for pulp production. For each pulping method, some of the variable processing parameters have been optimized to achieve suitable properties such as kappa number as low as and the viscosity and yield values as high as possible to match writing and printing papers. In pulp bleaching, TCF bleaching method which has consisted of oxygen-based reagents was used and each stage of “AOPaQPPa” bleaching sequence was also optimized. To compare the changes in the properties of pulps bleached with TCF method, the pulps also has been brightened with an ECF method consisting of “DEDED” stages. Owing to highly selective properties of chlorine dioxide which is used in ECF bleaching sequence, ECF bleaching method has been more successful than TCF bleaching method. In general insignificant decrease was observed in the strength properties of TCF bleached pulps compared with ECF bleached pulps. As a result SO pulp has been the most resistant pulp type both in terms of delignification performance and in terms of degradation of carbohydrates compared with the other pulps. According to delignification performance of S and S-AQ pulps and brightness results of AS and AS-AQ pulps have showed more positive results when compared with other pulps. The highest delignification performance has been achieved with TCF bleached S-AQ pulp. At the same time, the structure of wheat straw stem which consists of high rate of hemicelluloses and inorganic substances has reduced the viscosity losses occurring in the pulps viscosity by protecting the structure of cellulose against the reagents used in TCF bleaching process. In terms of the brightness values, SO pulp has had the lowest and AS-AQ pulp has had the highest brightness values as the initial part of bleaching.