Browsing by Author "Fatehi P."

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Fungal pretreatment of wheat straw and its effect on the soda-AQ pulps
(2009-01-01) Fatehi P.; Ates S.; Ni Y.
In this study, the effects of Ceriporiopsis subver-mispora (C.S.) and Phlebia subserialis (P.S.) fungal pre-treatments of wheat straw on the pulp and paper properties of soda-AQ pulps were investigated. The results showed that both fungal pretreatments enhanced delignification and carbohydrate degradation. Also, the P.S. pretreatment increased the brightness and decreased the kappa number and viscosity of pulps more than the C.S. pretreatment. Generally, the bulk, brightness, and tear index of papers increased by the fungal pretreatments, while the tensile and burst indices decreased at all refining levels applied. The C.S. pretreatment had more pronounced effect than the P.S. pretreatment on increasing the bulk and decreasing the tensile and burst indices. Furthermore, cationic-modified poly(vinyl alcohol), CPVA, was used as a dry strength additive to compensate for the loss in the strength properties. The results showed that, upon similar CPVA adsorption, the strength properties of the papers made of the C.S. pretreated fibers were improved more than those of the P.S. pretreated fibers. The application of CPVA on unrefined or refined fungal pretreated fibers showed the possibilities of decreasing the basis weight of papers to achieve the same tensile strength.
Impact of cationic polyvinyl alcohol on properties of papers made from two different pulps
(2009-07-01) Fatehi P.; Ates S.; Ward J.; Nl Y.; Xiao H.
In this study, the effect of cationic polyvinyl alcohol (CPVA), with charge density of 0.4 meq/g, on the properties of papers made from a bleached softwood sulfite pulp and from an unbleached straw pulp was systematically investigated. The CPVA adsorbed more on the unbleached straw pulp than on the bleached sulfite pulp. Increasing the dosage of CP VA significantly increased the strength properties of the papers made from the unrefined bleached sulfite pulp, but produced only a limited increase in the strength properties of the papers made from the unrefined unbleached straw pulp. Refining was more effective at changing the characteristics of fibres and papers made from the bleached sulfite pulp than those from the unbleached straw pulp, regardless of the CPVA application. At the same sheet density, applying CPVA increased the tensile index of papers made from the unbleached straw pulp more significantly than that of papers made from the bleached sulfite pulp. Over the CPVA dosage range investigated, applying CPVA was more effective than refining at enhancing the strength properties of the papers made from the unbleached straw pulp. In contrast, refining was more effective than applying CPVA at enhancing the strength properties of the papers made from the bleached sulfite pulp. The effect of CPVA on the structural and optical properties of the papers was comprehensively assessed.