مجله تحقیقات علوم چوب و کاغذ ایران
سال بیست و ششم شماره 2 (پیاپی 35، تابستان 1390)

Poplar lumbers with nominal thickness of 5 cm from Taleghan region, located in west of Karaj were dried under three different schedules including T8-F4 (recommended schedule by F.P.L for poplar), T8-F5 and T9-F4. The purpose of this research was to study the effects of the kiln’s rows (upper, middle, lower) on the quality of the dried boards. Dry bulb temperatures for the schedules were adjusted at 54, 54 and 60 °C, while the final temperatures were adjusted at 82, 82 and 71 °C, respectively. The severity of warping, internal checking and surface checking in kiln dried lumbers were measured and analyzed. The results indicated that the boards in upper, middle and lower rows of the kiln, in all three schedules, did not have any significant difference in 95% confidence interval. Also, the final moisture content of the boards in all three rows and all three schedules were in acceptable quality.

This work investigated effect of height and cultivar on morphological properties of bast and core fiber of tobacco stalk (Nicotiana tabacum). Also, in this research cultivar effect on chemical properties of tobacco stalk were investigated. Selected cultivars include Barley and Virginia, and investigative height positions were chosen 5, 50 and 75% of stalk height. Results indicated that bast fiber length, diameter and wall thickness are more effective than those of core fiber. Chemical analysis of stalk’s parts indicated that cellulose and ash contents of bast were higher than those of core, but lignin content of bast was significantly less than that of core. Also, extractive material of bast was less. Statistic results showed that length and wall thickness of Barley’s bast fiber were higher compare to Virginia, but there was no significant difference in terms of morphological properties of core fibers between these cultivars. Cellulose percentage of Barley cultivar was higher, where as lignin, extractives and ash contents of Barley were lower than that of Virginia cultivar. Also, cultivar type didn’t have significant effect on contents of tobacco stalk parts (bast, core and pith). Results indicated that, fiber length, diameter and wall thickness of bast decreased as height increases, but in core fiber, just fiber length decreased and other properties of core fiber had different behavior. Moreover, bast and pith percentages increased by height increasing while, core percentage decreased. In general, results of this research showed that, tobacco stalk are a suitable row material for pulp and paper production, re fiber dimensions and chemical components.

The impact of chemical treatment variables including treatment time and temperature, chemical charge as well as pulp freeness on fiber quality of Colza stem chemi-mechanical pulp was studied using Fiber Quality Analyzer (FQA). Three treatment times (15, 30 and 45 minutes), two treatment temperatures (125 and 145 °C), two chemical charges (4% NaOH + 8% Na2SO3 and 8% NaOH +12% Na2SO3) as well as pulp refining were evaluated. The results revealed that at higher values of treatment variables, fiber average length was reduced and varied between 0.49 and 0.65 mm. However, the influence of pulp refining on fiber average length was not very pronounced. Pulps contained between 55 -63 % fines, which is on the high range and refining increased the fine content by 5%. Fiber coarseness varied between 10 and 41 mg/100m which was raised to 14 and 53 mg/100m upon refining. Even though refining did not alter fiber curl, but fiber kinks were increased.

Using high consistency pulp especially in bleaching plant is highly attractive due to considerable reduction in energy and water consumptions and low effluent volume. This research investigates the effect of consistency CMP pulp on bleaching by hydrogen peroxide. For this purpose, unbleached mixed hardwood CMP pulp of Mazandaran wood and paper CO. mill was used. Bleaching was carried out with QP sequences. Pretreatment or Q stage was carried out by DTPA as a chelating agent for removing transition metals. Chelating stage had a similar condition for all pulps. bleaching with hydrogen peroxide was carried out in three levels of hydrogen peroxide 2, 3, 4% and proportion NaOH to H2O2: 0.8, 0.7, 0.6 by adding 3% sodium silicate in 70˚C and 150min at four consistency level (10, 15, 25 and 30%). After bleaching, handsheets were made with grammage 60gr/m2 from bleached pulp. The experimental results showed that high brightness and opacity and lower yellowness was obtained at 30% consistency by 2 and 3% peroxide charge. However, by using 4% hydrogen peroxide, higher brightness and lower yellowness attained at 25% consistency. Brightness is increased continuously by increasing consistency from 10 to 30% at 2, 3% peroxide. But at 4% peroxide charge, brightness is increased from 10, 15 and 25%, and then at 30% consistency is decreased significantly. Also under conditioning of 2% peroxide and 30% consistency and 2% peroxide at 25% consistency can obtain similar brightness to 3% peroxide and 25% consistency and 4% peroxide at 10% consistency. That it means of 25, 30% decrease in consumption peroxide and sodium hydroxide.