فصلنامه پژوهشهای علوم و فناوری چوب و جنگل
سال هجدهم شماره 4 (زمستان 1390)

This research was conducted to investigate the effect of acetylation on weathering resistance of solid wood and particleboard produced from acetylated particles of Fagus orientalis. After 12 hours soaking in acetic unhydride, in order to achieve three levels of weight gain, 5, 9 and 16%, acetylated particles of Bech wood were heated in oven at 120oC for 30, 90 and 240 minutes, respectively. Also, after 12 hours soaking iacetic unhydride and heating at 120 oC for 240 minutes, the weight gain of solid wood reached to 10%. The particles were glued with 12% melamine urea formaldehyde (solids on oven dry mass of particles) and then, pressed. Results showed that resistance to weathering increased by acetylation. By increasing level of acetylation from zero to 16%, difference between weathered and unweathered acetylated Particleboard samples became more invisible. After weathering for 300 hours, the radial surface SEM of acetylated Beech solid wood showed that, with increasing of acetylation level, depth of surface cracks decreased and bordered pits approximately did not change.

This research was conducted to investigate the effect of acetylation and type of resin on fire resistance of one and three layered Populus particleboard. Populus particles were acetylated at three levels of acetyl content (WPG of 0, 8.39% and 17.27%). In manufacturing of one and three layered boards with acetylated particles in all thickness or surface of the boards two type of resin, urea formaldehyde and isocyanate (were used). Fire resistance test was carried out in cycles 20, 40, 60 and 120 seconds. At first 20 second, flammability of boards made from isocyanate was less than that for boards containing urea formaldehyde resin, and with time passing, this effect decreased. Regarding to weight loss, three layered boards showed less weight loss than single layered boards. By increasing of acetylation level, the extent length of fire extension and coal surface was increased and during distinct time, burned depth and weight loss decreased. This effect was more obvious at 120 second. Indeed, acetylation not make boards resustant to fire, but retarded their combustion.

Influences of the wood fiber acetylation as well as the compatibilizer MAPP on water absorption, thickness swelling and dimensional stability of acetylated wood/ polypropylene composites (WPCs) were the main concerns of this research. Wood fibers were acetylated with acetic anhydride without using any catalyst to achieve weight percent gains (WPGs) of 4.5, 7.5 and 17.6%. The acetylated fibers were mixed with MAPP (0, 2, 3 and 5%) and matrix polymer polypropylene (PP) to prepare samples of the WPCs. The samples were made at 180°C with a hot press. Tests specimens were cut and soaked in the water for 1512 hours to determine the water absorption, the thickness swelling, the anti-swelling as well as the water repellent effects in the acetylated WPCs. The interfaces between acetylated wood fibers and the polypropylene were studied with a scanning electron microscope. Results revealed that acetylation of the wood fibers reduced significantly the water absorption and the thickness swelling in the WPCs. Addition of the MAPP decreased those properties as well. However, influence of the fiber acetylation was more effective than that of the MAPP. Electron microscopy of the interfaces showed reduction of micro-gaps in the WPCs and also improved interfaces between matrix polymer (PP) and the wood fiber. It was also revealed that the acetylated WPCs had smooth surfaces.

This research has been conducted to investigate the influence of steam temperature and densification percentage on withdrawal strength of nail and screw joints as well as flexural strength in compressed wood of eastern cottonwood (Populus deltoeides). For this purpose 15 healthy standing trees of eastern cottonwood were selected from Dr. Bahramnia forest located in Shasht-Kola (Gorgan). The flatsawn samples were selected and prepared from defect free parts of sapwood. Densification was done at 4 percentages, namely 20%, 30%, 40% and 50%. Steaming treatment was selected at 3 temperature levels, 120, 140 and 160 °C for this purpose. Density, withdrawal strength of nail and screw joints and also flexural strength (MOR and MOE) of compressed specimens were measured. Also, the microscopic images of compressed samples were studied. The results showed that the percentage of densification may significantly influence the density of samples, especially at the higher percentages. Furthermore, it was found that the amount of densification has significant influence on the withdrawal strength of nails (up to 220%) and screws (up to 120%). Regarding the flexural strength, MOR and MOE possessed higher amount as their amount were increased by 70% and 40%, respectively, compared with control samples. In addition, the microscopic images showed that more homogenous material could be obtained at higher densification percentages.

Mixed office waste papers are considered as a large source of high quality papers that were printed with non impact printing methods. This papers have involved and economical problem in deinking with conventional chemical methods. In this research Enzymatic deinking was done as an alternative for conventional chemical method. Enzymatic deinking of Xerox machine printed papers with cellulase from Aspergillus niger at three different dosages of 0.025, 0.05 and 0.1 percent on OD pulp (25, 50 and 100 IU), and repulping treatment times of 10 and 15 minutes at 50 °C were carried out and the effects of this treatmens on appearance and optical properties of handsheets were studied. The results were shown that treatment with 0.05 percent enzyme at 15 minute was better than other enzymatic treatments and caused improvement in appearance properties of handsheets compared with control (without any chemical or enzyme).

The effect of the filler content and the different type of wood flour on the mechanical properties of polyethylene- date palm wood flour (DPWF) composite which are gathered from date palm tree annual pruning was studied. The different types of DPWF were stem, leaf and the mixture of stem and leaf. Composites were made at 45, 60 and 75 % by weight filler contents. The particle size was 25-40 mesh and maleic anhydride modified polyethylene was also added at 2% of total weight of each board. Linear Low Density Polyethylene (LLDPE) was used as control in this research. First, the palletized feedstock from DPWF and plastic were provided by a twin screw extruder and then, the compound pellets were ground and the final boards were made by a hot-press. It was observed that by increasing the filler content, modulus of rupture and tensile strength decreased, while the flexural modulus increased. The tensile strength did not show significant differences as a function of the filler type. The flexural modulus of the boards made from leaf flour, was significantly higher than boards made from mixed and stem flour respectively, while there was no significant difference between these two treatments. The modulus of rupture of the boards made from mixed flour was higher than the boards made from leaf flour but there was no significant difference between them, while there was significant difference between modulus of rupture of the boards made from stem flour with other two treatments.

The present research has been conducted to investigate the soda and soda-anthraquiuone pulping from whole kenaf (V36). In this respect, anatomical characteristics of kenaf bast and core fibers as well as the soda and soda-AQ pulp properties produced at four sodium hydroxide concentrations, namely 25, 30, 35 and 40 (g/lit), have been evaluated. The pulping results indicated that pulp yield and kappa number for both pulps reduced by increasing sodium hydroxide concentration and the pulp yield loss was more severe at higher alkali concentrations. The slope of yield loss in soda-AQ process was lower than soda process. At similar concentrations, kappa number in soda-AQ process was lower than soda process, but pulp yield in soda-AQ was higher than soda pulp at almost similar kappa number. Statistical analysis indicated that the independent and interaction effects of process type and sodium hydroxide concentration on pulp yield and kappa number were significant at 1% experimental error level. In addition, the results of physical and strength properties of the handsheets showed that soda-AQ pulp had higher density than soda pulp but it was not significant statistically. Soda-AQ pulp had higher strength properties than soda pulp for both unrefined and refined samples and the differences were statistically significant for tensile strength at 1% experimental error level and burst strength and tear strength at 5% experimental error level. Since the handsheets properties were analyzed at almost similar kappa number, no significant differences were observed in the handsheet brightness between soda and soda-AQ pulps.

Lack of forest management plan and forest road network caused that the traditional tree felling and processing was developed in Hyrcanian forest. In this system, trees are felled, limbed and topped motor-manually. Felled trees are processed with chainsaws into lumber and/or pulpwood. In order to evaluate this system, lumber processing was studied in two compartments of Namkhaneh district in Kheyroud forest. Objects of this study were time study of lumber processing, estimating productivity and costs, developing regression model, and obtaining wood waste and value loss. Factors affecting on regression model of lumber processing were dbh and log length. The hourly productions of lumber processing, based on production of lumber, with and without delay time were 0. 69 m3/h and 0.93 m3/h, respectively. Number of produced lumber in this method increased exponentially in relation to dbh. The unit cost of lumber processing with and without delay time were 245950 and 183140 Rials/m3, respectively. The unit cost of lumber processing decreased exponentially when dbh increased. Average cycle time of the lumber processing with and without delay was 30.35 and 22.06 minutes, respectively. Value losse associated with log degrade averaged 34.24 percent per processed log volume.

In this study, the effect of nanoclay particles content on the physical properties and flammability of composite made of high density polyethylene and wood flour was investigated. For this aim, wood flour was combined with HDPE at 50% by weight, and nanoclay was used in 0, 2, 4 and 6%, also 2% of MAPE as the coupling agent was used in all formulations. The samples were made in injection molding, and physical properties and flammability were tested. Results indicated that water absorption, thickness swelling, burning rate, heat release rate and total smoke production of wood polymer composite decreased with nanoclay loading. However, char residue and ignition time increased by increasing nanoclay particles amount. Also, the morphological study with XRD showed that nanoclay was distributed as intercalation structure in polymer matrix, and the d-spacing of layers decreased with increasing of nanoclay particles content.

Paulownia is one of the fast-growing species that was attended to supply industrial requirement in recent years. The application of this species is limited because of low density, so wood modification via compression and densification is an effective method. For this purpose, the paulownia boles were prepared from Shastkalateh forest and cut into blocks with 60×20×20 mm dimension. The variable factors of this test were effective factors in press process consist of compression percentage and direction and percentage of compression, press time and press temperature. Specimens were impregnated with 10% concentration PF resins before compression. Densification was done at 3 percentages (30%, 40% and 50%) and two directions (radial, tangential). Pressing process were done at two temperature levels (170 and 190oc), and two periods of time (8 and 12 minute) residual compression was determined after 24 hour submerging in the water. Results showed that compression percentage and direction in modified wood had significant difference compared with control samples. But the effects of press temperature and time were not significant. The best treatment for paulownia wood was obtained in radial direction and 50% compression. But it depends on conditions.

In this study, medium density fiberboard (MDF), was produced by dry process using refined fibers from Choob Khazare Caspian Amol factory, with 3 levels of urea formaldehyde adhesive at 8, 10, and 12 percent, and 3 levels of paraffin at 0.5, 1, and 1.5 percent. From every treatment, cylindrical samples for permeability measurement with 13 mm in diameter, and 30 mm of height were cut using hole-saw. Gas permeability of the boards was measured in two directions, parallel and perpendicular to the boards, as well as in central and marginal sections of the boards. Results indicated that increase in adhesive content decreased gas permeability. In addition increase in paraffin content decreased gas permeability. Gas permeability perpendicular to the boards showed greatest values. The highest value of gas permeability was measured to be 6.26 10-13 m3.m-1 with the lowest adhesive and the lowest paraffin content. The lowest value of gas permeability though was measured in the direction prependicular to the boards (0.38×10-13 m3.m-1) with the highest adhesive and paraffin contents. It can therefore be concluded that both adhesive and paraffin contents may decrease gas permeability. This would modify the previously belief that used to consider paraffin as a water proof agent in MDF composite and clarifies that water absorption and thickness swelling decrease may also be related to the lower permeability values.

Lignocellulosic resources of Khoozestan province are usable for wood and paper industry. The main questions are that, which places have the best conditions are select for development of wood and paper industries? Since, the methodologies of research were analytical and estimated. The research questions were tested by method of analytic hierarchy process (AHP). The results of the research were showed that priority places of Khoozestan on the basis of effective criteria with 0.02 inconsistency-ratios for these factories are include; Mahshahr, Gotvand&izeh, Behbahan, Khoramshahr, Abadan, Andemeshk, Ahvaz, Shoshtar and Dezful respectively. Some of effective criteria with 0.01 inconsistency-ratios are included; tax rate, the number of competitors and market conditions and spare parts respectively. Therefore, Mahshahr for factories of fiber preparation and Gotvand and Izeh for composites or particle board factories can be proposed, because of; important effective criteria and easy accesses to water resources.

The saprophyte fungi such as Penicillium are common microorganisms on Oak seed that have negative effects on germination. for isolation and identification species of Penicillium associated with Chestnut-leaved oak (Quercus castaneifolia) seed and investigation the effect of moisture on its frequency, during in autumn 2007 four sampling at any region was selected in Gorgan province including: Shast-Kalate, Ghorogh, Loveh and Golestan forest. For isolation of fungus of seed, cultured on potato dextrose agar medium and Penicillium implicatum was identified. The result indicated that the most seed moisture percent and frequency of fungus was in Shast-Kalate and the lowest was in Golestan. Considering the results of statistical analysis using Pearson Correlation Coefficient significant relation exist between moisture and frequency of P. implicatum (α <0.01). Thus the increase frequency of fungus to raise of the moisture.