Journal of Forest and Wood Products
Year:2010 | Volume:63 | Issue:1|Papers Count:11

Cationic Starch is widely used in papermaking as dry-strength additive. By developing the use of nanoparticles in recent years, adding nanoparticles to some common papermaking high mass polyelectrolytes, is widely applied to improve drainage and simultaneously retention of fine materials and fillers. However, there is still little knowledge about this phenomenon and the performance mechanism of these additives in relation with other variables. In this study the performance of anionic nanosilica particles at different cationic starch dosages and their relation with zeta potential was investigated in terms of retention and drainability in fine paper furnish. The results showed that 0.5% cationic starch, by itself, increased the drainability just up to about 12 ml (CSF) and then even decreased it at higher dosage levels. The same trend was also observed in retention of fines and fillers with the highest figure (41%) at 1% cationic starch dosage. Nanosilica particles addition modified this mild trend and significantly improved drainage and retention with better performance at higher cationic starch dosage while zeta potential was still negative. A reduction in nanosilica performance was observed when higher cationic starch dosage resulted in wet end system positive charge. Therefore, zeta potential can be a good indicator in determining cationic starch dosage.

Tree and shrub communities comprise some stands and groups on southern slopes of Alborz Mountains. These sites are mountainous forests of Iran-o-Turanian region. They have not been studied in an appropriate way while considered just generally until now. In this research, we selected a proper watershed which is rich in forest coverage and has an expanded elevation range to consider the forest profile along the gradient of elevation above sea level. “Strip transect” method was used to study the species, vegetation types and variations. As a result, we separated 15 vegetation types throughout the “Latian Dam” watershed, which were classified later in 8 major types including: Juniperus excelsa (syn. J.polycarpos), Pistacia atlantica, Cotoneaster kotschyi, Ulmus sp., Amygdalus lycioides, Malus orientalis, Rhus coriaria, Berberis spp. and riparian forests. The current stands disperse from 1700 m a.s.l. to 2850 m a.s.l. Amygdalus lycioides, Rhus coriaria and Pistacia atlantica types exist on low slopes of the watershed (lower than 2300 m). Cotoneaster type grows up on middle slopes while Malus orientalis, Ulmus sp., Berberis spp. types appear on high slops (higher than 2300 m). In addition, Juniperus polycarpos type includes an expanded dispersal from 1900 to 2850 m a.s.l. Also, we analyzed and perceived forest communities of southern slopes of Alborz in the considered area, in this manner: - Mixed Pistacia atlantica, Amygdalus spp. vegetation: 1700-1900 (2000) m a.s.l.- Juniperus excelsa mixed with Cotoneaster kotschyi, Cotoneaster nummularioides & Cerasus microcarpa: 2000-2500 (2600) m a.s.l. - Juniperus excelsa mixed with Berberis spp. and Rosa spp.: 2500-2850 m a.s.l.

Possibility of utilization of Eucalyptus cameldulensis in particleboard industry was investigated in this study. Experimental boards were manufactured from mixture of Eucalyptus and Paulownia particles. The variables were percentage of mixture of eucalyptus and paulownia, particles at four levels :(100E+ 0P, 80E+20P, 60E+40P and 40E+60p), resin content at two levels (8% and 11%), hardener content at two levels (1 and 2%) and pressing time at two levels (7 and 10 min.). Other factors were kept constant. Modulus of Rupture (MOR), Internal Bond (IB) and Thickness Swelling of specimens were evaluated following DIN 68763 standard. The results showed that increasing paulownia particles in mixture in almost all boards caused in increasing of modulus of rupture, internal bond and reducing of thickness swelling. The reason for these results may be because of increasing compact ratio of particle mat and reducing negative effect of eucalyptus by increasing of paulownia. On the other hand, in all cases, increasing of pressing time and resin content improved modulus of rupture, internal bond and thickness swelling. These results show that panels made of two percent of hardener had significant effect on internal bond and thickness swelling in rather than one percent hardener.

In this research, radial variation in longitudinal permeability of beech (Fagus orientalis( wood containing red heartwood was investigated. The boards prepared from pith to bark were dried under temperature of 50ºC and relative humidity of 63% to the final moisture content of 7%. Then, cylindrical samples of 18 mm in diameter and 15 and 30 mm in length were longitudinally cut from the boards. The lateral surfaces of the samples were coated using epoxy resin to confine the fluid (air) flux along the longitudinal direction. Then, the longitudinal permeability of the samples was measured by a gas permeability device. For each thickness, the pattern of radial variation in permeability was similar. The results showed that the longitudinal permeability of samples close to bark was greater that that of those close to the pith. Also, a sharp reduction in permeability occurred near the pith. The microscopic studies revealed that regardless of vessel diameter and proportion which significantly affect the longitudinal permeability, the presence of tyloses in the vessels as a result of red heart wood formation is the main factor for the decreased longitudinal permeability.

In this research, influence of thermo-mechanical degradation of polypropylene (PP) on physical and mechanical properties of wood- PP composites made from virgin and degraded PP blends was studied. For this purpose, a virgin PP was thermo-mechanically degraded by twice extrusion under controlled conditions with a twin-screw extruder. Virgin PP and degraded PP in each stage were mixed and the blends and beech sawdust (-40/+60 mesh) were compounded (at 60% weight sawdust loading) in a counter-rotating twin-screw extruder in presence and absence of compatibilizer to produce the sawdust-PP composites. The results showed that replacing 50% of virgin PP by degraded PP, impact strength of wood-PP composites decreases but water absorption, thickness swelling, flexural modulus and hardness increase. Compatibilizer improved the mentioned properties.

The objective of this study was to evaluate relative light intensity within 18 years old plantations of Alder (Alnus subcordata C. A. Mey.), Oak (Quercus castaneifolia C. A. Mey.), Maple (Acer velutinum Bioss.), Cypress (Cupressus sempervirens var. horozontalis) and an adjacent natural forest in Darabkola (Mazandaran, Iran). For this purpose one sample plot, each 1 ha; was selected in every plantation as well as in the natural stand. In each treatment, 10 micro-sample plots were selected random systematically. To determine seasonal relative light intensity, one hemispherical photograph was taken from each micro-sample and a total of 200 photographs from 50 micro-plots in different treatments were taken. Also the method for determination of canopy class (percent) has been implemented in each plot. In respect to two methods for determination of relative light intensity in various treatments, the use of hemispherical photograph was more accurate than determination of canopy class (P<0.01). The seasonal differences of relative light intensity in each treatment and also the differences of relative light intensity in each season between treatments were statistically significant (p=0.05). The analysis of PCA in relationship with the effective parameters in relative light intensity in various treatments showed that, in the basis of first axis, when abundance of trees in plots have been increased (plantations of Cypress, Oak and Maple) this parameter takes an important role and with the diminution of abundance in plots (natural forest and plantation of Alder) the parameters of diameter at breast height (dbh) and height of trees get an important role. In relationship with second axis, the parameter of crown canopy in natural forest with characteristics of uneven aged, trees mixture and stands with consisting of several layer has an important role in summer season and with fall of leaves in broad leaves plantations, the parameter of relative light intensity get an important role in winter season. Silviculture activities in plantation areas have been caused the parameters of diameter at breast height (dbh) and height of trees has an important role instead of abundance of tress also the gradual development of crown canopy take an important role in relationship with differences of relative light intensity in vegetation period.

The genetic variation of Quercus brantii populations in Chaharmahal va Bakhtiary province was evaluated using AFLP molecular markers. Fifty-five trees of Q. brantii belonging to eight populations distributed in different regions of Chaharmahal va Bakhtiary province, were sampled. Young leaves were collected from each tree and used for molecular analysis. Thirteen selective primer pairs were produced a total of 398 AFLP fragments, out of which 371 (92.1%), were polymorphic. The mean of Polymorphism Information Content was 0.7. The coefficients of genetic similarity vary from 0.32 to 0.74. Similarity matrices were submitted to cluster analysis by UPGMA method. AFLP diversity among and within populations have been analyzed for eight populations of Q. brantii with and without regional structure. Analysis of molecular variance showed that most genetic variation was comprised within populations. A small proportion of the total variation was assigned to differences among populations denoting little differentiation of populations in this study. 0.58% of the genetic variance was attributed to differences among regions denoting little differentiation of populations over a range of 100 km. The vast majority of variation present in the dataset was attributed to the within population level. Finally, we found a high level of genetic diversity within Quercus brantii populations in Chaharmahal va Bakhtiary province.

In this research, hourly production and wood extraction costs of HSM-904 and Timber jack C-405 wheeled skidders were evaluated. This research was carried out in compartments 6 and 8 of Sorkh Kolah district in Wood and Paper Industries Forest of Mazandaran. Skidding factors (costs and production) were evaluated using work study and time study techniques. A mathematical model of skidding time was determined for each skidder. The effective factors of the mathematical model for Timber jack skidder was volume per turn, skidding distance and winching length and for HSM-904 skidder was volume per turn and skidding distance. Hourly system production was calculated using time study based on IUFRO guideline. Hourly cost was calculated using guideline from Forest, Rangeland and Watershed Management Organization of Iran. The results showed that the net production (without delay time) was 11.3 and 8.7 cubic meters per hour for Timber jack and HSM-904 skidders, respectively. Skidding costs (with delay time) were 60442 and 88400 Rials per cubic meters for Timber jack and HSM-904, respectively.