IRANIAN JOURNAL OF NATURAL RESOURCES
Year:2000 | Volume:53 | Issue:3|Papers Count:7

This investigation was carried out to evaluate the possibility of utilization of recycled newspaper fibers as reinforcer in unsaturated polyester to be used in the making of Wood Fiber Polyester Composite (WFPC). The objectives of the study were: to compare reinforced with unreinforced polyester; to study the effect of Silan as a coupling agent, and percent by weight of fibers, as reinforcer, on the Properties of WFPC.Six treatments were employed, one of which was pure polyester and among the rest, four contained 5, 10, 15 and 20 percent Silan - coated fibers while the last one carried 10 percent uncoated fiber. All treatments were carried out using only chemical processes and moulding methods without application of any external heat. The results of mechanical tests revealed improvement of polyester properties when reinforced by recycled newspaper fibers. Positive effect of Silan on WFPC became evident too.

In order to investigate the production potential of different sites under different growth conditions and to present an optimum figure for the growing stock per hectare in forest management planning as well as knowing whether or not there is any difference between growing stocks whith change in slope and altitude, the western forest stands of Gilan province were selected as the study area.In this area five localities of different conditions have been studied. The analysis of the data obtained show that there is a significant difference between the means in different growing stocks. This difference can be further explained as in the following three groups: The first group with excellent growing stocks like Moshkali-chal; the second with good growing stocks like Shah-gerdab, Sereni-chal and Piceson; and the third group whith average growing stocks for which Varga-dara area can be cited as an example. The analysis of variance and Duncan Multiples Range Test also revealed the significance of these differences.More investigations reveal that the areas that have a north ward direction possess excellent growing stocks and the areas that are on the western, eastern and north-western slope foot have good, while north-eastern direction sites show average growing stocks. The effect of altitude in this study area was also shown to be significant.

To study the possibility of the use of cellulosic fibers as reinforce in the manufacture of fiber high-density polyethylene, three kinds of fibers namely; pure alpha cellulose, wood flour, and waste paper fiber were mixed with high density polyethylene at rates of 10, 20, 30 and 40 percent by weight. Also, maleic acid was added to mixture as a compatibilizer. The results revealed that impact energy, modulus of elasticity and elongation decreased but tensile strength and hardness increased due to addition of cellulose fibers. The best properties were found in composites that contained alpha cellulose and waste paper fibers, but since the difference between these two kinds wasn't significant and waste paper fibers being cheaper than alpha cellulose, the use of waste paper was suggested in fiber high density polyethylene composites. Two percent by weight maleic acid was suggested as a compatibilizer between polymer and cellulosic fibers.

The main objective of this study was to determine the drought resistance potential of Stipa barbata, Agropyron cristatum and Agropyron desertorum.The study was carried out in the greenhouse at Karadj Natural Resources Faculty of Tehran University. The experiment was based on a completely randomized design of three Plant species, three irrigation periods and four replications.Morphological and physiological characteristics such as amount of wilting, leaf water potential, shoot and root weight and root/shoot ratio were measured in the first phase of the study. Anatomical changes of leaf such as epiderm, parenchyma, and stomata condition were also assessed carefully. Besides, the amount of species soluble carbohydrate was measured. Overall results indicated that the highest amount of wilting belonged to Stipa barbata. In terms of leaf water potential, there was no significant difference between the three species under study. Shoot weight and total weight of all three species decreased with increasing water stresses during the study period, while root weight and root /shoot ratio increased greately. Agropyron desertorum and Ag. critatum showed the same morphological and physiological characteristics while Stipa barbata was quite different from the above mentioned two species. Leaf anatomical changes indicated that Ag. cristatum and Ag. desertorum are of high adaptation potential for drought resistance.Soluble carbohydrate increased with increasing stresses during the study period, but differences between the three species were not highly significant.

In this research the anatomical, physical and chemical characteristics of kenaf as well as pulp properties of Plant's bark and whole stem were evaluated through the processes of soda, Soda-anthraquinone and kraft in three alkali conditions of 16%, 18% and 20%. The results show that bark less kenaf is not suitable for paper manufacturing pulp, but because of its low density, can be used in composite board, especially acoustic board industries.Kenaf bark is much more appropriate for paper manufacturing because of having a large amount of cellulose (54%), long fibers (2.4 mm), but little amount of extractives and lignin (14%).Pulp characteristics show that the best method for producing pulp is the Soda - anthraquinone process with 18% effective alkali. In these conditions, the pulp yield is about 0.5% more than the kraft process and about 1.2% more than the Soda process.Freeness of Soda-anthraquinone pulp was less than that of Soda pulp, the difference being insignificant because of the fact that the main factor effective in the amount of Freeness is the nature of the substance and not the nature of the process. Survey of hand made paper strength properties also revealed that strength values for papers produced from kraft pulp process are similar to those for the paper produced from kraft pulp process of softwoods, but they show a lower tear strength. The burst strength of papers produced from kraft pulp process of kenaf without bark is more than that in kraft pulp process of hardwood, and their other strength properties are almost comparable.The strength properties of papers produced from whole stems of kenaf as compared with those produced from bark less kenaf has been considerably improved, so that such properties as bursting, tearing, folding and tensile strength have had an increase of 90%, 130%, 72% and 18% respectively.

In order to study the structure of natural beech stands, four plots each of one hectare area were selected in Gorazbon district (Kheyroudkenar forest).Forest stand characteristics including species composition, number, basal area and volume per hectare were measured, the scatter diagram being drawn. Considering this decreasing diagram, five model functions were analyzed for the best fitting one.Theoretical models which were tested, consisted of regression, Beta distribution, Weibule distribution, exponential model and power model. Among the tested models, three (regression model, Beta and Weibule distributions) proved acceptable. The regression model, because of the minimum value of chi-square (x2) in the test was the best fitting and, thus suggested for planning and conducting beech stands in Kheyroudkenar forest.The scatter diagram of number in diameter classes and evaluated models were indicative of unevenness of age in the investigated stands.

Fragmentation of industrial lignin into non-polymeric products, especially phenols, has always attracted attentions. Obstacles in achieving this objective have been: macromolecular structure of lignin and the existence of non-phenolic groups in the phenyl propane structural units of lignin. These feature reduce lignin reactivity and make the cleavage of ß-aryloxy bonds a difficult process.In this research, by performing acidolysis reactions in the presence of suitable strong nucleophiles, such as phenols and thioethanol, oily products were obtained from hardwood kraft lignins. Spectroscopic studies, especially GC-MS, suggest that these oils are mainy phenolic mixtures.