جستجوی مقالات مرتبط با کلیدواژه « پلی پروپیلن » در نشریات گروه « جنگلداری »

The main lignocellulosic raw material used in the particleboard industry is wood. The production of panel products from agricultural residues is important considering the increasing worldwide wood fiber shortage. Agricultural residues, which are produced with large quantities annually throughout the world, are the main renewable resources. Compared with synthetic fibers such as glass, natural straw fibers have more advantages such as low cost, low density, abundant and wide distribution, recyclability and biodegradability. Rice is the primary food for more than 40% of the worlďs population, with about 596 million tons of rice and 570 million tons of rice straw produced annually in the world. At present, most of these residues are burnt in situ after harvest. The field burning of rice straw and other agriculture residues in wide areas not only results in serious environment issues, but also wastes precious resources. Faced with worldwide shortages of forest resources, environmental pollution and waste of biological resources resulting from field burning of rice straw and other agricultural residues, there has been a revival of interest in using rice straw and other agriculture residues to produce composite panels. This research investigated the use of the rice straw –industrial particle wood with polypropylene powder on the mechanical and physical properties of single layer particleboard.
The variable in this research were the ratio of rice straw to industrial wood particle (at four levels; 0:100, 15:85, 30:70, 45:55) and polypropylene powder (at three levels; 0, 5, 10%). Industrial wood particles from Sanate Choube Shomal Company were used. Urea formaldehyde resin used at 10 percent level of dry weight of raw material as well as ammonium chloride was used as a catalyst at 2 percent level of the dry weight of adhesive. After the mixing process raw material together, mat at temperature of 170°c for 5 minutes under hot press was placed. After making particleboard, physical and mechanical properties of panels analyzed using variance analysis in 5% probability level.
The results showed, increasing polypropylene percent resulted in increasing the bending strength, modulus of elasticity and internal bonding of the boards. The results also indicated that water absorption and thickness swelling after 2 and 24h in water decreased with increased polypropylene percent.
Results showed, there was usability of the rice straw up to 30 percent and polypropylene up to 10 percent for general purpose boards for use in dry conditions.

In this study , the physical and mechanical properties of polypropylene composites reinforced with bagasse alkaline-Sulfite-Anthraquinone, Soda-Anthraqouinone, Monoethanolamine-Anthraquinone chemical pulps and mechanical pulp (CMP) known as Pulp-Plastic Compostes (PPC) were investigated and the results were compared among PPCs and with polypropylene composites reinforced with bagasse flour known as Wood-Plastic Composite (WPC) . The ratio of the matrix (polypropylene) to reinforcement agent (pulp) was 50/50. The results showed that elastic modulus, tensile strength, bending strength and impact strengths of the produced composites were influenced by the pulping processes significantly. Furthermore, the composites which contained chemical pulps had higher strength and dimensional stability as well as less water absorption than that of containing mechanical pulp. In comparison to WPCs , the water absorption and dimensional stability of PPCs decreased and increased, respectively. Generally, the results showed very superior physical and mechanical properties in pulp - plastic composites than flour bagasse- plastic composites.

Tobacco is planted extensively in Golestan province and high volume of its stem wastes remained without using and it is burned. As a useful purpose of these wastes and to reduce the environmental problems، in this the mechanical properties of polypropylene composites reinforced with tobacco stalk flour were studied. For this purpose، the tobacco stalk flour as the reinforcement، in three levels of 30، 40 and 50%، maleic anhydride grafted polypropylene as a coupling agent in two levels of 4 and 6% as variable factors were used. The results showed that with increasing the amount of tobacco stalk flour، tensile stress decreased significantly but tensile modulus increased. Also increasing the amount of coupling agent improved tensile strength. Bending strength and bending modulus increased with increasing the amount of tobacco stalk flour and coupling agent. In the case of impact strength، no significant effects were observed between the different levels of the treatments. Therefore it is recommended to use50 % tobacco stalk flour as a natural and biodegradable material with 6% coupling agent to make wood-plastic composite with desired mechanical properties.

In this study, The effect of alternative humidity stages on Physical and mechanical properties of Rice stem flour (RSF)-Polypropylene Composites was considered. Panels composites were built in 1g/cm3 nominal density and 25×15×1cm dimension that including, treatment of PP and RSF with 45, 60 and 75% weight ratios. Physical and mechanical properties of composites were measured and data were compared with randomized design. The Results showed that increasing of filler ratio, and passing of humidity stages result in decrease of Physical and Mechanical properties of composites. Adding 2 percent MAPP result in partial improve in Mechanical properties and decrease in water absorption and thickness swelling of composites.

In this study, the effects of fiber content, type and size on board density and withdrawal strength of fasteners (nailed and screwed) in joints made in natural fibers-plastic composites produced through a dry process were investigated. Wood-plastic boards were made at a nominal density of 1 g/cm3 and dimensions of 30×20×1 cm. Polypropylene (PP) as the matrix and poplar wood fiber and rice straw fibers as the reinforcement were used together with 4% (based on weight) maleic anhydride grafted polypropylene (MAPP) as the coupling agent. Three levels of dry poplar and rice straw fibers, namely 45%, 60%, and 75% based on the composition by weight at two particle sizes of 20-40 mesh and 40-60 mesh were mixed with PP. Totally, 12 formulations with 3 replications were considered. The final composites were made by pressing the prepared mats between the hot plates of a compression press by employing combinations of temperature and pressure in three stages. After storing the composites at room temperature for 15 days, the density of the boards and withdrawal strength of fasteners were measured. The results showed that fiber content may significantly influence the density of the samples and the fiber size of 40–60 mesh may lead to a higher density. In addition, it was found that poplar fibers (the type of fiber) results in higher withdrawal strength of fastener in the composites than rice straw fibers. Furthermore, the withdrawal strength of fasteners was reduced as the fiber content was increased. However, this effect is dependent on fiber size and may be negligible at higher fiber contents.

In this research, the decay resistance of sawdust–polypropylene composite has been evaluated by microscope. The scope of research was to assess the effect of different weight percentages of sawdust (45%, 60% and 75%) sawdust distribution on the fungal decay. ASTM D1413-99 test method was used to carry out decay test and Trametes versicolor was chosen as a white rot fungus. After 12 weeks exposure of the composites samples to the fungi, the weight losses were determind using Soil Block test. Analyzing the data using ANOVA one way statistical method, it has been shown that the weight losses of the composite due to decay were proportional to the sawdust weight percentages. Also, it was found that weight losses were higher in those treatments with upper sawdust percentages. In order to microscopic study, a light microscope was used. The results showed that increasing in the weight percentage of sawdust, led to particles aggregation, their nonuniform dispersion, decreasing in particles encapsulating by polymer and increasing in hollows and voids between sawdust and polypropylene which made the composite susceptible for fungi attack.

In this research, the sanding dust was used to manufacture wood –plastic composite its their properties were compared with wood flour–Polypropylene composite. Sanding dust and wood flour were separately mixed with of Polypropylene at three levels of 50%, 60% and 70%. Coupling agent (MAPP) was used at two levels (4% and 6%). Totally twelve composites were produced. The composites were manufactured using hot press. After preparation of test samples, mechanical properties (bending and hardness) and physical properties (water absorption and thickness swelling) were measured. Results showed that addition of both fillers reduced modulus of rupture and increased modulus of elasticity, water absorption and thickness swelling. The urea – formaldehyde resin present in sanding dust caused a reduction in mechanical and physical properties of polypropylene-sanding dust composite compared with polypropylene -wood flour composite at the same levels of fillers.

In this research, the decay resistance of bagasse-polypropylene composite has been evaluated. The scope of research was to assess the effect of different weight percentages of bagasse (40, 55 and 70%) and coupling agent, (MAPP) maleic anhydride grafted polypropylene (0, 4 and 6%) on the fungal decay of the composite. ASTM D1413-99 modified test method was used to carry out the decay test, Trametes Versicolor using as a white rot fungus. One sample of Alder was also used in decay test, to ensure the soundness and right activity of the fungus. Analyzing the data using variance analyze statistical method, has shown that the weight loss of composite due to decay was proportional to the bagasse weight percentage. In addition, the samples without coupling agent showed more weight loss in comparison with those having coupling agent, and, the higher the amount of coupling agent, the lower the decay of the composite.

In this research, the possibility of using high percentage of lignocellulosic fibers in making natural fiber-thermoplastic composite was studied. Three weight percentages of bagasse flour namely 40, 55 and 70 percents were chosen. MAPP was used as coupling agent at two weight percentages of PP, namely 0, 4 and 6 percents. Tensile strength was measured applying Instron 6025. The results showed that with increasing bagasse flour percentage, tensile modulus of elasticity improved, but tensile stress, tensile strain and work at proportional limit decreased. Also, addition of the coupling agent led to the improvement of tensile stress and tensile modulus of elasticity and decreasing work at proportional limit and tensile strain.