فهرست مطالب معین دهقان

Wood and wooden products are one of the most important materials that have been traditionally used for building constructions. In this study, Mazandaran Sangdeh Beech and imported Georgian Beech wood were used. Physical properties (including dry and critical densities, shrinkage and swelling) and mechanical properties (including bending strength, modulus of elasticity, compression parallel to grain, shear parallel strength to grain, tensile strength parallel and perpendicular to grain, screw withdrawal strength and hardness) were investigated. Physical and mechanical tests were performed according to international standard methods such as ISO 3129 (2012) and ASTM (D143-14). The moisture content of all samples was 12% during mechanical tests. The mean dry densities of Sangdeh and Georgian beech were 0.61(g/cm3) and 0.65(g/cm3), respectively. The result showed that significant differences were observed among the properties of the mentioned species after T-test, except in critical density, radial shrinkage and radial swelling. Moreover, the obtained strengths of Georgian timber were significantly higher than the Iranian beech, which was attributed to the higher density of Georgian timber.

In the present research, the mechanical and physical properties of poly lactic acid-canola stem flour composites made by compression molding technique were studied according to ASTM standards. According to the results achieved, it was found that modulus of rupture, tensile strength and impact strength were decreased by increasing the amount of Canola stem flour in comparison with pure PLA. In contrast, the elastic properties including Young's modulus, flexural modulus, and surface hardness increased. The addition of canola stem flour also increased water absorption and thickness swelling. Furthermore, a significant increase in the composite crystallinity degrees was observed in the study of thermal properties by DSC test. It can be concluded that the use of Canola stem as a cheap and renewable lignocellulose source can as well as having a filler role in making composites, improve some of the mechanical properties of the same composites.

In the present research the biodegradability Properties of poly-lactic acid-canola stem flour composites in three levels of 25, 35, and 45% canola stem flour made by compression molding technique were studied . In order to study the biocompatibility behavior of the composite, three methods of biological degradation were used for Trametes versicolor and Gloeophyllum trabeum fungi, long-term water absorption and composites burial in the soil for 4 months. The results of statistical analyzes showed that the amount of composites weight loss increased against the degradation by fungi and burial in the soil by increasing the amount of rapeseed canola stem flour while pure poly-lactic acid had a very high durability against these factors. In addition, there was no effect on the weight loss of samples in the long run leach test so that the weight of composites and poly- lactic acid samples was constantly increasing and there was no effect on weight and thickness loss. The growth of myceliums fungi was clearly detectable and detectable in reviewing the images of electron microscopy from the fracture properties of composites, unlike poly-lactic acid so that fungi crossed their polymer into rapeseed shoot flour and reduced the weight of the composites. The results of the FTIR spectroscopy on poly-lactic acid prepared before and after exposure to the Gloeophyllum trabeum fungus confirmed the validity of the above results. According to the results of this study, poly-lactic acid, as a biodegradable polymer, has been shown to be very durable against degradation by natural biological agents.

The purpose of this study was to evaluate the biodegradability of composites made from bamboo flour and poly lactic acid using physical properties and biodurability examinations. On the other hand, the effect of the amount and size of the bamboo flour particles on the physical properties and durability of the biocomposites was another objective of the research. the bamboo flour and polymer were mixed up in a counter-rotating twin screw extruder. the biocomposites boards were produced by compression molding method. The samples were cut and evaluated according to the suggested specifications in the ASTM and EN-113 standards. The results showed that the thickness swelling and water absorption of the composites were increased significantly by increasing the amount and size of bamboo flour particles. Also, biodurability of the biocomposites samples against the studied three fungi species showed that Gloeophyllum trabeum sharply caused high mass losses in all samples by increasing the amount of bamboo flour, while pure polymer (PLA) had a very high durability against the fungi.