M.Sc. Tezi Görüntüleme | |||||||||||||||||||||
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| Summary: Because of a rising demand for material features such as renewability, sustainability, and biodegradability, bio-based materials are increasing their importance, particularly with regard to composites. In order to manufacture fully biodegradable sandwich panel, all the constituents of sandwich panel must be fully biodegradable. Cellulose films were prepared by dissolving lyocell fibers in LiCl/N,N-dimethylacetamide solvent and subsequently coagulating and drying them under ambient conditions. Some of the films produced were uniaxially drawn to 1.5 draw ratios. Balsa sheets were coated by the undrawn or drawn cellulose films by using polyvinylacetate (PVAc), biodegradable glue, at ambient conditions. Two type thicknesses and two type densities of balsa wood were used; (4 and 6mm) and (100 and 230kg/m3), respectively. According to fiber direction of the balsa wood, the films were glued on balsa wood in five different angels; 0o, 22.5o, 45o, 67.5o and 90o. Flexural properties were characterized by means of bending test with the lightweight sandwich panel. In the sandwich samples coated by the drawn films, in the values of Modulus of Elasticity and Modulus of Rapture at 0 degree to fiber direction were found 2 times higher than those of balsa sheets and 1.5 times higher than those of undrawn films-coated balsa sheets. These values at 90o to fiber direction were found 5 times higher than those of balsa sheets. For 0.11mm of the cellulose film, the best values were found in the samples with 4mm thickness balsa core.In addition, while lyocell fibers are dissolving in LiCI/DMAc, zinc borate was added to the solution in five different ratios (0.35%, 0.75%, 1.5%, 2.5% and 3.5%). Tensile properties of the cellulose films were determined by means of Zwick Roell universal testing machine. Fire-retardant tests were performed by Thermo Gravimetric Analysis (TGA) device. It is shown that adding zinc borate in 0.35% and 0.75% ratios to the solution increased tensile properties of cellulose films and the fire-retardant of cellulose films with zinc borate increased with increasing the ratios of zinc borate. Keywords: Drawn and undrawn cellulose films, lyocell fibers, LiCI/DMAc solvent, zinc borate, flexural properties, and lightweight sandwich panel, fully biodegradable | |||||||||||||||||||||