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Využití mikrovlnné plastifikace dřeva při výrobě ohýbaných nábytkových dílců
Nováčková, Kateřina
This bachelor thesis is dealing with microwave plasticization for wood shaping and its potential utilization in furniture industry. European beech (Fagus sylvatica L.) specimens of dimensions 20 × 20 × 300 mm were sorted into 8 groups (each group consisted 15 specimens). Reference specimens (Ref1) were tested as oven-dried at room temperature, furthermore reference specimens (Ref2) were tested as oven-dried at 80 °C and last reference group (Ref3) was conditioned to fiber saturation point (FSP). Specimens of conventional, steam plasticization (Vp) were conditioned to FSP and heated at 100 °C for 1 hour. Microwave plasticization was carried out at 1,5 and 3,5 kW using continuous laboratory MW device All MW specimens were soaked in water in order to reach approx. 60 % of MC.Output moisture content (MC) of MW treated specimens was 20 % (MW1), 30 % (MW2, MW4) and 40 % (MW3). Moreover, additional specimens of dimensions 30 × 30 × 450 mm were used to up-scale its possibilities of use. These specimens were sorted into 2 groups (Ref and MW), each group consited 20 specimens. Effect of plasticization was measured by means of static 3-point bending test. Plasticity of wood was evaluated by modulus of elasticity (MOE), modulus of rupture (MOR) and deflection. Results of reference specimens confirmed influence of temperature and moisture content on MOE and MOR. Influence of moisture content (0 % and FSP) was found to be more significant and 65 % decrease of strength MOR and 40 % of MOE is reported. Steam plasticization, as a conventionally used method for shaping, led to increase of plasticity (decrease of MOE about 65 %) and deflection (70 %) when compared to Ref1. Significantly higher deflection (up to 1,5 mm) and increase of plasticity (MOE decreased about 72 %) was found for specimens plasticized by MW at 1,5 kW and 3,5 kW from initial moisture 60 % to output moisture 30 %. Based on results, it can be stated that microwave technology have similar effects on wood plasticity, when compared to conventional method wood plasticization – steaming. Results of present thesis confirmed high potential of MW plasticization for wood shaping. Reduction of time and safe energy might be considered as a great advantage for furniture production. Futher studies should be done in future in order to reveal effect of MW on structural changes, eventually to optimize process for specific shapes.
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