عنوان مقاله [English]
Background and objectives: In this study, effect of treatment of reed (Arondo donax) particles used in core layer of sandwich panel in three levels (untreated, heat treated and hot-water- treated particles), press closing time in two levels (5 mm/s and 9 mm/s) and almond shell powder / melamine formaldehyde + urea formaldehyde resin ratio used in glue line in three levels (3:97, 18:82 and 33:67) on the some physical and mechanical properties of sandwich panel were evaluated based on ASTM.
Materials and methods: Reed particle with the 7 % MC was used in core layer of sandwich panel. The manufacturing panels in two stages: producing core layer and veneering core layer with fir species was done. UF and MF resins with the 50:50 weight ratio was used as binder. After gluing and forming cake, particles were transformed into the press. Temperature, time and pressure level applied by press were 180°C, 12min and 30 kg/cm2, respectively. After the core layer manufacturing and gluing the surfaces of upper and under veneers, the core layer was arranged between veneers and was pressed under 150°C, 120s and 0.2kg/cm2 press situations. After trimming, determination tests of modulus of elasticity, internal bonding, tensile strength of screw and nail and water absorption was done. The results were analyzed, statistically. It was used the Duncan’s multiple range test in order to comparison of mean values.
Results: panels manufactured from hot –water treated reed particles in core layer pressed with longer press closing time (5 mm/s) had the maximum MOR(15.6 N/mm2),tensile strength of screw (136.32 N/mm), nails (14.01 N/mm), dry internal bonding (0.26 N/mm2) and wet internal bonding (0.16 N/mm2).
Conclusion: the almond shell powder / melamine formaldehyde + urea formaldehyde resin ratio in glue line had no effect on the studied properties of panels, significantly, but it affected the bending strength, significantly. Besides, the type of treatment of particles used in core layer, and press closing time had effect on all of the panel properties, significantly. According to the obtained FT-IR spectral from specimens manufactured from different treated reed particles, hot-water-treated causes to increment of hydrogen bond quantities. Moreover, macroscopic photos showed that the hot-water-treated formed the best surface quality in order to create suitable chemical bond.