A Comparative Study on the Mechanical and Physical Properties of Plywood Panels Prepared by Chitosan as Green Composite

Abstract The goal of this study is to make green wood products that are acceptable both in terms of mechanical and physical properties using chitosan as a natural binder. Five-layer poplar plywood specimens prepared with two different commercial adhesives namely urea formaldehyde (UF) and methylene diphenyl isocyanate (MDI), and compared with chitosan (CH). For the purpose of evaluation, mechanical properties such as modulus of rupture (MOR), modulus of elasticity (MOE), glue line shear strength (SS), surface soundness and physical properties such as thickness swelling (TS), water absorption (WA) of the samples were studied. Variable parameters were: adhesive type (UF, MDI and CH), adhesive content (2, 4 and 6 wt%), and adhesive spread rate (150 and 180 g/m2). Other parameters such as pressing time (10 min), press pressure (30 kg/m2) and press temperature (140 ºC) were held constant. Based on the findings of this study, MOR properties of the panels slightly increased when the resin content was increased from 150 to 180 g/m2. The results of shear strength and surface soundness showed that boards made with chitosan as a binder, had the same results as the boards made with UF resin. Analysis of data revealed that the mechanical properties were significantly different among the board types. In general, WA and TS decreased (improved) with the increase of resin content. According to the test results, the lowest TS observed in chitosan boards was 4% chitosan with 180 g/m2 spread rate, which is not only better than UF plywood, but also close to the results of MDI specimens. According to the measured parameters, 4% chitosan with spread rate of 180 g/m2 can be considered as the optimal binder composition for plywood manufacturing. Finally, it can be stated that chitosan has potential as replacement resin material for plywood manufacturing.