Mechanical and water resistance properties of birch plywood bonded with low-density polyethylene film: Effects of polymer dosage and pressing temperature

In this study, low-density polyethylene (LDPE) thermoplastic film was used as an alternative to conventional synthetic adhesives for the production of formaldehyde-free birch plywood. The work aimed to determine the effect of pressing temperature (140°C, 160°C, and 180°C) and thermoplastic polymer dosage (130 g/m 2 , 150 g/m 2 , 170 g/m 2 , and 190 g/m 2 ) on the physical and mechanical properties of plywood panels. The adhesive ability of the LDPE film was evaluated by measuring the shear strength of the panels. Additionally, water absorption, thickness swelling after 24-h water immersion, bending strength, and modulus of elasticity of the panels were investigated. The results showed that the shear strength of the plywood samples bonded with LDPE film ranged from 1.5 to 1.7 MPa, exceeding the minimum requirement of 1.0 MPa specified in EN 314-2 and satisfying the criteria for bonding Class 1 (dry conditions), which is intended for interior applications only. Increasing the pressing temperature from 140°C to 180°C had a positive effect on shear strength, bending strength, and modulus of elasticity; however, it led to increased water absorption and thickness swelling. An increase in polymer dosage from 130 to 190 g/m 2 also positively influenced shear strength, bending strength, and modulus of elasticity. Considering mechanical performance, panel thickness, and economic factors, the optimal pressing conditions for bonding veneer sheets with LDPE film were determined to be a temperature of 160°C and a polymer dosage of 150 g/m 2 .