Abstract
Thermoplastic films exhibit good potential to be used as adhesives for the production of veneer-based composites. This work presents the first effort to develop and evaluate composites based on alder veneers and high-density polyethylene (HDPE) film. The effects of hot-pressing temperature (140, 160, and 180 °C), hot-pressing pressure (0.8, 1.2, and 1.6 MPa), hot-pressing time (1, 2, 3, and 5 min), and type of adhesives on the physical and mechanical properties of alder plywood panels were investigated. The effects of these variables on the core-layer temperature during the hot pressing of multiplywood panels using various adhesives were also studied. Three types of adhesives were used: urea–formaldehyde (UF), phenol–formaldehyde (PF), and HDPE film. UF and PF adhesives were used for the comparison. The findings of this work indicate that formaldehyde-free HDPE film adhesive gave values of mechanical properties of alder plywood panels that are comparable to those obtained with traditional UF and PF adhesives, even though the adhesive dosage and pressing pressure were lower than when UF and PF adhesives were used. The obtained bonding strength values of HDPE-bonded alder plywood panels ranged from 0.74 to 2.38 MPa and met the European Standard EN 314-2 for Class 1 plywood. The optimum conditions for the bonding of HDPE plywood were 160 °C, 0.8 MPa, and 3 min.
Highlights
The wood-based composites sector plays an important role in national economies in many countries.Plywood is widely used for different applications, such as construction, furniture manufacturing, means of transportation, packaging, decorative purposes, and many others
The highest shear strength was achieved at 160 ◦ C when the pressing time was increased to 3 min
The smallest shear strength was achieved at 140 ◦ C and the pressing time 1–2 min
Summary
The wood-based composites sector plays an important role in national economies in many countries.Plywood is widely used for different applications, such as construction, furniture manufacturing, means of transportation, packaging, decorative purposes, and many others. One of the main disadvantages of plywood products is using a large amount of adhesive during its manufacture, which can be up to 20% of its total mass [1]. This disadvantage decreases the plywood product’s ecological balance and makes it less favorable than solid wood, especially when considering resins derived from petrochemical resources. Global production of plywood reached 157 mln m3 in 2017 [2] To produce such an amount of plywood, approximately 15 mln tons of resin are used. Synthetic thermosetting resins based on phenol, urea, formaldehyde, and isocyanates are usually used
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