Technological properties of Paulownia and mixed poplar-Paulownia plywood

Abstract

Interest in paulownia cultivation is growing across Europe, highlighting the need to explore the properties of this material and its suitability for the different manufacturing processes. The study investigates the suitability of paulownia wood as raw material for plywood production, both as pure paulownia plywood and in combination with poplar, and compares the results with those of pure poplar plywood. For this research, paulownia trees were harvested from a six-year-old plantation in Northern Italy. The logs were peeled to produce veneers, which were then used to manufacture plywood panels. Veneers were classified based on surface appearance according to the European standard EN 365:1995, with the 46% rated as Excellent and the remaining 54% assigned to Class I. Plywood panels were produced using poplar, paulownia, and a mix of both species in a 5-ply configuration. These panels were evaluated for appearance, mechanical performance, and bonding quality. Bending tests were conducted in both longitudinal and transverse directions to determine the modulus of elasticity and strength; density was also measured. Bonding quality was assessed through shear tests after pretreatment, considering intended applications in both interior dry environments and exterior covered environments. Overall, paulownia plywood exhibited more surface defects, such as cracks, bubbles, and areas with adhesive exudation, compared to mixed poplar-paulownia panels. Its density was also lower than that of poplar and mixed panels. From the mechanical perspective, paulownia plywood showed lower strength and stiffness compared to poplar and mixed panels, with the mixed panels performing similarly to or slightly below poplar. While paulownia wood can be used for plywood production, it is most effective when used as internal layers in mixed panels with poplar.