PEER-REVIEWED BRIEF COMMUNICATION bioresources.com Silva et al. (2019). “Physical properties of MDF,” BioResources 14(1), 1618-1625. 1618 Physical Properties of Medium Density Fiberboard Produced with the Addition of ZnO Nanoparticles Ana Paula Santos da Silva, a, * Bruno Santos Ferreira, b Higor Rogério Favarim, b Maria Fernanda Felippe Silva, b João Vítor Felippe Silva, a Maximiliano dos Anjos Azambuja, c and Cristiane Inácio de Campos b The use of wood-base panels in humid environments, in general, presents low durability due to contact with water. In order to increase durability and reduce the attack of fungi, studies had been developed using resin with zinc oxide (ZnO) nanoparticles. This work aimed to produce medium density fiberboard with urea-formaldehyde resin and melamine- formaldehyde adding 0.5% and 1.0% of ZnO nanoparticles for the physical properties evaluation. All treatments were classified as medium density according to ABNT NBR 15.316-2 (2015) with values ranging between 550 and 800 kg*m - ³. No differences were found between the two commercial adhesives used. The addition of 1.0% of nanoparticles resulted in lower density panels, higher moisture contents, and, after immersion in water for 24 hours, higher values of swelling in thickness. These results are explained by the lower compaction of the boards due to rapid cure of the adhesive using higher percentages of ZnO nanoparticles. The best treatment of the panels was with melamine-formaldehyde resin and 0.5% of nanoparticles. Keywords: Fiberboard; Physical characteristics; Nanotechnology Contact information: a: Department of Mechanical Engineering, São Paulo State University (UNESP), Avenida Ariberto Pereira da Cunha, 333, Guaratinguetá/SP, Brazil; b: São Paulo State University (UNESP), Campus of Itapeva, Rua Geraldo Alckmin, 519, Itapeva/SP, Brazil; c: Department of Civil Engineering, São Paulo State University (UNESP), Avenida Engenheiro Edmundo Carrijo Coube, 14-01, Bauru/SP, Brazil; * Corresponding author: Ana Paula Santos da Silva (ana.paula1@outlook.com) INTRODUCTION Wood panels have a great number of applications in the civil construction and the furniture industry, especially particulate and fiber panels. The production of medium density fiberboard (MDF) panels is carried out by a continuous hot-pressing process with the addition of adhesives. The adhesives employed by the industry are urea-formaldehyde and melamine-formaldehyde. Dimensional changes may occur, decreasing the mechanical strength of MDF panels when exposed to more aggressive conditions. To lessen the possible negative effects on the panels, other materials can be added during the manufacturing process in addition to the products already used. New studies have the objective of improving properties of the panels in terms of physical and mechanical performance and durability of the product. In this context, nanoparticles are an example of materials that show good results, such as a decrease of swelling and lower mass gain when in contact with water. Research on the synthesis of nanomaterials is mainly focused on controlling their shapes, sizes, and compositions. Each of these factors is key in determining the properties of the materials and lead to different technological applications (Ghorbani et al. 2017).