Physical and mechanical properties of thermally modified and densified MDF

Abstract

As the first step of the research project, elements made of medium density fiberboard (MDF) were subjected to thermal modification in a laboratory dryer (temperature: 160, 170, 180 and 190°C; time of primary modification: 0·5, 1·0 and 1·5 h) in an atmosphere of hot air or limited contact with air. Half of the total set of samples were covered with aluminum foil to cut them off from oxygen. After the modification, samples were soaked in water to determine swelling and find optimal parameters from the point of view of reduction of MDF swelling. The samples were thermally modified using the following parameters: temperature of 180°C, time of primary modification of 0·5 h and full contact of the modified MDF with hot air. Some of the modified samples, which were still hot at the end of the primary process of modification, were cold pressed to obtain higher density MDF. Tests on the mechanical and physical properties of this material were carried out to investigate the effects of combined thermal modification and densification on MDF properties. The modulus of rupture and modulus of elasticity in bending, thickness swelling, Brinell hardness and color changes were determined according to EN 310, EN 317, EN 1534 and EN 7224. Thermal properties of the thermally modified MDF and densified MDF were determined using a portable heat transfer analyser.