Step-closing pressing of medium density fiberboard; Part 1. Influences on the vertical density profile

Abstract

Medium density fiberboard (MDF) is one of the most rapidly growing composite board products available in the market. A key product attribute of MDF is the density profile through the panel thickness. A superior MDF panel for laminating, gluing and finishing should have an unbalanced density profile, in which the face density is considerably higher than the core density. The homogeneous core of MDF makes it especially suitable for embossing, moulding, and general machining. A uniform density throughout the panel thickness results in better fastening properties. A step-closure schedule to change the density profile of lab-made MDF panels is presented. MDF mats were pressed using eight different step-closure schedules. Our in-press density monitoring system was used during pressing to provide additional information about the formation of the density profile. The effects of step-closure on the density profile formation are discussed. The step-closure schedules significantly changed the traditional shape of the vertical density profile of the laboratory, made MDF panels. The step-schedules resulted in multiple densification peaks rather than the traditional two peaks associated with conventional pressing. The step-schedules resulted in increased core density, which was greater than the face density. Comparison is made to traditional MDF closing schedules and OSB step-closing schedules.