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

Medium density fiberboard (MDF) is one of the most rapidly growing composit e 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. Th e homogeneous core of MDF makes it especially suitable for embossing, mould ing, and general machining. A uniform density throughout the panel thicknes s results in better fastening properties. A step-closure schedule to change the density profile of lab-made MDF panels is presented. MDF mats were pre ssed using eight different step-closure schedules. Our in-press density mon itoring system was used during pressing to provide additional information a bout the formation of the density profile. The effects of step-closure on t he density profile formation are discussed. The step-closure schedules sign ificantly changed the traditional shape of the vertical density profile of the laboratory, made MDF panels. The step-schedules resulted in multiple de nsification peaks rather than the traditional two peaks associated with con ventional 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.