Resin and wax distribution and mobility during medium density fibreboard manufacture

Abstract

Fluorescently labelled UF resin and paraffin wax have been used at a medium density fibreboard (MDF) production facility to characterise resin and wax distribution and mobility on MDF fibre and panels. The major findings from these comprehensive mill-scale trials have been the mobility of UF resin on fibre throughout the MDF process, while wax mobility occurs only on panel pressing. Complex interactions exist between resin distribution and wood fibre wall penetration which collectively provide evidence for three-dimensional resin movement on fibre through the production process. Fibre exiting the blowline had relatively high rates of resin coverage with resin droplet sizes dominated by the process of resin smearing through fibre-fibre contacts. On passing through the dryer resin coverage of fibre reduces, before increasing again on panel pressing. Wax distribution on unpressed fibre was dependent on the mode of application with emulsion and slack wax addition at the refiner being relatively similar, but differing to emulsified wax added via the blowline. On pressing, wax distribution in panels was distinguished by wax type, and was independent of the addition points.