Variação das propriedades tecnológicas de painéis MDF em uma linha de produção industrial no Brasil

Abstract

In the present study the technological properties of medium density fibreboard (MDF) were characterised, at different production times in a Brazilian industrial line, with the aim of assessing the technological variability of the boards and their quality in relation to the commercial technical standard. MDF panels made with fibers from Eucalyptus spp. (70%), Schizolobium parahyba (20%) and sawmill waste wood (10%), bonded with urea-formaldehyde resin were collected at two-hour intervals from one of the company's production shifts. Physical properties (moisture, bulk density, surface absorption, water absorption, thickness swelling and thickness non-return rate) and mechanical strength (static bending, janka hardness, perpendicular traction and screw pull-out) were determined. The panels from the beginning and end of the shift were submitted to the accelerated ageing cycle, and then evaluated for density, tensile and static bending. Of the total properties assessed in the MDF panels, a percentage of 55% showed no variations between the production times, and conformed to the values of the standard. Only the properties of swelling in thickness (IE 24h) and traction in 80% of the times, did not meet the values stipulated by ABNT NBR 15316-1, ranging from 11.2 to 15.6% and 0.42 to 0.62 N/mm², respectively, between the beginning and end of the shift. Accelerated ageing caused a significant decrease in the quality of the sheets. The MDF panels studied present good technological performance for use in dry environments, and their technological variation was due to the use of fibres from different woods in the production of the boards.