Manufacture of MDF panels with a blend fibers of Saccharum sp (cane sugar) associated with fibers of Eucalyptus grandis: anatomical characterization and physico-mechanical properties

Technological characterization of panelboards from eucalyptus wood fibers, Eucalyptus grandis, and stalk particles of sugarcane bagasse, Saccharum sp 

The increased consumption of wood and its products, such as wood panels, stimulates the development of technology for products that use inputs characterized as waste. In this respect, Brazil has competitive advantages regarding the large area of high-yield eucalyptus crops; Brazil is the world’s major sugarcane producer and has an industrial sector with advanced technology for fiberboards and particleboards production. Therefore, this study aimed to develop the manufacture and technological characterization of wood fibers from eucalyptus, Eucalyptus grandis, and stalk particles of sugarcane bagasse, Saccharum sp. Laboratory analyses included, initially, the macroscopic characterization of raw materials and their mixtures as well as sorting granules of crushed sugarcane bagasse. Then, two steps were established for the panel-making process, called phase A (0-100% of sugarcane bagasse, with variations of 25%, 14% UF resin) and phase B (0 - 25% of sugarcane bagasse, with variations of 5%, 13 and 16% UF resin). The technological characterization of the panels comprised the morphology analysis (SEM microscopy, X-ray microtomography / microCT), X-ray densitometry, physical properties (density, swelling in thickness, absorption and moisture content), mechanical (MOR, MOE, internal bond, surface resistance and axial withdrawal of screw); optical analysis by deflectometry, chemical (NIR spectroscopy, free formaldehyde content of sand content) and natural durability (bioassays of fungi and termites). The results indicated morphological differences of anatomical structure of raw materials and particle size of sugarcane bagasse. The morphological evaluation of the panels showed, through the microCT, the homogeneity of the fibrous matrix, whose anatomical composition was different through SEM. In the characterization of physical-mechanical properties, the density profiles of the panels, typical of fiberboards, indicated the influence of raw materials and their mixture. Still, there was a reduction of mechanical properties, notably MOR, MOE and internal bond to the panels made with more than 50% of sugarcane bagasse particles; regarding the resin, 16% resulted in better technological performance compared to 13%. The MOE values of the panels were similar to those obtained by applying the deflectometry technique. The percentage of sugarcane bagasse particles in the panels resulted in reduction of the level of free formaldehyde and increase of the sand content. The use of the NIR methodology allowed the differentiation of eucalyptus wood fibers and particles of sugarcane and their percentage applied. In bioassays, the panels (step B) showed no significant differences in resistance to fungi and termites. The results indicate that the panels of eucalyptus fibers and particles of sugarcane bagasse, as an alternative raw material and at percentages between 5-25% showed technological properties that meet the standards, indicating the potential use of this biomass for products with higher value added.