Abstract
Particles of flooded gum (Eucalyptus grandis) were bonded using three bio-based adhesives - anhydrous citric acid (CA), tannin-citric acid (TCA) and ricinoleic acid (RA) - from renewable sources and hot pressed to produce medium density particleboard (MDP). The bonding capacity of such adhesives and properties of the MDP were evaluated and compared to the requirements of seven grades of particleboards, according to the EN 312 (2010) standard. The RA did not create adhesion reaction with the wood particles. Adhesives formulated with CA and TCA presented capacity to bond eucalyptus particles into MDP confirmed by esterification reactions of the FTIRS analysis. MDP bonded with CA met requirements as high as grade P5 of the EN 312 (2010) standard for static modulus of elasticity (MOE) and internal bond (IB) and P2 for modulus of rupture (MOR). Panels bonded with TCA met requirements up to grade P3 for MOE, however, did not withstand water absorption.
Highlights
According to Randriamanantena et al (2009), this range corresponds to the zone of thermal stability, which is limited by the initial thermal degradation temperature of the main components of wood
This indicates that the ideal temperature for pressing eucalyptus particleboards should be in between this range
When compared to citric acid (CA) particleboards, ricinoleic acid (RA) bonded panels presented a lower peak in the band 1737 cm-1. These results indicate a little or no esterification reaction that is related to the lack of adhesiveness in RA particleboards
Summary
Medium Density Fiberboard (MDF), Hardboard or fiberboard (HB) and High Density Fiberboard (HDF) are reconstituted wood-based panels composed of wood fibers, while Medium Density Particleboard (MDP) is produced with wood particles and adhesive, pressed under high pressure and temperature. MDF and HDF are produced with the addition of a synthetic adhesive using a dry process and their density ranges from 600 to 900 kg/m3, and HB results from hot pressing that uses a wet process without the addition of adhesives that reactivates the natural binders of wood, such as lignin. The Brazilian production of reconstituted woodbased panels in 2018 was 8.2 million m3, 40 % MDP and 60 % MDF/HDF. The production of MDF/HDF and HB dropped 2.5 % and 0.4 %, respectively; MDP increased 3.4 % (IBÁ, 2019)
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