Low resin medium density fiberboard made from chemical activated hardwoods fibers

Abstract

This study was conducted to determine properties of medium density fiberboards (MDF) made from treated hardwoods fiber furnishes containing different amounts of two oxidizers, and the addition of limited amounts of synthetic resin. The effects of urea-formaldehyde (UF) resin content (two levels as 5 and 7%), oxidizer type (nitric acid and potassium dichromate), and oxidizer percent (three different levels as 4, 6, and 8%) on some static mechanical and physical properties of dry process interior grade MDF such as modulus of rupture (MOR), and modulus of elasticity (MOE) in bending in dry condition, compression-shear strength (CS sth ), water absorption (WA) and thickness swelling (TS) after 2-and 24-h soaking in cold water were investigated. Thirty six oxidative activated laboratory MDF panels were tested. Test results showed that increasing resin content significantly improved all physical and mechanical properties of treated MDF boards. Nitric acid had better mechanical and physical properties than potassium dichromate. Increasing oxidizer percent improved the physical and mechanical properties of MDF boards. Finally, three-way interaction of variables showed the best values for MOR, MOE and CS sth and WA and TS after 2-and 24-h soaking were discerned for T 6 treatment, i.e. the combination of 7% UF resin content together with 8% nitric acid. The properties for T 6 met the mechanical strength requirements of ANSI standard (ANSI A208. 2-2002) for 120-grade MDF.

Optimization of the Hot-Pressing Regime in the Production of Eco-Friendly Fibreboards Bonded with Hydrolysis Lignin

“…Although the most common residual product is Kraft lignin, obtained by the Kraft process [61], hydrolysis lignin, derived by enzymatic hydrolysis process, contains a certain amount of cellulose. Cellulose in hydrolysis lignin increases the contact areas between lignin and wood fibres, which leads to the formation of additional hydrogen and other bonds [62][63][64][65]. The aim of the present study was to fabricate eco-friendly dry-process fibreboards using hydrolysis lignin as a main binder by modifying the adhesive system and optimising the hot-pressing regime, without any modifications of the lignin.…”