The goal of this project, carried out at Forintek’s Quebec MDF Pilot Plant, was to develop an enhanced fibreboard product for exterior applications. The experimental work consisted of three different phases. Phase I consisted of selecting a suitable resin system from among five types of resin exposed to the same process conditions. Panels produced with the MUPF resin (resin R03) had the best overall moisture resistance and dimensional stability properties. Phase II defined optimal refining and hot pressing process conditions. Based on the experiment results and statistical analysis, a numerical optimization was carried out using Design Expert® computer software. Phase III examined the chemical modification of wood fibre by acetylation. The following conclusions can be reached from this research project:
Among the five different resin systems, resin R03 (an MUPF resin) produced the best overall panel properties for moisture resistance and dimensional stability and was most cost effective.
For resins R03 and R04 (MUF), post-press heat treatment showed marginal improvements in panel bonding strength, moisture resistance, and dimensional stability.
Panels made with MDI resin were comparable to R03 panels in terms of dry IB, but resulted in lower water resistance (lower one-hour boiling IB).
With resin R03, panel series S7 had the best overall panel properties among the 8 different types of panels made under the different process conditions.
Resin content of R03 in the panel had the greatest effect on IB, water resistance, and dimensional stability.
Higher steam temperature in the preheater improved panel moisture resistance and dimensional stability.
All properties tested in S7 produced results higher than those typical of wood plastic.
The cost to produce S7 is about 40% of the cost of wood plastic panels for similar applications.
Acetylated wood fibre demonstrated a great improvement in water resistance and dimensional stability. However, further research is required in order to find better adhesives and application methods to optimize MDF panel processes with acetylated fibre.
Wood fibre-based panel can replace wood plastic for exterior applications at a significant cost advantage.
Further work is required to optimize the process and to fully evaluate panel properties under long term outdoor conditions.