Effect of Panel Moisture Content on Internal Bond Strength and Thickness Swelling of Medium Density Fiberboard

Wood-based products usually have serious limitations concerning contact with water, both because wood is a hygroscopic material and because the commonly used binder has low moisture resistance. This paper studies the effect of panel moisture content (MC) on the physico-mechanical properties of medium density fiberboards (MDF). Several commercial MDF boards produced in Europe were stored at room temperature and relative humidity (RH) for 9 weeks (approx. range 15-20 degrees C and 50-85% RH). Every week, a strip of each MDF board was cut out, divided into 5 x 5 cm test pieces and its internal bond strength (IB) was measured. A strong influence of MDF moisture content on internal bond strength was observed and therefore IB test pieces were stored in a climatic chamber (either at 20 degrees C, 55% RH and at 20 degrees C, 70% RH). A decreasing linear relation was established between IB and MC. It was found that this effect is reversible: after drying, internal bond strength rises again (following a slight hysteresis). This work reinforces the importance of conditioned storage before board properties analysis, as described in European Standard EN 319.

Automated summary

This paper investigates the effect of panel moisture content on the physico-mechanical properties of MDF boards. It was observed that moisture content has a strong influence on internal bond strength, with a linear relationship between IB and MC. The study also found that this effect is reversible, with internal bond strength increasing again after drying.