Bending Creep Behavior of Medium Density Fiberboard and Particleboard During Cyclic Moisture Changes

Yaguang Zhou, Masami Fushitani, D. Pascal Kamdem

Abstract


Bending creep behavior of four types of medium density fiberboard (MDF) and two types of particleboard during cyclic moisture changes was investigated in this study. Tests were made at 20°C with three cyclic relative humidity changes between 65% and 95% under the 10% short-term breaking stress. The effect of moisture content (MC) change on initial compliance and mechano-sorptive (MS) compliance was examined. The results indicated that relative deflection and total compliance of the samples increased over the history of cyclic moisture changes, and their magnitudes varied with board types. Melamine- and phenol-resin bonded boards had smaller relative deflection and total compliance than did urea-resin bonded boards. Both relative deflection and total compliance increased in adsorption and showed reduction in desorption. Initial compliance followed a linear relation with MC and had some influence on total compliance behavior under moisture cycles. MS compliance increased in adsorption while showing slight reduction or increase in desorption. The first adsorption led to the largest MS compliance, followed by subsequent adsorption. With increasing MC change, MS compliance increased linearly in the first adsorption, while it increased nonlinearly in the subsequent adsorption. The MS compliance coefficient KM was product-dependent. Resin type appeared to be an important factor influencing the variations in KM. In this study, urea-resin bonded boards had a greater KM compared to melamine- and phenol-resin bonded boards.

Keywords


Mechano-sorptive effect;MDF;particleboard;cyclic moisture change;bending;resin type

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