Effects of moisture content on bending properties and creep behavior of phenolic-resin-treated particleboards

摘要

Low molecular-weight (Mn = 369) phenolic impregnating resin and high molecular-weight (Mn = 1 143) bonding phenolic resin were mixed and sprayed on Japanese cedar (Cryptomeria japonica) semi-strand (22.8 mm x 2.6mm x 0.6mm) particles,and then 10mm thick single-layer particleboards (PBs) (SG = 0.7) were produced. The effects of moisture content (MC) on bending properties and creep behavior of the PBs were investigated. The maximum value of modulus of rupture (MOR) was achieved at 7 to 9 percent MC,and at 19 to 28 percent MC the PBs retained 60 to 70 percent of the MOR value in the oven dry condition. The modulus of elasticity of PBs decreased with increasing MC. The creep compliance of PBs increased with increasing MC and decreased with increasingtotal resin content. The creep compliance after 48 hours under bending load at 7 to 9 percent MC was aboutl.8 times the value in the dry condition.