HUMIDITY CONTROL EFFICIENCY OF LOW-DENSITY PARTICLEBOARDS FOR INTERIOR WALLS .2. MEASUREMENT OF EMC AND CALCULATION OF MOISTURE CAPACITIES

For particleboards made with phenol-formaldehyde (PF) and isocyanate ( IC) resins in addition to low-density particleboard (LDPB) and wood-li ning board (WLB) used in the previous paper, equilibrium moisture cont ent (EMC) curves at 15, 20, and 25-degrees-C were obtained as fundamen tal data to discuss the differences in hygroscopicity and moisture cap acities among them. EMC curves at 20-degrees-C were also obtained for the raw material particles and binders, which were used to investigate the decline in hygroscopicity of particles by hot-pressing. The EMCs of PF-bonded boards were approximately 1% higher than those of IC-bond ed boards because of the noticeable difference in EMCs between the bin ders. It was found that hygroscopicity of the particles was decreased approximately one-tenth by hot-pressing. For this reason in addition t o the presence of binders, the EMCs of PF- and IC-bonded boards were a bout nine-tenths and eigth-tenths those of the law material particles, respectively. Moisture capacities of LDPB were almost equal to those of WLB because of the difference in densities of the two products. Moi sture capacities of PF- and IC-bonded boards were estimated to be appr oximately four-fifths of those of solid wood with the same density. Hu midity dependence of moisture capacities was observed. Values of kappa , one of the moisture capacities defined in Equation (1), changed on a quadratic curve with its minimum at about 50% relative humidity, wher eas values of nu, the other one, changed almost linearly with relative humidity.