Abstract:Researches on the rheological behaviours of particleboard with defferent densities under compression perpendicular to its surface have further confirmed the feasibility of using the Rhoological Parameter Seperating Method. The influences of density on the rheological properties are mainly due to: instantaneous elastic deformation and parameter B in the compliance formula C=A+Blogt for the retarded elastic deformation decreasing with the increase of the density; instantaneous plastic deformation decreasing also as the density increases, and the "turning point" of the curve of plastic deformation vs. compressive stress which is of special importance in the thickness tolerance control of the overlaid particleboard moving along the increasing direction of stress with the density; the parameter B in the compliance formula C=A+Blogt for the time-dependent plastic deformation decreasing with the increase of the density, and the "three-stage development" of this deformation moving along the increasing direction of stress with density. These primary results are of great importance in determining the conditions for overlaying process and for the requirement for the particleboard, and in controling the thickness tolarance of the overlaid particleboard.