Effects of mat moisture content and press closing speed on the formation of density profile and properties of particleboard

Isocyanate resin-bonded 0.5 and 0.7 g/cm(3) lauan (Shorea sp.) particleboar ds were produced from mats with uniform and distributed moisture content (M C) distributions, using three hot press closing speeds. The effects of thes e processing variables on the formation of density profile in particleboard and board properties were analyzed statistically. A definition of the dens ity profile was introduced, and the correlations among the various defining factors were established. The results are summarized as follows. (1) The p eak density (PD) of particleboard could be increased, with a slight reducti on in the core density (CD), using mats with different MC distributions. (2 ) In a conventional density profile, CD and PD are highly dependent on the board mean density (MD); and the gradient factor (GF), peak distance from t he faces (Pdi), and peak base (Pb) are significantly correlated to each oth er, at the 99% significance level. (3) Greater press closing speed reduces Pdi and Pb, with an increase in GF. (4) Greater press closing speed could i ncrease the PD in board of low MD, with minimal effect on CD. (5) The modul us of elasticity (MOE) of particleboards from mats with high MC near the fa ces were consistently higher than those from mats with uniform MC, irrespec tive of the press closing speed, whereas their modulus of rupture (MOR) bec ame indifferent at higher MD under slow and fast closing speeds. (6) Sandin g does not improve the MOR and MOE of particleboard significantly.