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/cm3 lauan (Shorea sp.) particleboards were produced from mats with uniform and distributed moisture content (MC) distributions, using three hot press closing speeds. The effects of these processing variables on the formation of density profile in particleboard and board properties were analyzed statistically. A definition of the density profile was introduced, and the correlations among the various defining factors were established. The results are summarized as follows. (1) The peak density (PD) of particleboard could be increased, with a slight reduction 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 the faces (Pdi), and peak base (Pb) are significantly correlated to each other, 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 increase the PD in board of low MD, with minimal effect on CD. (5) The modulus of elasticity (MOE) of particleboards from mats with high MC near the faces were consistently higher than those from mats with uniform MC, irrespective of the press closing speed, whereas their modulus of rupture (MOR) became indifferent at higher MD under slow and fast closing speeds. (6) Sanding does not improve the MOR and MOE of particleboard significantly.

[1]  T. Laufenberg.  Using gamma radiation to measure density gradients in reconstituted wood products , 1986 .

[2]  M. D. Strickler.  Effect of press cycles and moisture content on properties of Douglas-fir flakeboard. , 1959 .

[3]  A. J. Bolton,et al.  The Hot Pressing of Dry-formed Wood-based Composites. Part IV. Predicted Variation of Mattress Moisture Content with Time , 1989 .

[4]  Qian Wang,et al.  Formation of the density profile and its effects on the properties of fiberboard , 2000, Journal of Wood Science.

[5]  A. J. Bolton,et al.  The Hot Pressing of Dry-formed Wood-based Composites. Part III. Predicted Vapour Pressure and Temperature Variation with Time, Compared with Experimental Data for Laboratory Boards , 1989 .

[6]  Alfred J. Stamm,et al.  Principles of Wood Science and Technology , 2013, Springer Berlin Heidelberg.

[7]  S Kawai,et al.  Production technology for low density particleboard. IV , 1987 .

[8]  M. W. Kelly,et al.  Critical Literature Review of Relationships Between Processing Parameters and Physical Properties of Particleboard. , 1977 .

[9]  E. Wong,et al.  Formation of the density profile and its effects on the properties of particleboard , 1999, Wood Science and Technology.

[10]  P. E. Humphrey.  Pressing issues in panel manufacture: internal behavior during pressing and its impact on time minimization, properties, and profit , 1991 .

[11]  A. J. Bolton,et al.  The Hot Pressing of Dry-formed Wood-based Composites - Part V. The Effect of Board Size: Comparability of Laboratory and Industrial Pressing , 1989 .

[12]  P. E. Humphrey.  The Hot Pressing of Dry-formed Wood-based Composites. Part II. A Simulation Model for Heat and Moisture Transfer, and Typical Results , 1989 .