Properties of low-formaldehyde-emission particleboard made from recycled wood-waste chips sprayed with PMDI/PF resin

The objective of this study was to manufacture low-formaldehyde-emission particleboard from recycled wood-waste chips using polymeric 4,4'-methylenediphenyl isocyanate (PMDI) and phenol-formaldehyde (PF) resins for use in indoor environments. The influence of PMDI/PF ratios in particles on the formaldehyde emission and its mechanical properties were investigated. The experimental results showed that the formaldehyde emission released decreased linearly with increasing PMDI/PF particle ratio. The relationship could be represented by a linear regression formula. Formaldehyde emission was below 0.3mg/L when the weight percentage of PMDI/particles was up to 70%. The formaldehyde emission from melamine-formaldehyde (MF) resin-impregnated paper-overlaid particleboard was 17% lower than that for particleboard. Moreover, the bending strength, internal bonding strength and screw holding strength increased with increasing PMDI/PF particle ratio. However, the percentage thickness swelling of the particleboard decreased with increasing PMDI/PF particle ratio. In addition, there were significant positive relationships between the ultrasonic velocity and the bending strength, internal bonding strength and screw holding strength of the particleboard, which allowed evaluation of the properties of the particleboard using ultrasonic velocity. (c) 2006 Elsevier Ltd. All rights reserved.