Reducing set-recovery of compressively densified poplar wood by impregnation–modification with melamine–formaldehyde resin

Densification of resin impregnated wood under hot-pressing is a method that along with the potential for the reduction of set-recovery could additionally increase the density of wood and further improve other technical properties. In this study, the effect of the methylated melamine-formaldehyde modification on the shape memory effect of densified Populous nigra wood at various compression ratio levels was investigated. Furthermore, the effects on moisture content and compression ratio were also assessed. The most important conclusion drawn was that MF can act as a means for reducing set-recovery of compressed poplar wood since it is obvious that the use of MF significantly improved the stability of densified wood due to the formation of new bonds between cell wall components and MF. In the case of densification under stress of 10 kg/cm2, the stabilization was improved by the use of MF to about 50% compared to water-treated specimens. The effect of MF on the stabilization of densified wood was not very clear for stresses higher than 10 kg/cm2 since due to the outflow of MF solution during the first minutes of compression.