Mild pyrolysis of fast-growing wood species (Caribbean pine and Rose gum): Dimensional changes predicted by the global mass loss

Dimensional changes of Caribbean pine and Rose gum (eucalyptus) were continuously measured during mild pyrolysis (heat treatment) with a dynamic mechanical analyzer (DMA) in creep mode with a negligible force. Mass loss was measured on matched samples by thermo-gravimetric analysis (TGA). All experiments were carried out at 220 °C (air and nitrogen), 250 and 280 °C (nitrogen) with a residence time up to 10 h. Eucalyptus exhibits a greater shrinkage and mass loss than pine. By normalizing the shrinkage (heat treatment shrinkage divided by total hygroscopic shrinkage), one single master curve is obtained per species, whatever the heat treatment conditions (temperature, nature of gas) and material direction. For each species, a unique expression is proposed to predict the dimensional changes due to mild pyrolysis as a function of mass loss and total hygroscopic shrinkage. The ability to predict heat treatment shrinkage is useful from industrial perspective (density prediction, change in bed thickness, modeling tools).