Multiple-Phase Pressure (MPP) Process: One-stage CCA treatment and accelerated fixation process. 4. MPP compared with other processes for achieving acceptable treatment of radiata pine heartwood
IRG/WP 98-40115
K Nasheri, J A Drysdale, G Durbin, M E Hedley
Although radiata pine sapwood is very amenable to preservative treatment, it is often difficult to achieve the required standard for heartwood treatment.
A preliminary investigation showed that to achieve the NZ Timber Preservation Council minimum penetration requirements for radiata pine heartwood using the Multiple-Phase Pressure (MPP) Process, a hydraulic pressure of at least 1250 kPa for 20 minutes was necessary.
Based on these observations, a further trial was undertaken to compare treatment quality of conventionally kiln-dried radiata pine using Bethell, Modified Bethell and MPP processes. All processes resulted in complete sapwood penetration but a marginally better penetration of heartwood using the MPP process than with Bethell- or Modified Bethell schedules. Both the MPP and Bethell processes had lower retention variability in mixed charges of sapwood and heartwood when compared with a Modified Bethell process.