Measurement of Cell Wall Moisture in Acetylated Radiata Pine Using Low-Field Nuclear Magnetic Resonance
H G Beck, C A S Hill
Understanding the interaction of water with acetylated wood is necessary to explain how the protective mechanism of acetylation functions. Low-field nuclear magnetic resonance is one technique for assessing water in wood. Pinus radiata earlywood sapwood samples were acetylated to various weight percentage gains and then analysed with this method. Increased levels of acetylation showed significantly increased T2 relaxation times for free water, indicating that the free water is less restricted. This can be explained by the increase in hydrophobicity of the acetylated cell wall. The fiber saturation point (FSP) was determined using the signal from the cell wall water. The FSP of unmodified samples was 43 ± 2% moisture content and increased levels of acetylation significantly decreased FSP. At high weight percentage gain (~22%) the FSP was 16%, below the 20% threshold for fungal degradation to occur.
Keywords: NMR relaxometry, acetylation, weight percentage gain, fiber saturation point