There is a complex link between the water sorption behavior and the presence of accessible hydroxyl groups in the wood cell wall, which can be altered by heat-treatment (HT). This study analyses the effect of changes in the cell wall ultrastructure caused by two HT techniques on the hydroxyl accessibility, water vapor sorption and dimensional changes of Scots pine (Pinus sylvestris L.) sapwood. HT of wood in pressurized hot water at 120–170 °C was applied to cause the preferential bond cleavage, whereas HT of wood in oven-dry state in superheated steam at 180–240 °C was performed to create additional covalent cross-links within the cell wall matrix. Removal of cell wall polymers by HT and water leaching reduced the oven-dry dimensions of wood and enhanced the cellulose aggregation during drying. Cellulose aggregation restricted the cell wall shrinkage in circumferential direction, resulting in inhomogeneous shrinkage of the cell wall with only little changes in lumen volume by HT. Cellulose aggregation also reduced the water-saturated dimensions, but a decrease in swelling was only achieved when additional cross-links were formed by HT in dry state. Additional cross-links in the cell wall matrix also resulted in an additional reduction in water sorption at 25 °C and 93% RH. However, this was not caused by a further reduction in the hydroxyl accessibility. Instead, cross-linking was shown to reduce the amount of accessible OH groups that are simultaneously active in sorption, which was explained based on the concept of sorption of water dimers at hydroxyl group pairs at high RH levels.

木材细胞壁的吸水行为与可及羟基的存在之间存在复杂的联系，这可以通过热处理（HT）进行改变。这项研究分析了两种HT技术引起的细胞壁超微结构变化对樟子松（Pinus sylvestris）的羟基可及性，水蒸气吸附和尺寸变化的影响L.）边材。在120-170°C的加压热水中使用木材的HT来引起优先的键裂解，而在180-240°C的过热蒸汽中的烘箱干燥状态下的木材HT可以在其中产生附加的共价交联。细胞壁矩阵。通过HT和水浸提去除细胞壁聚合物可减少木材在烘箱中的干燥尺寸，并增强干燥过程中的纤维素聚集。纤维素的聚集限制了细胞壁在圆周方向上的收缩，从而导致细胞壁的不均匀收缩，而HT的管腔体积只有很小的变化。纤维素的聚集也减小了水饱和的尺寸，但是溶胀的减少仅在干燥状态下由HT形成额外的交联时才实现。在细胞壁基质中的其他交联还导致在25°C和93％RH时水吸附的进一步降低。但是，这不是由于羟基可及性的进一步降低引起的。取而代之的是，显示出交联可减少同时具有吸附活性的可及的OH基团的数量，这是基于在高RH水平下羟基对上的水二聚体的吸附概念来解释的。