Glyoxal-based condensation resins like 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) have been used to modify wood and improve its resistance against decaying fungi. High biological durability of DMDHEU-treated wood has already been confirmed in laboratory and field tests in the past. However, the modes of protective action behind an improved decay resistance are not fully understood yet. Furthermore, it is questionable how the use of formaldehyde-poor N-methylol and formaldehyde-free N-methyl compounds instead of DMDHEU affects the moisture behavior and durability, respectively. In this study, wood blocks were treated with N-methylol (DMDHEU, methylated DMDHEU) and N-methyl compounds (1,3-dimethyl-4,5-dihydroxyethyleneurea; DMeDHEU). Untreated and modified specimens were exposed to different moisture regimes and wood-destroying fungi in order to study the indicators that control changes in the wetting ability and decay resistance. Both N-methylol and N-methyl compounds decreased the water uptake and release and increased the durability of Scots pine sapwood from ‘not durable’ (DC 5) to ‘very durable to durable’ (DC 1–2). However, high fluctuations were observed in water uptake and release as well as mass loss (ML) caused by fungal decay, when modified specimens were tested without passing through a cold-water leaching. Consequently, a significant effect of the leaching procedure according to EN 84 on the durability classification could be established. The latter appeared more pronounced for treatments with N-methyl compounds compared to N-methylol compounds. Finally, wetting ability (k_wa) and resistance indicating factors (k_inh) enabled a forecast of high biological durability for both treatments with N-methylol and N-methyl compounds under real service life conditions.

乙二醛基缩合树脂如 1,3-二羟甲基-4,5-二羟基亚乙基脲 (DMDHEU) 已被用于改性木材并提高其对腐烂真菌的抵抗力。DMDHEU 处理过的木材的高生物耐久性已经在过去的实验室和现场测试中得到证实。然而，尚未完全了解改善抗腐性背后的保护作用模式。此外，使用不含甲醛的 N-羟甲基和不含甲醛的 N-甲基化合物代替 DMDHEU 如何分别影响潮湿行为和耐久性是值得怀疑的。在这项研究中，木块用 N-羟甲基（DMDHEU，甲基化 DMDHEU）和 N-甲基化合物（1,3-二甲基-4,5-二羟基亚乙基脲；DMeDHEU）处理。为了研究控制润湿能力和抗腐性变化的指标，未经处理和改性的样品暴露于不同的水分状况和破坏木材的真菌中。N-羟甲基和 N-甲基化合物都减少了吸水和放水，并将苏格兰松边材的耐久性从“不耐用”（DC 5）提高到“非常耐用到耐用”（DC 1-2）。然而，当对改性样品进行测试而不通过冷水浸出时，观察到水吸收和释放以及由真菌腐烂引起的质量损失 (ML) 的高波动。因此，可以确定根据 EN 84 的浸出程序对耐久性分类的显着影响。与 N-羟甲基化合物相比，后者在用 N-甲基化合物处理时显得更明显。最后，k _wa ) 和阻力指示因子 ( k _inh ) 能够预测在实际使用寿命条件下使用 N-羟甲基和 N-甲基化合物的两种处理的高生物耐久性。