Although γ-methacryloxypropyltrimethoxysilane (MPS) was proved to be an effective reagent for improving the dimensional stability of wood, a bottleneck in ASE value (around 50%) existed. The reason was that MPS with low polarity opened few hydrogen bonds in the amorphous region of cellulose, while these hydrogen bonds could be reopened by water. Therefore, citric acid (CA) is chosen to cooperate with MPS to further enhance the dimensional stability of wood. In this paper, MPS and CA were used to modify wood individually (MW and CW) or with different combinations, that is, one-step modification (M/CW) and two-step modification with MPS first (M-CW) or CA first (C-MW). CA and MPS concentrations were optimized at 5 wt%. The ASE value for M/CW was only 25.74% at a weight percent gain (WPG) of 6.43%, which was only 0.6 times to MW or 0.7 times to CW. For M-CW, the ASE value gradually decreased with the soaking cycles, from 65.64% at a WPG of 9.05% to 51.20%. The C-MW had the best dimensional stability, with the ASE value 75.35% at a WPG of 11.50%. Although it decreased during the first soaking cycle, it stabilized at 62.20% at last. SEM and EDS images showed that the polymer mainly distributed in cell walls and few in cell lumen in C-MW. Thus, the enhanced dimensional stability of C-MW could be explained by CA opening the hydrogen bonds in the amorphous region of cellulose first, which provided more binding sites for MPS.

中文翻译：

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基于组合试剂的细胞壁改性高效提高木材尺寸稳定性


虽然γ-甲基丙烯酰氧基丙基三甲氧基硅烷（MPS）被证明是提高木材尺寸稳定性的有效试剂，但其ASE值（50%左右）存在瓶颈。原因是低极性的MPS在纤维素的无定形区域打开很少的氢键，而这些氢键可以被水重新打开。因此，选择柠檬酸（CA）与MPS配合，进一步增强木材的尺寸稳定性。本文分别使用MPS和CA对木材进行改性（MW和CW）或以不同的组合进行改性，即一步改性（M/CW）和先MPS（M-CW）或CA的两步改性首先（C-MW）。 CA 和 MPS 浓度优化为 5 wt%。在增重百分比 (WPG) 为 6.43% 时，M/CW 的 ASE 值仅为 25.74%，仅为 MW 的 0.6 倍或 CW 的 0.7 倍。对于M-CW，ASE值随着浸泡周期逐渐下降，从WPG为9.05%时的65.64%下降到51.20%。 C-MW具有最好的尺寸稳定性，在WPG为11.50%时ASE值为75.35%。虽然在第一个浸泡周期中有所下降，但最终稳定在62.20%。 SEM和EDS图像显示，C-MW中聚合物主要分布在细胞壁中，少量分布在细胞腔中。因此，C-MW 尺寸稳定性的增强可以通过 CA 首先打开纤维素无定形区域中的氢键来解释，这为 MPS 提供了更多的结合位点。