胶合木层板间界面起传递应力的作用, 是构件承载的重要参数, 其高温胶合性能决定了构件的抗火性能。 以兴安落叶松结构材, 以及结构用间苯二酚-酚醛树脂胶粘剂(PRF)和三聚氰胺-脲醛树脂胶粘剂(MUF)为研究对象, 研究了20～280 ℃中木材含水率、 密度、 顺纹弦向抗剪强度和木材-胶粘剂界面胶合性能等216个试件在高温中的物理力学性能变化规律, 通过傅里叶变换红外光谱分析高温中胶粘剂官能团变化, 揭示了高温对木材-胶粘剂界面性能的劣化机理。 结果表明, 20～150 ℃时, 兴安落叶松主要发生由水分释放导致的木材密度降低等物理反应, 木材颜色未发生明显变化; 150～200 ℃时, 木材热降解开始, 密度下降速度变缓, 木材颜色逐渐加深; 温度继续升高时, 木材热降解加剧, 颜色急剧加深, 木材密度损失快速增加; 当温度升至280 ℃时, 木材发生炭化、 完全转化为黑色, 密度降至常温的72.49%。 高温对兴安落叶松顺纹弦向抗剪强度有明显的劣化作用; 20 ℃时木材抗剪强度为9.654 MPa, 20～110 ℃时木材抗剪强度下降较快, 150 ℃时降至常温的60.68%; 150～280 ℃时, 木材顺纹抗剪强度急剧下降, 280 ℃时降至1.054 MPa。 木材-胶粘剂界面的高温性能与胶粘剂的耐热性能密切相关; 常温时, 兴安落叶松与PRF和MUF均有较好的胶合性能, 其界面抗剪强度分别为9.071和9.619 MPa, 木破率均在80%以上; 随着温度的升高, 两种胶粘剂的界面抗剪强度均明显降低, 木材-PRF界面较木材-MUF具有更好的耐高温性能。 20～150 ℃时, 两种胶粘剂界面抗剪强度劣化规律与木材抗剪强度相似, 150 ℃时木材-PRF和木材-MUF的界面抗剪强度分别为常温的60.61%和60.92%, 木破率均高于70%。 150～280 ℃时, 木材-PRF界面抗剪强度劣化规律仍与木材顺纹抗剪强度相似, 280 ℃时降至0.774 MPa; 木材-MUF界面胶合性能受温度影响更大, 220 ℃时其木破率为10%, 280 ℃时界面抗剪强度降至0 MPa。 傅里叶变换红外光谱图中, 20～150 ℃时PRF化学结构无明显变化; 温度高于150 ℃时主要发生胶粘剂的进一步交联, 以及醚键和亚甲基桥的断裂, PRF开始热解, 但化学结构仍较完整; 20～150 ℃时MUF的化学结构无明显变化, 温度高于200 ℃时, 羟甲基特征峰减弱、 异氰酸酯基团产生, 热降解剧烈, PRF较MUF具有更高的耐热性能。 研究结果将为木结构工程合理选择原材料提供数据支撑, 并为完善木结构抗火设计理论和方法提供依据。

The wood-adhesive joints played an important role in transferring stress, which was an important parameter for bearing capacity of wood members. So, the bonding performance in high temperature determined the fire resistance of wood members. Larch wood, structural resorcinol-phenol-formaldehyde (PRF) and melamine-urea-formaldehyde adhesive (MUF) were selected as objects, and wood moisture content, density, parallel-to-grain tangential shear strength of solid wood, and bonding properties of joints with different adhesives of a total of 216 specimens exposed to elevated temperature ranging from 20 to 280 ℃ were tested. Fourier transform infrared spectroscopy (FTIR) was used to reveal the influences of high temperature on wood-adhesive joints. The results showed that physical reactions occurred to larch wood, and wood color change was not obvious, because there was only density reduction caused by water release at a temperatures ranging from 20 to 150 ℃. When the temperature increased until 200 ℃, thermal degradation of larch wood started, the density decreased slowly and the color gradually deepened. When temperature continued to increase, the wood specimens sharply darkened, and thermal degradation was intensified. So the density loss increased. At 280 ℃, larch wood was charred, and its color was completely converted to black. The density was 72.49% of that at room temperature. The relationship between parallel-to-grain tangential shear strength of larch wood and high temperature was negatively correlated. The shear strength of larch wood was 9.654 MPa at 20 ℃. The shear strength decreased with the increase of high temperature ramped from 20 to 110 ℃. At 150 ℃, wood shear strength decreased to 60.68% of that at room temperature. The shear strength of larch wood decreased obviously when exposed to elevated temperature ranging from 150 to 280 ℃. At 280 ℃, wood shear strength decreased to 1.054 MPa. The bonding properties of joints exposed to high temperature attributed to the thermal stability of adhesives. At room temperature, larch wood has good bonding properties with PRF and MUF. The shear strengths of joints of larch wood with PRF and MUF were 9.071 and 9.619 MPa, respectively, and the wood failure percentage was above 80% at room temperature. With the increase of high temperature, the shear strength of wood-adhesive joints decreased obviously, and the joints with PRF exhibited better than MUF when exposed to a higher temperature. The shear strengths of joints with PRF and MUF both decreased at 20～150 ℃, and was similar to that of larch wood. At 150 ℃, shear strength of joints with PRF and MUF were 60.61% and 60.92% of that at room temperature, respectively, and the wood failure percentage was more than 70%. The shear strength of wood-PRF joints decreased rapidly at the temperatures ranging from 150 to 280 ℃, which was similar to that of larch wood, and was 0.774 MPa at 280 ℃. The bonding properties of wood-MUF joints were more affected by high temperature. Wood failure percentages of joints with MUF were 10% at 220 ℃, and the shear strength was 0 MPa at 280 ℃. FTIR analysis showed that there was no obvious change in the chemical structure of PRF at 20～150 ℃. The further chemical crosslinking and the breaking of ether bond and methylene bridge occurred to PRF as the temperature was higher than 150 ℃. A slight pyrolysis occurred to PRF, but the chemical structure still remained entire. There was no obvious change in chemical structure of MUF exposed to high temperature ranging from 20 to 150 ℃ as same as that of PRF. When the temperature was higher than 200 ℃, the characteristic peak of hydroxymethylwas weakened, the isocyanate group appeared, and the thermal degradation grew severe. So, PRF had a higher heatresistance than MUF. The study can provide data support for the selection of raw materials, and provide a basis for improving the theory and method of fire resistance design for timber structure.