外力作用下聚氨酯胶粘剂在NaCl水溶液中的耐久性

Durability of polyurethane adhesive in NaCl solution under load

用聚氨酯胶粘剂和铝片制备胶接试样并在NaCl溶液中浸泡,考察了NaCl溶液的温度、NaCl的质量分数以及应力对胶粘剂粘结强度的影响。采用拉伸实验法测试胶接试样的拉伸剪切强度,分别用扫描电子显微镜图、红外光谱图分析浸泡前后胶层的表面形貌和胶粘剂分子结构的变化。结果表明,胶粘剂的粘结强度随载荷的增加而急剧下降,失效所需时间从1000N的150h快速降至2000N下的30h以下;在恒载荷时,失效所需时间从NaCl的质量分数为5%的60h上升至15%时的160h。温度的作用主要表现为在浸泡初期能加速聚氨酯胶粘剂的降解和粘结强度的下降,粘结强度从35℃的93.5%下降到70℃的65.0%左右;但是在浸泡中后期,则其作用变小,剪切强度维持在35℃时的64.0%、70℃时的63.0%和50℃时的44.0%。

Samples of polyurethane adhesive bonded to aluminum were prepared and soaked in NaCl solution. The effects of varying temperature, NaCl concentration and load on the bonding strength of the adhesive were investigated. The tensile shear strength of the adhesive samples were measured by the lap shear strength test, and their surfaces were investigated by SEM and FT-IR. The results showed that the bonding strength of the polyurethane adhesive decreased rapidly with increasing load; for example, the failure time decreased significantly from 150 h under a load of 1000 N to 30 h under a load of 2000 N. With a constant load, the failure time increased from 60 h in 5 % NaCl to 160 h in 15 % NaCl. Increasing temperature accelerated the degradation of the polyurethane adhesive. The bonding strength decreased rapidly from 93.5 % at 35 ℃ to 65.0 % at 70 ℃ in the early stages of immersion, while the effect of temperature was less marked in the middle and latter stages of immersion. The tensile shear strength was 64.0 % at 35 ℃ and 63.0 % at 70 ℃ but only 44.0 % at 50 ℃.