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首页> 外文期刊>International Journal of Adhesion & Adhesives >Some permanent effects of hygrothermal and outdoor ageing on a structural polyurethane adhesive used in civil engineering applications
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Some permanent effects of hygrothermal and outdoor ageing on a structural polyurethane adhesive used in civil engineering applications

机译：湿热和户外老化对土木工程应用的结构聚氨酯粘合剂的一些永久性影响

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摘要

This paper presents an experimental study about the effects of hygrothermal and outdoor ageing on a polyurethane (PUR) adhesive used in civil engineering applications. Small-scale adhesive coupons were exposed to different types of ageing environments for up to two years: (i) immersion in demineralised water at 20 and 40 degrees C, (ii) immersion in salt water at 20 and 40 degrees C, (iii) continuous condensation environment at 40 degrees C, and (iv) outdoor ageing in Lisbon, Portugal. At predetermined times, after a desorption period until constant mass, the effects of such exposure on the physical and mechanical responses of the PUR adhesive was investigated using the following techniques: (i) water sorption, (ii) dynamic mechanical analyses (DMA); (iii) flexural; and (iv) in-plane shear tests. The diffusion mechanisms observed were not purely Fickian; a long relaxation period was noticed, with water molecules being continuously incorporated in the adhesive until the end of the experiments; two alternative analytical modelling approaches were successfully used to simulate the diffusion processes. After immersion in water and salt water for two years, the viscoelastic behaviour of the adhesive showed signs of postcuring phenomena, and some of the physical degradation was found to be reversible due to drying, although it was not explicitly quantified; accordingly, the T g showed increasing trends (11-14%). The mechanical properties of the adhesive showed signs of irreversible degradation mechanisms, more relevant on the in-plane shear properties, with reductions up to 26% in strength and 44% in modulus under the harsher conditions. Flexural properties also exhibited irreversible degradation, with maximum reductions up to 30% in strength and 36% in modulus. Increased temperature did not have a significant effect in the flexural and shear strength, but caused higher degradation in the corresponding moduli. The degradation caused by salt water immersion and continuous condensation was comparable to that in demineralized water immersion (at the same temperature).
机译：本文介绍了湿热和户外老化对土木工程应用中使用的聚氨酯（PUR）粘合剂的影响的实验研究。小规模的粘合剂优惠券暴露于多达两年的不同类型的老化环境：（i）在20和40℃，（ii）浸入20℃和40℃，（iii）的盐水中浸泡在脱矿质水中在葡萄牙里斯本的40摄氏度和（iv）户外老化的连续凝结环境。在预定时间，在解吸期直到恒定质量之后，使用以下技术研究这种暴露对Pur粘合剂的物理和机械响应的影响：（i）水吸附，（ii）动态机械分析（DMA）; （iii）弯曲; （iv）面内剪切测试。观察到的扩散机制不是纯粹的;注意到长弛豫期，水分子在粘合剂中连续掺入粘合剂直至实验结束;两种替代的分析建模方法成功地用于模拟扩散过程。浸入水和盐水中两年后，粘合剂的粘弹性行为显示出消除现象的迹象，并且发现一些物理降解由于干燥，虽然没有明确量化;因此，T G显示出越来越长的趋势（11-14％）。粘合剂的机械性能显示出不可逆的降解机制的迹象，对面内剪切性能更相关，在骚扰条件下，减少高达26％的强度和44％的模量。弯曲性能也表现出不可逆的降解，最大减少高达30％的强度和36％的模量。增加的温度在弯曲和剪切强度下没有显着影响，而是在相应的模量中引起更高的降解。由盐水浸渍和连续缩合引起的降解与脱矿质水浸渍（在相同温度下）相当。

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