聚氨酯脲涂层砂浆的耐氯盐浸渍性能研究

Study on Chloride Resistance of Polyurethaneurea-Coated Mortar

研究了采用3.5%氯盐浸渍30～120 d对聚氨酯脲涂层砂浆的氯离子扩散系数、阻抗谱和表面性能的影响;并通过涂层的红外光谱(FT-IR),结合表面接触角变化,探讨了耐氯盐浸渍性能的机理。研究结果表明:氯离子扩散系数随浸渍时间变化规律符合Fick第二定律,120 d后,聚氨酯脲涂层砂浆氯离子扩散系数为0.41×10^(-12)m^2/s,明显低于无涂层砂浆;聚氨酯脲涂层砂浆试件Nyquist图显示,随氯盐浸渍时间增加,低频部分的曲线半径缩小并且向高频区收缩,低频阻抗模值|Z|_(0.01 Hz)呈下降趋势,初始值24 045.02Ω,120 d后降至6 381.39Ω;砂浆电阻值随浸渍时间不均匀降低,电容增加;涂层接触角随氯盐浸渍时间增加而减小,120 d后降低了9.78%,表面能升高,涂层亲水能力提高,总体变化幅度不大,浸泡后依然具有较好的耐氯离子渗透性能。FT-IR谱图揭示出导致上述变化的原因是由于浸泡过程中,涂层表面的N—H、C=O、C—H等基团有轻微断键现象,对涂层防护性能有轻微影响,故涂层表面性能有所下降,但变化幅度较小。

Abstract:The effects of chlorine salt impregnation on the chloride ion diffusion coefficient,impedance spectrum and surface properties of polyurethaneurea-coated mortars were studied.The impregnation performance of chlorine-resistant salts was discussed by the combination of the infrared spectra (FTIR)of the coatings and the changes of surface contact angles.The results showed that the content of chloride ions increased with the immersion time. After 120 days,the chloride ion diffusion coefficient of polyurethaneurea-coated mortar was 0.41×10^-12m^2/s/s,which was significantly lower than that of uncoated mortar.The Nyquist dia- gram showed that after being submerged,the radius of the low-frequency part of the curve gradually shrinked and approached to the high-frequency area;The low-frequency impedance modulus decreases,with an initial value of 24 045.02Ω which was down to 6 381.39 Ω after 120 d;The resistance of the mortar decreased with the immersion time while the capacitance increased.The coating contact angle decreased,and reduced by 9.78% after 120 days.The surface energy increased and the hydrophilicity of the coating increased.Generally the coated mortars showed good resistance to chloride ion penetration after immersion.FTIR spectra revealed that the breakdown of N-H,C=O and C-H of the coating resulted in the slight variation mentioned above which had a slight influence on the protective performance of the coating.