Preparation of Epoxy Resin-Based Hydrophobic Coating by Solvent Volatilization and Phase Separation
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摘要: 以氟硅改性的环氧树脂为基体,采用二甲苯/乙酸乙酯混合溶剂制备疏水涂层,研究氟硅含量、溶剂种类对涂层疏水性能和微观形貌的影响。结果表明,随着氟硅含量的增加,涂层的接触角逐渐变大。仅以二甲苯为溶剂时,制备的涂层表面较为光滑,接触角最高为105.0°;在二甲苯/乙酸乙酯体系中,由于溶剂挥发速率的差异,涂层表面形成了5~15 µm微孔。同时,氟硅与环氧链段的相分离遵循成核-增长机制,微孔中产生0.1~0.6 µm突起。涂层成膜过程中氟、硅自发向外表面迁移以降低其表面能。当氟硅的含量(质量分数)增加到30%时,涂层表面微孔和孔内凸起可以截留更多的空气,涂层的最大接触角提高到115.5°,疏水性明显提高。并且涂层具有强附着力(5B)和高硬度(6H),表明其应用性能优良。Abstract: Hydrophobic coatings were prepared in xylene or xylene/ethyl acetate solvent by using 10% and 30% (mass fraction) fluorosilicate modified epoxy resin as the matrix. The influence of fluorosilicon content and solvent type on hydrophobicity as well as micromorphology of the coatings were investigated. The results show that with the increase of fluorosilicon content, the contact angle of the coating enhances. When only using xylene as the solvent, the surface of the coating is relatively smooth, and the maximum contact angle is 105.0°. In xylene/ethyl acetate system, 5~15 µm micropores are formed attributing to the difference of solvent volatilization rate. Meanwhile, 0.1~0.6 µm bumps are generated in those micropores along with phase separation of fluorosilicon and epoxy segments according to nucleation-growth mechanism. The surface energy of coatings reduces with the spontaneous migration of F and Si to the outer surface in the process of film formation. When the content of fluorosilicon segments increases to 30%, much more air could be trapped in the micropores and protrusions. The highest contact angle of the coating rises to 115.5° and the hydrophobicity is improved obviously. The coating also exhibits high adhesion of 5B and hardness of 6H, suggesting its excellent application performance.
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Key words:
- epoxy resin /
- fluorosilicon content /
- solvent volatilization /
- phase separation /
- hydrophobic coating
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图 1 不同质量分数氟硅改性环氧树脂以二甲苯、二甲苯/乙酸乙酯为溶剂所获涂层的SEM图
Figure 1. SEM images of coatings prepared fluorosilicon modified epoxy with different mass fractions in xylene and xylene/ethyl acetate solvents, respectively
(a1), (a2)— 10%, Xylene; (b1), (b2) — 30%, Xylene; (c1), (c2) — 10%, Xylene/Ethyl acetate; (d1), (d2) — 30%, Xylene/Ethyl acetate
表 1 二甲苯和乙酸乙酯的Hansen溶解度组合参数与比挥发速度
Table 1. Hansen solubility parameters and specific volatilization rates of xylene and ethyl acetate
Solvent δd/(J·cm−3)1/2 δp/(J·cm−3)1/2 δh/(J·cm−3)1/2 δa)/(J·cm−3)1/2 Specific volatilization rateb) Xylene 17.8 1.0 3.1 18.2 75 Ethyl acetate 15.8 5.3 7.2 18.1 430 a) Hansen solubility parameter is composed of dispersion force (δd), polarity force (δp) and hydrogen bonding force (δh), and satisfies ${{\rm{\delta }}^{\rm{2}}}{\rm{ = \delta }}_{\rm{d}}^{\rm{2}}{\rm{ + \delta }}_{\rm{p}}^{\rm{2}}{\rm{ + \delta }}_{\rm{h}}^{\rm{2}}$;b) Specific volatilization rate = Mass/(Area × Time), generally, the volatilization rate of butyl acetate is taken as the standard, which is recorded as 100; and the ratio of the volatilization rate of other solvents to that of butyl acetate is the specific volatilization rate of the solvent 表 2 w=30%氟硅改性环氧涂层不同位置的表面元素相对含量(EDS)分析
Table 2. Surface element relative content of 30% fluorosilicate modified epoxy coating at different positions
Surface of the hole w/% C O Si SiTheory F FTheory Inner surface 56.44 17.04 23.98 10.44 2.54 1.63 Outer surface 68.71 16.86 11.93 10.44 2.50 1.63 -
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