Modified diatomite with enhanced moisture-regulating by surface hydrophobicity and its effect on water vapor permeability of polyurethane film
摘要: 水性聚氨酯(PU)是一种环保绿色的涂层材料，广泛应用于皮革、纺织、建筑涂层等领域。作为皮革、纺织涂层时，聚氨酯的透湿性决定服装的穿着舒适性，而常规水性聚氨酯的透湿性较差，需要对其进行改性获得透湿性优异的涂层。本文采用CaCl2和十七氟癸基三甲氧基硅烷(FAS-17)对硅藻土进行改性，研究了改性条件对硅藻土结构和性能的影响，将调湿性能较好的改性硅藻土(FAS-17-CaCl2-D)与PU复合，研究复合膜的透湿性。结果表明：采用质量浓度为30wt%CaCl2和0.8wt%FAS-17改性的硅藻土综合性能最好，改性后硅藻土的比表面积、孔隙结构增大，调湿性能提高，FAS-17表面疏水修饰进一步强化了其调湿作用。将性能最好的FAS-17-CaCl2-D与PU复合后，FAS-17-CaCl2-D/PU透湿性随着FAS-17-CaCl2-D用量的增加先增大后减小，复合膜的疏水性提高。1%FAS-17-CaCl2-D与PU复合制备的复合膜透湿率最大，较纯PU膜提高了16.3%，SEM-EDS显示该复合膜表面和截面有Si、Ca和F等FAS-17-CaCl2-D的特征元素，PU与FAS-17-CaCl2-D相界面出现了孔隙，为水蒸气的透过提供通道，从而使透湿性增强。本文制备的透湿聚氨酯材料，有望用于纺织品和皮革涂层，改善湿热舒适性。Abstract: Waterborne polyurethane (PU) is a kind of environment-friendly coating material, widely used in leather, textile, construction coating and other fields. As a coating for leather and textile, the water vapor permeability (WVP) of polyurethane determines the wearing comfort of clothing. However, the water vapor permeability of conventional waterborne polyurethane is poor and needs to be modified to obtain coatings with excellent WVP. CaCl2 and Heptafluorodecyl trimethoxysilane (FAS-17) were used to modify diatomite to prepare hydrophobic diatomite base materials. The effects of modification conditions on the structure and properties of diatomite were investigated. The modified diatomite with excellent performance was combined with PU emulsion and the WVP of composite film was studied. The results indicate that the diatomite modified with 30wt%CaCl2 and 0.8wt%FAS-17 present the best comprehensive performance with increased specific surface area and pore structure. The moisture-regulating performance is improved and further enhanced by surface hydrophobic modification of FAS-17. After modified diatomite FAS-17-CaCl2-D with best performance is combined with PU, the WVP of FAS-17-CaCl2-D/PU composite film increase first then decrease with the increasing of FAS-17-CaCl2-D dosage, and the hydrophobicity is improved. The composite PU film with 1% of FAS-17-CaCl2-D shows the largest WVP, which increased by 16.3% compared with pure PU film. The SEM-EDS reveal that the the surface and cross section of FAS-17-CaCl2-D/PU composite film appear the characteristic elements of FAS-17-CaCl2-D such as Si, Ca and F. The pores appeared at the interface between PU and FAS-17-CaCl2-D provided channels for the transfer of water vapor, resulting in improved WVP. The WVP enhanced PU in this work are expected to be applied in textile and leather coatings to improve the thermal comfort.
- modified diatomite /
- moisture-regulating /
- hydrophobic /
- polyurethane film /
- water vapor permeability
图 5 吸湿后的FAS-170.8-CaCl2-D 经挤压的照片：((a), (b))吸湿样品；(c)用载玻片挤压样品有渗水印迹；((d), (e))玻璃片上的水滴；(f)挤压后样品仍成粉末状态；(图(b)和图(f)的插图分别为挤压前后样品的表面水接触角)
Figure 5. Photo of moisture-adsorption FAS-170.8-CaCl2-D after pressed: ((a), (b)) Moisture-adsorption FAS-170.8-CaCl2-D; (c) Water seepage imprinting of sample with pressing; Water on the glass slide after pressed ((d), (e)) and the pressed sample (f) (Insets of (b) and (f) were the contact angle of original and pressed samples)
表 1 样品名称缩写
Table 1. Sample name abbreviation
Sample CaCl2/wt% FAS-17/wt% PU/wt% D – – – 10%CaCl2-D 10 – – 20%CaCl2-D 20 – – 30%CaCl2-D 30 – – 40%CaCl2-D 40 – – FAS-170-CaCl2-D 30 – – FAS-170.2-CaCl2-D 30 0.2 – FAS-170.4-CaCl2-D 30 0.4 – FAS-170.6-CaCl2-D 30 0.6 – FAS-170.8-CaCl2-D 30 0.8 – FAS-171.0-CaCl2-D 30 1.0 – (FAS-17-CaCl2-D)1%/PU 30 0.8 99 (FAS-17-CaCl2-D)2%/PU 30 0.8 98 (FAS-17-CaCl2-D)3%/PU 30 0.8 97 Notes: D—Diatomite; FAS-17−Heptafluorodecyl trimethoxysilane; PU—Polyurethane.
表 2 FAS-17-CaCl2-D和D的孔结构参数
Table 2. Pore structure parameters of FAS-17-CaCl2-D and D
BJH adsorption cumulative
volume of pores/(cm³·g−1)
BJH adsorption average pore
width (4 V/A)/nm
FAS-17-CaCl2-D 2.6235 0.006103 10.7674 D 1.9396 0.002341 6.3299 Notes: BET—Brunauer-Emmett-Teller; BJH—Barret-Joyner-Halenda.
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