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This topic demonstrates a simple, feasible, and low-energy-consuming strategy for preparing waterproof and moisture-permeable membranes. The hydrophobicity, pore structure and mechanical properties of the waterproof and moisture-permeable nanofiber membrane have been optimized, and a waterproof and moisture-permeable membrane with good comprehensive waterproofness, high moisture permeability and excellent mechanical properties has been obtained. It has potential in outdoor sportswear, separation membranes, etc. application prospects.
This article first introduces polypropylene butyral (PVB) with a low softening point as a binder into the Si-PU/PMMA spinning solution, and further optimizes the fiber membrane through heat treatment to obtain a Si-PU/PMMA/PVB waterproof and breathable membrane with physical welding structure. The effects of heat treatment temperature and PVB content on the micromorphology and properties of fiber membranes were systematically studied.
Secondly, based on the research on Si-PU/PMMA fiber membrane, this article introduces thiol and tetramethyltetravinylcyclotetrasiloxane (TMTVSi) as hydrophobic agents and chemical cross-linking agents. Under the action of octadecanethiol and TMTVSi, a thiol-ene click chemical reaction occurs, effectively reducing the maximum pore size of the Nanofiber Membrane and improving its waterproof performance.
Use environmentally friendly materials:
From the perspective of environmental protection and pore size reduction, silicone-modified polyurethane, polymethyl methacrylate, and polyvinyl butyral are blended and modified, and electrospinning technology combined with heat treatment methods is used to prepare environmentally friendly, pore size It is a fluorine-free waterproof and breathable membrane material with small size, high porosity and physical welding structure.
Figure 1 SEM images of nanofiber membranes prepared at different Si-PU/PMMA-3 concentrations: (a) 9%, (b) 11%, (c) 13%, (d) 15%, (e) Average fiber diameter , (f) Fiber diameter distribution.
Introducing physical welding structure:
The low softening point component polyvinyl butyral (PVB) is introduced into the electrospinning solution. When the Nanofiber Membrane is heated, the PVB is heated and melted, and a physical welding structure is generated between adjacent fibers, which can change the pore structure of the Nanofiber Membrane. Control the system to enhance its waterproof performance. At the same time, the generation of the welded structure can limit the relative slip between fibers and enhance its mechanical properties when theNanofiber Membrane is acted upon by external forces.
Figure 2 SEM images of nanofiber membranes prepared at different PVB contents: (a) 0%, (b) 20%, (c) 40%, (d) 60%.
Figure 3 Effect of PVB content on the contact angle, maximum pore size, water pressure resistance, porosity, moisture permeability, and air permeability of Si-PU/PMMA/PVB fiber membrane and smooth membrane
Figure 4 Mechanical properties of Si-PU/PMMA/PVB fiber membranes under different PVB contents
Figure 5 Demonstration of waterproof and breathable performance of Si-PU/PMMA/PVB-40 fiber membrane.
Introducing hydrophobic agents and cross-linking agents to enhance comprehensive performance:
Introducing octadecanethiol and TMTVSi as hydrophobic agents and cross-linking agents in the spinning solution, and using electrospinning technology combined with thiol-ene click chemical reactions to prepare waterproof and moisture-permeable membranes, which can not only build a hydrophobic surface, but also form chemicals between Nanofiber Membrane. Cross-linked structure, thereby achieving simultaneous improvement in waterproofing and mechanical properties.
Figure 6 (a) Si-PU/PMMA/TMTVSi-thiol fiber membrane preparation process, (b) waterproof and breathable mechanism.
Figure 7 (a) Thiol-ene click chemical reaction, (b) Fourier transform infrared spectra of the reactants (TMTVSi and n-octadecanethiol) before (lower) and after (upper) UV irradiation.
Figure 8 SEM images of Si-PU/PMMA/TMTVSi/thiol nanofiber membranes with different octadecanethiol contents before UV irradiation (a) 0, (b) 15, (c) 30, (d) 45%. SEM images of Si-PU/PMMA/TMTVSi-thiol nanofiber membranes with different thiol contents after UV irradiation (e) 0, (f) 15, (g) 30, (h) 45%. (i) Elemental mapping image of selected areas on Si-PU/PMMA/TMTVSi-thiol-30 nanofibrous membrane. (j) Energy spectrum analysis of Si-PU/PMMA/TMTVSi-thiol-30 nanofiber membrane.
Overcome the problem of poor feel of waterproof and moisture-permeable membranes after heat treatment:
Based on the light-initiated thiol-ene click chemical reaction, a thin and soft fluorine-free electrospun waterproof and moisture-permeable membrane is prepared with high efficiency and low energy consumption. On the premise of ensuring the waterproof and moisture-permeable performance of the fiber membrane, it solves the problems of impregnation, coating, heat treatment, etc. The finishing method brings about the problem of deterioration of the fiber membrane's feel, and has better wearing comfort.
Table 1 Softness of different waterproof and breathable membranes
Figure 9 (a) Demonstration of the softness of fluorine-free Si-PU/PMMA/TMTVSi-thiol-30 nanofiber membrane after UV irradiation. (b) Mechanical properties of nanofiber membranes with different octadecanethiol contents. (c) Comparison of the waterproof performance and mechanical properties of Si-PU/PMMA/TMTVSi-thiol-30 nanofiber membrane and other nanofiber membranes.
Figure 10 (a) Hydrophobicity display of fluorine-free Si-PU/PMMA/TMTVSi-thiol-30 nanofiber membrane after UV irradiation. (b) Demonstration of waterproof performance of Si-PU/PMMA/TMTVSi-thiol-30 nanofiber membrane after UV irradiation. (c) Moisture permeability display of Si-PU/PMMA/TMTVSi-thiol-30 nanofiber membrane after UV irradiation.
Paper link:
https://d.wanfangdata.com.cn/thesis/ChhUaGVzaXNOZXdTMjAyNDA5MjAxNTE3MjUSCUQwMjY2NTA3NhoINjR1YThxNHU%3D
