Facile Fabrication of Robust and Fluorine-Free Superhydrophobic PDMS/STA-Coated Cotton Fabric for Highly Efficient Oil-Water Separation

Abstract

Oil–water separation using special wettability materials has received much attention due to its low energy consumption and high separation efficiency. Herein, a fluorine-free superhydrophobic cotton fabric (PDMS/STA-coated cotton fabric) was successfully prepared by a simple impregnation method using hydroxyl-capped polydimethylsiloxane (PDMS-OH), tetraethoxysilane (TEOS), and stearic acid (STA) as precursors. The investigation found that the cross-linking reactions between the hydroxyl groups of PDMS-OH and hydrolyzed TEOS enabled a strong interaction between PDMS-OH and cotton fabric. Furthermore, a suitable roughness surface of coated cotton fabric was established by introducing STA due to its long chain structure. The contact angle of this composite can reach 158.7° under optimal conditions due to its low surface energy and desired roughness. The oil/water separation efficiency of PDMS/STA-coated cotton fabric is higher than 90% even after 10 cycles of oil–water separation, and the oil flux can reach 11862.42 L m−2 h−1. In addition, PDMS/STA-coated cotton fabric exhibits excellent chemical stability and durability under extreme conditions such as strong acid (HCl, pH = 1~2) and alkali (NaOH, pH = 13~14), and the hydrophobicity of PDMS/STA-coated cotton fabric was decreased to 147° after 300 cycles of abrasion testing.

Synthesis of a water-based TEOS–PDMS sol–gel coating for hydrophobic cotton and polyester fabrics

“…Innovative prospects arise as TEOS–PDMS coatings find their way into fabric applications, offering fire retardancy 19 and hydrophobicity, with potential for oil–water separation. 20–22 By using the combination of TEOS and PDMS, it is possible to create a coating that is both mechanically stable and highly hydrophobic. The hydrophobic properties of the resulting coating are due to the low surface energy of PDMS and the roughness of the surface created by the TEOS-derived silica nanoparticles.…”

“…While there have been significant advancements in the utilization of TEOS–PDMS coatings on fabrics, the existing literature predominantly explores the use of organic solvents. For instance, studies conducted by Tang (2023) 21 and Hasanzadeh (2022) 22 employed n -hexane and toluene, respectively, in the formulation of their coating solutions. This study focuses on producing water-based hydrophobic coatings for cotton and polyester fabrics using a one-step sol–gel method under acidic conditions.…”

A One-Step Approach for a Durable and Highly Hydrophobic Coating for Flax Fabrics for Self-Cleaning Application

“…PDMS films display very stable chemical bonds on their surfaces, and their silica (-Si-O-) network is also able to be incorporated with another function group to increase the mechanical properties [ 36 ]. Many researchers have used PDMS in the design and production of hydrophobic fabrics [ 37 , 38 , 39 , 40 ]. For example, Talebizadehsardari et al [ 41 ] have prepared a hydrophobic cotton fabric via the dip-coating method using hydroxyl-terminated PDMS with tetraethyl orthosilicate (TEOS) as a curing agent, dibutyltin dilaurate (DBTDL) as a catalyst and THF as a solvent.…”

Superhydrophobic TiN-Coated Cotton Fabrics with Nanoscale Roughness and Photothermal Self-Healing Properties for Effective Oil–Water Separation

“…It is generally believed that water repellency is provided by the nanorough structure and low surface free energy of the interface. , Nanorough structures are usually provided by nanoinorganic particles, and low surface energy layers are provided by low surface energy polymers. Tang and Liu used hydroxyl-terminated polydimethylsiloxane (HPDMS) to provide low surface energy, and HPDMS has a stronger interaction with cotton fabrics . However, the water repellency of superhydrophobic materials is susceptible to damage from chemical corrosion, mechanical friction, and air oxidation, and this damage can affect the lifetime of superhydrophobic materials.…”

“…Tang and Liu used hydroxyl-terminated polydimethylsiloxane (HPDMS) to provide low surface energy, and HPDMS has a stronger interaction with cotton fabrics. 17 However, the water repellency of superhydrophobic materials is susceptible to damage from chemical corrosion, mechanical friction, and air oxidation, 18 and this damage can affect the lifetime of superhydrophobic materials. For this reason, it is essentially important to improve the durability of superhydrophobic materials.…”