Haiqing Jiang

Laundering Durability of Superhydrophobic Cotton Fabric

www.MaterialsViews.com C O M Laundering Durability of Superhydrophobic Cotton Fabric M U N I By Bo Deng , Ren Cai , Yang Yu , Haiqing Jiang , Chunlei Wang , Jiang Li , Linfan Li , Ming Yu , Jingye Li ,* Leidong Xie , Qing Huang , and Chunhai Fan C A IO N A superhydrophobic surface, displaying a contact angle (CA) of water greater than 150 ° , [ 1 ] is a fascinating phenomenon in nature, which attracts not only academic but also industrial interest. It is well known that a superhydrophobic surface generally has a low surface energy chemical structure combined with a particular micro-structural roughness. [ 2 ] Using this principle, numerous superhydrophobic surfaces have been developed based on different materials using various methods and techniques, which have been reviewed recently. [ 3 ] There are many potential applications for artifi cial superhydrophobic surfaces in our daily life, among which waterproof textile is considered to be one of the most promising ones. [ 4 ] In this work, we report a convenient radiation-induced graft polymerization method to prepare an extremely stable, superhydrophobic cotton fabric, which is chemically stable over the entire pH range (0–14), and durable for more than 250 commercial or domestic launderings. Cotton fabric is widely used in daily life, it is a hydrophilic woven textile with numerous holes in its woven structure that make cotton fabric-based clothes comfortable. It is expected that a cotton fabric that is endowed with superhydrophobic properties, a so-called “superhydrophobic cotton fabric” (SCF), simultaneously possesses the properties of being waterproof as well as being air-breathing, which would lead to comfortable waterproof clothes. [ 5 ] In addition, because of the existence of air layers, its surface may not be wetted even upon full immersion in water, which makes it a good candidate for life vests. Because of the above-mentioned merits, many publications have been reported on the study of SCFs, which were mainly fabricated by doping of the cotton fabric with low surface energy nanoparticles. [ 6 ] However, the laundering durability, which is one of the most important characteristics for a fabric, has been largely ignored in these previous studies. Forming covalent bonds between cotton fi bers and low surface energy compounds is a critical point to enhance the stability of the SCF, and, as a consequence, should be the way to improve the laundering durability. [ 7 ] It is mainly the strength

Laundering Durability of Photocatalyzed Self-Cleaning Cotton Fabric with TiO2 Nanoparticles Covalently Immobilized

Photocatalyzed self-cleaning cotton fabrics with TiO2 nanoparticles covalently immobilized are obtained by cograft polymerization of 2-hydroxyethyl acrylate (HEA) together with the surface functionalized TiO2 nanoparticles under γ-ray irradiation. The covalent bonds between the TiO2 nanoparticles and cotton fabrics bridged by poly(2-hydroxyethyl acrylate) (PHEA) graft chains is strong enough to survive 30 accelerated laundering circles, equivalent to 150 commercial or domestic launderings.

Preparation of the antifouling microfiltration membranes from poly(N,N-dimethylacrylamide) grafted poly(vinylidene fluoride) (PVDF) powder

Poly(vinylidene fluoride) (PVDF) powder is graft polymerized with N,N-dimethylacrylamide (DMAA) by a pre-irradiation induced graft polymerization technique. The existence of the graft chains in grafted PVDF (PVDF-g-PDMAA) powder has been proven by FT-IR spectroscopy and X-ray Photoelectron Spectroscopy (XPS) analysis. Then, the microfiltration (MF) membranes are prepared by isothermal immersion precipitation from PVDF-g-PDMAA powder in 1-methyl-2-pyrrolidone (NMP) solution from a water bath. The hydrophilicity of the MF membranes is determined by measuring the contact angles. The asymmetric morphology of the grafted membranes is studied by scanning electron microscopy (SEM), and water filtration properties are tested. The interaction between the membranes and proteins is studied by comparing the fluorescence microscopy images of these MF membranes cast from pristine PVDF and PVDF-g-PDMAA with a degree of grafting (DG) of 17.1% after surface fouling by Fluorescein Isothiocyanate (FITC)-conjugated Human Albumin solution. The antifouling property is determined by measuring the recovery percentage of pure water flux after the MF membranes have been fouled by bovine serum albumin (BSA) and lysozyme aqueous solution, separately. The results confirm that the existence of PDMAA graft chains improves the hydrophilicity and reduces protein adsorption of these MF membranes cast from PVDF-g-PDMAA powder.

Self-healing of the superhydrophobicity by ironing for the abrasion durable superhydrophobic cotton fabrics

Self-healing of the superhydrophobic cotton fabric (SCF) obtained by the radiation-induced graft polymerization of lauryl methacrylate (LMA) and n-hexyl methacrylate (HMA), can be achieved by ironing. Through the steam ironing process, the superhydrophobicity of the SCFs will be regenerated even after the yarns are ruptured during the abrasion test under a load pressure of 44.8 kPa. SCFs made from LMA grafted cotton fabric can ultimately withstand at least 24,000 cycles of abrasion with periodic steam ironing. The FT-IR microscope results show that the migration of the polymethacrylates graft chains from the interior to the surface is responsible for the self-healing effect.

Designing breathable superhydrophobic cotton fabrics

Superhydrophobic cotton fabrics were prepared through radiation induced graft polymerization by applying a series of alkyl methacrylates as the functional monomers. We found that the superhydrophobic cotton fabrics exhibited considerable resistance to air permeability whereas the water vapour transport is almost the same as pristine cotton. The mechanism is that the air permeability is mainly determined by the thickness and pore size of the fabric, while the lower degree of interaction between the grafted cotton fabrics and water molecules along with an enhanced capillary effect are the key factors responsible for the high water vapour transmission rate. The combination of opposing properties – a decreased air permeability and ideal water vapour transmission rate, creates a breathable and comfortable fabric as a dressing material.

Fabrication of PES-based membranes with a high and stable desalination performance for membrane distillation

Polyethersulfone (PES)-based membranes with a high and stable desalination performance for vacuum membrane distillation (VMD) were fabricated by spraying a dispersion containing hydrophobic-modified PES grafted copolymers onto porous PES membranes. The copolymer (PES-g-PFMA-C8) with different degrees of grafting (DG) was synthesized by grafting 1H,1H,2H,2H-perfluorodecyl methacrylate (FMA-C8) onto PES by simultaneous irradiation in a homogeneous system wherein the kinetics of the radiation-induced graft polymerization was studied. The copolymers, pristine PES membrane and fabricated PES-based membranes were also characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. After spraying, the hydrophobicity of the membrane increased and its maximum pore size reduced, which enhanced its desalination stability. During an intermittent 80 h VMD desalination operation, a flux of approximately 50.5 kg m−2 h−1 and a stable salt rejection of 99.98% were achieved when a 3.5 wt% NaCl solution was treated at 70 °C under vacuum of 92 kPa by the PES-based membrane using the copolymer with a DG of 20.3%, whereas salt leakage obviously occurred since the 52nd hour of operation when the pristine PES membrane was used. These results indicate that the modified PES membrane developed in this study is a promising candidate for VMD desalination due to its comparable flux.