Studies On Functionalization Of Self-Healing Superhydrophobic Cotton Fabric

Superhydrophobic materials have been used in diverse fields due to their special wettability,which could be applied in national defense,medical care,agricultural production and daily life.For the moment,the superhydrophobic surfaces are difficult to fabricate because the complex preparation process,expensive equipment and harmful environment,which hampers their applications.Because the micro-/nanoscale rough structures and low surface-energy materials that construct superhydrophobic surface are easily damaged by physical crush,sunlight,friction,it is still difficult to maintain the superhydrophobic property.However,combination of the superhydrophobic properties and the self-healing abilities show a productive approach to improve the long-term durability of the superhydrophobic materials.Therefore,it is an urgent requirement to fabricate surfaces with superhydrophobic using simple and effective method and realize the high stability of superhydrophobic.This thesis focuses on the fabrication of superhydrophobic surface in a facile and effective method and realize their self-healing performance.The dissertation has carried out a series of research work including the preparation,optimization and characterization of superhydrophobic cotton fabrics,and also studied the self-healing performance of superhydrophobic induced by temperature.The main contents about this dissertation are summarized as follows:(1)The ethylenediamine tetraacetic acid(EDTA)was used as crosslinking agent to graft hexadecyl trimethoxy silane(HDTMS)onto the surface of cotton fibers.Nano-silica(SNP)was used to create a rough structure on cotton fabric.The influence of monomer ratio on the water repellent properties of cotton fabric was discussed through univariate analysis and optimization experiment.The optimum synthesis process was obtained:the concentration of SNP,EDTA and HDTMS was 1.0 wt%,1.0 wt%and 4.0 wt%,respectively.The superhydrophobic functional finishing of raw cotton fabric by immersion method,the prepared cotton fabrics showed a superior hydrophobicity with water contact angles(WCA)larger than 160.5°,with glycerol contact angles larger than 155.0°.Besides,the superhydrophobic coatings also displayed fairly washing durability.After laundering for 6cycles,the surface still maintained high water CA above 150.0°.(2)The nano-silica with radial wrinkle structures was prepared via a the bi-continuous microemulsion phase of a Winsor III system.The cetyltrimethylammonium bromide(CTAB)was used to prepare nano-silica as a template,HDTMS was used to functionalize the nano-silica to obtain CH₃-RWNs ethanol dispersion.The superhydrophobic surface onto hard or soft substrates was created by spraying or immersion process with the ethanolic dispersion of functionalized nano-silica molecules.The superhydrophobic glass presented a rough coral-like morphology in Cassie-Baxter state with extremely low adhesion,with a sliding angle(SA)below 4.13°.Besides,it also displayed excellent self-cleaning property,highly mechanical robustness,and acidic(p H=1.0)/alkaline(p H=14.0)stability.(3)The HDTMS emulsion was prepared using O₂-plasma and ultrasound for the superhydrophobic functional finishing of raw cotton fabric by immersion method.The prepared cotton fabrics showed a superior hydrophobicity with water contact angles(WCA)larger than 158.7°.Temperature stimulation can accelerate the migration rate of the hydrophobic long chain(-CH₂)on the fiber surface,repair the damaged surface,and restore the superhydrophobic performance.After 1000 cycles of abrasion,the WCA value reduced to120.0°.The superhydrophobicity of cotton fabric was regained after thermally stimulated(WCA>150.0°).Similarly,the superhydrophobic cotton fabric became hydrophilic after oxygen plasma treatment with the contact angle of 0°.Due to the preserved long-chain alkyl groups in cotton fibers were released by heating for 30 min at 80?,the cotton fabric recovered hydrophobicity with the WCA increased to 155.4°±1.2.The repair process can be repeated many times,which the self-healing process could be repeated,which improve their durability and lifetime.Besides,the superhydrophobic coatings also displayed fairly washing durability and chemical stability.