Study On Fluorine-Free Superhydrophobic Finish Of Cotton、Polyester Fabric Based On Waterborne Polyurethane

Superhydrophobic coating materials have important characteristics such as self-cleaning,oil/water separation,anti-corrosion,drag reduction,and anti-icing.They have attracted wide attention in many fields of both scientific research and industrial production.However,such coating materials still have some problems in practical applications,including the use of organic solvents and fluorine-containing compounds,and poor mechanical stability.In order to effectively solve these problems,this work used the hydrophobic interaction between the hydrophobic long alkyl chain in the long-chain alkyl silane and the dispersed phase in the aqueous polyurethane emulsion to achieve the effective dispersion of the long-chain alkyl silane in the aqueous polyurethane emulsion,thus enabling the preparation of fluorine-free super-hydrophobic finishing agent for cotton and polyester fabrics.Silica nanoparticles were added into the long-chain alkyl silane-containing aqueous polyurethane emulsion to increase the roughness of the fiber surface after finishing,thereby improving the superhydrophobic properties.The main work of this thesis is as follows:(1)Superhydrophobic modification of cotton fabric based on ordinary water-based polyurethane:Firstly,commercially available ordinary water-based polyurethane(NPU)was used.Cetyltrimethoxysilane(HDTMS)was dispersed in it by stirring,and then silica nanoparticles and a crosslinking agent(IPDI)were added to prepare the finishing solution.Cotton and polyester fabrics were then finished by means of padding.The results showed that the hydrophobic polyester fabric became hydrophilic after finishing,while the static water contact angle of the finished cotton fabric reached 157.7±2.0° and the shedding angle was 20±1.2°.The air permeability of cotton fabric wa■s little affected.It slightly decreased from 178.6±3.5 mm s-1 to 153.8±4.3 mm s-1.But the cotton fabric finished with this finishing agent had a poor water repellency rating,only 70 points(AATCC 22-2005 standard),and the washing resistance and abrasion resistance also need to be improved.The finished cotton fabric after 5 times of laundering(AATCC-61 standard),the contact angle dropped to 145.0±2.2°,and the shedding angle was 39.2±1.1°;after 100 cycles of abrasion(GB/T 3920-2008 standard),the contact angle and shedding angle was 150.3±2.9° and 34.1±1.3°,respectively.(2)Synthesis of hydrophobic water-based polyurethane:Hydrophobic hydroxyl-terminated polydimethylsiloxane(PDMS)was used together with polyethylene glycol(PEG)as soft segment,and isophorone diisocyanate(IPDI)was used as hard segment to synthesize a hydrophobic water-based polyurethane(SiWPU).The effects of the amount of PDMS on the hydrophobicity,emulsion stability and particle size of the modified polyurethane were determined.The optimal amount of PDMS was determined to be 49.0%of the total mass of the prepolymer.The SiWPU coating on glass was colorless and transparent.The original water contact angle of the glass slide was 69.8°2.3°.After coating with SiWPU,the water contact angle of the glass slide changed to 107.8°2.4°.(3)Superhydrophobic modification of cotton、polyester fabric based on hydrophobic water-based polyurethane:SiWPU was used instead of WPU to prepare superhydrophobic finishing agent.Both cotton and polyester fabrics were finished by means of padding.The results showed that both the finished cotton and polyester fabrics achieved superhydrophobic property,with a water repellency rating of 100 points.Meanwhile,the washing and abrasion resistance of the coating were improved.After finishing,the water contact angle of the cotton fabric was 167.4±2.0° and the shedding angle was 8.6±0.5°;the water contact angle of polyester fabric was 161.1±1.8° and the shedding angle was 4.2±0.4°.After 10 laundering cycles,the water contact angle of the cotton fabric was 154.8±4.2° and the shedding angle was 17.5±0.8°;the water contact angle of polyester fabric was 151.8±2.3° and the shedding angle was 8.5±0.6°.After 200 cycles of abrasion test,the water contact angle of the cotton fabric was 161.1±2.7° and the shedding angle was 34.2±1.4°;the water contact angle of polyester fabric was 153.3±2.1° and the shedding angle was 9.6±0.8°,After superhydrophobic finishing,the air permeability of cotton and polyester fabrics decreased from 178.6±3.5 mm s-1 to 145.3±3.0 mm s-1 and from 2225.5±39.8 mm s-1 to 1805.5±33.4 mm s-1,respectively.