Hydrophobic Modification Of Cotton Fabric By Laccase

With the continuous improvement of people’s living standards,the demand for functional textiles has also increased.More and more functional textiles have been developed,such as antibacterial fabrics,UV resistant fabrics,water and oil repellent fabrics et.al.At present,the functional modification of cotton fabrics is mainly achieved by traditional chemical methods or physical methods.With people’s awareness of environmental protection increaseing,it is valuable to seek a more green and environmentally friendly cotton fabric modification method.Inspired by mussels,scientists have discovered the potential of dopamine in the surface modification of materials.A series of studies have shown that dopamine can spontaneously polymerized under alkaline conditions and form polydopamine coating on almost any surface.With this property,dopamine is widely used for surface modification of various organic or inorganic materials,and its application in textile functional finishing has also received more and more attention.In this paper,laccase was used to catalyze the polymerization of dopamine,and the difference between the polymerization of dopamine under two different conditions was investigated.It is mainly explored from three aspects,including the oxidative polymerization rate of dopamine under two reaction conditions,the structure of polydopamine（PDA）and the surface morphology of polydopamine coating.The experimental results show that the oxidative polymerization rate of dopamine by laccase is faster,and the higher the concentration of laccase,the higher the oxygen concentration,the faster the oxidative polymerization rate of dopamine.The reaction rate is affected by pH.pH 5.5 is more favorable for the oxidative polymerization of dopamine.The structure of the polydopamine catalyzed by laccase has an ether bond between the monomers,and this connection does not exist in the polydopamine produced under the oxygen,and the dopamine coating is more dense and uniform by laccase.Next,the polydopamine deposited cotton fabrics by laccase or under traditional alkaline conditions were recorded as PDA_L-C and PDA_O-C,respectively.First,the differences of physical and mechanical properties of the two kinds of cotton fabrics were compared.Second,polydopamine coating was used as the secondary platform for the hydrophobic finishing of cotton fabrics.The hydrophobic monomer octadecylamine was finally grafted onto the PDA coating.The experimental results show that both the two kinds of dopamine deposited cotton fabrics have good UV resistance,washing fastness and dry rubbing fastness,but the wet rubbing fastness is poor;The acid-base stability of PDA_L-C fabric is stronger than PDA_O-C;The polydopamine coating has no significant effect on the breaking strength and thermal stability of the cotton fabric,but PDA coating reduces the moisture permeability and gas permeability of the cotton fabric.The comparative analysis of OA-treated PDA_L-C fabric and cotton fabric by ATR-IR test showed that the primary amine monomer-octadecylamine containing a long alkyl chain was successfully grafted onto the surface of the PDA_L-C fabric.The grafting of octadecylamine on PDA_L-C fabric was quantitatively characterized by micro-Kjeldahl method.The grafting ratio of OA monomer on PDA_L-C fabric was 1.14%,and the grafting efficiency was 11.45%.After grafting octadecylamine,the surface hydrophobicity of the PDA_L-C fabric was improved.The static contact angle of the untreated PDA_L-C fabric was 0°,the wettability of the water droplets was 1 s,and the PDA_L-C grafted with octadecylamine fabric has a static contact angle of 134°and a wetting time of over 20 min.Finally,the laccase/2,2,6,6-tetramethoxypiperidine-1-oxide（TEMPO）system was used to catalyze the polymerization of dopamine under acidic conditions,and then the PDA coating was used for laccase catalyzed reaction.The PDA coating was catalyzed for grafting a hydrophobic monomer-lauryl gallate（DG）by laccase to prepare a hydrophobic cotton fabric.UV-vis proved that laccase/TEMPO system can catalyze the oxidative polymerization of dopamine.SEM and XPS showed that the surface of PDA deposited cotton fiber was rough,and there was the single of N element other than C,H,O.FT-IR showed typical peaks of alkyl chain（-CH₂）on the grafted cotton fabric,indicating that DG was successfully grafted onto dopamine-deposited cotton fabric,and the grafting ratio was calculated by weighing method（1.06%）.The surface hydrophobicity of PDA-C fabric is significantly improved after grafting DG and has good anti-staining properties.The static contact angle of PDA-C fabric is 0°,and the static contact angle of PDA-C fabric after grafting DG.It is 133°.