Study On Modification Of Silk And Cotton Fabric Using Fluorine Containing Acrylate Monomers Via ATRP Method

Fluorine containing compound can impart grafted materials with water and oil repellency, which would widen its application area. Conventional potassium persulfate(KPS) initiation grafting had some disadvantages, such as monomers homopolymerization and radical coupling, disproportionation, chain transfer reaction, which could affect the properties of the grafted polymer. Atom transfer radical polymerization(ATRP) is a kind of controllable active polymerization, which could avoid the defects of KPS initiation. And it possessed some advantages, such as wide monomer range, mild polymerization conditions, and control of molecular structure. Meanwhile, ATRP grafting is helpful to study on the relationship between materials structure and properties.This work focuses on the grafting modification of silk and cotton fabric using fluorine containing acrylate monomers such as trifluoroethyl methacrylate(TFEMA), hexafluorobutyl methacrylate(HFBMA), hexafluorobutyl acrylate(HFBA) and dodecafluoroheptyl methacrylate(DFHMA) via ATRP method. The reaction conditions and reactivity of fluorine containing acrylate monomers on silk and cotton grafting were discussed. The structure and properties of grafted silk and cotton were investigated. In addition, the structure and properties of the grafted silk and cotton via ATRP and KPS initiation methods were compared.Silk fabric was grafted using TFEMA, HFBMA, HFBA and DFHMA via ATRP. The effects of grafting conditions were determined. The optimum grafting reaction conditions were as follows: monomer 150%(owf), reaction liquid p H 8~9, reaction time 150 min, reaction temperature 80℃, catalytic systems ratio 1.5:1~3:1, concentration of catalyst 0.32~0.37 mmol·L-1. The reactivity of the four monomers was compared in silk ATRP grafting. It was found that the reactivity of the four monomers decreased with the growth of fluorocarbon chain. Living polymerization of the graft reaction was confirmed from the aspects of the relationship between ln([M]0/[M]) and reaction time, polymer molecular weight and conversion rate, conversion rate and polymerization time, and the molecular weight distribution.Cotton fabric was grafted using TFEMA, HFBMA, HFBA and DFHMA via KPS and ATRP methods. The reactivity and reaction conditions of four fluorine containing acrylate monomers were discussed in cotton grafting. The optimum grafting reaction conditions using KPS method were as follows: monomer 125~150%(owf), KPS 2~2.5%(owm), reaction liquid p H 3~3.5, reaction temperature 80~85 ℃, reaction time 120 min. And grafting reaction rate equations of the four monomers grafted cotton fabric were obtained according to the experimental data. The optimum grafting reaction conditions using ATRP method were as follows: monomer 150%(owf), reaction liquid p H 8~9, reaction time 150 min, reaction temperature 80℃, catalytic systems ratio 1.5:1~2:1, concentration of catalyst 0.32~0.37 mmol·L-1.The structure and properties of grafted silk and cotton were investigated. Fourier transform infrared spectroscopy and Raman spectra of the grafted silk and cotton showed adsorption peaks at 1020~1286 cm-1 and 1283~1325 cm-1, which corresponded to the stretching vibration of the C-F bond. Solid state nuclear magnetic resonance spectra of the grafted silk and cotton indicated the chemical shifts of-75.66 ppm,-122.89 ppm, and-214.24 ppm represented the characteristic absorption peak of-CF3,-CFH, and-CF2. It could be concluded that the fluorine containing acrylate monomers were grafted onto silk and cotton fabric. X-ray photoelectron spectroscopy indicated the tendency to fluorine elemental content of the grafted silk and cotton fabric decreased from surface to the interior. Furthermore, the fluorine groups of monomers existed on the surface of the grafted silk and cotton fabric. When the grafting yield was similar, the surface fluorine element content of grafted silk and cotton fabric using ATRP method was higher than that of using KPS method. X-ray diffraction of the grafted silk and cotton fabric results showed that the grafting reaction mainly occurred at the amorphous region of silk and cotton fibers. The amino acid analysis of grafted silk indicated that the reaction of fluorine containing acrylate monomers grafted silk mainly occurred at the amino acid of the fiber amorphous region which had some reactive groups. It could be observed from scanning electron microscope images that the surface of ATRP grafted silk and cotton was smooth. The surface of grafted silk and cotton via KPS method was smooth at low grafting yield, however, the surface of grafted silk and cotton appeared monomer homopolymers at high grafting yield. Atomic force microscope images showed the surface of the grafted silk and cotton from larger clusters concave convex structure converted into smaller punctate concave convex structure, and the surface punctate concave convex structure of the grafted silk and cotton using ATRP method was more orderly than that of using KPS method.As grafting yield increased gradually, the contact angle of the grafted silk and cotton fabric increased, the adhesion force and water shedding angle decreased. When the grafting yield increased to a certain degree, it had no promoting effect to the contact angle, adhesion force and water shedding angle. The grafted silk and cotton fabric with good water repellence property and excellent washing durability were obtained. And with fluorine containing carbon chain of monomer growing, the water repellence property of the grafted silk and cotton fabric increased. Compared with the KPS method, the grafted silk and cotton fabric via ATRP method possessed larger contact angle, smaller adhesion force and water shedding angle when the grafting yield was similar. And the contact angle of the grafted silk and cotton fabric via ATRP method was more stable than that of via KPS method. The thermal properties analysis showed that the oneset decomposition temperature and maximum decomposition rate temperature of the grafted silk increased, the thermal properties were improved. The oneset decomposition temperature of the grafted cotton decreased, the maximum decomposition rate temperature had almost no changed. The surface property and bending property tests showed the grafting had little impact on the silk and cotton fabric handle. Whiteness, breaking strength, air permeability and moisture regain of grafted silk and cotton fabric decreased somewhat.