| In this thesis,atmospheric non-thermal dielectric barrier discharge(DBD)plasma was employed to chemically modify and physically etch the surfaces of several kinds of chemical fiber yarns.It is found that,under proper plasma treatment condition,the air drag force of yarns increased significantly.Based on a series of verification experiments and characterization of yarn properties,it is indicated that the surface chemistry and morphology of treated yarns changed obviously,which might directly affect the viscous effect at the interface between the air flow and yarn surface(or drag coefficient C_d),and hence the air drag in the given flow field.This study provides a new route to improve the air-jet weaving efficiency for synthetic fabrics.Furthermore,the results obtained pave the way for the practical application of this plasma technique and the realization of―weaving-modification integration‖.We have reached to below research points:1)Two DBD plasma treatment methods,including dynamical treatment and remote treatment,were used to modify polyethylene terephthalate(PET)yarns.It is found that,compared with untreated sample,the air drag forces of PET yarn samples treated by two plasma treatment methods all changed significantly,which reflected the dependence of air drag on treatment time and treatment intensity.After dynamical treatment,the maximal growth rate of air drag(R_d)of PET yarns was 18.9%,while the maximal R_d reached 17.4%after remote treatment.After dynamical treatment,the maximal R_d for polyacrylonitrile(PAN),polyethylene(PE)and polypropylene(PP)yarns were 10.9%,43.0%and 40.0%respectively.2)The air drags of untreated PET yarns and the ones treated by dynamical and remote treatment were measured under different flow humidities.It is found that the air drag of untreated sample decreased with the increase of flow humidity;by contrast,that of treated samples improved with the rise in flow humidity.The results verified that the grafting of polar groups on fiber surface via plasma treatment was the key factor to cause the change of air drag.3)After plasma treatment,the moisture regain of PET yarn samples improved dramatically.With the increase of plasma intensity,the variation tendency of moisture regain agreed well with that of air drag,which could be considered as an important adminicular evidence for the explanation of mechanism of air drag improvement via plasma treatment.4)The surface chemistry and morphology of untreated and treated PET yarns were characterized by X-ray photoelectron spectroscope(XPS),scanning electron microscope(SEM)and atomic force microscope(AFM)respectively.The XPS results indicated that,after dynamical and remote treatment,O-and N-containing polar groups were grafted on the fiber surface,which improved the surface polarity of PET yarns and hence increased the H-bonds between fiber surface and water molecules in air jet.The SEM and AFM characterization showed that many nano-sized grooves were generated on the fiber surface along its length after dynamical treatment while numerous nano-sized projections were generated after remote treatment.Moreover,proper plasma treatment condition could enhance the tensile strength of PET yarns.5)The diameters of untreated and treated yarns were measured after dynamical and remote treatment.The results showed that the yarn diameter changed in a narrow range with the variation of treatment time and treatment intensity.The variation trend of growth rate of F_d/d(R_c),which is equivalent to C_d,was similar to that of R_d,indicating that the varying C_d caused by plasma treatment is the main reason for the change of air drag.6)The tail gas component was characterized during the plasma treatment of chemical fiber yarns and compared with that of a control group.The results indicated that the yarn was not only the etching object,but also the source of partial free radicals,which further clarify the plasma reaction mechanism of air drag improvement via plasma treatment.7)The effect of particular molecules(aniline molecules)modification on PET yarn surface on its air drag was also studied.The results showed that with the increase of amount of polyaniline,the air drag of the yarns improved obviously.Moreover,the conductivity of the treated yarns enhanced dramatically and the volume resistivity was reduced maximally by 5.6×10~4 times compared with that of untreated one.Additionally,the superhydrophobic and superamphiphobic fabrics were prepared by plasma treatment.The results obtained paved the way for the preparation of functionalized fiber/fabric. |
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