Discharge Mechanism Of An Atmospheric Pressure DBD Plasma Jet And Its Application On Surface Modification Of PET Fabrics

One of the most attractive features of low-temperature atmospheric pressure plasmatechnique is the ability to achieve chemical reactions without the dangers and inconvenience ofelevated temperatures. This attractive characteristic allows for implementation into a wide rangeof applications such as surface modification on polymer materials and preparation ofbiomaterials. In this dissertation, the preliminary discharge characteristics of an atmosphericpressure plasma jet (APPJ) setup with highly conductive liquid-electrode were studied.Meanwhile, the different polymerizing characteristics of Ar and He APPJs were investigated.Moreover, we developed a novel two-step process for the surface modification of PET fabrics byplasma polymerization.It was found that the Ar and He plasma gas temperature were not higher than310K whenthe applied power was lower than50W. This temperature was nearly equal to the roomtemperature and the plasma was very suitable for treating organic materials and inducingchemical reactions. The discharge current of the plasma increased with the increase of appliedpower, and the discharge current of Ar plasma was significantly higher than that of He plasmaunder the same applied power. When the plasma was mixed with O2or acrylic acid monomer,discharge current decreased. According to the OES results, many reactive species such as O+2、OH、O were detected which played a very important role in plasma polymerization process.The noticeable feature on the surface of acrylic acid polymer (PAA) deposited by APPJ isthe presence of nanocones with a base radii of300nm. The density and uniformity of nanoconeson PAA film deposited by He plasma jet were higher than that of Ar plasma jet. The depositionrates of Ar and He plasma jets were50nm·min-1and15nm·min-1under an Ar or He flow rate of0.4m3·h-1and an O2flow rate of0.1m3·h-1. Meanwhile, the water resistance property of PAAfilm deposited by He plasma jet was better than that of Ar plasma jet. Through XPS analysis, itwas found the COOH/R ratio of PAA film deposited by He plasma jet was about80.93%higher than when Ar plasma jet was used.FTIR and XPS results revealed that many nitrogenous groups were introduced onto thesurface of PET fabrics through the two-step plasma polymerization process. The concentration ofO=C-NH on sample modified under an applied power of50W was approximately four timeshigher that that of30W. The water contact angle decreased dramatically from90°to0°afterplasma polymerization modification, and the contact angle value remained unchanged for a longstorage time. It implied that this plasma polymerization process was a promising techniquebecause it can overcome the aging drawback which usually occurs in many conventional plasmaprocesses. Moreover, when the treated PET fabrics were dyed with reactive dye, the K/S valuesrose to2.01.