Anti-static Properties Of Acrylic Fibers By Plasma Treatment

Acrylic fiber is one of leading synthetic fibers due to its high strength, goodelasticity and excellent dyeability. However, the inherent poor absorbency,accompanied by the high build-up of static charges limits its further development.These shortcomings might be alleviated by chemical and physical modificationof the materials. Although chemical modification of the fibers has been somewhatsuccessful in improving hydrophilic and anti-static properties, there areenvironmental concerns related to the disposal of chemicals after treatment. Plasmatreatment, as a clean, dry and environmental friendly physical technique, opens up anew possibility in this field.Acrylic fibers were treated with three different plasma treatment methods, i.e.glow discharge plasma treatment, dielectric barrier discharge plasma treatment andplasma graft treatment. The wettability and anti-static ability of treated acrylic fiberswere researched firstly under different gas atmosphere, processing time, cabinetpressure and discharge power conditions.The oxygen or nitrogen glow discharge plasma treatment can improve surfacewettability and anti-static ability of acrylic fibers. A better anti-static property wasobtained with a longer plasma treating. But the excessive long treatment brought areverse result. When the power increased, the anti-static property increased. Theanti-static property was best around 25Pa, the lower or higher pressure also resultedanti-static property decreasing.The argon or argon/nitrogen dielectric barrier discharge plasma treatment canalso improve the anti-static property of acrylic fibers. The optimum processingcondition was as follows: the voltage 7000V, the frequency 19kHz, the processingtime lmin.Scanning electron microscopy (SEM) photographs and specific surface area(BET) analysis showed that plasma treatment causes the increase of surfaceroughness and the specific surface area.X-ray photoelectron spectroscopy (XPS) analyses revealed that plasma treatment introduces an amount of amide and carboxyl groups on the fiber surface.These polar groups will incorporate with moisture through hydrogen bonding andhelp moisture penetration and binding on the fiber surface. Under the action ofwater molecular, these polar groups will also generate ionization and lead to astructural layer of conduct electricity on the fiber surface, which enhances theelectrostatic dissipation. Therefore, the anti-static property of acrylic fiber increasedafter plasma treatment.The plasma graft treatment can introduce the quaternary ammonium saltgroups onto the fiber surface, so the anti-static property of acrylic fiber increaseddrastically. After plasma graft treatment, the moisture permeability increased andthe breathability decrease lightly.Dyeing was used to evaluate the result of plasma modification of acrylic fibers.Plasma treatment introduced the amide and carboxyl groups onto the fiber surface.The amide groups can incorporate with acid dye and the carboxyl groups canincorporate with cation dye. Therefore, the uptake of two dyes can be used to reflectthe change of the introduced amide and carboxyl groups.The dyeing results show that the uptake and K/S value of two dyes increasedobviously after glow discharge plasma treatment, indicating that an amount ofamide and carboxyl groups have been introduced on the fiber surface. Theincreasing time resulted an increase of the uptake and K/S value at first. But alonger processing time resulted a decrease of dye behavior. When the dischargevoltage increased, the uptake and the K/S value were increased too. An increasingpressure induced the increase of dyeing behaviors, but extremely higher pressurebrought opposite result.Plasma treatment is a very useful method for modifying the surface propertiesof polymer materials. However, the modification of the surface is not permanent.Often the hydrophilicity obtained is lost with time. In this paper, we also investigatethe ageing behavior of the plasma treated acrylic fibers.The results showed that the surfaces of glow discharge plasma treatment showdifferent ageing process of the modification. The ageing process can be mainly ascribed to the molecular movement of polymer chains, leading to the reorientationof polar groups. The crystallinity of the treated samples has a critical influence onthe degree of ageing since the process involves the mobility of polymer chains.Increasing crystallinity reduces the rearrangement of polar groups and thus preventsthe ageing process of the modification. In addition, the environment andtemperature that the surface is stored also play an important role in the ageingprocess. A hydrophobic environment promotes faster recovery of the originalproperties. A hydrophilic environment prevents the surface from losing the polarcharacter obtained from the plasma treatment. As the temperature is high, thesample exhibits a significant ageing process since the mobility of polymer chains ispromoted. At extremely low temperature (in liquid nitrogen), the sample is expectedto maintain its hydrophilic character after plasma treatment since there is nodiffusion migration of polar groups.There is no obviously ageing behavior for plasma graft treated surfaces. Thisresult indicates that the effect of plasma graft is more stable than that of plasmasurface processing.It can be summarized that plasma treatment can enhance the wettability andanti-static ability of acrylic fibers. The application of plasma technology can greatlyreduce the consumption of water, energy and chemicals. At the same time, less toxicsubstance or pollutions will be released during process. So plasma technology offersthe potential for simultaneous economic and environmental gains in the textileindustries.