410 87 Surface Modification of Polypropylene Nonwoven Fabric with Plasma Activation and Grafting Ahmad Mousavi Shoushtari 1 , Aminoddin Haji 2* , Azadeh Jafari 1 (1. Textile Engineering Department, Amirkabir University of Technology, Tehran, Iran 2. Islamic Azad University, Birjand Branch, Birjand, Iran) Abstract: Polypropylene fiber has the advantages of high tensile strength, excellent chemical and biological resistance and low production costs. But some drawbacks such as dyeing problems and low wettability, raised from highly crystalline and hydrophobic nature of polypropylene chain, has restricted the usage of this fiber in some applications. In this study, plasma induced grafting as an effective procedure for modifying the surface characteristics of polypropylene nonwoven fabrics has been applied. Atmospheric pressure plasma was used to generate active sites on the polymeric chains of polypropylene fibers, and then the plasma activated samples were grafted with acrylic acid. The effects of plasma treatment time, monomer concentration, grafting time and temperature on graft yield and water absorption behavior of treated samples were evaluated. To evaluate the surface morphology changes, SEM images were employed. FTIR analysis was used to examine the chemical changes made on the fabric sample surfaces. The FTIR analysis showed that carbonyl and carboxyl groups have been created on the surface of plasma treated and grafted fibers. Water absorption of untreated and plasma grafted samples were evaluated using contact angle measurements. The results show that water absorption of plasma grafted polypropylene nonwoven samples has been improved significantly. Keywords: Plasma, Polypropylene, Graft, Acrylic acid, Surface modification 1 Introduction Polypropylene (PP) is one of the most versatile fibers because of its chemical inertness, better tensile strength, and low cost. However, the hydrophobic nature of the polymer restricts its application in a number of technologically important areas [1] . Several chemical modification processes such as oxidation, grafting, etc. have been developed to improve the characteristics of PP fiber [2] . The functionalization of polymeric materials by plasma and high energy radiation has attracted wide attention to introduce desirable functional properties in the material surface [1] . Plasma treatment of textiles may result in desirable surface modifications, including but not limited to surface etching, surface crosslinking, chain scission, decrystallization and oxidation, without affecting bulk properties of the fibers. Compared with conventional wet finishing, plasma processes have the decisive advantage of less water, chemicals and energy usage with the possibility to obtain typical textile finishes without changing the key textile properties [3,4] . Efficacy of the treatment depends on the choice of the process gas, plasma density and energy [5] . When using special gases, a plasma-induced deposition polymerization may occur [6] . In atmospheric pressure plasmas, the surface activation typically takes place with oxygen-containing gas mixtures such as air. Surfaces with low functionality become more reactive by enhancing the concentration of oxygen containing or other polar groups at the surface. After plasma activation in air a great variety of different oxygen-containing functional groups, such as -OH, -C=O, -COOH will be introduced onto the surface of the material. Activation can also mean the increased wettability of surfaces whose surface energy is increased by the polar surface groups [7] . Many studies have already been carried out with low pressure plasma [3-4, 8-12] , but atmospheric pressure plasma treatments would be ideal for the continuous processing of textile materials. Atmospheric plasma devices and treatments could be utilized for use in high-speed continuous processing operation, and when optimized, could replace or increase many current wet chemical finishing processes [13] . Several studies have been done on atmospheric pressure plasma treatment of PP fibers. McCord et al used He and He/O2 gases for plasma treatment of PP fabrics and showed that the surface oxygen and nitrogen of PP fabric increased significantly, along with a slight decrease in tensile strength of the fabric [5] . Kuwabara et al have made an atmospheric plasma jet and confirmed the etching of the material at suitable positioning of the device [14] . Cheng et al reported the decrease of water contact angle of PP fibers after treatment with * Corresponding author’s email: aahl58@yahoo.com