Surface Nanostructuring of Kevlar Fibers by Atmospheric Pressure Plasma-Induced Graft Polymerization for Multifunctional Protective Clothing Mohamad Widodo, 1 Ahmed El-Shafei, 2 Peter J. Hauser 2 1 Department of Textile Chemistry, School of Textile Technology, Jl. Jakarta No. 31, Bandung 40272, Indonesia 2 Fiber and Polymer Science Program, NC State University, 2401 Research Drive, Raleigh, North Carolina 27695-8301 Correspondence to: A. El-Shafei (E-mail: Ahmed_El-Shafei@ncsu.edu) Received 29 January 2012; revised 24 April 2012; accepted 24 April 2012; published online DOI: 10.1002/polb.23098 ABSTRACT: Atmospheric plasma-induced graft polymerization was employed successfully to generate free radical on the surface of Kevlar V R (poly-(p-phenylene terephthalamide or PPTA), and to initiate and control graft polymerization of cationic antimicrobial precursors diallyldimethylammonium chloride (DADMAC) or 3- (trimethoxysilyl)propyl-dimethyloctadecyl ammonium chloride (TMS) onto the fabric surface, which eliminates the need for sep- arate processes that may involve thermal energy or UV irradia- tion. It was demonstrated that when the radiofrequency of the plasma power was 400 W, the radical density generated on the surface was 10 15 to 10 16 radicals cm 2 , which were enough to generate a poly-DADMAC or poly-TMS with surface charge of at least 2  10 17 N þ /cm 2 , which is the minimum threshold for an effective cationic biocidal surface. In both cases, the grafted poly- mers were characterized and confirmed using SEM, FTIR, and XPS. The antimicrobial activity was measured using the AATCC Test Method 100, which showed that at least 3-log reduction of bacteria colonies was achieved in the case of grafted poly-DAD- MAC or grafted poly-TMS on Kevlar V R . V C 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 000: 000–000, 2012 KEYWORDS: antimicrobial; atmospheric pressure plasma; dia- llyldimethylammonium chloride; Kevlar V R ; plasma-induced graft polymerization INTRODUCTION Contamination by microorganisms is of great concern in a variety of areas 1 and is particularly criti- cal in the area of medical textiles and protective clothing. In studies to assess the performance of protective clothing for emergency responders, RAND reported that the available garments do not provide sufficient protection against biologi- cal and infectious hazard. 2,3 The RAND Corporation is a non- profit institution that helps improve policy and decision making through research and analysis focusing on the issues of health, education, national security, international affairs, law and business, and the environment. For firefighters, mul- tiple protection against fire and heat exposure, as well as against the chemical and biological hazards, which also include bacterial infections, would be a highly desirable qual- ity standard of protective clothing. Functionalization of aramid fabrics for antimicrobial proper- ties was reported recently by Sun and coworkers. 4–7 They used halamine chemistry, which allows the regeneration of biocidal function by simple chlorine bleaching. It must be noted though, while regeneration is a safe treatment for Nomex V R (poly-(m-phenylene isophthalamide), it leads to seri- ous decomposition of Kevlar V R (poly-(p-phenylene terephtha- lamide or PPTA), 8 which is also a widely used material for protective clothing beside Nomex V R . The chemical inertness and the exceedingly high crystallinity of the fiber make sur- face functionalization of Kevlar by classic organic reactions a complex and difficult task. The chemical process is far from simple and involved complex multistep reactions employing hazardous chemicals. 9–12 Plasma, known for its high concentrations of energetic and chemically active species, has long been used to improve the adhesion properties of PPTA fibers for their use in fiber-rein- forced composites. 13 Surface functionalization of such an inert substrate was achieved quite conveniently with various chemistries in a straightforward and controllable fashion by plasma. In recent years, there has been a considerable pro- gress in conferring antimicrobial properties on polymeric materials by plasma graft polymerization. 13 For instance, Cen et al. reported an antimicrobial functionalization of poly(eth- ylene terephthalate) film and filter paper (cellulosic sub- strate) via graft polymerization of 4-vinylpyridine using a combination of low-pressure plasma and UV irradiation. 14 Other workers employed similar techniques to graft N-vinyl- 2-pyrrolidone onto the surface of polyethylene nonwoven fabric and demonstrated that using crosslinking agent (N,N 0 - methylene bisacrylamide) increased the grafting yield Additional Supporting Information may be found in the online version of this article. V C 2012 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM JOURNAL OF POLYMER SCIENCE: PART B: POLYMER PHYSICS 2012, 000, 000–000 1 JOURNAL OF POLYMER SCIENCE WWW.POLYMERPHYSICS.ORG FULL PAPER