Ammonia/Acetylene Plasma Deposition: An Alternative Approach to the Dyeing of Poly(ethylene terephthalate) Fabrics at Low Temperatures M. M. Hossain, 1 J. Mu ¨ ssig, 2 A. S. Herrmann, 3 D. Hegemann 1 1 Empa, Swiss Federal Laboratories for Materials Testing and Research, Lerchenfeldstrasse 5, CH-9014 St. Gallen, Switzerland 2 Hochschule Bremen University of Applied Sciences, Biomimetics–Biological Materials, Neustadtswall 30, D-28199 Bremen, Germany 3 Faserinstitut Bremen e.V., Geba ¨ude IW 3, Am Biologischen Garten 2, D-28359 Bremen, Germany Received 30 August 2007; accepted 12 August 2008 DOI 10.1002/app.29289 Published online 25 November 2008 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: It has long been recognized that dyes other than disperse dyes would play a much larger industrial role if they could be applied to poly(ethylene terephtha- late) (PET) fabrics at low temperatures. This research is related to a new process for the dyeing of hydrophobic PET with hydrophilic acid dyestuffs. The process is based on low-pressure plasma polymerization using an ammo- nia/acetylene gaseous mixture, which provides a nanopo- rous plasma coating containing accessible amine groups. Surface functionalization and crosslinking have been ana- lyzed with X-ray photoelectron spectroscopy. The color strength (absorption coefficient/scattering coefficient) of dyed PET is evidently improved by the attachment of dye molecules to the plasma polymer coating. The dyeability strongly depends on the plasma exposure time, gaseous mixture, and energy input. The permanency of the bond between the dye molecules and the plasma film can be characterized as the fastness property of dyed PET. The stability of the plasma coating has been examined with an abrasion and pilling tester. V V C 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 2545–2552, 2009 Key words: dyes/pigments; functionalization of polymers; thin films; plasma polymerization; polyesters INTRODUCTION Poly(ethylene terephthalate) (PET) fabrics, a type of polyester fabric, possess excellent physical and chemical properties. 1 In addition to their common uses in textiles and clothing, they have great impor- tance in technical textiles, home textiles, the automo- bile industry, and medical textiles. It is well known that polyesters are dyed with dis- perse dyes at high temperatures ( 130  C; sublima- tion becomes a more critical factor) in a closed system because of their hydrophobic nature. 2 The selection of dyestuffs is also limited to disperse dyes for polyesters because of their compact structure and high crystallinity. 3 The low and finite water sol- ubility of these dyes is considered a critical factor in determining the leveling properties and the dyeing rate. 4 High-temperature dyeing leads to difficulties for polyester/natural blends, causing damage to the natural fibers during the dyeing process. Because of dye reduction and migration, the washing fastness has been found to be satisfactory for dyeing with this dye class. 5 Moreover, although textile dyestuffs rarely cause allergic reactions, nevertheless, they are the most frequent textile allergens. A significant number of dyes (two-thirds of all allergic dyes) that are potentially injurious to health belong to the class of dispersion dyes. 6 The disperse dyes with an allergy-releasing effect are predominantly yellow, or- ange, red, and blue dyes, which can also be hidden as mixtures in black textiles. Synthetic fibers bind less firmly with certain types of dyes. This can lead, particularly in damp environments, to an increased migration of dyes from synthetic fiber fabrics, which might result in a contact allergy. 7 In this context, an alternative dyeing method at low temperatures (or with alternative dyes) for poly- esters is of growing interest. There has been very little attention focused on the application of hydro- philic acid dyes to hydrophobic PET fabrics. Acid dyes, which show excellent color brightness and good wet fastness, can easily be applied to plasma- activated polyesters at a low temperature ( 80  C) within an hour of dyeing time; plasma modification Journal of Applied Polymer Science, Vol. 111, 2545–2552 (2009) V V C 2008 Wiley Periodicals, Inc. Correspondence to: M. M. Hossain, Textilveredlungs GmbH Grabher Gu ¨ nter, Augartenstrasse 27, A-6890 Lustenau, Austria (mokbulbd@yahoo.com). Contract grant sponsor: Commission of Technology and Innovation, Bern, Switzerland.