Enzymatic Hydrolysis of Nylon 6 Fiber Using Lipolytic Enzyme Amir Kiumarsi, 1 Mazeyar Parvinzadeh 2 1 Department of Organic Colorants, Institute for Color Science & Technology, Tehran, Iran 2 Department of Textile, Islamic Azad University, Shahre Rey Branch, Tehran, Iran Received 23 October 2008; accepted 4 June 2009 DOI 10.1002/app.31756 Published online 22 February 2010 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: This study confirms the structural changes of nylon 6 fibers using lipase by measuring the dyeability, hydrophilicity, chemical changes, and fastness properties. For this purpose, nylon 6 fabrics were first treated sepa- rately with different concentrations of lipase enzyme. The dyeing process was then carried out on the treated fabrics with two disperse and acid dyes. A UV-vis spectrophotome- ter was used for determination of dyebath exhaustion. Acid and disperse dyes showed higher dyebath exhaustion on the enzyme treated samples compared to raw material. The intensity of major peaks in FTIR spectra of the lipase treated samples are in favor of chemical changes of the polypeptide functional groups in fabric. Tensile strength of treated fab- rics was decreased due to enzyme treatment. The results of color measurements in the CIELAB system showed that the darkness of the samples increased with an increase in the enzyme percentage in the solution. The results of moisture regain showed that treatment of nylon fabrics with lipolytic enzymes caused to increase the moisture absorbency. The wash and light fastness properties of samples were meas- ured according to ISO 105-CO5 and Daylight ISO 105-BO1 and discussed. V C 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 3140–3147, 2010 Key words: nylon 6; lipase; hydrolysis; FTIR spectroscopy; moisture regain INTRODUCTION Nowadays, textile processing based on biotechnology has gained importance in view of stringent environmen- tal and industrial safety conditions. 1–3 The best estab- lished application of biotechnology in textile industry is the use of enzymes. These vital parts of all living organ- isms are specific organic catalysts in the reaction cata- lyzed and substrates selectivity. Traditional chemical treatments are replaced by enzymatic ones because of their lower product quality, higher manufacturing cost, more waste, and added energy consumption. The main enzymes used in textile processing are amylases, cellu- lases, proteases, esterases, nitrilases, catalases, peroxi- dases, laccases, and pectin-degrading enzymes. 1,2,4,5 Many studies have been carried out on the applica- tion of enzymes on natural fibers, including cotton sur- face modification to enhance the softness and appear- ance 5–8 ; removing undesirable byproducts from the unscoured cotton 5,9 ; desizing by enzymatic hydroly- sis 3,5 ; enzyme treatment of bleaching effluent 10,11 ; soft- ening woody fibers during retting 12,13 ; shrink-proofing, softening, improving dyeability and pilling behavior of wool and cotton 14–31 ; and silk degumming. 32,33 Recently, enzymatic hydrolysis of synthetic fibers to improve some undesired properties such as hydrophobicity, low dyeability, and insufficient washability is considered to chemists. 34–38 Many research articles have been published on enzy- matic surface hydrolysis of polyester and on its dyeing behavior 36,39–41 but few have been reported on dyeing of hydrolyzed polyamides. Studies showed that enzy- matic hydrolysis can be achieved on nylon oligom- ers. 42–46 Researchers claim that surface of PA66 and PA6 can be modified by oxidative enzymes without reducing the fiber diameter. 47 Furthermore, different types of enzymes can hydrolyze the surface of polyam- ide fibers. 38,48–50 It was indicated that the metal-free, tannic acid/enzyme after treatment of acid dyed PA 66 fibers is highly effective on improving its wash fast- ness. 51 Surface amino groups formed during the enzyme hydrolysis can also be determined based on dyeing with reactive dyes. 49 Thus, to fulfill further studies on dyeing behavior of enzyme treated polyamide, the present research work focuses on the physical and chemical properties of acid and disperse dyed-lipase treated PA 6 fibers. MATERIALS AND METHODS Plain weave PA 6 fabric with warp and weft yarn count of 40/2 tex was used. Nonionic detergent (SDL Correspondence to: M. Parvinzadeh (mparvinzadeh@ gmail.com). Contract grant sponsor: Islamic Azad University of Shahre rey (Tehran, Iran). Journal of Applied Polymer Science, Vol. 116, 3140–3147 (2010) V C 2010 Wiley Periodicals, Inc.