Carbohydrate Polymers 118 (2015) 183–198 Contents lists available at ScienceDirect Carbohydrate Polymers j ourna l ho me page: www.elsevier.com/locate/carbpol Flame retardant cotton fibers produced using novel synthesized halogen-free phosphoramide nanoparticles Zahra Shariatinia a,∗ , Nasrin Javeri a , Shahla Shekarriz b a Department of Chemistry, Amirkabir University of Technology (Polytechnic), P. O. Box 15875-4413, Tehran, Iran b Colour and Polymer Research Centre, Amirkabir University of Technology (Polytechnic), P. O. Box 15875-4413, Tehran, Iran a r t i c l e i n f o Article history: Received 11 September 2014 Received in revised form 31 October 2014 Accepted 14 November 2014 Available online 24 November 2014 Keywords: Cotton fiber Flame retardant Nanoparticle Phosphoramide Antibacterial activity a b s t r a c t Flame retardant cotton fibers were successfully produced using five new nanosized phosphoramide com- pounds synthesized by ultrasonic method. The 1 H NMR spectra of compounds 1–3 illustrate 3 J(H,H) cis and 3 J(H,H) trans corresponding to the splittings of cis and trans protons present in the CH CH 2 bond. Comparing the char lengths of cotton fibers treated with phosphoramides 1–5 indicates that the samples with greater degree of grafting (DG) provide smaller char lengths so that the least and the greatest char lengths are observed for the treated fibers with phosphoramides 1 and 5, respectively. The very close DG and char lengths of compounds 1 and 2 can be described based on their chemical structures containing 4- nitroaniline and 4-chloro-3-trifluoromethyl aniline groups that both can release electrons through their resonance effects to their corresponding P N bonds and enhance the P N system synergistic effect. The TGA/DSC analyses on the treated fibers revealed that the maximum weight losses at 800 ◦ C are occurred within the range 43.52% (for fiber treated with 1) to 56.37 (for fiber treated with 5) which are all smaller than that of the raw fiber (56.83%). The in vitro antibacterial activity experiments on phosphoramides 1–5 displayed the greatest and the least antibacterial activities for compounds 2 and 4, respectively. Fur- thermore, when these phosphoramides are applied on the cotton fibers, they also demonstrate the above order for the antibacterial activities. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Cotton is one of the most important natural fibers employed in the textile industries. However, it is also one of the most flammable fibers with low limiting oxygen index (LOI = 18.4%) and onset of pyrolysis at 350 ◦ C. Improvement of thermal stability of cellulose based textiles is still a challenging issue. Numerous investigations have been conducted in finding innovatory solutions for confer- ring enhanced and durable flame retardant cotton fibers both at the academic and the industrial levels to achieve the performances of the major industrial target compounds known as Proban ® and Pyrovatex ® (Alongi et al., 2013a; Weil & Levchik, 2008; Xie, Gao, & Zhang, 2013). To overcome the thermal instability of cotton, surface treatment either with durable (e.g. monomers containing phospho- rus and nitrogen along with reactive moiety) or with non-durable (usually inorganic salts containing ammonium, urea, phosphate ∗ Corresponding author. Tel.: +98 2164542766; fax: +98 2164542762. E-mail address: shariati@aut.ac.ir (Z. Shariatinia). and poly phosphates) flame retardants are performed (Edwards, El-Shafei, Hauser, & Malshe, 2012; Horrocks, 2011). Indeed, the flame retardants (FRs) are chemicals added to materials both to prevent combustion and to delay the spread of fire after ignition. FRs may have different compositions so that they may contain halogens (bromine and chlorine), phosphorus, nitrogen, metals, minerals based on aluminum and magnesium, or they may be based on borax, antimony trioxide, molybdenum, or the FR may be a nanocomposite. The most used FRs for rendering cotton fabrics flame retardant were halogen-containing compounds. However, it was estab- lished that the halogen-based compounds are not environmentally friendly because they generate toxic gases, which can be endocrine disruptive (Legler & Brouwer, 2003; Rahman, Langford, Scrimshaw, & Lester, 2001), and may cause liver, thyroid, and neuro develop- mental toxicity. Also, it was demonstrated that they result in liver cancer in laboratory rats and mice (US EPA, 2012). In addition, it was evidenced that they persist in the environment and accumulate in living organisms (Legler & Brouwer, 2003; Rahman et al., 2001; US EPA, 2012). Therefore, the production of the halogenated FRs were http://dx.doi.org/10.1016/j.carbpol.2014.11.039 0144-8617/© 2014 Elsevier Ltd. All rights reserved.