Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol Thermal and flame retardant behaviour of cotton fabrics treated with a novel nitrogen-containing carboxyl-functionalized organophosphorus system Giuseppe Rosace a, ⁎ , Angela Castellano a , Valentina Trovato a , Giuseppina Iacono b , Giulio Malucelli b a Department of Engineering and Applied Sciences, University of Bergamo, Viale Marconi 5, 24044, Dalmine, BG, Italy b Department of Applied Science and Technology, Politecnico di Torino, Viale T. Michel 5, 15121, Alessandria, Italy ARTICLE INFO Keywords: N-(Phosphonomethyl)iminodiacetic acid Sol-gel Self-extinguishing Textile finishing Cotton fabric ABSTRACT In this paper, a carboxyl-functionalized organophosphorus oligomer was immobilized onto cotton fabrics using 1,2,3,4-butanetetracarboxylic acid as an environmentally-friendly binder, in the presence of sodium hypopho- sphite, used as a catalyst, and triethanolamine, which contributes to phosphorous-nitrogen synergism. Moreover, with the aim of reducing the formation of insoluble calcium salt during home laundering, due to the free car- boxylic acid groups bound to the cotton fabric, the treated samples were recoated employing three sol-gel precursors, namely 3-aminopropyltriethoxysilane, tetraethoxysilane and 3-glycidyloxypropyltriethoxysilane. Samples were thoroughly characterized to understand the bonding between coatings and substrate, as well as the related surface morphology. The thermal behaviour was investigated by thermogravimetric analysis, flame and combustion tests. The results revealed that the treated fabrics were able to achieve self-extinction. Comparing to the untreated sample, tearing strength of PMIDA/BTCA/SHP fabric was reduced in both warp and weft direc- tions, while fabrics coated with an additional sol-gel layer were affected more significantly. 1. Introduction Although it has been an important tool throughout human history, fire can generate dramatic consequences if not properly controlled. According to the data from 2016 National Fire Protection Association (NFPA) (Haynes, 2017), the public fire departments in the U.S. re- sponded to 1,342,000 fires that caused 3390 civilian deaths, 14,650 civilian injuries, and an estimated $10.6 billion loss in direct property. Since a wide range of commonly used materials is flammable, this means that the use of flame retardants can reduce these hazards and significantly contribute to save lives and resources. As the main com- ponent of cotton, cellulose is employed for manufacturing apparel, home furnishings and industrial products, even though its low limiting oxygen index (18%) and combustion temperature (360–425 °C) make this material highly flammable (Wakelyn et al., 2006). To overcome this drawback, a chemical modification of the cellulose structure is necessary. In the last years, several treatments have been extensively studied to modify the combustion characteristics of cotton, in order to meet fire safety regulations and expand the use of cotton in textile applications that require flame retardancy. The majority of these flame retardant treatments can be classified into four distinct groups, as they can be based on the use of halogenated organic, inorganic, organophosphorus, and nitrogen formulations (Ghanbari & Salavati-Niasari, 2015; Ghanbari, Salavati-Niasari, & Sabet, 2013; Ghanbari, Salavati-Niasari, & Ghasemi-Kooch, 2014; Jamshidi, Ghanbari, & Salavati-Niasari, 2014; Nguyen, Chang, Condon, & Smith, 2014). Despite their effectiveness, some of these products, like halogen-containing compounds, turned out to be hazardous for human health, due to the use of textile materials that are typically in close contact with skin. The aforementioned dis- advantages stimulated the scientific community towards the develop- ment of phosphorus-based compounds. Indeed, although all phosphorus compounds cannot be considered generically non-toxic, the develop- ment of new phosphorus-based compounds with flame retardant properties has shown that they have lower toxicity profiles as compared to halogen-based counterparts. This finding has been witnessed by several papers (Bruchajzer, Frydrych, & Szymańska, 2015; Grümping, Opel, & Petersen, 2007; Horacek & Grabner, 1996; Salmeia & Gaan, 2015; Salmeia, Gaan, & Malucelli, 2016; van der Veen & de Boer, 2012; Weil, 1978). In the last decades, phosphorus has become the subject of https://doi.org/10.1016/j.carbpol.2018.05.012 Received 7 March 2018; Received in revised form 22 April 2018; Accepted 4 May 2018 ⁎ Corresponding author. E-mail address: giuseppe.rosace@unibg.it (G. Rosace). Carbohydrate Polymers 196 (2018) 348–358 0144-8617/ © 2018 Elsevier Ltd. All rights reserved. T