Bulk or surface treatments of ethylene vinyl acetate copolymers with DNA: Investigation on the flame retardant properties Jenny Alongi ⇑ , Alessandro Di Blasio, Fabio Cuttica, Federico Carosio, Giulio Malucelli Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, sede di Alessandria, and Local INSTM Unit, Viale Teresa Michel 5, 15121 Alessandria, Italy article info Article history: Received 23 October 2013 Received in revised form 6 December 2013 Accepted 11 December 2013 Available online 19 December 2013 Keywords: Ethylene vinyl acetate copolymers Deoxyribonucleic acid Flame retardancy Combustion Cone calorimeter Burning-through tests abstract Deoxyribose nucleic acid (DNA) has recently proven to be an efficient flame retardant for ethylene vinyl acetate (EVA) copolymers, when added in bulk via melt-blending. Indeed, thanks to its char-former features, DNA was able to quite efficiently protect an EVA copolymer (containing 18 wt.% of vinyl acetate) against an irradiative heat flux of 35 kW/m 2 , strongly reducing the combustion kinetics and favouring a remarkable decrease of CO and CO 2 yields. In the present work, the evolution of the DNA flame retardant concept is presented: in spite of bulk compounding, DNA has been confined as a coating on EVA surface. Thus, a comparative study on the flame retardant properties of EVA loaded or coated with DNA has been thoroughly carried out. The collected results have shown that the DNA coating blocks the ignition of the copolymer when tested by cone calorimeter under a heat flux of 35 kW/m 2 , increasing the time to ignition by 228s (+380%, with respect to pure EVA), while it greatly postpones (102s, +625% with respect to pure EVA) and reduces the combustion kinetics under a heat flux of 50 kW/m 2 . Finally, unlike melt-compounded DNA, the bio-macromolecule coating is able to protect the underlying material from a butane/propane torch applied three times consecutively to the specimen for 5s. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Generally speaking, a polymer combustion is fuelled by pyrolysis products escaping from its surface due to the heat transferred from the flame to the polymer surface and also radiated from the flame itself, as schematised in Fig. 1. This process can be modelled at the laboratory scale by cone calorimeter [1,2]. The oxygen required for sustaining the flaming combustion diffuses in and from the surrounding air environment. Solid particles escape from the flame as smoke, which is accompanied by gaseous species, some of which can be toxic [3]. As already documented [1], the most significant polymer degradation reactions usually occur in the condensed phase, as they take place mainly within 1 mm of the interphase between the flame and polymer, where the temperature raise is high enough. These reactions involve the polymer and any additives (in particular flame retar- dants) included in the formulations or applied as surface treatments. Experimental studies of this region have been published by Price and co-workers [4] and by Marosi and coworkers [5,6]. The volatile species formed during com- bustion escape into the flame zone, whilst heavier species undergo further reactions and may eventually turn into char: this multi-lamellar carbonaceous structure acting as a thermal insulator protects the surrounded polymer. It is common consensus that the flame retardants operating in the condensed phase may be considered the unique and worthy alternative to halogen-based flame retardants (that are currently under scrutiny by governments because of environmental and human safety issues) [1], although their action mechanism is significantly different. Indeed, these systems are able to facilitate the char formation and to reduce the evolution of the flammable volatile species. In this scenario, DNA has proven to exhibit the same 0014-3057/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.eurpolymj.2013.12.009 ⇑ Corresponding author. Tel.: +39 0131 229337; fax: +39 0131 229399. E-mail address: jenny.alongi@polito.it (J. Alongi). European Polymer Journal 51 (2014) 112–119 Contents lists available at ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj