Influence of copper chloride and potassium iodide mixture in poly(vinyl chloride) exposed to gamma irradiation Williams B. da Silva, Katia Aparecida da S. Aquino * , Henrique M. de Vasconcelos, Elmo S. Araujo Department of Nuclear Energy, Federal University of Pernambuco, Av. Prof. Luiz Freire,1000, 50740-540, Recife, PE, Brazil article info Article history: Received 26 May 2012 Received in revised form 20 September 2012 Accepted 5 October 2012 Available online 16 October 2012 Keywords: PVC Radiolytic stabilization Salt mixture Gamma irradiation abstract Samples of commercial PVC containing a salt mixture of CuCl 2 /KI (PVC-salt) were investigated. The samples were irradiated with gamma radiation ( 60 Co) at dose 25 kGy. PVC and PVC-salt system showed a decrease in viscosity molar mass values on irradiated samples reflecting the main chain random scissions effect. However the PVC-salt at 0.5 wt% concentration showed no significant degradation index value. This result suggests that salt keeps the good radiolytic stabilization behavior of gamma-irradiated PVC. The CuCl 2 /KI mixture at 0.5 wt% in the PVC matrix also influenced the thermal behavior of the polymer increasing the maximum thermal degradation temperature in 42  C. In addition, the salt mixture influences significantly the Young’s Modulus of PVC increasing the rigidity of polymer. Specific interactions between PVC and CuCl 2 /KI mixture were observed in the FT-IR spectra. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Poly(vinyl chloride), PVC, is the most widely used vinyl polymer and plasticized PVC has been popularly used in a number of medical applications. The sterilization of these products can be performed by electron-beam or gamma irradiation. The most commonly radiation dose used for sterilization of commercial medical devices is at 25 kGy and the devices are sterilized by gamma radiation in air at room temperature [1]. Radiation chemistry of PVC is well studied [1e3]. The PVC gamma irradiation interaction gives rise to polymeric radicals deriving from CeCl or CeH bond scission. In the presence of air the polymeric radical produced by irradiation react with oxygen, producing the peroxyl macro radicals [4]. Ionizing radiation also causes polyenyl radical formation, which can react with oxygen also giving rise to peroxyl radicals [4,5]. This radical can then undergo further reactions leading to chain scissions, formation of various products (ketones and alcohols), discoloration, cross- linking, etc. [5,6]. Depending upon irradiation conditions, the different degree of crosslinking and scissions produces complex macroscopic behavior in polymer matrix [6] and may lead to sharp changes in chemistry and physical properties of the PVC as were shown in ours previous study [7]. Metal salts are capable of forming coordination complexes with specific groups and can affect the thermo-oxidative stability of some classes of polymers [8,9]. Some studies on thermo-oxidative behavior of polyamide containing different combinations of metal salts have shown that copper, especially when combined with iodides, are able to stabilize the polymer against thermal oxidation in a very efficient manner [8]. The main reaction pathways proposed of the copper salt activity on polymer matrix consist of a reaction sequence in which polymer and peroxyl radicals are converted in non-reactive ionic species [10,11]. It is not known whether such a mechanism operates also for the stabilization of polymers against radiolytic degradation. In this paper we report the results of gamma irradiation experiments performed in air in PVC matrix containing a mixture of copper chloride and potassium iodide (CuCl 2 /KI) in order to determine if the salt mixture is able to stabilize the PVC against gamma irradiation degradation. For this purpose, degradation index values (DI) were obtained by means of viscosity technique. The infrared spectra study, mechanical properties and thermal behavior of PVC and PVC-salts systems also were performed. * Corresponding author. Tel.: þ55 81 2126 7987; fax: þ55 81 2126 8250. E-mail addresses: barbosa3320@yahoo.com.br (W.B. da Silva), aquino@ufpe.br (K.A.daS. Aquino), hmv_quimica@hotmail.com (H.M. de Vasconcelos), elmoaraujo@gmail.com (E.S. Araujo). Contents lists available at SciVerse ScienceDirect Polymer Degradation and Stability journal homepage: www.elsevier.com/locate/polydegstab 0141-3910/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.polymdegradstab.2012.10.006 Polymer Degradation and Stability 98 (2013) 241e245