Effect of radiation-induced oxidative degradation on the non- isothermal crystallization of ethylene-butene copolymer V.A. Alvarez a , M.D. Failla b , C.J. P  erez c, * a Grupo Materiales Compuestos Termopl asticos (CoMP) Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), Facultad de Ingeniería, Universidad Nacional de Mar Del Plata (UNMdP) and Consejo Nacional de Ciencia y Tecnología de Materiales (CONICET), Col on 10850, 7600, Mar Del Plata, Buenos Aires, Argentina b PLAPIQUI (CONICET) - Departamento de Ingeniería (UNS) Camino “La Carrindanga” Km 7, 8000, Bahía Blanca, Buenos Aires, Argentina c Grupo Ciencia e Ingeniería de Polímeros, Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), Facultad de Ingeniería, Universidad Nacional de Mar Del Plata (UNMdP) and Consejo Nacional de Ciencia y Tecnología de Materiales (CONICET), Col on 10850, 7600, Mar Del Plata, Buenos Aires, Argentina article info Article history: Received 15 April 2019 Received in revised form 8 October 2019 Accepted 15 October 2019 Available online 15 October 2019 Keywords: Non-isothermal crystallization Ethylene-butene copolymer Gamma radiation oxidative degradation abstract A random ethyleneebutene copolymer was irradiated with high ionizing energy in environments with different oxygen concentration. The non-isothermal crystallization process of the materials was studied by differential scanning calorimetry. When the polymer was exposed to radiation under free oxygen ambient, the temperature and the crystallinity degree decreased almost linearly with dose because chain-linking reaction prevails. On the contrary, those thermal parameters increased in the material obtained by irradiating the copolymer in environments with oxygen availability where chain scission reactions dominate. It was also found that, at equivalent irradiation dose, the crystallization rates decreased with the dose at a given cooling rate and with the reduction in oxygen content. The param- eters obtained from different applied models also confirm the tendencies observed for the experimental variables. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction The use of gamma irradiation provides an alternative mecha- nism for initiating oxidations of polyethylene's at temperatures close to the ambient one. The oxidative process is initiated by gamma irradiating the polymer in the presence of oxygen that causes chemical changes including chain scission, chain linking and the incorporation of polar oxygen-containing groups, such as acid, alcohol and ketone among others [1e5]. The oxidation worsens some important properties of the polymer, for instance the me- chanical ones, but it can favorably affect others. For example, the introduction of functional groups increases the adhesion of the polyethylene to other materials with polar characteristics, making it easier to create more homogeneous blends containing polar ad- ditives or polymers, or to enhance adherence to other material [6]. Furthermore, the oxidized polymer might be used as additive for enhance the photo degradability of polyethylene's or changes its hydrophobic nature making it less resistant to microorganism's absorption and so increasing its biodegradation rate [7 ,8]. The improvement in the mentioned properties has led to foresee oxidation by gamma radiation as alternative method for recycling polyolefins [9]. The crystallization of polyethylene's from the molten state has been extensively studied and the main factors controlling the dy- namics of the process are reasonably known [10e12]. However, literature data relative to the crystallization process of oxidized polyethylene's are very scarce, even though this has an inherent importance in the recycling of the degraded materials [13e15]. The crystallization of oxidized polyethylene from the melt is probable to depend on the average molecular weight and on the chemical molecular structure. These two factors are altered respect to the untreated polymer, thus some differences in the crystallization of the materials are expected to exist. The objective of this work was to study the non-isothermal crystallization process of a set of materials obtained by the oxida- tive degradation of a random ethylene-butene copolymer induced by gamma ray irradiation under environments having different oxygen concentrations. This article follows a previous one dealing * Corresponding author. E-mail address: cjperez@fi.mdp.edu.ar (C.J. P erez). Contents lists available at ScienceDirect Polymer Degradation and Stability journal homepage: www.elsevier.com/locate/polydegstab https://doi.org/10.1016/j.polymdegradstab.2019.109001 0141-3910/© 2019 Elsevier Ltd. All rights reserved. Polymer Degradation and Stability 170 (2019) 109001