Characterization of irradiation-induced crosslink of epoxidised natural rubber/ethylene vinyl acetate (ENR-50/EVA) blend M. Zurina a, * ,1 , H. Ismail a , C.T. Ratnam b a Division of Polymer, School of Materials and Mineral Resources Engineering, University Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, Seberang Perai Selatan, Pulau Pinang, Malaysia b Malaysian Institute for Nuclear Technology Research (MINT), Bangi 43000, Kajang, Malaysia Received 10 March 2006; received in revised form 6 April 2006; accepted 8 April 2006 Available online 21 June 2006 Abstract The effect of irradiation on tensile, dynamic mechanical properties, thermal properties and morphology of ENR-50, EVA and ENR-50/EVA blend was investigated. All the samples were irradiated using a 3.0 MeV electron beam (EB) machine with doses ranging from 20 to 100 kGy. Results indicate that the gel fraction of ENR-50, EVA and ENR-50/EVA blend increases with irradiation dose. Concerning tensile properties, it can be seen that EB radiation increases the tensile strength of all the samples, increases the elongation at break of ENR-50 and ENR-50/EVA blend, reduces the elongation at break of EVA, increases M200 (modulus at 200% strain) of ENR-50 and EVA, while decreases M200 of the ENR-50/EVA blend. For dynamic mechanical studies, it was found that EB radiation increases the T g of all the samples due to the effect of irradiation-induced crosslinking. The compatibility of ENR-50/EVA blend also found to be improving upon irradiation. In the case of thermal properties, it was detected that T m , T c and the degree of crystallinity of ENR-50/EVA blend increase with an increase in irradiation dose. This was due to the perfection in the crystal growth occurring upon radiation. Morphology changes play a major role in the changes of the properties of ENR-50/EVA blend. Finally, it can be concluded that ENR-50/EVA blend can be vulcanized by EB radiation. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: EB irradiation; ENR-50/EVA blend; Irradiation-induced crosslink; Blend characterization 1. Introduction Blending of polymers is a common technology, frequently applied in order to develop a product with superior mechanical properties from inexpensive polymer material and small amounts of compatibilisers. The aim of polymer blends, i.e. mixtures of two or more polymers, is to obtain materials, which as far as possible combine the advantages, but not their disadvantages. However, most of the polymer blends are immiscible on the molecular scale and form heterogeneous systems that affect their physico-mechanical behavior. There have been a few at- tempts to improve the miscibility by using irradiation to mod- ify one or both polymers [1e3]. Therefore, a study of the influence of irradiation on the morphology, crystallization and melting behavior of the component polymers in the blend is essential for an understanding of how to optimize processing condition and properties. Epoxidised natural rubber, ENR-50 is a chemically modi- fied natural rubber. The epoxidation of NR to produce ENR- 50 involves the random introduction of epoxide groups onto the double bond of the NR polymer chain. ENR-50 poses ex- cellent properties like oil resistance, gas impermeability, good wet grip and high damping characteristics [4]. The oil resis- tance of ENR-50 is due to the polarity of the epoxide group. The resistance to hydrocarbons of NR found to be improved * Corresponding author. Tel.: þ60 6045937788x6113; fax: þ60 6045941011. E-mail addresses: r-zurina@utm.my (M. Zurina), hanafi@eng.usm.my (H. Ismail). 1 On study leave from Department of Polymer Engineering, Faculty of Chemical and Natural Resource Engineering, University Technology Malaysia 81310 Skudai, Johor, Malaysia. 0141-3910/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymdegradstab.2006.04.010 Polymer Degradation and Stability 91 (2006) 2723e2730 www.elsevier.com/locate/polydegstab