Modified ethylene-propylene-diene elastomer (EPDM)-contained silicone rubber/ethylene-propylene-diene elastomer (EPDM) blends: Effect of composition and electron beam crosslinking on mechanical, heat shrinkability, electrical, and morphological properties Chandan Ashokrao Fuke, 1 Prakash Anna Mahanwar, 1 Subhendu Ray Chowdhury 2 1 Department of Polymer and Surface Engineering, Institute of Chemical Technology, Matunga, Mumbai 400 019, India 2 Isotope and Radiation Application Development, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India Correspondence to: S. R. Chowdhury (E-mail: rcsubhen@barc.gov.in) or (E-mail: rcsubhendu@gmail.com) ABSTRACT: In this investigation, a gamma radiation-induced methacrylic acid (MAA)-grafted ethylene-propylene-diene elastomer (EPDM) was used as a third component (g-EPDM) in silicone rubber (SiR)/ethylene-propylene-diene elastomer (EPDM) blends. These blends were electron beam (EB) crosslinked. The effect of blend composition, the presence of g-EPDM, and EB crosslinking on the mechanical, heat shrinkability, electrical, and morphological properties of SiR/EPDM blends have been studied. To investigate the effect of grafted EPDM (g-EPDM), 10 wt % of g-EPDM was added to immiscible SiR/EPDM blends. Both silicone and EPDM are blended in different proportions (70:30 and 30:70) with and without g-EPDM followed by compression molding. To improve the properties and investigate the crosslinkability of binary and ternary blends further, the SiR/EPDM blends were irradiated by electron beam at different doses (50, 100, and 150 kGy). The gel content was found to increase with EPDM content, the presence of g-EPDM, and radiation dose. The addition of g-EPDM led to improvement of tensile properties (tensile strength, Young’ s modulus, percentage elongation, and toughness), electrical properties, and shrinkability of blends. EB crosslinking further enhanced the above properties. Surface morphology (SEM) revealed that the presence of g-EPDM and the incorporation of EB crosslinking improved the above properties of blends. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47787. KEYWORDS: blends; elastomers; morphology; rubber Received 27 December 2018; accepted 6 March 2019 DOI: 10.1002/app.47787 INTRODUCTION Polymer blending has achieved considerable importance for improvement of properties. Since the last decade many researchers have focused on the improvement of novel insulating materials. Polymer blends are capable in both harsh and normal environ- ment stresses. 1,2 Ethylene-propylene diene rubber (EPDM) has saturated main backbone chain structure, due to which it shows excellent electrical properties, good heat resistance, good mechani- cal properties, heat shrinkage, and weathering properties such as oxidation and ozone resistance. 3 In silicone elastomer (Si), Si-O bond has less alkyl group and bond length is also larger than that of C C bond, due to which it has weak molecular force in poly- meric chain structure. As a result, silicone shows poor mechanical properties but exhibits excellent thermal stability, weathering resis- tance, low surface tension, and good dielectric properties. Therefore, silicone is used as the thermal shielding material, high-performance gaskets, and weather resistance coating. 4,5 The blending of these two polymers (EPDM and silicone rubber [SiR]) may be a suitable way to develop a new material with combined properties. 6–8 But EPDM and SiR are not compatible. To mix two polymers, an interfacial agent is generally added to reduce interfacial tension between two uncompatibilised phases. 9 Many researchers have made different compatibilizers in different ways to compatibilize the immiscible phases, which include both chemical and physical methods. Among them, a radiation-induced grafting technique has been used to graft monomer at the polymer backbone by radiation (gamma and electron beam) in a control manner. 10–14 Some SiR/EPDM blends have been reported, where various types of interfacial agents were used 15–18 such as malaeic anhydrite (MA), MAA, and so forth. Some investigators have focused on grafting of silane monomer on EPDM using dicumyl peroxide for com- patibilization between SiR/EPDMblend. 19 In this investigation, we have focused to increase the interaction between two immiscible phases of SiR and EPDM by incorporating gamma radiation induced MAA-grafted EPDM with the virgin EPDM. The EPDM has been grafted by MAA in aqueous medium at controlled dose of gamma radiation. Over the decades, electron beam (EB) crosslinking has become useful technique for property © 2019 Wiley Periodicals, Inc. 47787 (1 of 8) J. APPL. POLYM. SCI. 2019, DOI: 10.1002/APP.47787