EPDM–chlorobutyl rubber blends in c-radiation and hydrocarbon environment: Mechanical, transport, and ageing behavior Neelesh Ashok, 1,2 Meera Balachandran, 1,2 Falix Lawrence, 3 Neethu Sebastian 2 1 Centre of Excellence in Advanced Materials and Green Technologies (CoE-AMGT), Amrita Vishwa Vidyapeetham, Amrita University, Coimbatore, India 2 Department of Chemical Engineering and Materials Science, Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Amrita University, Coimbatore, India 3 Indira Gandhi Centre for Atomic Research, Kalpakkam, India Correspondence to: M. Balachandran (E - mail: b_meera@cb.amrita.edu) ABSTRACT: In nuclear applications, ethylene propylene diene monomer (EPDM) rubber is the material of choice as gaskets and O- rings due to its radiations resistance. In nuclear fuel reprocessing, in addition to radiation, the elastomeric components have to with- stand paraffinic hydrocarbons as well. But, EPDM has poor resistance to hydrocarbons. To enhance the durability of EPDM in such environments, EPDM–chlorobutyl rubber (CIIR) blends of varying compositions were developed and characterized for mechanical, thermal, dielectric, and solvent sorption behavior. Spectroscopic and morphological analysis was used to evaluate the compatibility of blends. Due to synergistic effect, the optimal composition of blends with superior mechanical properties and solvent resistance were found to be 60 to 80% EPDM and 20 to 40% CIIR. The optimized blends were irradiated with gamma rays at cumulative doses up to 2 MGy. Based on spectroscopic, morphological, mechanical, thermogravimetric, and sorption properties, blend containing 80% EPDM was found to have superior retention of properties after irradiation. V C 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45195. KEYWORDS: blends; degradation; mechanical properties; rubber; swelling Received 13 December 2016; accepted 5 April 2017 DOI: 10.1002/app.45195 INTRODUCTION Elastomers, an important class of polymers, have several uses in specialty applications like nuclear technology, aerospace, under- water, and defense. In nuclear applications, elastomeric compo- nents find utility in O-rings, gaskets, seals, booting materials, belts, and gauntlets for use in hot cells, glove box, and belt drives. These components have to withstand aggressive environ- ments such as radiation, chemicals, and corrosion. Among elas- tomers, EPDM has the highest resistance to radiation and hence it is the material of choice in the above-mentioned nuclear applications. In addition, EPDM rubbers have high resistance to heat, ozone, cold temperature, and moisture. 1 In nuclear reprocessing plant, some of the elastomeric components are exposed to radiation as well as hydrocarbon solvents. Though the ability of EPDM to withstand radiation is superior to other elastomers, they do not withstand environments that involve hydrocarbons. This drawback can be overcome without com- promising the radiation resistance by blending EPDM with a suitable polymer. Blending of two or more polymers enables us to overcome the drawback of one polymer by another polymer and in general, enhances the mechanical properties, ageing resis- tance, and processing characteristics. Chlorobutyl rubbers (CIIR) have low permeability to gas and moisture, high thermal stability, and good resistance to weather- ing and hydrocarbon solvents. Hence a combination of superior properties of both EPDM and CIIR can be attained by blending these rubbers and EPDM–CIIR blends would be suitable for applications requiring radiation as well as hydrocarbon resis- tance. To obtain good properties in blends, it is necessary that the blends are compatible and have minimum interfacial ten- sion between the two polymer phases. EPDM and chlorobutyl rubber are compatible with each other as evident from their sol- ubility parameters of 16.7 MPa 1/2 and 16.6 MPa 1/2 respectively. 1 Several studies have been reported in literature to achieve better physical properties, improve elastomeric properties, achieve better processing behavior, and to lower cost by blending two polymers. The effects of blend ratios and crosslinkages have shown to be significant in achieving specific improvements in properties of blends. 2,3 Investigations on the effect of blend ratios and crosslinking on mechanical and ageing behavior of V C 2017 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2017, DOI: 10.1002/APP.45195 45195 (1 of 11)