Mechanical Properties of Thermoplastic Elastomers Based on Silicone Rubber and an Ethylene–Octene Copolymer by Dynamic Vulcanization U. Basuli, T. K. Chaki, K. Naskar Rubber Technology Center, Indian Institute of Technology, Kharagpur 721302, India Received 9 November 2006; accepted 15 October 2007 DOI 10.1002/app.27611 Published online 22 January 2008 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Thermoplastic vulcanizates (TPVs) are a special class of thermoplastic elastomers that are generally produced by the simultaneous mixing and crosslinking of a rubber with a thermoplastic polymer at an elevated tem- perature. Novel peroxide-cured TPVs based on blends of silicone rubber and the thermoplastic Engage (an ethylene– octene copolymer) have been developed. These TPVs ex- hibit very good overall mechanical and electrical proper- ties. With an increasing concentration of dicumyl peroxide, the tensile strength, modulus, and hardness of the TPVs increase, whereas the elongation at break decreases. Signif- icant correlations have been obtained from oscillating disc rheometer torque values with various physical properties, such as the modulus and tension set of the TPVs. The aging characteristics and recyclability of the silicone-based TPVs are also excellent. Scanning electron microscopy pho- tomicrographs of the TPVs have confirmed a dispersed phase morphology. Ó 2008 Wiley Periodicals, Inc. J Appl Polym Sci 108: 1079–1085, 2008 Key words: blends; elastomers; thermoplastics; rubber; vulcanization INTRODUCTION Nowadays, thermoplastic elastomers (TPEs) are among the rapidly growing materials in the polymer industry and have extremely high potential growth in the future. They combine the processing charac- teristics of thermoplastics with the elastic and me- chanical properties of conventional vulcanized rub- bers. TPEs have both advantages and disadvantages in comparison with conventional vulcanized rubbers, including the following: Advantages:  No vulcanization and very little compounding are required.  They are suitable for methods of thermoplastic processing, such as injection moldings, blow molding, thermoforming, and heat welding.  Scrap can be recycled and reused without sig- nificant deterioration in performance.  Properties can very easily be manipulated for different requirements by just a change in the blend ratio. Disadvantages:  TPEs soften or melt at an elevated temperature, above which they lose their rubbery character.  On extended use, TPEs show creep behav- ior. 1–3 TPEs based on rubber/thermoplastic compositions are generally classified into two main categories: the first category consists of simple blends and is com- monly designated as thermoplastic elastomeric ole- fins, and in the second category, the rubber phase is dynamically vulcanized in the presence of a suitable crosslinking agent, leading to a thermoplastic vul- canizate (TPV) or dynamic vulcanizate. The first TPE was introduced to the market in 1972 by Fisher. 4 Significant improvements in the properties of these blends were achieved in 1978 by Coran and coworkers 5,6 by fully vulcanizing the rubber phase under dynamic shear while maintaining the thermo- plasticity of the blends. These blends were further improved by Abdou-Sabet and Fath 7 in 1982 by the use of phenolic resins as curatives. A series of exten- sive studies on dynamically vulcanized TPEs were car- ried out by Coran and Patel in the 1980s. 8–15 Bhow- mick and coworkers 16–24 also reported various TPEs and TPVs. Very recently, Naskar and coworkers 25–30 extensively studied the effects of various peroxides, including multifunctional peroxides, as crosslinking agents for polypropylene (PP)/ethylene–propylene– diene rubber (EPDM) TPVs. TPVs are typically charac- terized by finely dispersed (micrometer-sized) cross- linked rubber particles distributed in a continuous thermoplastic matrix. Generally, the rubber particle size varies in the range of 0.5–2 lm. Correspondence to: K. Naskar (knaskar@rtc.iitkgp.ernet.in). Journal of Applied Polymer Science, Vol. 108, 1079–1085 (2008) V V C 2008 Wiley Periodicals, Inc.