ORIGINAL PAPER The synergistic effect of fluorosilicone and silica towards the compatibilization of silicone rubber and fluoroelastomer based high performance blend Sipra Khanra 1 & Debabrata Ganguly 1 & Sanjoy Kumar Ghorai 1 & Debottam Goswami 2 & Santanu Chattopadhyay 1 Received: 7 September 2019 /Accepted: 27 February 2020 # The Polymer Society, Taipei 2020 Abstract Fluoroelastomer and silicone rubber lie in the two different poles of elastomer family in terms of polarity. Hence, combining them in a single material and making it as at least technologically compatible substance is a great challenge. In this article, the compatibilization effect of fluorosilicone rubber (block copolymer) (trifluoropropylpolydimethylsiloxane) with various loading of modified silica filler on the novel advanced polymer architecture based fluoroelastomer (copolymer of hexafluoropropylene, vinylidene fluoride, and tetrafluoroethylene) and silicone rubber (poly methylvinylsiloxane) blends has been studied in details. The mechanical properties show significant improvement at room temperature (13%) and remarkably more at high temperature (54%) for the compatibilized system. Tan delta peak shifting in DMA study indicates better compatibilization for 2.5 phr loading of fluorosilicone and 15 phr loading of silica at 50/50 blend ratio. The reduction in domain size (from 3 μm to 200 nm) of the fluorocarbon phase by the synergistic effect of silica and fluorosilicone proves the decrease in interfacial tension and better compatibilization. This blend can be judiciously applicable in the sealing system as oil and fuel resistant O-rings and gaskets for a very wide range of temperature. Keywords Fluorosilicone . Fluoroelastomer . Silicone rubber . Compatibilization . Silica . Blend Introduction The intention of polymer blending is to coin the unique attri- butes of individual polymer components together in an eco- nomical way. This may be in the point of view of processing, mechanical properties, high-temperature properties and so on. In order to blend polymers, some obstacles are to be faced that are inherent immiscibility and incompatibility [1, 2]. These are raised due to the difference in polarity and solubility parameters of the constituent polymers of the blend [3]. It has been seen that thermodynamically immiscible blend where free energy, ΔGm ≈ ΔHm > 0, can be made technologically compatible if stress can be transferred from one phase to another in an effi- cient way [4]. In order to increase the interfacial interaction between two different polymer phases, compatibilizers are used [5]. Indeed the main role of a compatibilizer is to reduce inter- facial tension thereby leads to the formation of refined micro- structure. Predominantly this is applicable in case of rubbers or elastomers which are generally viscoelastic amorphous poly- mers with low Young’ s modulus. Fluoroelastomer (FKM) is the class of specialty elastomer that excels in high-temperature stability, chemical as well as oil and fuel resistance. These properties led them to be extensively used in seals, gaskets, O-rings production [ 6–8]. The new fluoroelastomers made with advanced polymer architecture (APA) technology provide more efficient curing, excellent bal- ance of processing and physical properties compared to earlier peroxide and bisphenol cure type fluoroelastomers [9]. These improvements of the properties are the effect of modification of molecular weight distribution, strategically placed cure site monomers and unique end groups. Viton GF, GLT, GBL, VTR are the series of APA based fluoroelastomers having Mooney viscosity in the range of 25–65 (ML 1 + 10 @121 °C) and Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10965-020-02062-z) contains supplementary material, which is available to authorized users. * Santanu Chattopadhyay santanuchat71@yahoo.com 1 Rubber Technology Centre, Indian Institute of Technology Kharagpur, 721302, Kharagpur, West Bengal, India 2 School of Nanoscience and Technology, Indian Institute of Technology Kharagpur, 721302, Kharagpur, West Bengal, India Journal of Polymer Research (2020) 27:96 https://doi.org/10.1007/s10965-020-02062-z