New Approach to Fabricate Novel Fluorosilicone Thermoplastic Vulcanizate with Bicrosslinked Silicone Rubber-Core/Fluororubber- Shell Particles Dispersed in Poly(vinylidene Fluoride): Structure and Property Yukun Chen,* ,† Youhong Wang, † Chuanhui Xu, ‡ Yanpeng Wang, † and Changyun Jiang § † The Key Laboratory of Polymer Processing Engineering, Ministry of Education, South China University of Technology, Guangzhou, 510640, China ‡ School of Chemistry and Chemical Engineering, Guangxi University, Nanning, 530004, China § Institute of Materials Research and Engineering, A*STAR, 3 Research Link, Singapore 117602 ABSTRACT: Herein, we report a new method, core-shell dynamic vulcanization, to prepare a poly(vinylidene fluoride) (PVDF)-based thermoplastic vulcanizate (TPV) with cross-linking-controlled silicone rubber (SR)/fluororubber (FKM) core- shell particles. The bicrosslinked SR-core/FKM-shell structure effectively stabilized the blending morphology of TPV, avoiding the direct contact of PVDF and SR. Results of transmission electrom microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and Fourier transform-infrared (FT-IR) confirmed the formation of core-shell structure. In the PVDF/FKM/SR (40/30/30) TPV, the size of core-shell particle was ∼2 μm, and the thickness of the FKM shell was ∼400 nm. The cross-link density of SR-core and FKM-shell could be controlled to tailor the properties of the TPV. It was found that the tan δ value of core-shell bicrosslinked TPV could be maintained at around 0.3 in range of 1-1000 cpm. The TPV exhibited good mechanical properties in which its tear strength was as high as 58 kN m -1 . The new PVDF/SR/FKM TPV can be an idea potential alternative for expensive fluorosilicone rubbers in some applications. 1. INTRODUCTION Core-shell structures assembled from various molecular building blocks, in which a core structural domain is covered by a shell domain, 1-4 have attracted the attention of many researchers. Core-shell structures own the special ability to encapsulate guest molecules to act as molecular flasks to confine chemical reactions, 5-7 centers to stabilize reactive molecules, 8-10 drug/gene carriers, 11 and catalysts. 12 Core-shell emulsion polymerization 13 is known as a typical way to synthesize core-shell particles. As shown in Figure 1a, it is usually a two-stage process that starts with the preparation of a seed latex first (monomer A) and then is mixed with another monomer B to grow a shell onto and around core A. The core-shell structures can also be formed in multiphase polymer blending to solve the interfacial incompatibility and stabilize blending morphology. 14,15 Typically, compatibilization is achieved by using block or graft copolymers with segments which concentrate at the interface between blend components and act as emulsifiers to reduce interfacial tension and inhibit coalescence during melt processing. 16 Similarly, the formation of core-shell structure in polymer blending was related to the interfacial tensions between different polymer pairs to minimize the surface free energy of polymer blends. 17,18 There has been considerable interest in the formation of core-shell structures in polymer blending. 17-24 Favis et al. 21 have studied the control of the microstructure in HDPE/PS/PMMA ternary blends. Ke et al. 20 have shown a facile method to obtain the core-shell structure in PA6/PB-g-MAH/LDPE blends. Li et al. 23 successfully predicted the core-shell morphology of PP/ EPDM/HDPE ternary blends in thermodynamic equilibrium by a minimum free energy model and controlled the morphology of ternary blends from core-shell structure to separately dispersed structure. Valera et al. 18 predicted the morphology of PMMA/PP/PS ternary blends by spreading coefficient, minimum free energy and dynamic interfacial energy phenomenological models. However, no reports has been involved the formation of cross-linked core-shell structures in the field of dynamic vulcanization. Fluorosilicone rubber, a kind of special and promising elastomers, plays many essential roles in various commercial and civil applications, especially for military applications. However, the strait technology barrier, high-cost synthesis, and the consequently high price of fluorosilicone rubbers limited their commercial use. Additionally, fluorosilicone rubbers must be vulcanized before practical use. After vulcanization, the thermoset fluorosilicone rubber lost its processability and recyclability, 8,9 this is a waste of the expensive fluorosilicone raw materials. From the view of sustainable development, to design and prepare a new fluorosilicone thermoplastic vulcanizate (TPV) 25 is a mean- ingful and charming topic. A typical TPV usually consists of high content of cross-linked rubber as dispersion phase and low content of thermoplastics as a continuous phase, and the rubber/thermoplastic must have good interfacial compatibil- ity, 26 so that it combines the resilience of conventional Received: December 7, 2015 Revised: January 9, 2016 Accepted: February 2, 2016 Published: February 2, 2016 Article pubs.acs.org/IECR © 2016 American Chemical Society 1701 DOI: 10.1021/acs.iecr.5b04676 Ind. Eng. Chem. Res. 2016, 55, 1701-1709