434 ISSN 1229-9197 (print version) ISSN 1875-0052 (electronic version) Fibers and Polymers 2015, Vol.16, No.2, 434-442 Improvement of the Interphase Between Basalt Fibers and Vinylester by Nano-Reinforced Post-Sizing Florent Gauvin, Patrice Cousin, and Mathieu Robert * Department of Civil Engineering, University of Sherbrooke, Sherbrooke J1K 2R1, Canada (Received June 4, 2014; Revised September 23, 2014; Accepted October 23, 2014) Abstract: Basalt fiber reinforced composites are innovative materials which may be used as an alternative to glass fiber- based composites in civil engineering applications. They exhibit high temperature resistance, corrosion resistance, low cost and excellent mechanical properties. However, according to previous studies, weak interfaces between the basalt fiber and the thermoset resin, such as polyvinylester, could be a problem for the use of basalt fibers reinforced polymers (BFRP) for civil engineering applications. To solve this problem, this study investigates the improvement of properties of basalt fibers coated with silica nano-reinforced epoxy resin. Three types of coatings were tested: epoxy resin, epoxy resin treated with fumed silica, and epoxy resin treated with silane-treated fumed silica. Silica nanoparticles were characterized by Fourier Transform Infrared Spectrometry (FTIR), Thermal Gravimetric Analysis (TGA) and micro-electrophoresis (Zeta-Nanosizer). Basalt fibers were dip-coated in diluted solutions/suspensions of epoxy coatings in acetone and analyzed using Scanning Electron Microscopy (SEM). Basalt fibers/vinylester (VE) composites were then prepared by compression molding. Tensile tests and interlaminar shear tests (ILSS) were performed on the different molded BFRP. Preliminary results show a 5-25 % improvement in mechanical properties depending on the type of coating. The presence of nanosilica at the interface between the basalt fiber and VE matrix leads to a significant enhancement of interlaminar and ultimate tensile strength. Keywords: Fibre/matrix bond, Mechanical properties, Basalt fiber, Nano-reinforcement, Microstructure Introduction Nowadays, the use of composites as replacements of conventional materials is increasing in many industrial sectors, such as aeronautics, sports and leisure, transportation and construction materials. Composites for civil engineering applications are typically constituted of continuous fibers (glass, carbon or aramid fiber) and thermoset resins (epoxy, vinylester, polyester) [1]. However, the market still requires the technical and the scientific communities to develop more cost-effective and higher performing systems. Recent development in fiber manufacturing technologies has allowed the production of new innovative composite materials made of basalt fibers (BF). BF is an inorganic fiber directly produced from basalt rock, a natural mineral material, through a melting process similar to glass fiber production. Unlike glass fiber production, it does not reject secondary materials such as sodium sulfate, boric acid or sulfur oxides [2]. BF chemical composition is highly dependent of the initial basalt mining site. It is slightly different from glass fiber, with a less complex composition and less metallic oxide contents [3]. Basalt fiber reinforced polymer (BFRP) can be used to produce different kinds of materials for civil engineering, such as bars for internal reinforcement of concrete [4], sheets for external reinforcement of structures [5] or rock bolts [6]. BF offers good thermal performance, high tensile strength, great electromagnetic properties and vibration, abrasion and impact loading resistance. It is inert and resistant to acids, radiations and UV light [7]. BFRP products are available in a variety of shapes, such as straight rods, loops, two-dimensional mesh, and spirals. Furthermore, the high mechanical properties of BF make possible the lightening of glass-fiber based structures [8]. BF offers a higher tensile strength than glass fiber and larger ultimate strain than carbon fiber [9]. Table 1 presents comparative characteristics for different types of fibers. Moreover, its low price and good compatibility with other materials, such as metals or plastics make it an outstanding candidate for reinforcing polymer composites [10,11]. Epoxy and polyvinylester (VE) matrixes are more and more used in composite materials. VE is extensively used in civil engineering applications [12]. Its mechanical properties are slightly lower than epoxy but its chemical resistance is far higher because of the presence of several large organic functions, such methyl or phenyl groups protecting the whole matrix from hydrolysis or acid attack by shielding weaker groups [13]. Epoxy offers very high mechanical and thermal properties as a result of the dense network formed during the polymerization process [14]. *Corresponding author: Mathieu.Robert2@USherbrooke.ca Table 1. Properties of different fibers Properties Basalt E-glass S-glass Carbon Tensile strength (MPa) 4840 3400 4580 3500-4000 Elastic modulus (GPa) 89 72 85 240-650 Elongation at break (%) 3.1 4.7 5.6 1.5-2.0 Diameter of filament (μm) 06-21 06-21 06-21 0.5-1.25 Density (g/cm ) 2.8 2.6 2.5 1.75-1.95 Price (year 2013) (USD/kg) 30 1-10 70 90-350 DOI 10.1007/s12221-015-0434-x