ORIGINAL PAPER An Investigation into the Influence of Filler Silanization Conditions on Mechanical and Thermal Parameters of Epoxy Resin-Fly Ash Composites Jolanta Sroka 1 • Andrzej Rybak 2 • Robert Sekula 2 • Maciej Sitarz 1 Ó Springer Science+Business Media New York 2016 Abstract The insulation material of electronic devices should offers high thermal conductivity whilst retaining suitable mechanical properties. Epoxy resin is an example of a material that is commonly used by industry for elec- tronic insulation, despite the fact that neither the thermal conductivity nor the mechanical properties are particularly satisfying. These properties can be enhanced by incorpo- rating filler, with silica flour representing the most popular filler. An economically appealing solution is to replace silica flour with fly ash as filler material, however it must be remembered that compatibility of fly ash and epoxy resin is not ideal. In order to improve the coupling between these two materials, fly ash particles covered with [3-(2- Aminoethylamino)propyl]trimethoxysilane were obtained with six different conditions of the silanization process, where the amount of silane, the temperature and the time of the reaction were changed. The presence of the silane layer was confirmed via Fourier Transform Infrared Spec- troscopy, Thermogravimetric Analysis and Scanning Electron Microscopy. The mechanical properties, including tensile strength, Young Modulus and fracture toughness, as well as the thermal conductivity of the final samples were investigated. In the case of composites with silanized fil- lers, all of the mechanical properties were improved, and an enhancement of thermal conductivity was observed for several composites. Moreover, the differences in coupling between the silanized fly ash and the untreated fly ash, and the epoxy matrix were precisely recorded by means of SEM. The presented studies confirm that an effective silanization process can significantly improve the proper- ties of composites, while also verifying the usefulness of waste material. The results highlight that fly ash may be utilized to create a more economically affordable insulation material. Keywords Fly ash Á Silanization Á Epoxy resin Á Mechanical properties Á Thermal conductivity Introduction Representing a key consideration in the design of elec- tronic devices, insulation must be made of materials which offer high thermal conductivity whilst retaining suit- able mechanical properties. Furthermore, industrial requirements will usually dictate that the material should fulfil requirements for long exploitation of the devices without overheating and damage. An insulation material which is commonly used in the power industry is epoxy resin, however the mechanical properties of pure epoxy are not ideal (i.e. tensile strength is 40 MPa) [1], and thermal conductivity is insufficient (0.2 W/mK) [2]. In order to improve mechanical properties, whilst also ensuring enhanced thermal conductivity, various fillers may be incorporated into the polymer matrix. Examples of filler that may be used include silica, which with a thermal conductivity of up to 10 W/mK [3–6] is the most popular filler material, or boron nitride which represents a more sophisticated (with a thermal conductivity of up to 600 W/ mK) but costly solution [7, 8]. One can find attempts to add & Jolanta Sroka jolsroka@agh.edu.pl 1 Department of Silicate Chemistry and Macromolecular Compounds, Faculty of Materials Science and Ceramics, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, Poland 2 ABB Corporate Research Center, ul. Starowislna 13A, 31-038 Krakow, Poland 123 J Polym Environ DOI 10.1007/s10924-016-0773-8